ALBERT

Notes: Abstract. Methane (CH4) is an important greenhouse gas. Flooded rice fields (paddies) are a significant source of atmospheric CH4; estimates of the annual emission from paddies range from less than 20 to 100 million Tg, with best estimates of 50 × 20 Tg. The emission is the net result of opposing bacterial processes: production in anaerobic microenvironments, and consumption and oxidation in aerobic microenvironments, both of which occur sequentially and concurrently in flooded rice soils. With current technologies, CH4 emission from rice fields will increase as production increases. Over the next 25 years rice production will have to increase by 65% from the present 460 Mt/y to 760 Mt/y in 2020. The current understanding of the processes controlling CH4 fluxes, rice growth and rice production is sufficient to develop mitigation technologies. Promising candidates are changes in water management, rice cultivars, fertilization, and cultural practices. A significant reduction of CH4 emission from rice fields, at the same time that rice production and productivity increase at the farm level, is feasible, although the regions where particular practices can be applied, and the trade-offs that are possible, have still to be identified.

Notes: Abstract. Increases in the emissions of globally important nitrogen (N) oxide gases have coincided with significant changes in land use in the tropics. Clearing of tropical forests and savannas for agriculture currently represents the most extensive alteration of land cover on the planet. Over the last several decades, N fertilizer use has increased globally, and in China and the developing world, use has recently surpassed that in the developed world. The potential contribution of land-use change in the tropics to the increase in N oxides is great, yet only a few studies have measured N oxide emissions after tropical land conversion. Our summary of available research shows some conversions to pastures and a few management practices, especially those using N fertilizers, increase emissions beyond those found in undisturbed ecosystems. However, not all studies show unequivocal increases in emissions. Accordingly, we call for a mechanistic understanding of the processes controlling trace gas fluxes to adequately predict under what conditions increased emissions may occur. More measurements are needed to build and test models that may improve management of N fertilizer use in tropical agricultural systems. Given the expected expansion of agriculture and increased use of N fertilizers in the tropics, increased emissions of N oxides from the tropics are likely.

Notes: Abstract. Grazing animals on managed pastures and rangelands have been identified recently as significant contributors to the global N2O budget. This paper summarizes relevant literature data on N2O emissions from dung, urine and grazed grassland, and provides an estimate of the contribution of grazing animals to the global N2O budget.The effects of grazing animals on N2O emission are brought about by the concentration of herbage N in urine and dung patches, and by the compaction of the soil due to treading and trampling. The limited amount of experimental data indicates that 0.1 to 0.7% of the N in dung and 0.1 to 3.8% of the N in urine is emitted to the atmosphere as N2O. There are no pertinent data about the effects of compaction by treading cattle on N2O emission yet. Integral effects of grazing animals have been obtained by comparing grazed pastures with mown-only grassland. Grazing derived emissions, expressed as per cent of the amount of N excreted by grazing animals in dung and urine, range from 0.2 to 9.9%, with an overall mean of 2%. Using this emission factor and data statistics from FAO for numbers of animals, the global contribution of grazing animals was estimated at 1.55 Tg N2O-N per year. This is slightly more than 10% of the global budget.

Notes: Abstract. Agricultural soils, having been depleted of much of their native carbon stocks, have a significant CO2 sink capacity. Global estimates of this sink capacity are in the order of 20-30 Pg C over the next 50-100 years. Management practices to build up soil C must increase the input of organic matter to soil and/or decrease soil organic matter decomposition rates. The most appropriate management practices to increase soil C vary regionally, dependent on both environmental and socioeconomic factors.In temperate regions, key strategies involve increasing cropping frequency and reducing bare fallow, increasing the use of perennial forages (including N-fixing species) in crop rotations, retaining crop residues and reducing or eliminating tillage (i.e. no-till). In North America and Europe, conversion of marginal arable land to permanent perennial vegetation, to protect fragile soils and landscapes and/or reduce agricultural surpluses, provides additional opportunities for C sequestration.In the tropics, increasing C inputs to soil through improving the fertility and productivity of cropland and pastures is essential. In extensive systems with vegetated fallow periods (e.g. shifting cultivation), planted fallows and cover crops can increase C levels over the cropping cycle. Use of no-till, green manures and agroforestry are other beneficial practices. Overall, improving the productivity and sustainability of existing agricultural lands is crucial to help reduce the rate of new land clearing, from which large amounts of CO2 from biomass and soil are emitted to the atmosphere.Some regional analyses of soil C sequestration and sequestration potential have been performed, mainly for temperate industrialized countries. More are needed, especially for the tropics, to capture region-specific interactions between climate, soil and management resources that are lost in global level assessments.By itself, C sequestration in agricultural soils can make only modest contributions (e.g. 3-6% of total fossil C emissions) to mitigating greenhouse gas emissions. However, effective mitigation policies will not be based on any single ‘magic bullet’ solutions, but rather on many modest reductions which are economically efficient and which confer additional benefits to society. In this context, soil C sequestration is a significant mitigation option. Additional advantages of pursuing strategies to increase soil C are the added benefits of improved soil quality for improving agricultural productivity and sustainability.

Notes: Abstract. The validity of the model described in Greenwood & Karpinets (1997) was tested against the results of single year, multi level K fertilizer experiments. Measurements of plant mass, %K in the plant and K activity ratio in soil had been made at harvest and at intervals during the growing season on spring wheat, summer cabbage and turnips. Reasonably good agreement was obtained between these measurements and simulated values when the two ‘crop’ parameters (defining the dependence of critical and maximum possible %K on plant mass) were adjusted for each crop. Also good agreement was generally obtained for plant weight and plant %K at harvest in less detailed experiments on 10 other crops. Values of the two ‘crop’ parameters for 12 of the crops were strongly correlated with one another suggesting that a single ‘crop’ parameter may be all that is required to define most inter-species differences in plant-K demand.Simulations with the model indicate that, in central England, no response of 10 crops to K fertilizer would be likely on soils containing more than 170 mg of 1 M ammonium nitrate extractable-K/kg of soil and having clay contents of between 15 and 45%. Shortcomings of the model and opportunities for advance are discussed.A simplified version of the model runs on the Internet at:

Notes: Abstract. The effect of rate and timing of autumn/winter straw incorporation on the immobilization of spring-applied N-fertilizer are studied. The immobilization of 15N-labelled fertilizer by straw was determined in pot trials with a sandy loam soil (Wick series) collected from two field experiments. In experiment 1, straw was incorporated at four different rates in the autumn; experiment 2 had a fixed rate of straw (7.5 t/ha) incorporated at monthly intervals from September to March. Immobilization in spring was not enhanced when only stubble was incorporated in autumn. However, autumn incorporation of 7.5 t/ha straw resulted in a significant increase in the immobilization of spring-applied N, equivalent to 10 kg/ha; when 15 t/ha straw was incorporated, immobilization increased to 18 kg/ha. The enhancement of immobilization, immediately following fertilizer application, was dependent on the extent of straw decomposition prior to N application. Thus immobilization was related to cumulative thermal time (day °C above 0°C; Tsum between the date of straw incorporation and fertilizer application). Straw which had been incorporated for Tsum 〉 1200 no longer caused appreciable immobilization of spring fertilizer.

Notes: Book reviewed in this article: Erosion and sediment yield: global and regional perspectives Edited by D. E. Walling and B. W. Webb.

Notes: Abstract. The restorative ability of herbaceous (Psophocarpus palustris, Pueraria phaseoloides) and woody (Leucaena leucocephala, Senna siamea, Acacia leptocarpa, Acacia auriculiformis) legume species and of natural regrowth was studied on an eroded and compacted Oxic Paleustalf in southwestern Nigeria. Compared to the control treatment that was continuously cropped for 15 years, four years of fallowing significantly improved test crop yields. However, fallowing with the above species did not substantially improve soil properties, particularly soil bulk density. A longer fallow period may be needed to amend soil physical conditions of this degraded Alfisol. Soil chemical properties were greatly improved following land clearing and plant biomass burning in 1993. However, the residual effect of burning on soil fertility was insignificant in the second cropping year. Among the fallow species, P. palustris and natural fallow showed the best residual effect on test crop performance. Despite the high biomass and nutrient yields of S. siamea and A. auriculiformis, test crop yields on these plots were low due to the border effects from the uncleared and fallowed subplots.

Notes: Abstract. To study the influence of different vegetation species and plant properties on the generation of surface runoff and soil erosion in south east Spain, a series of rainfall simulation experiments was conducted on small (c. 1.5 m2) plots. These were carried out in October 1993 and May 1994 on two sites close to Murcia. Six vegetation types were studied, with some at different stages of maturity, giving a total of nine vegetation treatments and two bare soil treatments. Four replicates of each treatment were exposed to a rainstorm of 120 mm/h for 15 minutes. The results of the experiments show that there are few significant differences in the ability of the vegetation types studied to control runoff or soil erosion. Of the plant properties considered, only plant canopy cover showed a significant relationship with soil loss and runoff with the greatest reduction in soil loss taking place at canopy covers greater than 30%. The implications of this research are that future efforts should be directed at developing ecological successions and revegetation methods which promote a substantial and sustainable canopy cover.

Notes: Abstract. This paper reports results from a four year study to investigate the suitability of porous ceramic cups to measure solute leaching on shallow chalk soils. Measurements were carried out in one field following surface applications of nitrate and bromide tracers and in two fields after only bromide was applied. Soil water samples were collected from porous cups at 30,60 and 90cm depth after every 25 mm of drainage, and soil samples from 0–30, 30–60 and 60–90 cm were collected monthly eachwinter. Soil matric suctions andvolumetric moisture content were measured in one winter. Leaching losses, measured with ceramic cups were compared with those measured by soil analysis. Porous cups installed in chalk at 60 and 90 cm depth were only able to collect samples regularly when soil matric suctions were less than 15 kPa. Water held at such low suctions is likely to move quickly through relatively large fissures in the chalk. The slow rate of equilibration between solute concentrations in water moving in macrofissures and those in water moving through micropores of the chalk matrix, means that porous cups may not provide good estimates of leaching losses if they are installed in chalk rock.

