Immobilization of metals by two materials (zeolite, AZ, and a synthetic, carbonate-rich material, “slovakite”, SL) was tested in a pot experiment with two soils from urban areas of Sevilla and two soils affected by a mine spill. Barley (Hordeum vulgare L. Hispanic) was grown in the pots, and metal contents were measured after 31 days in shoots and roots. Available metal was estimated by extraction with CaCl₂ (readily soluble), ethylenediaminetetraacetic acid (EDTA; plant available), a mixture of organic acids (soluble by root exudates), and glycine (bioaccessible by ingestion). Neither treatment caused significant differences on plant growth or metal contents of shoots, whereas roots contained more Cu in the SL treatments. Root Zn uptake was reduced in all cases, but reduction of Pb in roots was observed only in AZ treatments of the mine-spill soils. The effects on metal availability were often method-dependent. Decrease of CaCl₂ data were observed only in the mine-spill soils. EDTA-soluble metals were clearly decreased by both materials. Bioaccessible Zn were decreased by either material in several cases (but not in the most heavily polluted soil), whereas Cu or Pb data were less conclusive.

The high radioactivity and trace elements in drinking water are common concerns for human health. The aim of this study was to investigate the eligibility of groundwater for drinking purpose in terms of both radioactivity and trace element contents in Eskisehir Region (Turkey). The study area is located in a highly populated residential area where water supply is mostly met from groundwater. The area is about 20,000 km², where igneous, metamorphic, and sedimentary rocks are exposed. The 209 water samples collected from 84 water resources (including thermal waters) were analyzed with respect to major ions, trace elements, and radioactivity (gross alpha and gross beta) during both in wet and dry seasons. Based on the analysis results, trace elements in 49 samples of 84 water resources were over the limits of Code TS 266 1997 (Turkish Drinking Water Standards) and WHO 1993 standards. Particularly, Fe, Mn, Al, As, Ba, Zn, Cr, Cu, and B ion concentrations exceeded the limits. The gross alpha values in 18 locations and gross beta values in three locations also exceeded the limits of aforementioned standards in terms of radioactivity (gross alpha = 0.1 Bq L⁻¹; gross beta = 1 Bq L⁻¹). Furthermore, water radioactivity levels were close to the allowable limits in 33 water resources. The obtained results explicitly indicate that there is a strong relationship between the higher radioactivity-trace element contents and geochemical composition of rocks, which controls the radioactivity and trace element concentrations present in the aquifer.

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.

A pot experiment was conducted to study the effect of 7 intercrops on Cd uptake by maize. The intercrops included cowpea (V. unguiculata (L.) Walp.), purple haricot (L. purpureus (L.) Sweet.), chickpea (C. arietinum L.), alfalfa (M. sativa L.), teosinte (E. mexicana Schrad.), amaranth (A. paniculatus L.) and rape (B. napus L.). The results showed that most legumes substantially increased Cd uptake by maize during vegetative growth. Leaf tissue of maize grown with legumes averaged 5.05 mg kg⁻¹ higher Cd than that grown with nonlegumes, or 2.42 mg kg⁻¹ higher than the control. However, the effect of intercrops on Cd uptake by maize became small during reproductive growth. Since chickpea resulted in a relatively large maize bioconcentration factor of 2.0 and large transfer factor of 0.55, it is regarded as the most valuable intercrop for enhancing Cd extraction from soil by maize. The results suggest that intercropping might be a feasible practice in facilitating phytoremediation.

To evaluate the long-term effect of wastewater application on soil physical properties, two treatment sites, close to Taupo and Levin, New Zealand, and non-irrigated control sites were compared. The soil at Taupo was a silt loam and has received wastewater application for 12 years. The soil at Levin is a sand, and has been wastewater irrigated for 22 years. The disposal blocks at both sites had a higher pH, a higher organic matter (OM) content, a lower bulk density, and thus higher total porosity, but a lower macroporosity than the control sites. The disposal block at the Levin site showed a higher hydrophobicity than the control block, which coincided with the higher soil carbon. In contrast, the Taupo soil showed a higher hydrophobicity at the control site, the site with the lower OM content. Long-term wastewater irrigation resulted in a higher aggregate stability, and changes of the total porosity following stress application were lower, suggesting higher internal soil strength. The hydraulic conductivity close to saturation was also higher in the disposal blocks. The soil mechanical strength, as determined by the precompression stress value was, however, slightly lower in the disposal blocks and not correlated with the aggregate stability.

