The acid volatile sulphide (AVS) and simultaneously extracted metals (ΣSEM) method is increasingly used for risk assessment of toxic metals. In this study, we assessed spatial and temporal variations of AVS and ΣSEM in river sediments and floodplain soils, addressing influence of flow regime and flooding. Slow-flowing sites contained high organic matter and clay content, leading to anoxic conditions, and subsequent AVS formation and binding of metals. Seasonality affected these processes through temperature and oxygen concentration, leading to increased levels of AVS in summer at slow-flowing sites (max. 37 μmol g-1). In contrast, fast-flowing sites hardly contained AVS, so that seasonality had no influence on these sites. Floodplain soils showed an opposite AVS seasonality because of preferential inundation and concomitant AVS formation in winter (max. 3-30 μmol g-1). We conclude that in dynamic river systems, flow velocity is the key to understanding variability of AVS and ΣSEM. Flow velocity is the key to understanding variability of AVS and ΣSEM in river sediment.

Artificial-lawn mats were used as sediment traps in floodplains to measure sediment input and composition during flood events. To estimate the natural variability, 10 traps were installed during two flood waves at three different morphological units in a meander loop of the River Elbe. The geochemical composition of deposited and suspended matter was compared. The sediment input showed weak correlations with concentration and composition of river water. It also correlated poorly with flood duration and level as well as distance of trap position from the main river. This is due to the high variability of the inundation, different morphological conditions and the variability of sources. The composition of the deposits and the suspended matter in the river water was comparable. Hence, for the investigated river reach, the expected pollution of the floodplain sediments can be derived from the pollution of the suspended matter in the river during the flood wave. The deposition of polluted sediments on floodplains is characterised by a high local variability.

A plot-scale, rainfall-simulation study measured edge-of-field pollutant losses from conventional-till, strip-till, and no-till treatments in a burley tobacco production system. The field experiment results show that the conventional-till treatment yielded more total runoff than strip- and no-till treatments. Compared to the conventional-till treatment, both no-till and strip-till reduced the total mass losses of total suspended solids (TSS), total nitrogen (TN), total Kjeldahl nitrogen (TKN), nitrate (NO-N), ammonia (NH₃-N), total phosphorus (TP), orthophosphate (PO₄-P), and the insecticide chlorpyrifos in runoff. Although statistical analyses indicated that there was no significant difference between the no-till and strip-till practices, the no-till practice consistently yielded less edge-of-field pollutant loss than the strip-till practice. This research reinforces the body of knowledge documenting the effectiveness of conservation-tillage practices in reducing edge-of-field pollutant losses.

The simulation of ecosystems by mesocosms might be affected by artefacts due to the scale reduction implied in such experiments. The physico-chemical properties of water leaching out of mesocosms made of only 50 kg of agricultural soil were measured to demonstrate that they constitute reproducible systems. The soils were artificially contaminated with lead, atrazine, benzo(a)pyrene and Phenochlor. Physico-chemical parameters (redox potential, conductivity, pH, dissolved oxygen) and major ions were monitored in the leachates for six months. Even though these changed with time, in each sampling campaign they were similar for all of the mesocosms despite possible independent development of microbial and biological activity.

Runoff events were analysed in separated sewer systems in the town of Luxembourg. The relationships between Event Mean Concentrations of different pollutants and runoff patterns were evaluated. In addition, the inter-storm and intra-storm variability of the material transport were determined. Primarily, the variations in pollutant concentrations and loads are determined by the antecedent weather conditions. The presence of illicit sanitary inputs in one of the sewers produced a significant first flush effect as well as higher Event Mean Concentrations for pollutants. Furthermore, near the town of Trier 40 storms were analyzed in a small natural basin mainly influenced by runoff from a separated sewer system. Natural and artificial storm events were investigated in order to estimate the relationship between the pollutant sources in the channel and from the separated sewer system. Just like in the canalization of Luxembourg City the pollutant dynamics during natural storms are strongly influenced by pre-event hydrological conditions. The artificial storms behave differently. Despite little pre-rain, the maximum concentrations of toxic substances are comparatively low. A resuspension of sediment only occurs in the natural channel system, without the introduction of fines from the sewer system.

Various amendments and/or a plant cover (Agrostis stolonifera L.) were assessed for their potential to reduce trace element leaching in a contaminated soil under semi-arid conditions. The experiment was carried out in field containers and lasted 30 months. Five treatments with amendments (leonardite (LEO), litter (LIT), municipal waste compost (MWC), biosolid compost (BC) and sugar beet lime (SL)) and a plant cover and two controls (control without amendment but with plant (CTRP) and control without amendment and without plant (CTR)) were established. Drainage volumes were measured after each precipitation event and aliquots were analysed for pH, electrical conductivity (EC) and trace element concentrations (As, Cd, Cu, Pb and Zn). Soil pH and trace element extractability (0.01 M CaCl₂) at three different depths (0-10, 10-20 and 20-30 cm) were measured at the end of the experiment. Incorporation of amendments reduced leaching of Cd, Cu and Zn between 40-70% in comparison to untreated soil. The most effective amendments were SL, BC and MWC. At the end of the experiment, extractable concentrations of Cd, Cu and Zn were generally lower in all amended soils and CTRP compared to CTR. Soil pH decreased and extractability of metals increased in all treatments in relation to depth. Results showed that use of these amendments combined with healthy and sustainable plant cover might be a reliable option for “in situ” stabilization of trace elements in moderately contaminated soils.