Notes: Abstract. The effect of superficial liming of acidic forest soils on CO2 and N2O emissions and CH4 uptake was investigated with closed chambers in two deciduous and two spruce forests, by weekly to biweekly measurements over at least one year. The flux rates of untreated areas varied between 1.94 and 4.38 t CO2-C/ha per y, 0.28 and 2.15 kg/N2O-N/ha per y and between 0.15 and 1.06 kg CH4-C/ha per y. Liming had no clear effect on CO2 emissions which may change in the long-term with decreasing root turnover and increasing C-mineralization. Apart from one exception, liming resulted in a reduction of N2O emissions by 9 to 62% and in an increase of CH4 uptake by 26 to 580%. The variability in N2O emissions between the forest sites could not be explained. In contrast, the variability of annual CH4 uptake rates could be explained by N content (r2= 0.82), C content (r2= 0.77), bulk density (r2= 60), pore space (r2= 0.59) and pH (r2= 0.40) of mineral soil at a depth of 0 to 10 cm, and by the quantity of material in the organic layer (r2= 0.66). Experiments with undisturbed columns of the same soils showed that between 1 and 73% of the total N2O emissions came from the organic layer. However, atmospheric CH4 was not oxidized in this layer, which represents a diffusion barrier for atmospheric CH4. When this barrier was removed, CH4 uptake by the mineral soil increased by 25 to 171%. These results suggest that liming of acidic forest soils causes a reduction of the greenhouse gases N2O and CH4 in the atmosphere, due to changes in the chemical, biological, and physical condition of the soils.

Notes: Abstract. Increases in the atmospheric concentrations of nitrous oxide (N2O) contribute to global warming and to ozone depletion in the stratosphere. Nitric oxide (NO) is a cause of acid rain and tropospheric ozone. The use of N fertilizers in agriculture has direct and indirect effects on the emissions of both these gases, which are the result of microbial nitrification and denitrification in the soil, and which are controlled principally by soil water and mineral N contents, temperature and labile organic matter.The global emission of N2O from cultivated land is now estimated at 3.5 TgN annually, of which 1.5 Tg has been directly attributed to synthetic N fertilizers, out of a total quantity applied in 1990 of about 77Tg N. This amount was 150% above the 1970 figure. The total fertilizer-induced emissions of NO are somewhere in the range 0.5-5 Tg N. Mineral N fertilizers can also be indirect as well as direct sources of N2O and NO emissions, via deposition of volatilized NH3 on natural ecosystems and denitrification of leached nitrate in subsoils, waters and sediments.IPCC currently assume an N2O emission factor of 1.25 ± 1.0% of fertilizer N applied. No allowance is made for different fertilizer types, on the basis that soil management and cropping systems, and unpredictable rainfall inputs, are more important variables. However, recent results show substantial reductions in emissions from grassland by matching fertilizer type to environmental conditions, and in arable systems by using controlled release fertilizers and nitrification inhibitors. Also, better timing and placement of N, application of the minimum amount of N to achieve satisfactory yield, and optimization of soil physical conditions, particularly avoidance of excessive wetness and compaction, would be expected to reduce the average emission factor for N2O. Some of these adjustments would also reduce NO emissions. However, increasing global fertilizer use is likely to cause an upward trend in total emissions even if these mitigating practices become widely adopted.

Notes: Abstract. Field measurement of landfill methane (CH4) emissions indicates natural variability spanning more than seven orders of magnitude, from less than 0.0004 to more than 4000 g/m2 per day. This wide range reflects net emissions resulting from production (methanogenesis), consumption (methanotrophic oxidation), and gaseous transport processes. The determination of an ‘average’ emission rate for a given field site requires sampling designs and statistical techniques which consider spatial and temporal variability. Moreover, particularly at sites with pumped gas recovery systems, it is possible for methanotrophic microorganisms in aerated cover soils to oxidize all of the CH4 from landfill sources below and, additionally, to oxidize CH4 diffusing into cover soils from atmospheric sources above. In such cases, a reversed soil gas concentration gradient is observed in shallow cover soils, indicating bidirectional diffusional transport to the depth of optimum CH4 oxidation. Rates of landfill CH4 oxidation from field and laboratory incubation studies range up to 166 g/m2 per day, among the highest for any natural setting, providing an effective natural control on net emissions. It has been shown that methanotrophs in landfill soils can adapt rapidly to elevated CH4 concentrations with increased rates of CH4 oxidation related to depth of oxygen penetration, soil moisture, and the nutrient status of the soil.Estimates of worldwide landfill CH4 emissions to the atmosphere have ranged from 9 to 70 Tg/y, differing mainly in assumed CH4 yields from estimated quantities of landfilled refuse. At highly controlled landfill sites in developed countries, landfill CH4 is often collected via vertical wells or horizontal collectors. Recovery of landfill CH4 through engineered systems can provide both environmental and energy benefits by mitigating subsurface migration, reducing surface emissions, and providing an alternative energy resource for industrial boiler use, on-site electrical generation, or upgrading to a substitute natural gas. Manipulation of landfill cover soils to maximize their oxidation potential could provide a complementary strategy for controlling CH4 emissions, particularly at older sites where the CH4 concentration in landfill gas is too low for energy recovery or flaring. For the future, it is necessary to better quantify net emissions relative to rates of CH4 production, oxidation, and transport. Field measurements, manipulative studies, and model development are currently underway at various spatial scales in several countries

Notes: Book Reviewed in this article: Phosphorus loss from soil to water: Edited by H. Tunney, O. T. Carton, P. C.

Notes: Abstract. Variously timed sub-optimal irrigation strategies were applied to sugarbeet grown on a light soil (loamy sand or sandy loam) over four seasons (1991 to 1994) to investigate the effect on crop growth and nitrate leaching risk. Data from the two dry seasons, (1991 and 1994) are reported here. In the driest year (1991) soil mineral N levels after autumn harvest were negatively related to crop water use (P 〈 0.05). In this season, there was little drainage from the soil profile, and full irrigation reduced residual soil N by 31 kg N/ha (0-90 cm) compared with the unirrigated treatment (79 kg N/ha). The potential for N leaching during the ensuing winter was consequently more than halved. In 1991 and 1994 there was a strong positive linear relationship between dry matter yield, N uptake and water use, but a negative relationship between plant N concentration and water use. These relationships were a function of the severity and not the timing of drought. The additional N uptake associated with increased irrigation and crop water use was biased towards a large concentration in the aboveground crop (tops), which are normally returned to the soil. The C:N ratio of sugarbeet tops was affected by crop water supply with droughted crops having lower values. This would also influence N release and subsequent leaching risk. However, the effects of drought on N leaching risk were relatively small when compared with other root crops such as potatoes.

Notes: Abstract. To provide a practical aid to improving fertilizer practice a mechanistic model was developed that can be readily calibrated for widely different crops. Most of the inputs are easy to obtain and the others, the amounts of fixed soil-K and the velocity constants for fixation and release of soil-K, can be readily measured by a novel procedure which is described.The model calculates for each day the potential increase in plant weight and the increment in root length, from the current plant mass, its %K and pan evaporation. It calculates the maximum amount of K that could be transported through soil to the root surfaces. It modifies this potential uptake by taking account of the ‘feedback’ of plant K on root absorption to give the actual uptake and a new %K in the plant. It calculates the radii of the depletion zones around each root increment and the interchange between the solution, exchangeable and fixed-K in these zones and also in the undepleted regions of soil. Routines are included for the effects of weather on the various processes. Differences between species are accommodated by selecting one of three algorithms for root growth and by adjusting the values of two crop-K parameters that define the decline in a critical and a maximum possible %K with increase in plant mass per unit area.A simplified version of the model runs interactively on the Internet at:

Notes: Abstract. Phosphorus concentrations and outputs have been compared and contrasted in six small agricultural catchments in the west and northeast of Scotland. The loss of P from soils to stream waters was more from catchments with intensive dairy cattle farming in the west than from the less intensively stocked/arable catchments in the northeast, with striking differences being seen between the two regions. In the northeast, intensive animal farming caused less P loss in drainage water than arable management.Larger mean annual concentrations were seen in the west (0.076-0.142 mg PO4-P/l as molybdate-reactive phosphate–MRP) compared with the northeast (0.012-0.025 mg PO4-P/l), a feature caused by the combination of limited P-retention in the western Gleysols and smaller inputs to the largely-podzolic northeastern catchments. Stream concentrations were decreased by dilution during winter storm flows and increased during summer baseflow and at the beginning of soil rewetting in autumn.

Notes: Book Reviewed in this article: Freshwater Contamination By B. Webb (editor).

Notes: Book Reviewed in this article: Biotechnical and soil bioengineering slope stabilization. A practical guide for erosion control By D. H. Gray & R. B. Sotir.

Notes: Abstract. An effective fertilizer recommendation system requires information on seasonal, soil-related and cultural variations in soil mineral nitrogen (N) and nutrient requirements of the crop. This can be provided by dynamic N turnover models, such as listed by Plentinger & Penning De Vries (1996). In this paper, we describe a survey of farmer opinion designed to ascertain what farmers want from such a decision support system. Over 100 farmers were surveyed. Surveyed farmers requested that default values be available for all model inputs. Inputs should be entered both by windows-based menu (for clarity) and tabular format (for speed), have user-selected units, and be fully supported by context-sensitive help. The system should have a hierarchical structure allowing access to fixed parameters, and be compatible with commonly used farm recording packages. Recommendations should be provided both for the field (single and optional application rates), and in tabular format across the whole farm. Simulations should be easily rerun using more recent crop and weather data. Turnover processes underlying recommendations should be illustrated by flow diagrams of flux between pools, pie charts of fertilizer fate, bar charts of movement down the soil profile and graphical plots of changes in N status against time.

Notes: Abstract. Field experiments undertaken at 14 sites, on a range of soil types, in lowland England, during the cropping years 1989–1993, tested the effectiveness of cattle or pig slurry as a source of nitrogen for cereal cropping. Slurry was applied in autumn, winter and spring, to autumn and spring sown cereal crops. Assessments included slurry nitrogen efficiency relative to N in spring applied fertilizer in terms of both grain yield and grain protein production, apparent crop recovery and content of mineral nitrogen in soil profiles. Crop response to nitrogen was poor at seven sites where high residues of soil mineral nitrogen (SMN) were present. On the seven responsive sites, spring slurry applications proved more efficient (mean 40%) as a source of N than autumn (mean 24%) or winter applications (mean 32%). These differences were smaller than reported in a number of other studies, probably as a result of relatively low excess winter rainfall, resulting in less nitrate leaching during the period of the investigation. Rapid incorporation into the topsoil of slurry applied in autumn, increased (28 kgN/ha) the SMN of samples taken early in the winter. However this increase did not lead to a consistent improvement in crop N uptake. Slurry dressings, whenever applied, can be expected to make a significant contribution to the N requirement of the succeeding crop and need to be taken into account when calculating the appropriate spring fertilizer application.