Selected trace metals were determined in stormwater runoff and sediments of the highly urbanized Brunette watershed in Metro-Vancouver. Surface sediment samples from three tributaries and a lake between 1974 and 1998 were analyzed for total and acid-extractable trace metals. Metal bioavailability was also investigated using Chelex-100 resin. Sediment geochemistry was determined by sequential extraction. Total trace metal concentrations decreased as stormwater moved through the hydrologic gradient of stormwater runoff, headwater stream to outflow river. The percentage of dissolved metals increased downstream largely due to disposition. Higher concentrations of particle-associated trace metals were flushed in stormwater runoff as the rainfall and total suspended solids transport increased. The highest trace metal levels were found in the lower reaches of a creek before entering the lake and in the lake where organic matter accumulated. Copper was associated with the organic/sulphur sediment components, whereas iron and manganese were mainly mineral-bound. Zinc concentrated in the easily acid reducible phase, augmented by increasing traffic and development. At least half of the sediment-bound lead was associated with the easily acid reducible and organic/sulphur-bound phases with an overall decrease as lead has been phased out as a gasoline additive.

The environmental behaviour of metolachlor and diuron was studied in the Central-western region of Brazil, by means of a field study where six experimental plots were installed. The soil was classified as a Latosol, and the soil horizons were characterized. Sorption of metolachlor and diuron was evaluated in laboratory batch experiments. Metolachlor and diuron were applied to the experimental plots on uncultivated soil in October 2003. From this date to March 2004, the following processes were studied: leaching, runoff and dissipation in top soil. K oc of metolachlor varied from 179 to 264 mL g⁻¹ in the soil horizons. K oc of diuron in the Ap horizon was 917 mL g⁻¹, decreasing significantly in the deeper horizons. Field dissipation half-lives of metolachlor and diuron were 18 and 15 days, respectively. In percolated water, metolachlor was detected in concentrations ranging from 0.02 to 2.84 μg L⁻¹. In runoff water and sediment, metolachlor was detected in decreasing concentrations throughout the period of study. Losses of 0.02% and 0.54% of the applied amount by leaching and runoff, respectively, were observed confirming the high mobility of this herbicide in the environment. In percolated water, diuron was detected with low frequency but in relatively high concentrations (up to 6.29 μg L⁻¹). In runoff water and soil, diuron was detected in decreasing concentrations until 70 days after application, totalizing 13.9% during the whole sampling period. These results show the importance of practices to reduce runoff avoiding surface water contamination by these pesticides, particularly diuron.

Bivalve mussels can concentrate pollutants which, in high amounts, can cause cellular, physiological and behavioral changes. The gill mucus is essential for many metabolic and behavioral procedures on marine mussels including the response to environmental pollution. The present work analyzed the mucous cell number in Mytella falcata gill filaments from three sites of Santos estuary (Brazil) with different levels of sediment contamination named as sites A, B, and C. Site A is located at a low impacted region of the estuary, and sites B and C are under influence of port activities, domestic sewage, and industries like a still mill located in front of site C (the most contaminated area with high amounts of polycyclic aromatic hydrocarbons). An increase in mucous cell number was detected in animals from sites B and C, when compared to site A; this increase occurred preferentially in the frontal zone and was related to sediment contamination. Mucous cell analysis can be used as an efficient biomarker. It is suggested that mucus produced in lateral and abfrontal zones is responsible for eliminating pollutants previously absorbed and mucus produced in frontal zone is responsible for pollutant arrest and elimination as pseudofeces.

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.