The processes impacting arsenic toxicity are a function of molecular speciation, where risk from chronic exposure to the reduced arsenic species is estimated to be four orders of magnitude higher than many oxidized arsenic species. While the adverse health effects of arsenic are generally well known, the impact of speciation on carcinogenic and noncarcinogenic adverse health effects has rarely, if ever, been considered in traditional chronic arsenic exposure risk assessments. Utilizing standard Environmental Protection Agency protocol, lifetime cancer risk and hazard quotient are calculated for chronic arsenic exposure at the local, regional, and national scale to characterize potential risk as a function of arsenic speciation. Additionally, the antagonistic and synergistic impacts of biogeochemical processes on arsenic bioavailability and bioaccessibility are discussed and show chronic exposure risk is likely to be reduced below some maximum value calculated for reduced arsenic species.

Petroliferous activities in Brazil have an accelerated development in the last years. As a consequence, the incidence of environmental accidents such as oil spills and contamination of soils has increased significantly. Therefore, it is extremely necessary to develop remediation techniques with lower costs, decontamination efficiency and impact minimisation. The aim of this work was to evaluate Sebastiania commersoniana phytoremediation potential in soil contaminated by petroleum. This species, which is a native tree, was selected due to its proven capacity for surviving in areas contaminated by petroleum. Experiments were carried out with soils that were vegetated but non-contaminated, soils that were freshly contaminated (25, 50 and 75 g kg⁻¹) but non-vegetated, and soils that were vegetated and contaminated, samples were collected 60 and 424 days after contamination with the purpose of evaluating the percentage of petroleum degradation in relation to the time. The results obtained in the present study allow us to state that S. commersoniana proves to be tolerant to petroleum contamination with respect to plant's growth. The degradation of petroleum hydrocarbons was evaluated by gas chromatography with a flame ionisation detector (GC-FID) equipped with a capillary column HP-5 (5% phenyl-methylpolysiloxane, 30 m; 0.25 mm; 0.25 μm). According to chromatographic analysis, samples in contact with S. commersoniana showed a significant area reduction of the hydrocarbon peaks. Analysis of the 60-day samples showed a reduction of petroleum hydrocarbons area higher than 60% and the 424-day samples showed a reduction higher than 94%, which demonstrates that a petroleum degradation process is occurring.

Extended persistence of enteric bacteria in coastal sediments and potential remobilization of pathogens during natural turbulence or human activities may induce an increased risk of human infections. In this study, the effect of sediment characteristics such as particle grain size and nutrient and organic matter contents on the survival of fecal indicator bacteria (FIB) including total coliforms, Escherichia coli, and Enterococcus was investigated. The experimentation was carried out for 50 days in microcosms containing lake water and different contaminated freshwater sediments in continuous-flow and batch conditions. Results of this study revealed: (1) extended FIB survival in sediments up to 50 days, (2) higher growth and lower decay rates of FIB in sediments with high levels of organic matter and nutrients and small (mainly silt) grain size, and (3) longer survival of Enterococcus sp. compared to E. coli and total coliforms. FIB survival in sediments and possible resuspension are of considerable significance for the understanding of permanent microbial pollution in water column and therefore human risk during recreational activities.

Chemical reduction of the hexavalent chromium, Cr(VI), present in contaminated soil and groundwater was carried out in a slurry reactor under dynamic conditions (120 rpm and 25°C) using different reductants [ferrous sulphate (Fe(II))], sodium bisulphite, sucrose, ascorbic acid and zerovalent iron (ZVI)] in order to evaluate the influence of the reductant on the redox process. Chemical analysis of the contaminated soil revealed a Cr(VI) concentration of 528 ± 31 mg kg⁻¹. Batch studies under dynamic conditions (slurry reactor) using different [Cr(VI)]/[reductant] molar ratios revealed that only Fe(II) and ZVI species can promote both reduction of Cr(VI) and immobilisation of Cr(III) (formation of an insoluble hydroxide compound). It was verified that 1.0 g of ZVI is capable of converting 104 ± 5 mg of Cr(VI) in Cr(III). A kinetic redox study was carried out using ZVI in different conditions. In all cases, it was verified that Cr(VI) reduction follows a pseudo-first-order kinetic behaviour. The dependence of the pseudo-first-order kinetic rate constant, k obs, on [ZVI] indicates that the redox process taking place in the slurry reactor is rather complex. A phenomenological kinetic equation for the redox process taking place in the slurry reactor was presented in order to describe the behaviour of k obs under non-ideal conditions.