Notes: Abstract. Nitrate leaching after one year of a cut grass/clover ley was measured in two succeeding years to investigate how the postponing of ploughing leys from early to late autumn or spring, in combination with spring or winter cereals affected leaching of nitrate. The experiment was conducted as three field trials, two on a coarse sandy soil and one on a sandy loam soil. For calculation of nitrate leaching, soil water samples were taken using ceramic suction cups. The experiments started in spring in a first year ley and ended in spring three years later. Total nitrate leaching for the three year periods for each trial ranged between 160–254 and 189–254 kg N/ha on the coarse sand and 129–233 kg N/ha on the sandy loam. The results showed that winter wheat (Triticum aestivum L.) did not have the potential for taking up the mineralized N in autumn after early autumn ploughing of grass/clover leys, and that the least leaching was generally found when ploughing was postponed until spring, and when winter rye (Secale cereale L.) was grown as the second crop rather than spring barley (Hordeum vulgare L.). Nevertheless, leaching was generally high in the winter period even when winter rye was grown. On these soil types ploughing out should be postponed, whenever possible, to spring. Crop systems that maximize the utilization of mineralized N and thereby minimize nitrate leaching need to be further developed. Based on N balances, the data were further used to estimate the biological N fixation by the clover.

Notes: Abstract. Ceramic suction cups were used to obtain samples of soil solution from permanently grazed swards receiving 200 kg N/ha/y. The suction cups were installed in 1 ha plots at 10, 30 and 60 an depth in a poorly drained, heavy clay soil in S. W. England. The plots were hydrologically isolated from each other by perimeter drains which channelled surface runoff water into v-notch weirs. In one treatment, artificial drainage by a system of field and mole drains also converged to outfalls through v-notch weirs, which enabled samples to be taken. Nitrate and a range of other ionic constituents were examined over a 12 month period in soil solutions taken from the suction cups and compared with leachate obtained from the field drains and surface channels. Field drain samples frequently exceeded the EC limit of 11.3 mg nitrate-N/1, but concentrations in suction cups obtained during the same period did not, and were up to ten-fold less. Although correlations for ions were found between different sampling depths and drainage samples, no clear patterns emerged. It was concluded that suction cups were inappropriate for the determination of the overall leaching losses in this soil type, but provided useful data on changes in ionic concentrations which occurred in different soil horizons through to drainage outfalls.

Notes: A standardized dataset of derived soil properties for the 106 soil units considered on FAO-UNESCO's 1:5 million scale Soil Map of the World is presented. It was derived from a statistical analysis of the 4353 soil profiles held in the WISE (World Inventory of Soil Emission) database, which was developed at the International Soil Reference and Information Centre (ISRIC) for the geographic quantification of soil factors that control processes of global change. Median values are presented by soil unit for selected soil properties including: pH(H2O); organic carbon content; cation exchange capacity; sum of exchangeable Ca2+, Mg2+ and K+; exchangeable sodium percentage; bulk density; total porosity; available water capacity; soil drainage class; and gravel content class. Medians for these variables are presented both for the topsoil (0–30 cm) and subsoil (30–100 cm), where applicable. The data set can help to refine ratings for soil quality in global environmental models pending the availability of comprehensive georeferenced databases on soil and terrain resources such as SOTER, the World Soil and Terrain Database. In a Geographical Information System (GIS) it can be linked to the units shown on the digital Soil Map of the World through the legend code.

Notes: Abstract. The effect of grazing pressure on infiltration, runoff, and soil loss was studied on a natural pasture during the rainy season of 1995 in the Ethiopian highlands. The study was conducted at two sites with 0–4% and 4–8% slopes at the International Livestock Research Institute (ILRI) Debre Zeit research station, 50 km south of Addis Ababa. The grazing regimes were: light grazing stocked at 0.6 animal-unit-months (AUM)/ha; moderate grazing stocked at 1.8 AUM/ha; heavy grazing stocked at 3.0 AUM/ha; very heavy grazing stocked at 4.2 AUM/ha; very heavy grazing on ploughed soil stocked at 4.2 AUM/ha; and a control with no grazing. Heavy to very heavy grazing pressure significantly reduced biomass amounts, ground vegetative cover, increased surface runoff and soil loss, and reduced infiltrability of the soil. Reduction in infiltration rates was greater on soils which had been ploughed and exposed to very heavy trampling. It was observed that, for the same % vegetative cover, more soil loss occurred from plots on steep than gentle slopes, and that gentle slopes could withstand more grazing pressure without seriously affecting the ground biomass regeneration compared to steeper slopes. Thus, there is a need for developing ‘slope-specific’ grazing management schedules particularly in the highland ecozones rather than making blanket recommendations for all slopes. More research is needed to quantify annual biophysical changes in order to assess cumulative long-term effects of grazing and trampling on vegetation, soil, and hydrology of grazing lands. Modelling such effects is essential for land use planning in this fragile highland environment.

Notes: Abstract. Use of either three or six occasions to spread similar total amounts of slurry was investigated over the late winter/early spring period in two years, on plots with underdrainage. Slurry was spread on four 7 m by 25 m plots which were instrumented to allow collection of drainflow and runoff. The ‘mobile water’ pore space allowed transport of a small proportion of applied slurry through the 0.75 m soil profile. Evidence of a polluted ‘mobile water’ pulse occurred after periods of up to 48 hours following spreading, suggesting subsurface rather than overland flow. Timing of the pulse depended on whether subsequent rainfall accelerated the flow The contaminated flow persisted for 6–12 hours. The worst contamination of 39 mg/l NH4+ -N occurred under ‘bypass flow’ conditions, when 52 mm of rain fell during the 48 hours after a 5.2 mm application. Two contributory factors appeared important. The first was the long duration of the high intensity storm and the second was an extended period of severe frost believed to have created fissures associated with frost heave. Making several applications of slurry in amounts less than 35 m3/ha is preferable to fewer larger applications during spring, for cereals on medium to heavy soils. This recognises the likelihood of there being underdrainage on arable land and the optimal use of well-drained, partially frozen ground to avoid compaction by slurry tankers.

Notes: Abstract. The large boreal peatland ecosystems sequester carbon and nitrogen from the atmosphere due to a low oxygen pressure in waterlogged peat. Consequently they are sinks for CO2 and strong emitters of CH4. Drainage and cultivation of peatlands allows oxygen to enter the soil, which initiates decomposition of the stored organic material, and in turn CO2 and N2O emissions increase while CH4 emissions decrease. Compared to undrained peat, draining of organic soils for agricultural purposes increases the emissions of greenhouse gases (CO2, CH4, and N2O) by roughly 1t CO2 equivalents/ha per year. Although farmed organic soils in most European countries represent a minor part of the total agricultural area, these soils contribute significantly to national greenhouse gas budgets. Consequently, farmed organic soils are potential targets for policy makers in search of socially acceptable and economically cost-efficient measures to mitigate climate gas emissions from agriculture. Despite a scarcity of knowledge about greenhouse gas emissions from these soils, this paper addresses the emissions and possible control of the three greenhouse gases by different managements of organic soils. More precise information is needed regarding the present trace gas fluxes from these soils, as well as predictions of future emissions under alternative management regimes, before any definite policies can be devised.

Notes: Abstract. The effects of tree crops on the soil physical properties of former agricultural land were compared with those of ley in a rotation with cereals on adjacent sites. Five sites in southern Sweden were investigated focussing on soil water retention characteristics, dry bulk density, macroporosity and saturated hydraulic conductivity. Three of the sites were on light textured soils and two on clay soils. The tree crops were 30 to 35-year-old hybrid aspen, Populus deltoides, and silver birch, Betula pendula, and the ley crops were one to five years old.The light-textured soils under tree crops showed bimodal pore size distributions in the macropore region, whereas under ley crops they showed unimodal distributions. Dry bulk densities were generally smaller and the macroporosities larger under tree crops compared with leyicereal crops. Saturated hydraulic conductivities tended to be larger under tree crops. Slopes of the linear regression lines between saturated hydraulic conductivity and each of the parameters dry bulk density, porosity and macroporosity were steeper in the soil under agricultural crops than under tree crops.Observed differences in physical properties were considered to be an effect of land use, which had brought about changes in aggregate stability, pore size distribution and pore continuity.

Notes: Abstract. The effects of straw disposal by burning and incorporation on soil and crop nitrogen (N) supply, were investigated on two light textured soils in central (ADAS Gleadthorpe) and eastern England (Morley Research Centre) over the period 1984 to 1995. Nitrogen balance calculations showed that after 11 years of contrasting straw incorporation versus burn treatments, the cumulative N returns in straw were c. 570kg/ha at Gleadthorpe and c. 330 kg/ha at Morley However, these N returns via straw incorporation were not reflected in increased total soil N levels in autumn 1994. There were no differences (P 〉 0.05) between straw disposal treatments in autumn soil mineral N supply, readily mineralizable N or organic carbon. Similarly, there were no consistent differences between the treatments in terms of crop yield, crop N uptake or optimum fertilizer N rates. Fertilizer N applications of 200 kg N/ha/y increased topsoil organic carbon from 1.18 to 1.28% and total N content from 0.091 to 0.102% on the loamy sand textured soil at ADAS Gleadthorpe, but not at Morley. Previous fertilizer N applications increased the quantity of nitrate-N leached in drainage water by c. 20 kg/ha at Gleadthorpe and c. 60 kg/ha at Morley overwinter 1994/95, and by 10–20 kg/ha at both sites overwinter 1995/96. There was some indication overwinter 1994/95 that straw incorporation reduced nitrate-N leaching by 10–25 kg/ha, but there were no differences between treatments overwinter 1995/96.

Notes: Abstract. Formulation of nitrogen balances on farms requires accurate information on all inputs of the nutrient. N2-fixation by legumes, particularly forage legumes, is an important input which is difficult to measure. Simple regression models have been established from the literature for predicting N2-fixation by grass–white clover (Trifolium repens) mixtures using dry matter yields.Linear relationships were obtained between the N2- fixation (Nfix) and the extra dry matter production of mixed swards (Md) compared with pure grass swards. Nitrogen fixation was given by Nfix= A + 0.067Md where A is the intercept having a value of 6.8 for cut swards and -168.1 for grazed swards. A common slope was adopted because the F statistics showed that slopes fitted separately were not significantly different. The value of the negative intercept represents the supply of N to the grazed sward from soil and excreta-derived N. The regression equation for the cut sward gave reasonable predictions (r2= 0.953) of values of N2-fixed for experimental data not used in establishing the relationship. For grazed grass, the approach over-estimated the N2- fixation by an average of 15%.

Notes: Abstract. Mubangwe Farm, northern Malawi, was brought into cultivation from savanna vegetation with Brachystegia between 1970 and 1983 to produce tobacco, maize and groundnuts. Because of poor yields even with inputs of lime, N, P and K the fields were soon abandoned. The soils were only moderately acidic with little likelihood of Al toxicity. They held only small amounts of exchangeable Ca2+ (down to 0.01 cmolc/kg) particularly at depth. Phosphorus availability was low particularly in the subsoil. A minus-one pot experiment showed that the growth of sorghum in topsoil samples was limited by lack of N, P, S and Ca. The lower availabilities of P and Ca in the subsoil are therefore likely to be major limitations to growth, allowing only limited root penetration. The loamy sand to sandy clay soils generally had small available water capacities (down to 0.07 cm3/cm3) which, with restricted root development, may have lead to drought in dry periods during the growing season. The findings emphasize the need to measure both subsoil and topsoil properties when new areas of land are being developed for crop production.

