The Tinto and Odiel rivers are heavily affected by acid mine drainage from mining areas in the Iberian Pyrite Belt. In this work we have conducted a study along these rivers where surface water samples have been collected. Field measurements, total dissolved metals and Fe and inorganic As speciation analysis were performed. The average total concentration of As in the Tinto river (1975 μg L-1) is larger than in the Odiel river (441 μg L-1); however, the mean concentration of As(III) is almost four times higher in the Odiel. In wet seasons the mean pH levels of both rivers (2.4 and 3.2 for the Tinto and Odiel, respectively) increase slightly and the amount of dissolved total arsenic tend to decrease, while the As(III)/(V) ratio strongly increase. Besides, the concentration of the reduced As species increase along the water course. As a result, As(III)/(V) ratio can be up to 100 times higher in the lower part of the basins. An estimation of the As(III) load transported by both rivers into the Atlantic Ocean has been performed, resulting in about 60 kg yr-1 and 2.7 t yr-1 by the Tinto and Odiel rivers, respectively. Total arsenic concentration decreases along the water basins, however the As(III)/(V) ratio increases.

Biodegradation of chlorobenzenes was assessed at an anoxic aquifer by combining hydrogeochemistry and stable isotope analyses. In situ microcosm analysis evidenced microbial assimilation of chlorobenzene (MCB) derived carbon and laboratory investigations asserted mineralization of MCB at low rates. Sequential dehalogenation of chlorinated benzenes may affect the isotope signature of single chlorobenzene species due to simultaneous depletion and enrichment of 13C, which complicates the evaluation of degradation. Therefore, the compound-specific isotope analysis was interpreted based on an isotope balance. The enrichment of the cumulative isotope composition of all chlorobenzenes indicated in situ biodegradation. Additionally, the relationship between hydrogeochemistry and degradation activity was investigated by principal component analysis underlining variable hydrogeochemical conditions associated with degradation activity at the plume scale. Although the complexity of the field site did not allow straightforward assessment of natural attenuation processes, the application of an integrative approach appeared relevant to characterize the in situ biodegradation potential. Lines of evidence for in situ biodegradation of chlorinated benzenes in an anoxic aquifer by combining hydrogeochemical and stable isotope data with multivariate statistics.

The objectives of this study were to quantitatively estimate the distribution of arsenic with its speciation and to identify potential pathways for transformation of arsenic species from samples of water, sediments, and plants in the ecosystem affected by the Cheongog Spring, where As(V) concentration reached levels up to 0.270 mg L−1. After flowing about 100 m downstream, the arsenic level showed a marked reduction to 0.044 mg L−1 (about 84% removal) without noticeable changes in major water chemistry. The field study and laboratory hydroponic experiments with the dominant emergent plants along the creek (water dropwort and thunbergian smartweed) indicated that arsenic distribution, reduction, and speciation appear to be controlled by, (i) sorption onto stream sediments in exchangeable fractions, (ii) bioaccumulation by and possible release from emergent plants, and (iii) transformation of As(V) to As(III) and organic species through biological activities. Biogeochemical reactions with emergent plants and sediments control the fate of arsenic along creeks originating from a high-As Spring.

A solid-phase microextration-based sampling method was employed to determine the concentrations of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and its metabolites, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD), 1,1-dichloro-2,2-bis(p-chlorophenyl)ethene (DDE) and 1-chloro-2,2-bis(p-chlorophenyl)ethene (DDMU), in two estuarine bays, Daya Bay and Hailing Bay, of South China. Six DDT components including p,p'-DDT, o,p'-DDD, p,p'-DDD, o,p'-DDE, p,p'-DDE, and p,p'-DDMU were detected in Hailing Bay, while only p,p'-DDD was found in Daya Bay. p,p'-DDD was the most abundant DDT component in both bays, sharply different from the previous finding in the water column of the Palos Verdes Shelf, California, USA that p,p'-DDE was prevalent. In addition, the occurrence of p,p'-DDMU (with a range of 0.047-0.21 ng/L in Hailing Bay) has not been reported around the globe, and its presence in our study region appeared to stem from dehydrochlorination of p,p'-DDD, favored under aerobic conditions, but further investigations are clearly needed to confirm the mechanism for generation of DDMU in estuarine environments. DDT and its metabolites, particularly p,p'-DDMU, are detected in the water column of two estuarine bays in South China using a SPME-based sampler.

The presence of triclosan, a widely-used antibacterial chemical, is currently unknown in higher trophic-level species such as marine mammals. Blood plasma collected from wild bottlenose dolphins (Tursiops truncatus) in Charleston, SC (CHS) (n = 13) and Indian River Lagoon, FL (IRL) (n = 13) in 2005 was analyzed for triclosan. Plasma concentrations in CHS dolphins ranged from 0.12 to 0.27 ng/g wet weight (mean 0.18 ng/g), with 31% of the sampled individuals having detectable triclosan. The mean IRL dolphin plasma concentrations were 0.072 ng/g wet weight (range 0.025-0.11 ng/g); 23% of the samples having detectable triclosan. In the CHS area, triclosan effluent values from two WWTP were both 190 ng/L and primary influents were 2800 ng/L and 3400 ng/L. Triclosan values in CHS estuarine surface water samples averaged 7.5 ng/L (n = 18) ranging from 4.9 to 14 ng/L. This is the first study to report bioaccumulation of anthropogenic triclosan in a marine mammal highlighting the need for further monitoring and assessment. Triclosan in bottlenose dolphin plasma and their environment.

