ALBERT

Description: There is a need to be able to differentiate the dissolved organic matter (DOM) fraction in river waters. Research in the 1970s and 1980s has attempted to utilize both absorbance and flourescence to distinguish between DOM fractions in river waters, but both were limited by the available technology. Total organic carbon content has, therefore, been widely used as a standard method of measuring DOM concentration, although it has little power to differentiate DOM fractions. Recent advances in flourescence spectrophotometry enable rapid and optically precise analysis of DOM. Here, we show how a combination of both flourescence and absorbance can be used to discriminate statistically between spatial variations of DOM in tributaries in a small catchment of the Ouseburn, NE England. The results of the discriminant analysis suggest that about 70% of the samples can be correctly classified to its tributary. Discriminant function 1 explains 60·8% of the variance in the data and the fulvic-like fluorescence intensity has the largest absolute correlation within this function; discriminant function 2 explains a further 21·5% of the variance and the fulvic-like fluorescence emission wavelength has the largest absolute correlation within this function. The discriminant analysis does not correctly classify all tributaries every time, and successfully discriminates between the different tributaries 70% of the time. Occasions when the tributary waters are less well discriminated are due to either episodic pollution events (at two sites) or due to tributaries that have strong seasonal trends in spectrophotometric parameters, which allows the sites to be misclassified. Results suggest that spectrophotometric techniques have considerable potential in the discrimination of DOM in rivers. © 2002 John Wiley and Sons, Ltd.

Description: Many upland catchments in the UK have undergone afforestation; their characteristic waterlogged soils require extensive pre-plantation ground drainage to allow tree establishment. In peatland areas this can result in very highly coloured runoff and enhanced dissolved organic matter (DOM) export in rivers of naturally high concentrations. In 1966, the Coalburn Experimental Catchment, northern England, was established to investigate the impact of afforestation on an upland peat catchment. Here we report the variations in DOM spectrophotometric properties of streamflow in the catchment at canopy closure, especially with respect to potential carbon sources within the artificial drainage ditches. Drainage ditches are characterized by water that has higher absorption coefficients and which is more highly coloured than in the catchment tributaries. Ditched, afforested areas produce more highly-coloured runoff waters that are more fluorescent and absorbent normalized to carbon concentration compared to ditches in open moorland. Ditches that had been experimentally re-excavated have organic matter of different spectrophotometric character, with higher dissolved organic carbon concentration and less aromatic or lower molecular weight material. It is hypothesized that this is due to the exposure of bare peat faces within and adjacent to the ditches that are more susceptible to drying compared to vegetated areas. The large extent of this drainage network acts as both a rapid transport network increasing hydrological connectivity and a pool for the storage of DOM, which is of different spectrophotometric character under low flow conditions, depending on management conditions. Copyright © 2007 John Wiley & Sons, Ltd.

Description: The results of a comparison between chemical water quality determinants and river water fluorescence on the River Tyne, NE England, demonstrate that tryptophan-like fluorescence intensity shows statistically significant relationships between nitrate, phosphate, ammonia, biochemical oxygen demand (BOD) and dissolved oxygen. Tryptophan-like fluorescence intensity at the 280 nm excitation/350 nm emission wavelength fluorescence centre correlates with both phosphate (r = 0·80) and nitrate (r = 0·87), whereas tryptophan-like fluorescence intensity at the 220 nm excitation/350 nm emission wavelength centre correlates with BOD (r = 0·85), ammonia (r = 0·70) and dissolved oxygen (r = -0·65). The strongest correlations are between tryptophan-like fluorescence intensity and nitrate and phosphate, which in the Tyne catchment derive predominantly from point and diffuse source sewage inputs. The correlation between BOD and the tryptophan-like fluorescence intensity suggests that this fluorescence centre is related to the bioavailable or labile dissolved organic matter pool. The weakest correlations are observed between tryptophan-like fluorescence intensity and ammonia concentration and dissolved oxygen. The weaker correlation with ammonia is due to removal of the ammonia signal by wastewater treatment, and that with dissolved oxygen due to the natural aeration of the river such that this is not a good indicator of water quality. The observed correlations only hold true when treated sewage, sewerage overflows or cross connections, or agricultural organic pollutants dominate the water quality-this is not true for two sites where airport deicer (propylene glycol, which is non-fluorescent) or landfill leachate (which contains high concentrations of humic and fulvic-like fluorescent DOM) dominate the dissolved organic matter in the river. Mean annual tryptophan-like fluorescence intensity agrees well with the General Water Quality Assessment as determined by the England and Wales environmental regulators, the Environment Agency. © 2004 John Wiley and Sons, Ltd.

Description: In this paper, we use a scanning electron microscope (SEM) coupled with X-ray spectroscopy and electron back-scattered diffraction patterns to examine firn in cores retrieved by the United States International Trans-Antarctic Scientific Expedition. From grain boundary grooves we were able to see where the previously existing snow crystals were joined, and can determine grain sizes. From the SEM images, the porosity and the surface area per unit volume of the pores were measured. Finally, we have shown that we can determine the microchemistry of impurities in firn and demonstrated that we can determine the orientations of the firn crystals. Copyright © 2007 John Wiley & Sons, Ltd.