Notes: Abstract. Nitrogen (N) leaching losses from a shallow limestone soil growing a five course combinable croprotation (oilseed rape, wheat, peas, wheat, barley) were measured from 1990 until 1995 using porous ceramic cups, at 60 cm depth, and drainage estimates. The crops were grown with three husbandry systems and two levels of N fertilizer. The husbandry systems were designed to reflect local practice (Standard), the best possible techniques to reduce N loss (Protective) and an Intermediate system which was a compromise between the two. Nitrogen was applied at full and half recommended rates. Drainage started during September in four years and November in one year, with above average drainage in three years. Losses of N were largest after peas (58 kg/ha) and oilseed rape (42 kg/ha), and least (17 kg/ha) before peas sown in spring after a cover crop. Over five years, the Protective management system, which used early sowing and shallow cultivation wherever possible, lost least N (31 kg/ha/y) and the Standard system, with conventional drilling dates and ploughing as the primary cultivation, lost most (49 kg/ha/y). Halving the N fertilizer decreased N loss by 11 kg/ha/y, averaged over the rotation. None of the treatments gave mean drainage water nitrate concentrations of less than 50 mg/l, averaged over the five years. Changes to arable cropping alone will not eliminate the need for other measures to control nitrate concen-trations in public drinking water supplies.

Notes: Abstract. Soil salinity and alkalinity reduce plant production and alter species composition of meadow grasslands in western Jilin Province, China. This study was designed to compare the survival and growth of three grass species (Aneumlepidium chinense, Puccinellia tenuijlora and Hordeum brevisubulatum) transplanted into saline-alkali soils in the field, and to evaluate the effects of gypsum amendments on soil properties and growth of these species. Gypsum treatments decreased soil pH, electrical conductivity, and chloride and sodium levels; water infiltration and calcium levels were increased. Survival of grass transplants was increased by gypsum treatments. Tiller number and height, and grass yields were all increased by the application of gypsum. Improvements in plant growth and survival with gypsum treatment appeared to be due to reduced chloride levels and increased Ca availability in the soil, and to changes in soil structure leading to improved infiltration rates. Revegetation of salinelalkaline soils in this region would be improved by application of gypsum in the range of 14–19 t/ha.

Notes: Abstract. As part of a study of recession farming on the ‘fadama’ lands on a segment of the Komadugu-Yobe floodplain, a survey was carried out to investigate the local farmers’ perception of soil types and management practices. The farmers are clearly aware of the differences in soil type on the fadama and they possess unique skills in managing their farm lands. The farmers classify fadama soils for recession farming by assessing soil texture and soil drainage conditions by feel and observation. Integrating such local knowledge into soil surveys will lead to better practical definition of mapping units and give soil names that have more meaning for the farmers.

Notes: Abstract. Crops grown on virgin upland Vertisols of Zambia, are reported to perform rather poorly. However, subsoiling followed by repeated cultivation over two years apparently improves crop growth. Highest yields were recorded under long-term cultivation (12 years). To evaluate the reasons for these differences in crop response to Vertisol management, physical and hydrodynamic characteristics of soil profiles were studied in three soil management systems. The management systems were: uncultivated or virgin land; land cultivated for two years; and land cultivated for 12 years. The mean soil aggregate size decreased with increased time of cultivation, mostly due to the decrease of the largest sized aggregates. The surface horizon dried more slowly on the long-term cultivation plot. A comparison of the hydraulic conductivities indicated that water intake in the deeper layers improved with increased period in cultivation. Oxygen diffusion measurements showed good aeration at field capacity, to a depth of 0.32m on the long-term cultivation plots, but only to 0.17 m and 0.25 m for 2 years cultivation and virgin plots respectively. Repeated cultivation was beneficial in improving surface soil tilth and in improving subsurface drainage, thus removing the problem of a perched water table which occurred close to the soil surface under natural conditions.

Notes: Abstract. The chemical extractability of heavy metals introduced into the soil during 7 years application of sewage sludge, composted municipal solid waste and sheep manure, and their availability to citrus plants were studied. The total content of metals in the soil (0-20 cm)was increased by the use of sludges and compost, but only the Ni content in the saturation extracts of soil was significantly increased. Total Cd, Cr, Cu, Ni, Pb, and Zn were sequentially fractionated into water-soluble plus exchangeable, organically bound, carbonate-associated, and residual fractions. Most of the heavy metals were present in carbonate and residual fractions, although substantial amounts of water-soluble plus exchangeable Cd, and organically bound Cu and Ni were found. No significant increases in the metal contents in leaves and orange fruits were observed, with the exception of Pb in leaves. Several statistically significant correlations between metal content in plants, metal content in soil fractions, and chemical characteristics of soil were also found.

Notes: Book reviewed in this article: Human impact on Erosion and Sedimentation By D. E. Walling & J.-L. Probst (editors).

Notes: Book reviewed in this article: Soil erosion by water in Africa: Principles, Prediction and Protection By D. Nill, U. Schwertmann, U. Sabel-Koscella, M. Bernhard & J. Breuer.

Notes: Abstract. The projected increase in sewage sludge used on land within many countries in the European Community will provide a major source of entry for several heavy metals into the soil. Although the application rate of sewage sludge to agricultural land is constrained by maximum annual additions of heavy metals, there is a need to know the sensitivity of those soils to heavy metal inputs which are physically suited for application. A rulebased classification using weighted parameters designed to assess the metal binding capacity of soil and the risk of groundwater pollution has been applied to soils data held within the Macaulay Land Use Research Institute's National Soils Inventory The classification uses soil pH, organic matter content, texture and soil colour as a surrogate for iron oxide concentration. The results indicate that some metals, for example cadmium and zinc are potentially more mobile in soils than others such as lead, but that the majority of soils display a strong or very strong binding capacity for all the metals. However this pattern can only be sustained if the soil pH values are maintained at their present values; a fall of one pH unit marks a dramatic shift towards the weak and moderate binding classes. The approach is largely unvalidated but does provide a useful framework for incorporating our mechanistic understanding of processes into wide area soil quality assessments and in identifying future research opportunities.

Notes: Abstract. Kriging is used to provide detailed quantitative information for a range of soil characteristics across the floodplain of the River Gambia. Application of spatial statistics to a large area with a coarse grid of data points produces spurious patterns unless the area is first partitioned into soil-geomorphic mapping units, each of which has a unique pattern of spatial variation. Even combining classical soil survey method with spatial statistics, the large short-range variability of acid sulphate soils means that single factor maps conceal a large element of uncertainty. A more robust procedure is to map the probability of occurrence of critical values of key characteristics.

Notes: Abstract. Ten chalk topsoils (0-25 cm) were repacked into columns in the laboratory. After leaching similar to one year's throughflow in the field, loss of K was equivalent to between 9 and 74kg K/ha. This represented between 3 and 30% of the initial exchangeable K with which loss was poorly correlated. Loss was dependant on the soil solution concentration and was inversely proportional to potassium buffer power.The loss of magnesium in the same columns was between 10 and 22 kg Mg/ha (6-21% of the initial exchangeable Mg). Magnesium loss was poorly correlated with exchangeable Mg.When KCl fertilizer was incorporated into the soils, the increase in leaching of potassium was 1–35% of the K addition. Application to the top of the column resulted in less leaching than when the K was incorporated. Leaching of magnesium was increased by up to 5 kg Mg/ha.Potassium leaching may be delayed by the underlying A/C horizon but pure chalk, with an extremely low buffer power for K, has little ability to retain K. Extremely calcareous topsoils were the most leaky although in practice it is the organic chalk soils on which it is most difficult to attain adequate K levels. On all chalk soils, maintenance of a high K level with K fertilizer is likely to cause unnecessary long-term leaching losses. Annual, rather than biennial, fertilizer applications are to be preferred.

Notes: Abstract. Soils in areas with high livestock density contribute to the eutrophication of aquatic ecosystems through loss of nutrients, especially phosphorus (P). In order to identify the potential for P loss from such soils we determined phosphorus extracted by water (H2O-P), by double lactate (DL-P), and P sorption capacity (PSC) and degree of P saturation (DPS) in soil samples from two counties, one with low (Harle-catchment) and the other with very high livestock density (Vechta). Both catchments are hydrologically connected with the tidal areas of the North Sea.The mean concentrations of H2O-P (0.4mmol/kg) and DL-P (3.9 mmol/kg) were lower in the Harle-catchment than in the Vechta area (1.2 mmol/kg, 6.8mmol/kg). Although oxalate-extractable Al (Alox) and Fe (Feox) and the derived PSCs varied according to soil type and to land use, the livestock density and the resulting high concentrations of oxalate-extractable P (Pox) were shown to be the main reason for the very high DPS of up to 179% in the county of Vechta. These values exceeded DPS reported from other intensive pig feeding areas in western Europe and indicate the potential for significant P loss. Less than 40% of the variation in Pox could be explained by the routinely determined H2O-Por DL-P. Geostatistical analyses indicated that the spatial variability of Pox depended on manurial history of fields and Alox, showed still smaller-scale variability. These were the major constraints for regional assessments of P losses and eutrophication risk from agricultural soils using available soil P-test values, digital maps and geostatistical methods.

Notes: Abstract. Although gypsiferous soils cover approximately 100 million ha in the world, it is only in the past two decades that their pedogenic and agronomic properties have been better understood and their classification improved. There is still no method to assess adequately their production potential.This paper focuses on gypsum accumulation forms as diagnostic criteria for a rapid soil suitability appraisal in the field. Pseudomycelia, gypsum spots, powdery coatings and other localized in situ precipitations usually indicate soils with less than 15% gypsum. Depending on their intensity and depth of occurrence in the root zone, they define a soil environment which is suitable for semi-sensitive and semi-tolerant crops. Continuous gypsum accumulations characterize soils or horizons with high (e.g. more than 25%) gypsum contents, and these can be used only for tolerant crops.The land use potential of gypsiferous soils is primarily determined by: (a) the depth of the impermeable layer, (b)the gypsum content within the root zone, and (c) the crop tolerance level. A method is proposed to assess the land suitability of gypsiferous soils on the basis of these criteria.

Notes: Abstract. The impact of soil erosion on soil productivity was estimated for a Rhodic Ferralsol and a Eutric Cambisol in Santa Catarina, southern Brazil. Over equivalent periods, total soil losses were an order of magnitude different (868 and 68 t/ha respectively on the bare soil control), yet the impact on maize yield per tonne of soil lost was far greater at the Cambisol site with less erosion. Similar interesting contrasts between sites were found for the other measures of impact with decline in pH and phosphorus and increase in free aluminium being the most obvious induced soil differences. The results demonstrate the variable nature of erosion impact according to soil type and they highlight the importance of examining a number of measures of impact before pronouncing on the sustainability of any particular agricultural practice.