The concentration of chemical oxygen demand (COD), a common proxy for dissolved organic matter (DOM), was measured at seven drinking-water reservoirs and four streams between 1969 and 2006. Nine of them showed significant DOM increases (median COD change +0.08 mg L−1 yr−1). Several potential drivers of these trends were considered, including air temperature, rainfall, land-use and water sulfate concentration. Temperature and precipitation influenced inter-annual variations, but not long-term trends. The long-term DOM increase was significantly associated with declines of acidic deposition, especially sulfur deposition. Surface water sulfate concentrations decreased from a median of 62 mg L−1–27 mg L−1 since 1980. The magnitude of DOM increase was positively correlated with average DOM concentration (R2 = 0.79, p < 0.001). Simultaneously, DOM concentration was positively correlated with the proportion of Histosols within the catchments (R2 = 0.79, p < 0.001). A focus on the direct removal of DOM by water treatment procedures rather than catchment remediation is needed. Rising DOM levels in surface waters are due to changes in soil chemistry caused by a reduction of acidic deposition.

This study monitored nitrate levels in well water and analyzed their association with well attributes (physicochemical parameters of water, location, livestock farming conditions) in a nitrate-polluted, animal industry district in central Miyakonojo Basin, southern Kyushu, Japan, to characterize the nitrate status of groundwater in the district. Water quality varied considerably among the wells, with nitrate-N concentration and natural nitrogen-15 abundance in nitrate-N (δ¹⁵N-NO₃) ranging from 1.1-44.6 mg L⁻¹ and 4.2-17.8[per thousand], respectively. There was a significant positive correlation between nitrate-N concentration and δ¹⁵N-NO₃. Nitrate-N concentration was higher in wells located at higher elevations, having larger areas of livestock barns within a 100-m radius and with higher animal populations. Wells in pig farms showed a higher nitrate tendency than those in the other situations (cattle farm, poultry farm, non-livestock farm and non-farmer). The results show that the nitrate status of groundwater in the district has not been drastically changed since 1996, and the nitrate in the wells is of multiple origins (e.g. chemical fertilizer, animal wastes) with a tendency for higher contribution of animal wastes in more heavily polluted wells. The results also highlight a need for further regular monitoring of groundwater quality in the district particularly for wells; (1) located at higher elevations, (2) with a large area of livestock barns nearby, (3) in farms with a high animal population and/or (4) in pig farms.

The southern sector of the Guadiana River basin (GRB) drains the central-western part of the Iberian Pyrite Belt, an area with many polymetallic sulfide deposits and residues of mining activities that under oxidizing conditions generate an acidic leachate with large quantities of sulfates, metals, and metalloids in solution. These acidic leachates seep into the fluvial system contaminating the surface water bodies and increasing the contamination risk for local populations and riparian habitats. The present study was carried out both in Portugal and Spain with the main aim of identifying the principal contamination sources that produce acid mine drainage (AMD) in the southern part of the GRB and to evaluate the seasonal variations of water quality affected by AMD. The physicochemical parameters determined in the field (temperature, electrical conductivity, pH, redox potential, and dissolved oxygen) are discussed and interpreted together with the hydrochemical analysis of surface water samples collected at 79 points of observation. The data show a strong seasonal variation of surface water quality with poorer water quality standards during the dry season. It is also possible to observe that there is a natural decrease in pollution levels with increasing distance from the pollution source (mining areas). Acidic leachates are gradually neutralized as they drain away from the mining areas depositing Fe-(Cu-Al) bearing secondary minerals. There is also an important contaminant load reduction in the estuary area as a result of the mixing process with seawater. This contributes to a loss of the metals in solution due to both dilution and precipitation, as a result of pH increase.

In Tabasco the petroleum industry pollutes soil recurrently by oil spills. We analysed Pb, V, Ni and Cr concentrations in water samples, and total metal contents and metal fractions in soil samples of contaminated and non-contaminated soils and in sediments. Besides, we determined Eh, pH, DOC and major ions in water and Eh, pH, Corg in soils and sediments. Sediments contained considerably larger heavy metal (HM) concentrations than soils. Local background concentrations of V, Ni and Cr in soils are larger than global means and oil spillages have not added these metals in quantities that exceed the natural variation. Spillage of formation water increases Pb concentrations in soils, particularly in mobile fractions. The contribution of the oil industry to HM loads is diluted by large fluvial water and sediment discharges and difficult to assess by comparison of total metal contents. Therefore, easily mobile metal fractions are much better indicators.

Episodic acidification of surface waters has been observed in the Great Smoky Mountains National Park, similar to other forested watersheds with base-poor bedrock in the eastern US receiving acids from atmospheric deposition. Three remote, forested, high-elevation streams were selected in the Little Pigeon River watershed for study; two of which brook trout have extirpated, and believed to have resulted from severe acidity during stormflows. This research characterized stream chemistry during episodes in order to better understand potential factors that contribute to rapid drops in pH and acid neutralizing capacity (ANC) during stormflows. Autosamplers initialized by sondes, collected samples during storm events for analysis of pH, ANC, cations, and anions over a 15-month period. ANC and pH depressions, and increased concentrations in sulfate, nitrate, and organic acids were observed for all storms at each study site. ANC contribution analysis indicated sulfate was the strongest contributor to ANC depressions, but nitrate, cation dilution, and organic acids were also significant in some cases. Acidic deposition appears to be the primary source of episodic acidification, supported also by the finding that larger stormflows preceded by long, dry periods resulted in significantly larger pH depressions. It appears stream acidification episodes may be driven by acid deposition. However, this study documents the variability of several ion contributors to observed stormflow ANC depressions illustrating the spatial and temporal complexity of watershed processes that influence this phenomenon.