The aim of this survey was to assess metal concentrations in precipitation over the Aegean Sea and to identify possible source regions that contribute to their long-range transport to the northeastern Mediterranean. Total metal concentrations in 37 rainwater samples collected on the island of Lesvos showed a high variability depending mostly on the origin of the air masses influencing the rain events assessed by 4-day back trajectories. Concentrations of Al, Fe, Mn, Cu, Pb, Zn, Cr and Ni were rather similar to those found at other coastal sites in the Mediterranean basin, but Cd was significantly lower. The calculation of crustal enrichment factors of the metals along with the statistical analysis of the results showed that Saharan dust storms supply significant amounts of natural Al, Fe, Mn, Cr and Ni to the northern Aegean atmosphere, although some amounts of Cr and Ni are also contributed from anthropogenic sources. On the other hand, anthropogenic emissions largely determine Pb, Cu, Cd and Zn loads, although not all four metals follow the same enrichment and transportation pattern.

Impacts of heavy metal concentrations in sediments on the gastropod community structure were assessed in the coastal waters of Dumai, Sumatra, Indonesia. The objective of this study was to relate the levels of heavy metal pollution with the changes of gastropod community structure in the study area. Concentrations of Cd, Cu, Pb, Zn, Ni, and Fe in surface sediments collected from five sampling stations were analyzed and correlated with the abundance, species richness, and diversity of gastropod populations. Sediments at stations with more anthropogenic activities accumulated higher concentrations of heavy metals and consequently displayed lower abundances, lower species richness and diversity; while stations with lower heavy metal concentrations in sediments showed the opposite pattern in gastropod community metrics. The above findings are complemented by significant negative correlations p < 0.05-0.01) between concentrations of Cd, Cu, Pb, Zn, and Ni in the sediments and gastropod abundance and species richness. Among the metals analyzed, Cu and Zn had strongest negative correlations with the gastropod diversity which suggests that these metals may be the most detrimental to gastropod populations in the mangrove area of Dumai coastal waters.

Roe deer (Capreolus capreolus) antlers are a useful tool for historical biomonitoring because they accumulate potential bone-seeking pollutants (Pb) and are naturally standardized environmental samples. Lead concentrations were measured in 45 antlers of roe deer, shot in the period 1925-2003 in the Upper Meža Valley, Slovenia, where lead production started at the end of the nineteenth century. Extremely high levels of lead were determined in the antlers (mean (SD) 54.7 (33.5) mg/kg, dry weight; range 2.69-554 mg/kg), exceeding previously reported levels of Pb in roe deer antlers from Europe. After the cessation of primary lead production in 1989, lead levels in antlers have been declining but are still high (period 2000-2003: mean (SD) 5.81 (6.60) mg/kg; range 2.69-7.74 mg/kg) compared with other areas of Slovenia. Spatial comparison confirmed that the lead contamination declines with distance from the emission source. The study confirmed the exceptional potential of roe deer antlers as a bioindicator of lead contamination of the environment.

Lura stream flows in the populated and industrialized conurbation North of Milan, Italy. The area suffers a sprawling urbanization which is leading to major alterations in water quality, hydrology and morphology of streams. These water bodies are known as effluent-dominated streams, because most of the baseflow is given by Wastewater Treatment Plant (WWTP) discharges. In this paper, a 5 year long assessment of Lura stream is presented and the collected data is discussed to understand overall ecological quality. Multivariate analysis carried out on macroinvertebrate assemblages and environmental variables suggests that invertebrate communities suffer severe alteration both upstream and downstream WWTP discharges. Results indicate that the high polluting loads coming from WWTP discharges affect seriously the stream water quality, but the most important cause of impairment are pulse perturbations related to the modified hydrology, causing droughts and flash floods, and to the spills of untreated sewage from overflows during rain events.

In Russia in 1950-1960 solutions for the localization and storage of large volumes of liquid radioactive waste produced during defensive tasks were accomplished using natural and man-made water objects. At present, they are non-isolated from the environment and radioactive waste storage facilities constitute a serious potential menace. These objects are not allowed by the current legislation of the Russian Federation on environmental protection and safety. However, they do exist and there are no definite and approved engineering solutions regarding their removal. One of these objects is the Techa Cascade of Reservoirs (TCR) of the Mayak plant. In this article, TCR protection requirements are based on and formalized taking into account the legislation of the Russian Federation and the biospheric approach to the radiation protection of humans and the environment. Special safety requirements are needed because the standard argument “from human exposure to discharge standards” is invalid owing to the fact that the possibility of using water objects that have had contact with the TCR is restricted by law.

Nitrogen removal in wetlands is achieved through two pathways: (a) N cycling and (b) storage. N cycling is a permanent removal pathway. There has been an increasing interest in the development of technologies to alleviate permanent nitrogen removal limitation in constructed wetlands by ensuring prevalence of conditions enhancing N cycling. The purpose of this study is to review an emerging technology of vegetated submerged bed constructed wetland system aimed at improving nitrogen removal in wetlands through rational system design. The design and performance of this system type is evaluated. The oxygen transfer capacity and nitrogen removal mechanisms on system performance are evaluated. Constructed wetland combinations most commonly consist of vertical flow (VF) and horizontal flow (HF) beds where VF and HF are aimed at nitrification and denitrification, respectively. Nitrate nitrogen accumulation is the most limiting factor in typical VF based systems.