Notes: Book reviewed in this article: Agricultural Recycling of Sewage Sludge and the Environment By S. R. Smith.

Notes: Book reviewed in this article: No-tillage seeding: science and practice By C. J. Baker, K. E. Saxton & W. R. Ritchie.

Notes: Abstract. The rates of CO2 production and decomposition of 13C-enriched Lolium perenne leaves and roots in soil from the surface five cm of two upland stagnohumic gley soils were measured in laboratory experiments. One of the soils had been limed (pH 6.8) 13 years earlier. The other was unlimed (pH 3.7). Liming increased the rate of CO2 release from soil to which no L. perenne had been added. About 30% of the 13C in L. perenne leaves remained in both limed and unlimed soil after 224 days. By contrast, less 13C-remained in the limed soil amended with L. perenne roots (44%) than in the limed soils (55%). Although the daily rate of CO2 from the plant material-amended soils was initially greater in the improved than in the unimproved soil, it subsequently declined more rapidly.

Notes: Abstract. The characteristics and variability of soils within a 30 ha experimental site in N. E. Nigeria are analysed in relation to tree establishment. Profile description and analyses for some 480 surface samples of the sandy to clayey surface soils from Lake Chad lacustrine sediments provide baseline properties against which any subsequent modifications resulting from agroforestry practices can be assessed and to which initial tree performance can be related. This has been undertaken using principal component and spatial analyses. Inherited soil properties show spatial variations across the site which can be related to the soil textural parameters. The initial survival of trees planted for agroforestry experimentation shows strong correlations with the inherited characteristics of the soil rather than with acquired soil properties.

Notes: Abstract. Field measurements of cumulative infiltration and of the matric potential prior to infiltration were made with double-ring infiltrometers and tensiometers, respectively, on two sandy loams in north-east Scotland. The time to ponding for constant-rate infiltration was also measured in the same infiltrometers by applying water at a constant rate until ponding commenced. Under the range of initial potentials studied (-2 to - 17 kPa), an exponential relation was adequate to describe the relation between sorptivity and initial matric potential. The time to ponding was also strongly dependent on initial matric potential and increased dramatically as the soil became drier. Measurements of time to ponding were in good agreement with values predicted from the theory of Clothier et al. (1981) using values for sorptivity and the A parameter obtained from the cumulative infiltration experiments. Measurements and predictions clearly showed the importance of the sorptivity versus initial matric potential relation in controlling the time to ponding of such sandy soils. These results have implications for determining the generation of runoff and the establishment of stream flows, as well as determining optimum rates and design of irrigation.

Notes: Abstract. When Albania emerged from its seclusion in 1991, the scientific community had its first opportunity to interact with its international counterparts. Soil resource assessment was made with systems developed in the early 1950s, laboratory facilities to provide supporting data were poor, and it was recognized that a new assessment was urgently needed.The country faces a major challenge in reforestation and soil conservation against a background of overgrazing by sheep and goats and clearing of trees and scrubs for fuelwood. Even orchard and olive trees were used as fuelwood during the winters of 1990 and 1991. Since then, gully and rill erosion has accelerated on many of the sloping lands. In addition to reforestation and conservation measures to reduce the pressures on the sloping land, it is necessary to enhance productivity on the fertile valley bottom soils where most of the agriculture is confined. In the recent past, grain yields have declined due to reduced fertilizer use (low purchasing capacity), and poor management practices. More recently productivity has slowly improved, but land degradation, particularly erosion, has visibly increased.USDA Natural Resources Conservation Service in collaboration with the Land Resources Institute of Albania, initiated work on a new national soil map through collation of existing information and field studies. The land unit for land use planning, evaluation, and general management decisions, is the Major Land Resource Area (MLRA). Each MLRA encompasses geographically associated soils, the majority of which have broadly similar patterns ofclimate, water resources, and land uses. The MLRAs presented here are based on the soil map of Albania at 1 : 200 000 scale. The MLRA information provides an overview of the landscape and natural resources. It can be used to assess land suitability for various crops, opportunities to achieve self sufficiency in food production, selection of areas for both field crops and highvalue crops for export, and identification of appropriate farming system technologies. Each MLRA will have a set of degradation processes which can be flagged, therefore each of them becomes a unit for decision making with respect to investments in research and mitigating technologies. The task is far from complete. Appropriate databases are needed to support the decisions that are being made at national level. To complement the MLRA and related database, decision support systems are needed for the important task of developing policy options.

Notes: Many ductile shear zones are interpreted to operate by simple shear flow but some form under other flow regimes. Lineations and foliations in such shear zones can lie obliquely to those in simple shear zones, which can lead to erroneous tectonic interpretations on the assumption of simple shear flow. This paper describes a gently dipping shear zone system from the N-central segment of the Palaeoproterozoic Nagssugtoqidian orogen of W. Greenland, which operated with a lateral constriction component. This resulted in the development of upright folds with axes parallel to the transport direction where the constriction component is weak. Where it is strong, a linear fabric and even a subvertical foliation normal to the rotation axis of bulk flow developed. This steep foliation is interpreted as the origin of the Nordre Strømfjord steep belt, previously interpreted as a crustal-scale sinistral transcurrent shear zone. Shear zones of this type may occur elsewhere and shear zone fabrics should therefore be carefully analysed before the direction of tectonic transpost can be determined

Notes: In a series of papers, Lohmann and Lohmann (1991, 1994a, 1994b, 1996) provide evidence for remarkable sensitivity of sea-turtles to the earth's magnetic field and suggest that it is used by these animals to determine global position and to navigate. In this paper, we emphasize that a consequence of these observations taken together is that sea-turtles should be able to accurately detect the full (vector) magnetic-field, and perhaps spatial gradients. In order to interpret these observations, we propose a simple model in which the turtle is considered as a small permanent magnet, on which the geomagnetic field exerts a torque. This torque varies as a function of turtle azimuth and field parameters which depend mainly on latitude. Although this simple model accounts for some of the observational evidence, discrepancies might be due to a number of other factors, such as speed of magnetic field changes during experiments or lack of field homogeneity. Also, the earth's field has varied significantly over the last few centuries and some of the magnetic features observed today and suggested by the Lohmanns for use in sea-turtle navigation were very different or even not present two or three centuries ago. This would place constraints on the rate at which genetically inherited magnetic behavioural preferences can change with time. Alternately, it may imply that the experimental results need to be re-evaluated and complemented.

Notes: The late Neoproterozoic (750–545 Ma) was a time of revolutionary environmental change, recurrent glaciation and tectonic upheaval, which culminated in the evolution of metazoans and animal biomineralization. Geochemical data are presented for a post glacial (∼ 700 Ma) limestone succession from W. Mongolia. 87Sr/86Sr is used to constrain the timing of early diagenetic exchange. Stratigraphic trends to high δ13C(carb)) and δ13C(org) mirror sea-level fluctuations, which, we argue, is consistent with the hypothesis that late Precambrian ocean chemistry, was controlled by vertical stratification. Repeated establishment of stratification 700–545 Ma would have led to greater oxygen availability in the surface environment. A causal link between this oxygenation and the further evolution of animals is proposed.

Notes: Unroofing of the western Tauern window involved both low-angle detachment faulting (Brenner Fault) and enhanced footwall erosion, contemporaneous with upright antiformal folding. This combination reflects orogen-parallel (˜E–W) extension during continued ˜N–S Alpine convergence. New fission-track ages establish the relative chronology of folding and faulting and demonstrate that displacement was not always accommodated on the same surface. During exhumation, some units migrated from the footwall to the hanging wall of the main detachment fault, due to the interplay between folding and faulting. The region can effectively be divided into 3 distinct domains. (1) The Penninic units of the western Tauern Window were always in the footwall to the fault, with maximum exhumation in the core of the dome, due to folding and erosion. (2) The Lower Austroalpine unit north of the Tauern Window was first part of the hanging wall to the Brenner Fault. At a later stage this unit was exhumed by a further 4–5 km as part of the footwall to a more discrete, through-going fault (the Silltal Fault). (3) The Middle and Upper Austroalpine units west of the Tauern Window were always within the hanging wall.Exhumation of the footwall from an initial depth of ∼ 25 km led to a transition in mechanical behaviour. The curviplanar (folded) ductile shear zone marking the boundary to the Tauern window was eventually transected by a more planar discrete brittle fault (Silltal Fault, with unit 2 now in the footwall), along which the pre-existing mylonites were passively exhumed to the surface.

Notes: The Sierra Nevada core, located in the Betic hinterland, features a N-S large-scale open antiform with a central relatively uplifted highly extended domain placed between two less extended domains (in the east and in the west) dipping eastwards and westwards, respectively. The core-bounding detachment system formed during the Serravallian (15–11 Ma) in an episode of ENE-WSW extension. The ESCI-Beticas 2 deep seismic reflection profile, a transect through the core, shows a highly reflective deep crust overlying a subhorizontal Moho, and a fairly transparent upper crust and upper mantle. The lack of Moho relief beneath this area, with differential values for supra-crustal thinning, suggests a mechanism of intracrustal isostatic compensation. Surface geology data together with seismic imaging indicate intracrustal flow and upward doming as a response to footwall unloading accompanying the middle Miocene supracrustal extension. A prominent mid-crustal reflector (MCR) is deemed to represent a decoupling zone between the upper and the deep crust. Subsequent N-S shortening and associated folding occurred in the late Miocene. The interference pattern of this folding over the middle Miocene core produced the current E–W dome-shaped tectonic windows where the deepest complex of the Betic hinterland crops out.

Notes: Sedimentological evidence indicates metre-scale, cyclic changes in global sea-level during Mesozoic greenhouse climates; the cyclicity is thought to be due to Milankovitch forcing. The absence of continental ice-caps requires other mechanisms than glacier build-up to explain these variations. We propose that thermal expansion of the entire oceanic water column may partly explain the observed sea-level variations on Milankovitch timescales. Using existing climate model results, we show that an increase in deep water temperature of ∼ 2°C and a corresponding sea-level rise of 1.7 m by thermal expansion can be induced by Milankovitch forcing via increased formation of warm deep waters in low latitudes.

Notes: Pervasive L and L ≪ S tectonites of the Mariánské Lázně eclogites include pencil fabrics, constrictional folds and mullions, that result from the first deformation increment observed. Petrological and microstructural data suggest that these structures formed by constrictional flow at deep subduction levels after, or even during, the eclogite facies stage and before the subsequent high-pressure granulite facies overprint. Constriction at mantle depths is explained by taking into account the geometry and seismic properties of recent subduction zones. Here, constrictional strain and associated L ≫ S tectonites should be expected below the rheologycontrolled slab bend (at about 40 km depth), where dip-parallel extension and a reduced viscosity of the downgoing slab are compatible with a coaxial flow regime.