Description: The flourescent properties of dissolved organic matter (DOM) enable comparisons of humic-like (H-L) and fulvic-like (F-L) fluorescence intensities with dissolved organic carbon (DOC) in aquatic systems. The fluorescence-DOC relationship differed in gradient, i.e. the fluorescence per gram of carbon, and in the strength of the correlation coefficient. We compare the fluorescence intensity of the F-L and H-L fractions and DOC of freshwater DOM in north Shropshire, England, featuring a river, wetland, spring, pond and sewage DOM sources. Correlations between fluorescence and DOC varied between sample sites. Wetland water samples for the F-L peak gave the best correlation, r = 0.756; the lowest correlation was from final treated sewage effluent, r = 0.167. The relationship between fluorescence and DOC of commercially available International Humic Substances Society standards were also examined and they generally showed a lower fluorescence per gram of carbon for the F-L peak than the natural samples, whereas peat wetland DOM gave a greater fluorescence per gram of carbon than river DOM. Here, we propose the strength of the fluorescence-DOC correlation to be a useful tool when discriminating sources of DOM in fresh water. Copyright © 2007 John Wiley & Sons, Ltd.

Description: Continuous monitoring of dissolved organic matter (DOM) character and concentration at hourly resolution is rare, despite the importance of analysing organic matter variability at high-temporal resolution to evaluate river carbon budgeting, river water health by detecting episodic pollution and to determine short-term variations in chemical and ecological function. The authors report a 2-week experiment performed on DOM sampled from Bournbrook, Birmingham, UK, an urban river for which spectrophotometric (fluorescence, absorbance), physiochemical (dissolved organic carbon [DOC], electrical conductivity, pH) and isotopic (D/H) parameters have been measured at hourly frequency. Our results show that the river had sub-daily variations in both organic matter concentration and characteristics. In particular, after relatively high-magnitude precipitation events, organic carbon concentration increased, with an associated increase in intensity of both humic-like and tryptophan-like fluorescence. D/H isotopic ratio demonstrates different hydrological responses to different rainfall events, and organic matter character reflects this difference. Events with precipitation 〈2 mm typically yielded isotopically heavy water with relatively hydrophilic DOM and relatively low specific absorbance. Events with precipitation 〉2 mm had isotopically lighter water with higher specific absorbance and a decrease in the proportion of microbially derived to humic-like fluorescence. In our heavily urbanized catchment, we interpret these signals as one where riverine DOM is dominated by storm sewer-derived 'old' organic matter at low-rainfall amounts and a mixed signal at high-precipitation amounts where 'event' surface runoff-derived organic matter dominate during storm sewer and combined sewer overflow routed DOM. Copyright © 2009 John Wiley & Sons, Ltd.

Description: The forested Coalburn catchment (1.5 km2) in northern England experiences episodic stream acidification. To plan for sustainable management of the plantation forest cycle, an understanding is required of the flow pathways and hydrochemical routing signatures of the organic and mineral soils that make up the source areas for runoff. A tentative mixing model, based on simple water chemistry exists for the major (terrestrial) sources and buffers of acidification; it is being expanded and consolidated by a detailed approach to the organic components of runoff, via sampling and analysis of the luminescence of surface waters at the catchment outlet and in two distinctive feeder streams. Luminescence measurements are presented that permit a simple apportionment of source areas. However, the technique also appears to have potential for identifying differential flow sourcing between the acrotelm and catotelm of intact peat deposits and for clarifying the influence of forest root systems in altering the organic chemistry of infiltrating waters. Applications may include the monitoring and prediction of coloured water events for the water supply industry. Copyright © 2001 John Wiley and Sons, Ltd.

Description: Selection of earthquake ground motions is considered with the goal of accurately estimating the response of a structure at a specified ground motion intensity, as measured by spectral acceleration at the first-mode period of the structure, Sa(T1). Consideration is given to the magnitude, distance and epsilon (ε) values of ground motions. First, it is seen that selecting records based on their ε values is more effective than selecting records based on magnitude and distance. Second, a method is discussed for finding the conditional response spectrum of a ground motion, given a level of Sa(T1) and its associated mean (disaggregation-based) causal magnitude, distance and ε value. Records can then be selected to match the mean of this target spectrum, and the same benefits are achieved as when records are selected based on ε. This mean target spectrum differs from a Uniform Hazard Spectrum, and it is argued that this new spectrum is a more appropriate target for record selection. When properly selecting records based on either spectral shape or ε, the reductions in bias and variance of resulting structural response estimates are comparable to the reductions achieved by using a vector-valued measure of earthquake intensity. Copyright © 2006 John Wiley & Sons, Ltd.

Description: Methods for using scalar and vector ground motion intensity parameters to estimate the probabilistic relationship between ground motion intensity and structural response are described and compared. Options include using regression analysis on structural analysis results from a set of unscaled (or uniformly scaled) ground motions, or fitting a probability distribution to the analysis results from scaled ground motions analysed using incremental dynamic analysis and related methods. Past methods for using scalar ground motion intensity are reviewed, and methods for utilizing improved vector-valued intensity measures (IMs) are proposed. 'Hybrid' estimation methods that obtain the benefit of vector-valued IMs using simplified techniques such as careful record selection are also discussed. The results are then combined with models for ground motion occurrence obtained from probabilistic seismic hazard analysis to compute seismic reliability, and the results obtained from the various methods are compared. In general, a tradeoff must be made between the accuracy of the functional relationship between ground motion intensity and structural response versus the number of structural analyses needed for estimation. Copyright © 2007 John Wiley & Sons, Ltd.