To assess strategies for mitigating Pb and As transfer into leafy vegetables from contaminated garden soils, we conducted greenhouse experiments using two field-contaminated soils amended with materials expected to reduce metal phytoavailability. Lettuce and mustard greens grown on these soils were analyzed by ICP-MS, showing that some Pb and As transfer into the vegetables occurred from both soils tested, but plant Pb concentrations were highly variable among treatment replicates. Soil-to-plant transfer was more efficient for As than for Pb. Contamination of the leaves by soil particles probably accounted for most of the vegetable Pb, since plant Pb concentrations were correlated to plant tissue concentrations of the immobile soil elements Al and Fe. This correlation was not observed for vegetable As concentrations, evidence that most of the soil-to-plant transfer for this toxic metal occurred by root uptake and translocation into the above-ground tissues. A follow-up greenhouse experiment with lettuce on one of the two contaminated soils revealed a lower and less variable foliar Pb concentration than observed in the first experiment, with evidence of less soil particle contamination of the crop. This reduced transfer of Pb to the crop appeared to be a physical effect attributable to the greater biomass causing reduced overall exposure of the above-ground tissues to the soil surface. Attempts to reduce soil Pb and As solubility and plant uptake by amendment at practical rates with stabilizing materials, including composts, peat, Ca phosphate, gypsum, and Fe oxide, were generally unsuccessful. Only Fe oxide reduced soluble As in the soil, but this effect did not persist. Phosphate amendment rapidly increased soil As solubility but had no measurable effect on either soil Pb solubility or concentrations of Pb or As in the leafy vegetables. The ineffectiveness of these amendments in reducing Pb transfer into leafy vegetables is attributed in this study to the low initial Pb solubility of the studied soils and the fact that the primary mechanism of Pb transfer is physical contamination.

To clarify the relationship between the transport distance of spheroidal carbonaceous particles (SCPs) and particle size, we investigated the spatial distribution of SCP sizes in swimming pool deposits in the central Osaka Plain, central Japan. Median particle size of SCPs generally decreases with distance (0 to ∼20 km) downwind from the local coastal industrial area where SCP sources are distributed widely. This suggests that most SCPs found in the study area are derived from the industrial area. Samples with >40 % of particles >20 μm were predominantly collected within 2 km of the industrial area, while samples with >40 % of particles <10 μm were mostly collected over 10 km from the industrial area. Based on the results of our study and previous studies, we conclude that a higher proportion of particles of size >20 μm indicates that the origin of SCPs is within a few kilometres upwind of the sample site, whereas the presence of higher proportion of particles <10 μm indicates that their source is generally further than 10 km upwind. However, other factors may affect the size distribution of SCPs at a given location (e.g. fuel type, quality of the particle precipitator and topography of the terrain). Pool deposits provide more suitable samples than lake sediments for investigating atmospheric precipitation.

Thus far, members of the genus Dehalococcoides are the only microorganisms known to dehalogenate chlorinated ethenes to ethene and thereby detoxify these common groundwater pollutants. Therefore, it is important to characterize the taxonomic and functional diversity of these key microorganisms and their reductive dehalogenase (RDase) genes in contaminated aquifers for assessing the natural attenuation potential. Little is known about the diversity of RDase genes under field conditions or in laboratory systems under selective pressure during dechlorination activities. Here, we evaluate the diversity of Dehalococcoides sp. and three RDase genes in groundwater as well as in water from a constructed wetland and microcosms setup with contaminated groundwater from the same field site in Bitterfeld (Saxony-Anhalt, Germany). The presence and relative abundance of Pinellas and Cornell subgroups of Dehalococcoides was evaluated by a novel direct sequencing method, which revealed that all sequences were identical and affiliated to the Pinellas subgroup. Contrarily, our results showed remarkable differences at the functional gene level between the systems. Of the vinyl chloride reductase genes, vcrA was detected in samples from the groundwater, wetland, and microcosms, whereas bvcA was only found in wetland and microcosm samples. The trichloroethene dehalogenase gene, tceA could not be detected at all, although complete dehalogenation activity of higher chlorinated ethenes was observed. Our study demonstrates that although the Dehalococcoides 16S rRNA gene sequences retrieved from the investigated systems were identical, the RDase gene diversity varied among the systems, according to the spectrum of the chlorinated ethenes present.