Notes: The origins and volumes of waters which mass-transport silica in sedimentary basins remain obscure. Many previous analytical studies have illustrated cases where quartz cements in sandstones originate from complex and variable fluids. By contrast we show, by using a combination of separation and analytical techniques, that in Lower Permian sandstones of the southern North Sea the cementing fluid was isotopically uniform during growth of quartz cement with a δ1BO of 19.6 + 1.0%‰ V-SMOW. In this relatively uniform fluid quartz cements grew and developed complex cathodoluminescence (CL) zonations. Petrographic data show that 8–10% quartz cement (locally 30%) was imported into this 380 km2× 180 m thick aeolian sandstone, and cement distribution controlled by depositional permeabilities. We infer a large-scale, high volume, flux of evolved meteoric fluid during 2 km deep burial, and show that complex CL zonation may arise from relatively subtle changes in water composition.

Notes: Magmatism in the central part of the Variscan orogenic belt in Europe has occurred in several distinct episodes. Each episode spanned a few million years and was characterized by a distinct geochemical signature and geodynamic setting: (i) between 340 and 330 Ma (Visean), high-K diorites and granitoids within a zone extending parallel the orogen axis, possibly tracing a palaeosuture; (ii) at 310–307 Ma (Westphalian), calc-alkaline granitoids in the Intra-Alpine domain; (iii) at 304–295 Ma (Stephanian), subalkaline granitoids in Intra-Alpine and Pennine domains; and finally (iv) at 280–270 Ma (Permian) granitoids in Pennine, Austroalpine and South-Alpine domains. The generation and emplacement of granitoid melts in the Variscan crust are suggested to be short-term pulses that are controlled by extensional processes in the lithosphere such as thermal erosion and relaxation of the lithospheric mantle, and decompressional melting.

Notes: Ion-microprobe U-Pb zircon ages of detrital zircons from a metasediment of the Loch Maree Group, Lewisian Complex, NW Scotland show striking similarities to those in coeval Palaeoproterozoic belts of Laurentia and Fennoscandia, and confirm previous suggestions of a connection between them. Late-Archaean zircons (3.06–2.48 Gyr old) represent derivation from Lewisian quartzofeldspathic gneisses, andlor a contemporaneous terrane. Palaeoproterozoic zircons (2.2–2.0 Gyrold) place a maximum age constraint upon deposition. An appropriate quartzofeldspathic source for these latter zircons is not presently known, either in the Lewisian or the wider Laurentia-Fennoscandia region, although its requirement would be consistent with a development of the Loch Maree Group, together with juvenile magmatic arc rocks, at an active margin which was probably removed by lateral tectonics. Comparisons are made with contemporaneous supracrustal sequences throughout the Laurentia–Fennoscandia region, which exhibit marked similarities in source region age characteristics, lithologies, and inferred depositional environment.

Notes: Until recently the Younger Dryas cooling event was thought to be restricted to the North Atlantic region. However, preliminary evidence based on magnetic susceptibility and stable isotope data from Lake Hetongchahannor, a hypersaline alkaline lake in Inner Mongolia indicates that this event is observed in NE Asia. In addition we find indications of wetter climatic conditions between 9000 and 6000 yr BP, possibly due to increased monsoon activity, followed by a progressive aridification towards the present time.

Notes: The Early Cretaceous carbonate carbon isotope stratigraphy established in pelagic limestones is marked by several pronounced excursions towards positive δ13C values. We investigated a biostratigraphically and palaeomagnetically calibrated Aptian section to see whether C isotope stratigraphy could be recognized in shallow-water carbonates. The chosen carbonate platform sections are located in southern Italy and have been dated by biostratigraphy. Bulk samples, chosen from the Barremian-Albian part of the sequence, were analysed for their O and C isotope compositions. The C isotope curve established shows two major positive excursions which can be correlated with the synchronous and globally recognized Aptian C isotope events. The data provide evidence that C isotope stratigraphy can be used as a powerful correlation tool between pelagic and shallow-water limestone sequences.

Notes: The frequently observed parallelism between rifts and the preexisting orogenic fabric of continents suggests that the inherited tectonic fabric of the lithosphere influences the rupture of continents. We propose that the existence of a pervasive fabric in the lithospheric mantle induces an anisotropic strength in the lithosphere, that guides the propagation of continental rifts. Subcrustal mantle mechanical anisotropy is supported by (i) the anisotropic strength of olivine, (ii) an ubiquitous tectonic fabric in exposed mantle rocks, and (iii) measurements of seismic and electrical anisotropy. During major episodes of continent assembly, a pervasive deformation of the lithosphere induces a lattice-preferred orientation of olivine in mantle rocks. Later on, this crystallographic fabric is ‘frozen-in’ and represents the main source of shear wave splitting. This olivine fabric may entail a mechanical anisotropy in the lithospheric mantle. During subsequent tectonic events, especially during rifting, mechanical anisotropy may control the tectonic behaviour of the lithosphere

Notes: Modern terrestrial speleothem-like calcareous deposits in streams draining a disused lime quarry on Black Mountain, South Wales have anomalously negative δ18O and δ13C compositions compared with other similar European deposits. Black Mountain water chemistry is unusual only in its locally very high pH (〉 11.5) and carbonate ion concentrations. The high pH is caused by dissolution of lime spoil, resulting in high OH– concentrations. This high alkalinity causes uptake of atmospheric CO2 and strong fractionation of both carbon and oxygen stable isotopes, resulting in calcite precipitates with unusually negative isotopic compositions. Since shifts in δ18O of 〈 1° are highly significant for Holocene palaeoclimate reconstructions, depletions caused by hyperalkaline waters must be avoided. While extreme lime spoil contamination should be obvious, less heavily affected sites will record smaller fractionation effects and might escape detection. Even small depletions from low-level contamination will have large effects on palaeotemperatures based on carbonate crust δ18O values.

Notes: General Circulation Models (GCMs) are currently used to predict future global change. However, the robustness of GCMs can, and should, be evaluated by their ability to simulate past climate regimes. Their success in ‘retrodiction’ can then be assessed by reference to the testimony of the geological record. Geological evidence provides a database which can be used in the estimation of sea surface temperatures and other proxy data useful in palaeoclimatic studies. These data can then be used to refine the prescribed boundary conditions for running GCMs themselves. Results of modelling experiments confirm a generally warmer Mesozoic earth with arid tropics and convective rainfall higher over the oceans than at present. Circum-polar wetlands are also indicated. Modelled cloudiness is also higher in the Mesozoic, contributing to greenhouse conditions and possibly influencing terrestrial biomes and marine ecosystems.

Notes: The sealing efficiency of shale layers is studied through the hydraulic parameters which are required for sustaining overpressure during geologically significant periods. Assuming a 1D sedimentary complex composed of a sealing layer overlying a permeable one, we give approximate solutions for the dissipation of a given initial overpressure. The time constant for relaxation involves the thickness, hydraulic conductivity and specific storage of the seal and also those of the permeable layer. The values of the various hydraulic parameters are discussed. It is argued first that the specific storage corresponding to plastic deformation during burial compaction is larger than the one which would correspond to elastic deformation. When taking into account (i) plausible values for specific storage of the upper shale layer and (ii) the storage effect of the lower permeable layer, it is found that a shale layer of several tens of m with an hydraulic conductivity of the order of 10-15 ms-1 maintains overpressure for 1 Myr. For such hydraulic parameter values, in the absence of on-going pressuring forces, initial overpressures would decay with a time constant (corresponding to a decrease by a factor e ∼, 2.7) of 1 Myr. This is interpreted as supporting a dynamic origin for observed abnormal pressures.

Notes: Structural mapping in the Southern half of the Oman ophiolite has revealed a palaeoridge organization with similarities to an EPR microplate, forming in superfast spreading conditions. A NW-trending propagator was rapidly opening in a lithosphere no more than 1 Myr older and itself created in a NE-SW ridge system. The NW-trending propagator, underlined by small mantle diapirs, was active or dying when detached as part of a future ophiolite. Local thrusting of the future ophiolite was also initiated very early, between 1 and 5 Myr after ridge accretion; it was accompanied by a 40° rotation within this time lapse. Such an activity supports the comparison of the Oman palaeoridge system with an oceanic microplate, and provides evidence to suggest the existence of thrusts at active microplates.

Notes: Large variations in clinopyroxene-garnet (cpx-grt) temperatures are recorded in thin peraluminous eclogite layers from Beni Bousera ultramafic massif (Morocco): cpx-grt temperatures in the core of layers 〈 20 cm thick are higher by up to 300°C than in the margins. The cpx-grt temperatures are correlated to both Al-concentration in cpx and Ca-concentration in grt, the two latter parameters being themselves closely intercorrelated. It is demonstrated that the regular interaction parameter ΔwgrtCa calculated from the Beni Bousera natural data is very close to ΔwgrtCa calculated from experimental data analysis for Ca-rich garnet. It is concluded that: (i) Al-concentration in cpx has no significant effect on the distribution of Fe and Mg between cpx and grt; and (ii) cpx-grt temperature variations observed across Beni Bousera peraluminous eclogite layers do not correspond to real thermal gradients, but merely result from the inadequacy of the thermometric equations in Ca-rich systems (XgrtCa 〉 0.15).

Notes: The Kostomuksha greenstone belt consists of two lithotectonic terranes, one mafic igneous and the other sedimentary, separated by a major shear zone. The former contains submarine 2.8 Gyr old komatiite-basalt lavas and volcaniclastic lithologies with trace element and isotopic compositions resembling those of recent oceanic flood basalts [ɛNd(T) =+ 2,8, μ.1= 8.73 (Nb/Th)N= 1.5–2.1 (Nb/La)N= 1.0–1.5]. We suggest that the mafic terrane is a remnant of the upper crustal part of an Archaean oceanic plateau derived from partial melting of a mantle plume head. When the plateau reached the continental margin, it collided with the sedimentary terrane but was too buoyant to subduct. As a result, the volcanic section of the plateau was imbricated and obducted thus becoming a new piece of continental crust. The deeper zones were subducted and disappeared from the geological record.

Notes: An integrated interpretation of seismicity, fault plane solutions and deep seismic reflection data suggests that the NE–SW to NW–SE trending Rhone–Simplon fault zone and the gently S-dipping basal Penninic thrust separate fundamentally different stress regimes in the western Swiss Alps. North of the Rhone-Simplon fault zone, strike-slip earthquakes on steep-dipping faults within the Helvetic nappes are a consequence of regional NW–SE compression and NE–SW extension. To the south, vertical maximum stress and N–S extension are responsible for normal mechanism earthquakes that occur entirely within the Penninic nappes above the basal Penninic thrust. Such normal faulting likely results from extension associated with southward movements (collapse) of the Penninic nappes and/or continued uplift and relative northward displacements of the underlying Alpine massifs. Geological mapping and fission-track dating suggest that the two distinct stress regimes have controlled tectonism in the western Swiss Alps since at least the Neogene.

