The effects of heavy metal contamination (Cr, Cu, Pb, Cd) in the lower basin of the Salado River (Argentina) were studied on the zooplanktonic community. The determination of heavy metals in water and sediments was carried out in a previous study. Zooplankton was analyzed quali- and quantitatively. Total density, by-group density (Copepoda, Cladocera and Rotifera), micro and mesozooplankton density, biomass, species richness (S), and species diversity (H) were studied. The results showed that total density of zooplankton was significantly higher in the river than in the channels and streams (p < 0.001), with dominance of rotifers but a higher copepod biomass. Calanoida dominated over Ciclopoidea and Harpacticoida. Total species richness was 74, showing the highest values (59 and 56) at the points corresponding to the Salado River at localities Manucho and San Justo (MSR, SJSR) and the lowest ones in North and South channels (NCH, SCH), with 16 and 17 species, respectively), and in the two sampling stations of Las Prusianas stream (LP1, LP2), between 13 and 38 species. The species diversity showed low values (1.8 to 2.3) in channels and streams, and higher values (3.0) in the Salado River, at Manucho and San Justo. Absolute biomass varied in the order SJSR > MSR > LP1 > NCH > SCH > LP2, similarly to absolute density, which varied in the order SJSR > MSR > LP1 > NCH > SCH > LP2. The comparison of the content of heavy metals in water between the control site (SJSR) and the most contaminated sites showed significant differences with the North and Las Prusianas 1 and 2 channels (ANOVA p = 0.001; 0.012 and 0.011, respectively) and non-significant differences, although close to the significance level, with the South Channel and Manucho (p = 0.08; p = 0.059). The following positive correlations were found: depth with mesozooplankton density, H and S (p < 0.001); temperature with microzooplankton density, H and S (p < 0.004), and dissolved oxygen with mesozooplankton density, H and S (p < 0.01), but not with microzooplankton, indicating a higher tolerance of the organisms belonging to this fraction. A negative correlation was found between biomass of copepods and concentration of Pb and Cu (p < 0.05 and p = 0.01, respectively). Rotifers were the most tolerant to heavy metal contamination, followed by copepods and cladocerans. Diversity (H) and richness (S) were good indicators of stress of contaminated systems. The clustering of biological variables and the concentration of heavy metals in water and sediments showed three groups of environments: the first one was the main course of the river, with lower contamination by heavy metals and higher density, biomass, H and S, which separated clearly from the other two groups of the tributaries, composed by channels and streams. In the tributaries, r strategists and a few tolerant species, such as Eucyclops neumani, proliferated. The results of this study show that zooplankton responds as good descriptor of water quality, constituting an efficient tool to assess heavy metal contamination.

Methane oxidation within a passive methane oxidation barrier (PMOB) and the downward migration of molecular O₂, whose presence is necessary for the oxidation reaction to occur, were simulated using the finite element simulator TOUGH2-LGM. The goals of the study were to validate the use of TOUGH2-LGM by reproducing real field profiles obtained under different conditions and to evaluate the depth of O₂ penetration under several conditions. TOUGH2-LGM handles both advective and diffusive gas fluxes. The oxidation reaction was simulated by imposing a Neumann condition, i.e. CH₄ was extracted from pre-determined elements. The main variables of concern were the degree of water saturation of the PMOB, the pressure differential between its base and the surface, the position and thickness of the oxidation front and, finally, the oxidation rate, i.e. the rate at which CH₄ was removed from the system. Other important variables, such as the gas permeability and diffusion coefficient were obtained in the laboratory. Inspection of the results shows that TOUGH2-LGM was able to quite accurately reproduce the field profiles. The simulator also makes it possible to predict the depth of O₂ penetration as a function of pressure differential and humidity within the PMOB. This type of information is fundamental for the design of effective biocovers.

Frame and daughters directives for evaluating the ambient air quality have been adopted by the EU as a part of the new strategies for pollution prevention and control and environmental management. Therefore, the prediction of ozone concentration and the identification of episodes by modeling are fundamental for protecting and preventing the population and environment against the harmful effects of this species. Under this approach, ambient air quality (immission) data in three zones: A Guarda, Corrubedo and Verín (two coastal and one interior) of Galicia (NW Spain), were collected and evaluated using statistical tools. Punctual and functional background and standard levels of ozone and NOx in the three zones have been determined for detecting abnormal situations and identifying possible emission sources. With this aim, threshold values were established by defining confidence levels. Finally, ozone concentration has been forecasted by time series modeling. Descriptive and predictive models of ozone involving different parameters depending of the area considered have been developed. Satisfactory estimation of ozone concentration was obtained in the three cases with proved efficiency, since predictive values did not exceed the 95% confidence level.

