Johannes A. C. Barth

Sorption of alkylphenols on Ebro River sediments: comparing isotherms with field observations in river water and sediments.

This study reports sorption isotherms of the endocrine disruptors nonylphenol (NP) and octylphenol (OP) in three sediment samples from the Ebro River basin (NE Spain), with organic carbon fractions (f(OC)) ranging from 0.0035 to 0.082 g(OC)g(-1). All isotherms were fitted to the Freundlich model with slightly nonlinear exponents ranging from 0.80 to 0.94. The solubility of the compounds as well as the organic carbon (OC) content had the strongest influences on the sorption behavior of these compounds. Comparison of the laboratory-spiked samples with the native contamination of NP of 45 water and concurrent sediment samples resulted in reasonable matches between both data sets, even though the lowest concentrations in the field were not completely reached in laboratory tests. This good agreement indicates that sorption laboratory data can be extrapolated to environmental levels and therefore the distribution of nonylphenol between sediments and water can be predicted with a precision of one order of magnitude. Furthermore, laboratory experiments with simultaneous loading of NP and OP revealed negligible competition for sorption sites at low concentrations.

Mobility, turnover and storage of pollutants in soils, sediments and waters : achievements and results of the EU project AquaTerra. A review

AquaTerra is one of the first environmental projects within the 6th Framework program by the European Commission. It began in June 2004 with a multidisciplinary team of 45 partner organizations from 13 EU countries, Switzerland, Serbia, Romania and Montenegro. Results from sampling and modeling in 4 large river basins (Ebro, Danube, Elbe and Meuse) and one catchment of the Brévilles Spring in France led to new evaluations of diffuse and hotspot input of persistent organic and metal pollutants including dynamics of pesticides and polycyclic aromatic hydrocarbons, as well as metal turnover and accumulation. While degradation of selected organic compounds could be demonstrated under controlled conditions in the laboratory, turnover of most persistent pollutants in the field seems to range from decades to centuries. First investigations of long-term cumulative and degradation effects, particularly in the context of climate change, have shown that it is also necessary to consider the predictions of more than one climate model when trying to assess future impacts. This is largely controlled by uncertainties in climate model responses. It is becoming evident, however, that changes to the climate will have important impacts on the diffusion and degradation of pollutants in space and time that are just at the start of their exploration.

Routine analysis by high precision gas chromatography mass selective detector isotope ratio mass spectrometry to 0.1 parts per mil

Stable isotope methods are potentially quite useful for validating natural or enhanced mineral degradation of contaminants. For this reason, a continuous flow gas chromatograph (GC), isotope ratio mass spectrometer (IRMS) has been coupled with a quadrupole mass selective detector (MSD) to allow simultaneous mass spectral and stable carbon isotope ratio data to be obtained from a single chromatographic analysis. This allows the target contaminant and any extra-cellular degradation intermediates to be both qualified and quantified. Previously acceptable limits of precision (0.3 parts per mil) are undesirable given the small fractionation observed during aerobic degradation. To further understand the fate of organic contaminants and to gain information about the metabolic degradative pathway employed by a microorganism, routine isotopic analyses on a range of analytes have been performed. Quantities of sample producing mass-44 ion beam signal (I(44)) of 2 x 10(-10) to 1 x 10(-8) A were analysed. When the IRMS was tuned for high sensitivity, ion source nonlinearities were overcome by peak height correction from an algorithm that was produced using known isotopic standards of varying concentrations. This led to sample accuracy of <0.01 per thousand and sample precision of 0.1 per thousand. Copyright 1999 John Wiley & Sons, Ltd.

Carbon isotope fractionation during abiotic reductive dehalogenation of trichloroethene (TCE)

Dehalogenation of trichloroethene (TCE) in the aqueous phase, either on palladium catalysts with hydrogen as the reductant or on metallic iron, was associated with strong changes in delta13C. In general, the delta13C of product phases were more negative than those of the parent compound and were enriched with time and fraction of TCE remaining. For dehalogenation with iron, the delta13C of TCE and products varied from -42/1000 to +5/1000. For the palladium experiments, the final product, ethane, reached the initial delta13C of TCE at completion of the dehalogenation reaction. During dehalogenation, the carbon isotope fractionation between TCE and product phases was not constant. The variation in delta13C of TCE and products offers a new monitoring tool that operates independently of the initial concentration of pollutants for abiotic degradation processes of TCE in the subsurface, and may be useful for evaluation of remediation efficiency.

