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  • 1
    Electronic Resource
    Electronic Resource
    The bonding of acetonitrile and CH2CN on Ag(110) determined by near edge x-ray absorption fine structure: Evidence for π-donor bonding and azimuthal ordering (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4338-4345 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Carbon K edge near edge x-ray absorption fine structure (NEXAFS) spectra of adsorbed acetonitrile and reactive intermediates derived therefrom on Ag(110) were studied in order to determine their orientation and bonding to the surface. For both the multilayer and the adsorbed monolayer there is excellent agreement between the spectra of the adsorbed acetonitrile and the gas phase species. For the multilayer coverage the orientation of the acetonitrile molecules is not completely random; the molecules prefer an orientation with their bond axes closer to parallel than perpendicular to the surface. At monolayer coverage acetonitrile bound to the surface is unrehybridized. It is bound with its linear molecular skeleton parallel to the surface and randomly oriented azimuthally. Annealing molecular CH3 CN to 325 K in the presence of coadsorbed atomic oxygen produces a linear CH2 CN surface intermediate, the molecular axis of which is parallel to the surface and perpendicular to the close-packed direction. The C–C and C–N bond lengths are essentially unperturbed from their values in gas phase CH3 CN. Bonding appears to occur between the methylene carbon and the metal, as expected. A broadening of the π* resonance for transition into the π* orbital perpendicular to the surface is interpreted in terms of π-donor bonding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456814
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  • 2
    Electronic Resource
    Electronic Resource
    Translocation of Herb-Rich Grassland from a Site in Wales Prior to Opencast Coal Extraction (1999)
    Boston, MA, USA : Blackwell Science Inc
    Restoration ecology 7 (1999), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Reinstatement of vegetation to a similar condition to that prior to disturbance is often required in industrial restoration schemes. Seeding with specially prepared seed mixes containing species suited to local soils is often the preferred option on grounds of practicality and cost. Turf translocation is more difficult and costly but, if successful, meets the reinstatement requirement more precisely. In a pilot study at a proposed opencast coal site in Wales, we compared the effectiveness of whole-turf translocation of herb-rich mesic grassland communities, with a less technically demanding and more cost-effective technique involving spreading turf over twice the area at the receiver site and rotovating it into the underlying soil. The translocated whole turf and rotovated turf plots were cut annually and the vegetation removed to simulate grazing that had occurred prior to translocation. Both the whole-turf and rotovated turf transplant techniques gave successful re-establishment of 50% or more of the species originally present. After three years, the cover and species composition were similar in “whole-turf” and “spread and rotovated” plots. This suggests that the “spread and rotovate” technique provides a satisfactory ecological alternative to whole-turf translocation. However, plant communities changed, in some cases substantially, after translocation using either technique. Altered soil hydrology and nutrition combined with the substitution of cutting for grazing are probably the main causes of these changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1526-100X.1999.72028.x
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of soil variability on tree establishment at an experimental agroforestry site in North East Nigeria (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 13 (1997), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1997.tb00549.x
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  • 4
    Electronic Resource
    Electronic Resource
    Synchrotron radiation x-ray absorption of ion bombardment induced defects on diamond (100) (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7483-7486 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface defect structures on diamond (100) surfaces induced by 500 eV neon ion bombardment and by subsequent annealing were studied in situ with x-ray absorption near-edge structure (XANES) spectroscopy using 250–800 eV synchrotron radiation and with low energy electron diffraction. Ex situ x-ray photoemission spectroscopy (XPS) was also used to characterize the defective layer. Significant changes in the XANES spectra were identified for the defects induced by ion bombardment and subsequent annealing. The diamond discrete exciton absorption at 289.0 eV was clearly suppressed even at the lowest ion fluence used in this study, i.e., 3×1014/cm2, and no such exciton could be observed at 7×1014/cm2. However, the changes in the multi-maxima shape-resonance absorption structure in the range of 290–310 eV indicated that a loss of the diamond long range order required a fluence of 1×1015/cm2. The structural changes were also manifested by the transformation of gap state absorption typical of clean 2×1 surfaces to the π* absorption typical of amorphous carbon. XPS showed that the defective layer was about 2 nm thick. For all samples prepared with the bombardment conditions in the study, both the XANES and XPS data also indicated no phase transformation from defective layers to graphite even after annealing to a temperature of 1100 °C. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357977
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  • 5
    Electronic Resource