This study determined the content of trace elements in coal ash collected from a coal-fired thermal power plant using local coal from Sawarak, Malaysia. This is crucial for the potential impact on the geoenvironment from its disposal and utilization; as coal ash has recently been produced locally in substantial amounts and very limited data is available. The trace elements concentrations presents in coal ashes are compared with the reported coal ash concentrations and the risk for the local wet tropical geoenvironment from the perspective of its vulnerability to these is studied for an indication of potential environmental implications on the wet tropics. The trace elements were found to be in concentrations that, if applied or inadvertently released into the environmental media, present a potential hazard and further necessary research in this regard is indicated.

The need for solutions to minimize the negative environmental impacts of anthropogenic activities Fhas increased. Sewage sludge is composed of predominantly organic matter and can be used to improve soil characteristics, such as fertility. Therefore, its application in agriculture is an adequate alternative for its final disposal. However, there is a lack of information on its long-term effects on soil changes in tropical areas. Thus, the objectives of this study were to determine (i) the effect of sewage sludge application on heavy metal build-up in soil and maize grains and leaves, and (ii) the effects of soil amendment with sewage sludge on the chemical properties of a Brazilian oxisol. Besides the increasing levels of Zn, Cu, Ni, and Cr, amending soil with sewage sludge also alters the distribution of these metals by increasing the mobile Phases, which correlated significantly with the increase in metal extraction with two single extractants, Mehlich 1 and DTPA (Diethylene triamine pentaacetic acid). The levels of Fe, Mn, Zn, and Cu in maize grains and leaves increased with the type and rate of sewage sludge application. Nevertheless, metal build-up in soil and plants was within the allowed limits. Significant differences were also found in soil characteristics like humic fractionation with the applied sewage doses. The data obtained does not indicate any expressive drawbacks in the use of sewage sludge as a soil amendment, as the heavy metal concentrations observed are unlikely to cause any environmental or health problems, even overestimated loadings, and are in accordance with the Brazilian regulations on farming land biosolid disposal.

The concentrations of As and Zn in 100 georeferenced soils uniformly distributed throughout the area affected by the spill from the Aznalcóllar mine (April 1998) were analysed at three depths (0-10, 10-30, and 30-50 cm) and on four dates (autumn-winter 1998, 1999, 2001, and 2004). For an estimate of the geochemical background, 30 unaffected soils near the edge of the spill were also analysed at the same depths. The soils were contaminated before the spill and, the accident seriously increased the concentration of As and Zn in the first 10 cm of almost all the affected soils. After the enormous efforts of cleaning up the tailings, around 45% of the soils had a concentration higher than 100 mg As kg⁻¹ dry soil, and some 35% had a concentration higher than 1,000 mg Zn kg⁻¹ dry soil. Both As and Zn penetrated between 10 and 30 cm in 25% and 45% of the soils, respectively, but reached 30 cm in only 12% of the soils. The remediation actions, especially the tilling and homogenisation of the uppermost 25 cm of the all soils, caused the As and Zn concentrations to decline in the soils, but this change was not very effective from the standpoint of pollution. Thus, 6 years after the spill, the uppermost 10 cm of 30% of the soils continued to have an As concentration higher than 100 mg As kg⁻¹, while the Zn concentration diminished considerably on the surface due to its greater mobility, accumulating between 10 and 30 cm in depth, where 20% of the soils continued to register more than 1,000 mg Zn kg⁻¹ dry soil.