Can conductivity and stable isotope tracers determine water sources during flooding? An example from the Elbe River in 2002

Abstract Despite drastic runoff variations, stable isotope data of water in the upstream part of the Elbe River showed remarkable similarity during, and two months after the flood of 2002. This homogeneity indicates that water sources remained the same and most likely represents dominant groundwater input regardless of the flood. While the latter remains the most plausible explanation, it was difficult to prove with water stable isotopes for the upstream part of the river. Overlapping isotope compositions of long‐term average precipitation data (as a proxy for the groundwater end member) and of the weighted average from precipitation events in August 2002 did not allow quantification of the groundwater component during flooding. This shows that better spatial and temporal sample resolution is necessary for enhanced understanding of water sources and mass balances during floods. Such mass balances were only possible in the estuary where conductivity and stable isotope tracers both revealed much stronger freshwater fluxes to the estuary during the flooding event of 2002 when compared to those of two months after the flood. Conductivity was also a good indicator for additions of more saline waters from the Saale River when the system was not affected by flooding. However, during the flood in August 2002, large volumes of low‐saline waters, most likely from shallow groundwater, masked these usually high conductivity values. This indicates that conductivity better reveals input of dissolved constituents, while the stable isotopes can better indicate sources of water input. Both tracers become most powerful when applied in combination for better understanding of water sources and river basin management.

Isotopic composition of inorganic carbon as an indicator of benzoate degradation by Pseudomonas putida: temperature, growth rate and pH effects

Degradation experiments of benzoate by Pseudomonas putida resulted in enzymatic carbon isotope fractionations. However, isotopic temperature effects between experiments at 20 and 30 degrees C were minor. Averages of the last three values of the CO(2) isotopic composition (delta(13)C(CO2(g))) were more negative than the initial benzoate delta(13)C value (-26.2 per thousand Vienna Pee Dee Belenite (VPDB)) by 3.8, 3.4 and 3.2 per thousand at 20, 25 and 30 degrees C, respectively. Although the maximum isotopic temperature difference found was only 0.6 per thousand, more extreme temperature variations may cause larger isotope effects. In order to understand the isotope effects on the total inorganic carbon (TIC), a better measure is to calculate the proportions of the inorganic carbon species (CO(2)(g), CO(2)(aq) and HCO(3)(-)) and to determine their cumulative delta(13)C(TIC). In all three experiments delta(13)C(TIC) was more positive than the initial isotopic composition of the benzoate at a pH of 7. This suggests an uptake of (12)C in the biomass in order to match the carbon balance of these closed system experiments.

Oxygen and Hydrogen Stable Isotopes in Earth’s Hydrologic Cycle

Today’s geochemistry would be hard to imagine without stable isotope research that enabled the investigation of many fundamental geoscientific questions. Stable isotopes play an important role in water research and proved to be essential for understanding basic hydrological processes including groundwater recharge, origin of precipitation, and runoff dynamics. Notably, freshwater is one of the most essential resources humans depend upon and isotopes are a valuable tool for tracing sources of water and its dissolved constituents. This work reviews some of the most recent applications in hydrology and hydrogeology with focus on the stable isotope ratio of the water molecule, namely hydrogen and oxygen. While stable isotopes have greatly improved our understanding of transport and reaction processes, they are equally important tools to unravel environmental conditions in the past. Overall, isotope research helps us to better understand and constrain fundamental processes in hydrogeochemical cycles and how ongoing man-made modifications affect their interaction with the Earth’s surface and subsurface.

New challenges in biogeochemical gradient research

At a recent workshop focusing on biogeochemical gradients predominantly in groundwater and sediments, 32 North American and German scientists discussed research needs in three areas including (1) redox and microbes; (2) contaminants, isotopes, and fluxes; and (3) instruments, monitoring, and modeling. n nThe presentation topics at the workshop at the Eberhard Karls University of Tubingen in Germany ranged from new concepts for monitoring contaminant attenuation, microgradients, microbial and abiotic recycling of iron and arsenic, porous media characterization, modeling in marine and groundwater environments, and stable isotope as well as radioisotope techniques.

Advanced tools and models to improve river basin management in Europe in the context of climate change: AquaTerra.

Advanced Tools and Models to Improve River Basin Management in Europe in the Context of Climate Change - AquaTerra has developed from an integrated project of the 6th EU RTD Framework Programme that aims to provide the scientific basis for an improved river basin management through a better understanding of the river-sediment-soil-groundwater system as a whole, by integrating both natural and socio-economics aspects at different temporal and spatial scales.nnThis book aims: nnThe work illustrates the dynamic behavior of the pathway of pollutants in soils, groundwater, surface water and sediments. It highlights the fundamental importance of integrating knowledge from sereral combineddisciplines on various environmental compartments in order to understand the large number of processes that govern pollutant input, transport and turnover. Results shows that a significant step forward has been made in the development new analytical methods and of process-based numerical models that are capable of making predictions of likely trends and environmental changes to be expected in the near or distant future at the basin-scale. These models can be used e.g. to generate hydrologic scenarios based on climate models and to simulate pollutant distribution and turnover rates from decades to millennia.nnThis title belongs to European Water Research Series .nnISBN: 9781843393726 (Print)nnISBN: 9781780401577 (eBook)