Notes: The distribution of barium and other elements related to biological productivity has been studied in two Palaeocene sections from the Middle East. In the bathyal Ben Gurion section, Israel, Ba* (= Ba/Al2O3× 15%) concentrations are low, in the range 0.04% to 0.3% in the lower Palaeocene, and very high, 1% to 2%, throughout most of the upper Palaeocene. In the neritic Gebel Aweina section in Egypt Ba* values are low, 〈 0.1%, throughout the entire Palaeocene. The Ba* enrichments at Ben Gurion and their correlations with increases in P2O5 and opaline silica, and local and global δ13C maxima, indicate that upwelling and high productivity were important in this region during the late Palaeocene. The absence of Ba* enrichments in the shallower Gebel Aweina section probably reflects the strong depth dependence of biobarium deposition.In the uppermost Palaeocene, at the level where the global benthic extinction event is registered, Ba* concentrations in the Ben Gurion section increase to anomalous 6%. which suggests that upwelling and possibly wind strengths intensified during this event. The results speak against deep-water formation in this region since downwelling and not upwelling is required.

Notes: Three-dimensional patterns of soft-sediment deformation, affecting middle Pleistocene fluvial deposits in the Lower Manzanares Valley (SW Madrid City), are reported. They promote a small-scale hummocky topography, defined by different-sized domes, mud volcanoes, wavy ridges and fissures on an ancient flood plain surface. Related channel fill deposits are pervasively dewatered, indicating liquefaction. The sedimentological context reveals that the deformation of both floodplain surface and channel-fill deposits, were contemporaneous (singular deformed level) and generated at, or near, the ground surface; this rules out the possibility of sediment-loading and indicates a possible earthquake-induced origin.

Notes: Cliff-front dunes are a common coastal feature, but this is the first time that the structures indicative of their formation are documented. A late Pleistocene cliff-front dune in southern Mallorca has been studied. Owing to early lithification of the calcarenite, its morphology is well preserved. The dune occurs in front of a curved, near-vertical coastal cliff, but the bedform cannot be classified as a fixed echo dune. The dune grew with time and its brinkline gradually moved closer to the cliff front. In the final stage of evolution the top of the dune reached a height of at least 23 m. The dune is composed of wind-ripple strata. These strata are arranged in critical to supercritical climbing-dune cross-stratification recording its growth stages. The angle of climb of the dune increases toward the cliff and reaches 50°. The morphological features of cliff-front dunes result from both cliff slope and whether the cliff front is curved or straight.

Notes: Compositions and distributions of mafic dykes in the Antarctic Peninsula continental arc show that tapping of several mantle sources was tectonically controlled. In the Cretaceous to Tertiary, between 135 Ma and 55 Ma, calc-alkaline dykes intruded the arc. In the late Cretaceous, however, between 95 Ma and 65 Ma, there was a pulse of compositionally diverse magmatism. This change resulted from collision of an ocean spreading centre with the trench. As a consequence, non-partitioned dextral transtensional shear in the overriding plate became partitioned into strike-slip and extensional domains. Calc-alkaline magmatism was, therefore, replaced by strike-slip-related shoshonitic magmatism towards the rear-arc and extensionrelated tholeiitic magmatism towards the fore-arc. OIB-like dykes were emplaced because of the break in otherwise continuous subduction. During the early Tertiary subduction continued but ceased after a late Tertiary ridge-trench collision.

Notes: Argand (1924) and later Holmes (1965) proposed that the Himalayan orogeny and Tibet uplift were the result of large underthrusting of the Indian continental crust beneath Tibet. Since then, plate motion studies have yielded new constraints on the relative displacements of India and Asia and a large number of geological and geophysical investigations have helped to determine the structure of the Himalayas and Tibet, the best natural laboratory for understanding mountain belts. The aim of this paper is to review briefly the various models of Himalayan mountain building in light of recent geological and geophysical data and to estimate the role of continental subductions.

Notes: Geological observation in the eastern end of the Himalaya shows that the Asia/India Suture is folded. Metamorphic rocks derived from India occur structurally below the suture, in the core of a regional antiform. Isotopic and fission track dating establish cooling-exhumation of rocks from c.30 km depth within the last 4 Myr. We argue that exhumation is caused by ∼ 10 mm yr-1 erosion coeval with crustal scale folding.

Notes: Two in situ permeable flow sensors, recently developed at Sandia National Laboratories, were field tested at the Brazos River Hydrologic Field Site near College Station, Texas. The flow sensors use a thermal perturbation technique to quantify the magnitude and direction of ground water flow in three dimensions. Two aquifer pumping tests lasting eight and 13 days were used to field test the flow sensors. Components of ground water flow as determined from piezometer gradient measurements were compared with ground water flow components derived from the 3-D flow sensors. The changes in velocity magnitude and direction of ground water flow induced by the pump were evaluated using flow sensor data and piezometric analyses. Flow sensor performance closely matched piezometric analysis results. Ground water flow direction (azimuth), as measured by the flow sensors and derived in the piezometric analysis, predicted the position of the pumping well accurately. Ground water flow velocities measured by the flow sensors compared well to velocities derived in the piezometric analysis. A significant delay in flow sensor response to relatively rapid changes in ground water flow was observed. Preliminary tests indicate that the in situ permeable flow sensor provides accurate and timely information on the velocity magnitude and direction of ground water flow.

Notes: Twenty polymeric tubings were filled with a test solution containing eight organic solutes. The test solutions were monitored for losses, indicating that sorption had occurred, and for signs that leaching of organic constituents had occurred. The tubings tested included seven flexible products and eight fluoropolymers. Among the rigid tubings tested, three fluoropolymers (fluorinated ethylene propylene [FEP], FEP-lined polyethylene, polyvinylidene fluoride) were the least sorptive tubings. However, even these tubings readily sorbed some of the analytes. Among the flexible tubings tested, a fluoroelastomer tubing and a tubing made of a copolymer of vinylidene fluoride and hexafluoropropylene were the least sorptive.Several of the tubings tested leached constituents into the test solution. The polyurethane, polyamide, flexible polyvinyl chloride (PVC), polyester-lined PVC, and silicone-modified thermoplastic elastomer tubings were found to leach the most constituents. We were unable to detect any constituents leaching from the polyethylene tubings, the rigid fluoropolymer tubings, and one of the plasticized polypropylene tubings.

Notes: Alight nonaqueous phase liquid (LNAPL) ground water contaminant plume has been discovered by purely geophysical means at the former Wurtsmith Air Force Base (AFB) near Oscoda, Michigan. It is located near another plume called FT-02, which is a well-studied area undergoing natural bioremediation. The plume was discovered by ground penetrating radar (GPR) profiling while extending a long line from FT-02 to establish background variability around that plume. The new plume was apparent because of a high-conductivity “shadow’ or GPR reflection attenuation observed below the conductive zone at the top of the aquifer, identical to the pattern observed at the FT-02 plume. Further GPR surveys were conducted by students of a Western Michigan University geophysics field course to outline the proximal part of the plume. The GPR survey was supplemented by an electromagnetic induction (EM) survey which showed a group of four cables crossing the area. Finally, a magnetometer survey was conducted to search for any buried steel objects which might have been missed by the EM survey. The results of the three geophysical surveys were then used by students of a University of Michigan field course to guide subsurface soil and fluid sampling, which verified the presence of residual LNAPL product and ground water with conductivities 2.5 to 3.3 times above background. The plume source is in the vicinity of a vaulted underground storage tank (UST) formerly used for the collection of waste solvents and fuels for subsequent use in the fire training exercises at FT-02. This newly discovered LNAPL plume, along with other “mature’ plumes, fits the electrical model which predicts conductive ground water below the decomposing but electrically resistive LNAPLs. Finally, this is a fine example of the cooperative use of a dedicated research site for training by students of two different universities.

Notes: The Sole Source Aquifer Program has helped prevent contamination of many community drinking water supplies. If an aquifer supplies the sole or principal source of a community's drinking water, a local ground water user may petition the Environmental Protection Agency (EPA) under the Safe Drinking Water Act for its designation and protection as a “sole source aquifer.” Since 1974, residents and officials of 65 communities and multi-community areas have petitioned and received assistance from the EPA to prevent contamination of their local ground water source of drinking water. This designation means that EPA may review federal financially assisted projects to determine if they would contaminate the aquifer and cause a public health hazard. If they could cause contamination, EPA can request that the project be modified or stopped. The significance of this program in terms of population served and funds affected has been substantial, indicating the Sole Source Aquifer Program has been an important local tool for protecting ground water used as a source of drinking water. Information is given on three different examples of sole source aquifer designations protected under this program: the New Jersey Coastal Plain Aquifer System, the Great Miami River Buried Valley Aquifer System (Ohio), and the Eastern Snake River Plain Aquifer (Idaho), serving populations of 543,000, 921,000, and 275,000, respectively. In all three examples, preventing ground water contamination through the Sole Source Aquifer Program has protected the community drinking water supply.

Notes: Arrays of unpumped wells can be used as discontinuous permeable walls in which each well serves both as a means to focus ground water flow into the well for treatment and as a container either for permeable reactive media which directly destroy dissolved ground water contaminants or for devices or materials which release amendments that support in situ degradation of contaminants within the aquifer downgradient of the wells. This paper addresses the use of wells for amendment delivery, recognizing the potential utility of amendments such as electron acceptors (e.g., oxygen nitrate), electron donors (primary substrates), and microbial nutrients for stimulating bioremediation, and the potential utility of oxidizers, reducers, etc., for controlled abiotic degradation. Depending on its rate and constraints, the remedial reaction may occur within the well and/or downgradient. For complete remediation of ground water passing through the well array, the total flux of amendment released must meet or exceed the total flux demand imposed by the plume. When there are constraints on the released concentration of amendment (relative to the demand), close spacing of the wells may be required. If the flux balance allows wider spacing, it is likely that limited downgradient spreading of the released amendment will then be the primary constraint on interwell spacing. Divergent flow from the wells, roughly two times the well diameter, provides the bulk of downgradient spreading and constrains maximum well spacing in the absence of significant lateral dispersion. Stronger lateral dispersion enhances the spreading of amendment, thereby increasing the lateral impact of each well, which allows for wider well spacing.