    Electronic Resource
    Bonding and adsorption structure of CO on W(100)-(5×1)–C (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 1847-1850 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The adsorption structure of carbon monoxide on W(100)-(5×1)–C has been characterized using high-resolution electron energy loss spectroscopy and near edge x-ray absorption fine structure measurements. A single C–O stretch of 2100 cm−1 is observed at a surface temperature of 130 K. The C–O bond vector is determined to be normal to the surface on the basis of near edge x-ray absorption fine structure measurements. The position in energy of the C(1s)→σ* resonance in CO was measured to be 304.2 eV. The empirical relation between the σ* resonance energy and bond length yields a bond length of 1.12 A(ring). All spectroscopic results are consistent with CO bound atop a single tungsten atom, normal to the surface plane with minimal C–O bond weakening. These results correlate with the known difference in the reactivity of the W(100)-(5×1)–C surface compared to clean W(100). The increased barrier for CO dissociation on the W(100)-(5×1)–C surface is explained on the basis of reduced backdonation of electron density from the tungsten d band to the CO 2π* orbitals. Tight-binding slab calculations for CO on W(100) and W(100)-(5×1)–C which support this contention are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453198
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  • 6
    Electronic Resource
    Electronic Resource
    The impacts of atmospheric n inputs on throughfall, soil and stream water interactions for different aged forest and moorland catchments in Wales (1994)
    Springer
    Water, air & soil pollution 73 (1994), S. 297-317 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A study of inorganic-N concentrations in streams, soil waters, throughfall and rainfall was conducted for one year in five moorland and 20 Sitka spruce plantation catchments in upland Wales. The forest ages ranged from 10 to 55 yr. Highly significant positive relationships with forest stand age existed for inorganic-N concentrations in streamwater, B and O horizon soil waters and throughfall. Inorganic-N in streams and B horizon waters was entirely NO3 −. Inorganic-N fluxes in throughfall also showed a significant, positive relationship with stand age. Throughfall flux of inorganic-N in the oldest stand was 25.1 kgN ha−1 yr−1, double that in incident rainfall. The older forest stands appear unable to utilise the available N. Nitrification is very active in the soils of these older stands, resulting in significant soil acidification. The processes responsible for the observed NO3 − leaching losses, and the implications for the debate on Nitrogen Critical Loads are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00477994
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  • 7
    Electronic Resource
    Electronic Resource
    Factors influencing nitrogen saturation in Sitka spruce stands in Wales, UK (1995)
    Springer
    Water, air & soil pollution 85 (1995), S. 1629-1634 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Preliminary empirical nitrogen critical load exceedance maps for the UK have identified large areas of Wales where nitrogen deposition exceeds the nitrogen critical load, indicating that some ecosystems are at risk from eutrophication. This paper synthesises the monitoring and experimental work which have been carried out to collect evidence for exceedance in spruce plantations in the uplands and to investigate the implications for acidity and eutrophication in these areas. The results have conclusively demonstrated that current nitrogen deposition to mature Sitka spruce stands, planted on freely draining acid soils, is in excess of ecosystem requirements and results in elevated nitrate leaching losses. In contrast, stands with large biological sinks such as aggrading stands or stands with high denitrification potential have low ntirate leaching losses. The controls on the magnitude of leaching losses in the mature stands on this soil type are discussed within the context of two categories: (i) “nitrate saturated” stands which exhibit no retention of incoming nitrate-N but retain incoming ammonium-N as demonstrated in the Welsh NITREX experimental site and (ii) more nitrogen-rich stands which are saturated for both nitrate-N and ammonium-N and respond directly to incoming ammonium-N with immediate increases in nitrate production and thus nitrate leaching losses. There is little evidence for any adverse effects on tree growth or health in response to excess nitrogen deposition, however, tree growth in the most mature stands is now limited by phosphorus and potassium deficiency. The risk of a reduction in soil and stream water quality in acid sensitive areas of Wales due to the link between nitrate leaching and aluminium concentrations has also been confirmed. The results are discussed within the framework proposed by Aber et al. 1989 for the sequence of changes in ecosystem function which occur following long-term chronic nitrogen deposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00477213
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of forest age on surface drainage water and soil solution aluminium chemistry in stagnopodzols in Wales (1994)
    Springer