The importance of the chemical composition in evaluating groundwater flow is discussed. Two different geological environments, a felsic volcanic region around San Luis Potosí (SLPB), Mexico, and a sedimentary basin, part of the Pannonian Basin (PB), in Hungary, were chosen to explore the effect of local, intermediate and regional groundwater flows on the chemical evolution of water in different geological circumstances. In the study areas contrasting stable isotopes and groundwater temperature values, as well as the chemical composition of groundwater were convenient tools to propose groundwater flow direction and to study contamination processes in the different groundwater flow systems. Results indicate that regardless of the geological framework variability of the chemical composition of the shallow (<100 m) groundwater is significant; at depth the chemical content of groundwater becomes homogeneous, and the concentrations are smaller than at shallow depths. The Cl- and NO- ₃ concentrations indicate mainly up- and downward vertical flow directions suggesting local flow systems in the shallow layers. The linear regression between Cl- and Na⁺ suggests that evaporation processes are the main control of the Cl- concentration. Deviations from the regression line suggest processes such as pollution at shallow depths in both study areas. Based on the distribution of Ca⁺², Mg⁺² and Na⁺, a lateral flow can be traced. The large dimensions of the geological units involved with the regional flow systems implies a long groundwater flow path, also these flows remain isolated from anthropogenic contamination, then groundwater has not been altered by human influence, although in the SLPB a communication between the local and intermediate flows has been found. Recharge areas of the local and intermediate flow systems are more vulnerable to contamination processes than the discharge areas, where the expected low dissolved oxygen content of ascending water could play a control. Differences in the lithology between the PB (sedimentary basin) and the SLPB (felsic volcanic basin) explain the contrasting saturation indices calculated for chalcedony and calcite and the lack of the expected development of HCO- ₃, SO-² ₄ Cl- facies and contrasting aerobic/oxidizing conditions.

In intensively cultivated areas, agriculture is a significant source of pesticides associated with storm runoff. When these pollutants enter aquatic receiving waters, they have potential to damage nearby aquatic ecosystems. Constructed wetlands are a best management practice (BMP) designed to help alleviate this potential problem. A constructed wetland system (180 x 30 m) comprised of a sediment retention basin and two treatment cells was used to determine fate and transport of a simulated storm runoff event containing the insecticide diazinon and suspended sediment. Wetland water, sediment, and plant samples were collected spatially and temporally over 55 d. Results indicated that 43% of the study's measured diazinon mass was associated with plant material, while 23 and 34% were measured in sediment and water, respectively. Mean diazinon concentrations in water, sediment, and plants for the 55-d study were 18.1 ± 4.5 μg/l, 26.0 ± 8.0 μg/kg, and 97.8 ± 10.7 μg/kg, respectively. Aqueous concentrations fluctuated in the wetlands between 51-86 μg/l for the first 4 h of the experiment; however, by 9 h, aqueous concentrations were approximately 16 μg/l. During the 55 d experiment, 0.3 m of rainfall contributed to fluctuations in diazinon concentrations. Results of this experiment can be used to model future design specifications for mitigation of diazinon and other pesticides.

A powerful 7.3 magnitude earthquake struck Taiwan on September 21, 1999. The stream water chemistry (pH, total alkalinity, conductivity, sodium, potassium, calcium, magnesium, ammonium, fluoride, chloride, sulfate, and nitrate) has been monitored since 1995 at the Guandaushi forestry riparian zone in central Taiwan. Collected data was used as a basis for comparing pre- and post-earthquake impacts. The pH, conductivity, and concentrations of Na, Ca, Mg, SO₄, and HCO₃ in stream water were lowest during the summer season, when stream water discharge was highest. On the other hand, the lowest concentrations of Cl, NH₄, and NO₃ in stream water occurred during the winter season, when stream water discharge was lowest. Also, K and F showed very little seasonal fluctuation in concentration. Downward trends in K and Ca were found 14 months prior to the earthquake; although, an upward trend occurred in NH₄ at the same time.

Extraction of natural gas from a confined coal aquifer requires the pumping of large amounts of groundwater, commonly referred to as produced water. Produced water from the extraction of coalbed natural gas is typically disposed into nearby constructed discharge ponds. The objective of this study was to collect produced water samples at outfalls and corresponding discharge ponds and monitor pH, electrical conductivity (EC), calcium (Ca), magnesium (Mg), sodium (Na), and alkalinity. Outfalls and corresponding discharge ponds were sampled from five different watersheds including Cheyenne River (CHR), Belle Fourche River (BFR), Little Powder River (LPR), Powder River (PR), and Tongue River (TR) within the Powder River Basin (PRB), Wyoming from 2003 to 2005. From Na, Ca, and Mg measurements, sodium adsorption ratios (SAR) were calculated, and used in a regression model. Results suggest that outfalls are chemically different from corresponding discharge ponds. Sodium, alkalinity, and pH all tend to increase, possibly due to environmental factors such as evaporation, while Ca decreased from outfalls to associated discharge ponds due to calcite precipitation. Watersheds examined in this study were chemically different form each other and most discharge ponds with in individual watersheds tended to increase in Na and SAR from 2003 to 2005. Since discharge pond water was chemically changing as a function of watershed chemistry, we predicted SAR of discharge pond water using a regression model. The predicted discharge pond water results suggested a high correlation (R ² = 0.83) to discharge well SAR. Overall, results of this study will be useful for landowners, water quality managers, and industry in properly managing produced water from the natural gas extraction.