This study examines the relationship between dissolved inorganic nitrogen (DIN: NH₄ ⁺ + NO₂ ⁻ + NO₃ ⁻) and dissolved organic nitrogen (DON) in river water and groundwater in an agriculturally-dominated catchment in south-east Spain, and estimates the contribution of DON to the total dissolved nitrogen (TDN) concentrations. The studied aquifer-dependent river system consists of Quaternary alluvial sediments deposited by the Guadalquivir River and its tributaries, with both river water and groundwater in the catchment being aerobic. DON is the predominant form of nitrogen in river water (72-97% of the TDN), whereas its proportion to TDN varies considerably in groundwater (<1-99%). A seasonal pattern in the concentration of dissolved nitrate in river water was observed, whereas DON concentrations showed no significant change during the study period. The export of DON from the Guadalquivir River is approximately 2 kg N ha⁻¹ year⁻¹ and is an order of magnitude higher than the export of DON from pristine catchments. Dissolved nitrate concentrations in groundwater were slightly higher in winter and DON concentrations were significantly lower (p < 0.05) in summer. It is found that agricultural soils constitute the main storage of organic nitrogen in the catchment with a steady leaching of high DON concentrations into the alluvial aquifer system (mean value 19.1 mg N L⁻¹), and so indicating that DON should not be overlooked in the nitrogen budgets of agriculturally-dominated catchments.

The loss of pendimethalin, a selective herbicide, was determined in runoff water from loamy soil plots of various surface slopes cultivated with tobacco, over a period of 193 days. Conditions were selected to simulate agricultural practices employed in the Mediterranean region. The surface slopes of plots were 0%, 2.5%, 5%, 7.5%, and 10% and both cultivated and uncultivated (control) areas were simultaneously monitored. The cumulative losses of pendimethalin in surface runoff, as percentage of the initial applied active ingredient, were 0.067% for tilled and 0.098% for untilled soil of 10% slope, while for the plots of 0% slope they were ten times lower, 0.006% and 0.009% respectively. The maximum concentrations in runoff water reached 15.87 μg L⁻¹ and were detected after the second run off event. The dissipation in top soil was studied for a period of 129 days. The half-lives that were calculated using first order kinetics ranged from 23 to 27.2 days in non-cropped soil and from 22.3 to 26.2 in tobacco plots.

Sampling was conducted at seven sites on, and at varying distances adjacent to, the Island of Montréal (Québec, Canada), and as far as 1,100 km away in Northern Québec, to explore the hazard potential of snowpacks in remote, rural, and urban environments. Ecotoxic effects of melted snow were ascertained with a suite of small-scale bioassays representing several aquatic taxonomic groups (bacteria, micro-algae, micro-invertebrates, fish liver cells) as well as with biomarker measurements determined with a rainbow trout primary hepatocyte (RTPH) assay. Bioassays undertaken with the cnidarian Hydra attenuata and RTPH cell assays, and to a lesser extent with the micro-alga Pseudokirchneriella subcapitata, proved particularly sensitive to infer the presence of bio-available pollutants in snow samples collected from all sites, thereby suggesting their contamination (at least) via atmospheric sources. Furthermore, biomarker responses indicated that snow samples presumably included metals (free Zn biomarker), organics (CYP 1A1 biomarker), estrogens (alkali-labile phosphate biomarker) as well as chemicals capable of causing oxidative stress (LPO biomarker), depending on the site being considered. Overall, effects data acquired during this preliminary investigation on the ecotoxicity of snowpacks submit that adverse impact toward aquatic biota is conceivable at some sites during spring meltdown. Because snow has a recognized affinity for sequestering solids and contaminants of atmospheric origin, future studies aimed at identifying sources and chemicals implicated in observed effects are legitimate endeavors.

The present research reproduces the chemical and microbiological reactions that occur naturally when a metal sulfide is discharged onto a natural soil, with special emphasis on iron cycle. The role of indigenous microbiota from an extremely acidic site on both weathering and attenuation processes related to the iron mobilization has been studied and the iron cycle has been reproduced at laboratory scale. In the first stage, the weathering phase, a residual sulfide mineral was bioleached using a mixed culture of iron-oxidizing bacteria isolated from the own substrate. The acid liquor obtained (pH 2), with a high metal concentration (160 mM in total iron), was filtered and neutralized. Solids obtained from the two sources (from the weathering process and after the neutralization stage) were characterized by X-ray and scanning electron microscope/energy dispersive X-ray spectroscopy, resulting ferric iron precipitates such as jarosites, goethites, and ferrihydrites with different crystalline properties. The contribution of ferric iron-reducing bacteria on the attenuation of high-content iron effluents was also studied. Mixed cultures of ferric iron-reducing bacteria, isolated from those acidic substrates, were active in reducing soluble ferric iron (60 mM in concentration), and a 66% of bioreduction was reached after 15 days. Dissimilatory ferric iron reduction has been achieved with adapted cultures at pH values from 7 to 4.