Notes: For this statewide assessment, 1808 wells were; sampled and a data base compiled that included water-quality data (NO3-N, pesticides, coliform bacteria) and site-specific data collected at each location. Domestic, rural Water quality in Nebraska varies substantially from one ground water region to another and is a function of well characteristics, distances to potential contamination sources, and hydrogeologic and site characteristics. The percentage of wells exceeding the 10 ppm MCL for NO3-N ranged from 3 to 39 percent, depending on the ground water region. This large range of values indicates the inadequacy of stating that an average of 19 percent of domestic wells in Nebraska are contaminated by nitrates. This statistic does not describe the nature, extent, and variability of the contamination problem. Depending on the ground Water region, the degree of nitrate contamination in rural domestic drinking water wells has remained generally unchanged or has only slightly increased since the last statewide assessment conducted from 1985 to 1989. Bacterial contamination has either remained the same or has decreased. The percentage of wells affected by bacteria ranged from 8 to 26 percent, depending on the ground water region. Statewide, about 70 wells, or 4 percent of the wells sampled, had detectable pesticide levels, of which atrazine was the most common. Eighty-two percent of the detections were in the Platte River Valley of in the South Central Plains, both of which are characterized by heavily irrigated corn and a statistical association between nitrate and atrazine contamination. To improve the quality of domestic drinking water will require a combination of activities, including the application of best management practices specific to a ground water region and individual action at rural households, such as conducting sanitary surveys of existing wells before installing new wells.

Notes: An algorithm is presented that allows estimation of the saturation and composition of a single of multi-component NAPL within a core sample. These estimates are possible because, in addition to distributing the organic chemicals between aqueous, sorbed, air, and NAPL phases according to traditionalpartitioning equations, the algorithm incorporates equations for the conservation of mass and volume. A unique solution is obtained by solvihg the set of nonlinear equations implicitly. The algorithm is built into a code called NAPLANAL, which is tested and applied to actual core samples collected in the field.

Notes: Current site assessment techniques do not always generate adequate information regarding the presence, type, or distribution of nonaqueous phase liquids (NAPLs) at sites with ground water contamination. Without this information, however, the design of remediation methods is uncertain, often resulting in costly and/or failed attempts to minimize risks associated with the contamination. In this work, it is proposed that a thorough multivariate analysis of data from ground water sampling efforts could improve our overall understanding of these sites. Multivariate analyses can provide considerable insight into the contaminant source characteristics by elucidating correlations in ground water concentrations that identify recurring chemical patterns or “signatures.” These correlations are related to the type of NAPL and proximity to the contaminant source.Multivariate plots and a principal components analysis (PCA) are used to interpret ground water data from a manufactured gas plant site in Iowa contaminated with both gasoline and coal tar. Conclusions from these analyses regarding the distribution of NAPL contaminants were generally consistent with those derived from direct physical evidence of the NAPL sources. The multivariate analyses, however, provide an additional level of interpretation regarding the distribution of coal tar in the subsurface that was not possible with the standard evaluation techniques used during the remedial investigation (RI). Comparison of chemical signatures of ground water samples among wells identified two distinct regions of coal tar contamination, and suggests which wells are impacted by each source providing greater confidence in the location of the DNAPL sources.

Notes: Previous research has shown that the most commonly used well casing materials-stainless steel. polyvinyl chloride (PVC). and polytetra-fluoroethylene (PTFE)-are not suited for all monitoring environments and applications. This study is part of a series of experiments that were conducted to determine the suitability of four other polymeric well casing materials-acrylonitrile butadiene styrene (ABS), fluorinalcd ethylene propylene (FHP), fiberglass-reinlorced epoxy (FRE), and fiberglass-reinforced plastic (FRP)- for use in ground water monitoring wells. In these studies, these four materials were compared with two other commonly used polymeric well casings, PVC and PTFE. Part I of these studies examines the resistance of these materials to degradation by chemicals. Future reports will consider sorption and leaching of organic and metal contaminants.In this study, the six materials were exposed to 28 neat organic compounds (including one acid) and to extremely acidic and alkaline aqueous solutions for up to 112 days. This was done to simulate the most aggressive environments to which monitoring well casings may be exposed. The casings were observed for changes in weight and signs of physical degradation (swelling, softening, deterioration, or dissolution).The two fluorinated polymers (FEP and PTFE) were not degraded by any of the lest chemicals. Among the nonfluorinated products tested. FRE was the most inert. Three organic chemicals caused the glass fibers to separate. and two organic solvents caused weight gains exceeding 10 percent. ABS was the most readily degraded material tested. By the end of the study, only the acid and alkaline solutions had little effect on ABS. FRP was more severely degraded by the organic chemicals than FRH but was less affected than PVC. FRP and FRE. lost weight when exposed to the highly acidic conditions.

Notes: Several sections of the thallus of an artic population of brown macroalga Laminaria saccharina (L.) Lamour were collected during April-June 1995, in the Kongsfjorden are at Ny-Aålesund, Svalbard and investigated for halogenating activity. Brominating activity was found in the blade only, while iodinating activity occurred in the whole thallus of L. saccharina. The highest activity occurred in the blade, while lower activity was detected in the stipe and holdfast. No evidence for chlorinating activity was found. Halogenating activity, which clearly depends on temperature, showed increasing rates with increasing tempertures between 5 and 35°C.

Notes: The existence of a large subglacial lake beneath the antarctic Ice Sheet at Terre Adélie indicates the presence of basal ice at its pressure-melting temperature. A numerical model of the ice-sheet thermal regime is employed using the balance velocity of the ice sheet as an initial model input in order to calculate ice-sheet basal temperatures. However, the results from this model show the Terre Adélie area to be characterised by basal freezing. Heat in addition to that accounted for in the model is thus required at the ice-sheet base in order for pressure melting temperatures to be attained. The sources for such heat are (1) an enhanced geothermal heat flux and (2) an increase in frictional heating caused by the flow of ice. In this paper the latter possibility is expanded by hypothesising that subglacial topography induces convergent ice flow around Terre Adélie, causing enhanced basal ice velocities. Model experiments indicate that an increase in ice velocity (from 7 to at least 42 m yr−1) is required to raise the temperature of the basal ice to the pressure melting value. Increased ice velocity, and consequent frictional heat production due to convergent ice flow, may therefore be important in explaining the location of the subglacial lake in this region. These results allow the process of convergent ice flow within a contemporary ice sheet to be quantified. A verification (or otherwise) of the model results may be possible if ice surface velocity measurements from modem GPS methods are made.

Notes: Abstract K-Ar ages have been obtained for mineral separates: plagioclases from two dolerites and biotites from one granite and four granodiorites in the Oban-Obudu massif of southeastern Nigeria. Dolerites in the Oban area give K-Ar plagioclase ages of 204.0 ± 9.9 Ma and 219.9 ± 4.7 Ma. The granite of the Obudu area yields a K-Ar biotite age of 507.6 ± 10.1 Ma whilst the granodiorites in the Oban area yield K-Ar biotite ages ranging from 474.6 ± 9.4 Ma to 511.8 ± 10.0 Ma. The dolerites are related to the tholeiitic basaltic magmatism at the early opening of the central Atlantic, and are compatible in age with the formation of the Ring Complexes and the rifting of the Benue Trough of Nigeria. The granites and granodiorites belong to the syntectonic Older Granite series in the Pan-African orogeny. The emplacement timing deduced from the reported Pb-Pb zircon age of 617 ± 2 Ma and the newly obtained biotite ages suggest that these older granites in southeastern Nigeria had a prolonged cooling history of ∼110 Ma.

Notes: Abstract Subduction thrust faults generate earthquakes over a limited depth range. They are aseismic in their seaward updip portions and landward downdip of a critical point. The seaward shallow aseismic zone, commonly beneath accreted sediments, may be a consequence of unconsolidated sediments, especially stable-sliding smectite clays. Such clays are dehydrated and the fault may become seismogenic where the temperature reaches 100--150°C, that is, at a 5--15 km depth. Two factors may determine the downdip seismogenic limit. For subduction of young hot oceanic lithosphere beneath large accretionary sedimentary prisms and beneath continental crust, the transition to aseismic stable sliding is temperature controlled. The maximum temperature for seismic behavior in crustal rocks is ∼ 350°C, regardless of the presence of water. In addition, great earthquake ruptures initiated at less than this temperature may propagate with decreasing slip to where the temperature is ∼ 450°C. For subduction beneath thin island arc crust and beneath continental crust in some areas, the forearc mantle is reached by the thrust shallower than the 350°C temperature. The forearc upper mantle probably is aseismic because of stable-sliding serpentinite hydrated by water from the underthrusting oceanic crust and sediments. For many subduction zones the downdip seismogenic width defined by these limits is much less than previously assumed. Within the narrowly defined seismic zone, most of the convergence may occur in earthquakes. Numerical thermal models have been employed to estimate temperatures on the subduction thrust planes of four continental subduction zones. For Cascadia and Southwest Japan where very young and hot plates are subducting, the downdip seismogenic limit on the subduction thrust is thermally controlled and is shallow. For Alaska and most of Chile, the forearc mantle is reached before the critical temperature, and mantle serpentinite provides the limit. In all four regions, the seismogenic zones so defined agree with estimates of the extent of great earthquake rupture, and with the downdip extent of the interseismic locked zone.

Notes: Abstract Past seismic catastrophes were unknown in Sakhalin Island before 1995 except those suggested from findings of paleoseismodislocations. The first time that dwellers have experienced such a catastrophe in the Sakhalin Island history was on 27 May 1995. The devastating Neftegorsk earthquake occurred in Northern Sakhalin (ϕ= 52.8° north; δ= 143.2° east; H = 18 km; Ms= 7.2), killed almost 2000 people in the small city of Neftegorsk, caused damage and destruction of buildings, bridges, railways and roads, breakage of oil and gas pipelines, electric and communication lines, and was accompanied by large-scale surface phenomena within a source area. It was felt all over the Sakhalin Island, as well as over the closest part of the Eurasian continent. Surface fracturing was the most impressive effect of the Neftegorsk earthquake. The 37-km long, right-lateral strike-slip fault, with a strike of north 15° east and a horizontal displacement up to a maximum of 8 m, has been observed from Taxon Mountain at the south to the junction of the Cadylanye and Keniga Rivers at the north. According to the results of a detailed geological survey and study of the aftershocks, the total extent of the source area was - 80 km. Various secondary phenomena have been observed at the Earth's surface, such as landslides, falls, soil liquefaction, mud volcanoes etc. The earthquake was followed by hundreds of aftershocks within the following 1-2 months. Spatially, the earthquake fault coincides with the pre-existing Upper Piltun fault, known earlier from geological studies. Recent high activity of the latter fault has been recognized only after the Neftegorsk event because of findings of traces of significant past dislocations within the fault zone. From a tectonic viewpoint it can be suggested that the Upper Piltun fault is a Riedel-type shear fracture located between two main regional faults: the Gyrgylanye-Dagy fault at the west and the Piltun-Ekhaby fault at the east. Therefore, its present activity, expressed by the destructive Neftegorsk earthquake, seems to be explained by a long strain accumulation within a broad zone of regional right-lateral shear faulting.