    Water, air & soil pollution 77 (1994), S. 115-139 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The influence of forest development on soil solution and surface drainage water aluminium chemistry was investigated in Sitka spruce (Picea sitchensis) plantations in Wales. Comparisons with semi-natural grassland and moorland sites are described. A highly significant positive relationship was shown between increasing forest age and soilwater aluminium concentrations in the B horizons. Shortterm/episodic peaks in Al concentrations were strongly related to incidences of high concentrations of neutral, marine-derived, salts in the soilwater. Nitrification may be an important factor in soil acidification and the mobilization of Al in soilwaters beneath the older mature-forest plantations in Wales. Labile monomeric Al concentrations were largest in surface waters draining the oldest forestry plantations compared with younger forest catchments and moorland, although response to discharge of soilwater acidity to the surface waters at individual sites was dependent on the acid neutralizing capacity of the groundwater component of the surface waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00483053
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  • 9
    Electronic Resource
    Electronic Resource
    Stream chemistry impacts of conifer harvesting in welsh catchments (1995)
    Springer
    Water, air & soil pollution 79 (1995), S. 147-170 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Hydrochemical data have been collected for between 6 and 9 years from forest harvesting experiments in small catchments (〉10 ha) at Plynlimon and Beddgelert, Wales, UK. Felling resulted in rapid increases in NO 3 − and K+ concentrations at both sites. A maximum of 3.2 mg N L−1 was observed at Plynlimon about one year after the start of felling. Concentrations declined to control stream values (0.5 mg N L−1) after 5 years. At Beddgelert, NO 3 − concentrations in the manipulated catchments remained above those in the unfelled control catchment for three years, before declining below control values. The NO 3 − pulse was related to increased rates of mineralization and nitrification in the soil after felling. The initial increase in K+ concentration after felling at Plynlimon was followed by a slow decline, but concentrations were still above those in the control stream after 5 years. From 4 to 8 years after felling at Beddgelert, K+ concentrations fell below and then generally remained lower than control values. The NO 3 − pulse after felling at Plynlimon sustained inorganic anion concentrations above those in the control stream for the first 18 months after felling. As the NO 3 − pulse declined, inorganic anion concentrations decreased to below those in the control stream about 4 years after felling. At Beddgelert, the smaller increase in NO 3 − concentrations had less of an effect on inorganic anion concentrations which decreased after felling relative to values in the control stream. The increase in NO 3 − was associated with temporary streamwater acidification in the felled catchments due to the increased rates of nitrification and nitrate leaching. At Plynlimon, streamwater filterable Al concentrations declined after felling, but controls on Al behaviour are complex and not explained by simple equilibrium relationships with Al(OH)3 or by variations in inorganic anion concentrations. At Beddgelert, felling had no effect on stream water filterable Al concentrations. Felling at Plynlimon led to a large reduction in streamwater Cl−, Na+ and SO 4 2− concentrations. At Beddgelert reductions in SO 4 2− and ‘sea salt’ ion concentrations were less clear, reflecting the smaller proportions of the catchments which were harvested. Felling had no deleterious effects on water quality, apart from a temporary slight further decline in stream pH at Beddgelert. Increases in NO 3 − concentrations were short-lived and concentrations were well below drinking water standards. Filterable Al concentrations were already higher than statutory standards, but were not increased or decreased through felling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01100435
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  • 10
    Electronic Resource
    Electronic Resource
    Dissolved inorganic nitrogen concentrations and fluxes in three British Sitka Spruce plantations (1990)
    Springer
    Plant and soil 128 (1990), S. 103-108 
    Details
    ISSN: 1573-5036
    Keywords: forest soils ; inorganic nitrogen ; nitrate leaching ; nitrogen loading ; Sitka spruce ; solute fluxes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A catchment approach was used to estimate mean dissolved inorganic-N concentrations and fluxes through three mature Sitka spruce plantations at Beddgelert (north Wales), Plynlimon (mid-Wales) and Kershope (Cumbria). Dissolved inorganic-N in bulk precipitation, throughfall, stemflow, soil water at 4 or 5 depths, and streamwater was measured every two weeks for periods of 1 or 2 years at all three sites. Bulk precipitation inputs at the three sites varied from 6 to 10.4 kg N ha-1 a-1 and stream outputs varied from 6.4 to 13.6 kg N ha-1 a-1. Beddgelert Forest had the highest inputs and outputs and is “Nitrogen saturated” according to certain Scandinavian criteria (Nilsson, 1986). All three sites had much higher outputs than might be expected from the magnitude of the inputs, since conifer forests are normally regarded as being ‘conservative’ with respect to N. Only at Plynlimon were reductions in dissolved inorganic N flux or concentration observed from bulk precipitation to throughfall and soil waters. At the other two sites, the tree canopies did not assimilate N in incoming rainfall, and active nitrification resulted in high concentrations of nitrate in soil and streamwater. It is proposed that many mature western upland Sitka spruce plantations may behave in a similar manner with respect to dissolved N, in contrast to sites in eastern Scotland where rates of nitrification are slower and nitrogen appears to be less available to plantation trees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009402
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