Chlorpyrifos (O, O-diethyl-O-(3,5,6-trichloro-2-pyridyl) phosphorothioate) is a broad-spectrum organophosphate insecticide and acaricide, widely used in our country. Nowadays, it is the principal insecticide in the market employed for agricultural purposes. A number of studies tending to study the affinity of different pesticides with soil have been performed, but only a few refer to chlorpyrifos. Because of its intensive use, a wide range of terrestrial ecosystems may be contaminated with chlorpyrifos, and there is a need to evaluate its environmental behavior and effects. The aim of our work is to study the interaction and persistence of a commercial formulation of chlorpyrifos on an agricultural soil from Provincia de Buenos Aires, Argentina. In this case, recovery percentages increased with the increase of initial concentration of the pesticide until a concentration of about 25 ppm is reached, and then a decrease was observed. The half-time life was not affected by an increase in chlorpyrifos concentration.

Heavy metals occur naturally in soil, at concentrations that depend on the parent material from which the soil was formed, the processes of formation, and the composition and the proportion of the components of its solid phase. Quantifying these concentrations is important for environmental studies of soil contamination and pollution, and choosing the methods for doing so is a key step in establishing heavy metal contents in soil samples. We evaluated two digestion methods (aqua regia and EPA 3051, both microwave oven-assisted) for assessing pseudo-total concentrations of Cd, Co, Cr, Cu, Ni, Pb and Zn in the surface layer (0–20 cm) of soil samples from the Brazilian agricultural frontier in the southwestern Amazon. Nineteen composite samples of the most representative soil classes for the states of Mato Grosso and Rondônia were collected under native vegetation undisturbed by human intervention. Canonical discriminant analysis and principal component analysis were used for multivariate exploration of the data. Aqua regia extracted higher amounts of Co, Ni, Pb, and Zn than EPA 3051, while levels of Cr and Cu did not differ between methods. In general, aqua regia recovered more of the metals when compared to reference soil samples.

Acid mine drainage (AMD) generated by some coal mines in New Zealand is currently treated by the addition of alkaline reagents which neutralize acidity, triggering the precipitation of dissolved metals as insoluble hydroxides. Some trace metals (Ni, Zn, Cu, Cd, and Pb) are discharged into receiving water bodies due to incomplete hydroxide precipitation at circum-neutral pH. This study investigated the incorporation of lignite-derived humic substances (HS) for metal complexation and removal during AMD treatment by Ca(OH)₂ and CaCO₃ neutralization. For Ca(OH)₂ neutralization, addition of HS (regardless of dosing sequence) enhanced the removal of Zn, Cu, and Cd, probably due to the incorporation of metal–humate complex into settling flocs (via aggregation, co-precipitation, and adsorption) that were subsequently removed by sedimentation. However, additional removal of Ni and Pb was statistically indeterminate, which was ascribed to the low complexation affinity of Ni and high removal of Pb by adsorption onto Fe/Al hydroxides. Conversely, for CaCO₃ neutralization, addition of HS only marginally enhanced Cd removal, with the removal of metals probably dominated by adsorption onto the abundant undissolved calcite. Equilibrium speciation modelling showed that about 25% and 38% of the remaining Cu and Pb in the treated AMD were complexed with HS, while only 5% of remaining Cd and less than 1 wt% of remaining Ni and Zn were organically complexed. In the AMD-receiving water bodies, about 20 mg l⁻¹ of HS would be required for complete complexation (>95%) of Cu and Pb and 50 mg l⁻¹ for Cd, whereas Zn and Ni complexation would not occur at natural stream HS concentrations.

The ubiquitous presence of chlorophenols (CPs) continues to be a cause of concern, owing to their recalcitrant nature. In this context, the present work investigated the degradation of model compounds, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol, by an organic oxidant, methyl ethyl ketone peroxide (MEKP) coupled with ultraviolet irradiation in basic media. Chemical analysis was followed by high-performance liquid chromatography and gas chromatography–mass spectrometry. Despite exhibiting varied patterns of decline, chemical oxygen demand was eventually noted to decrease to the extent of up to 70 %. Simultaneous increase/decrease in the release of chloride ions and decrease in pH indicated that parallel reactions were occurring, which led to the formation of acidic reaction products. First-order dynamics was approximated for all CP congener degradation. The degraded compounds showed absolutely no presence of chlorine atoms, which was a noteworthy feature testifying to the fact that MEKP action was capable of detoxification of CP congeners.

Anaerobic digestion is one of the most effective means for the stabilisation of sludge. However, it has a very slow rate-limiting hydrolysis phase which is attributed to the low biodegradability of cell walls and the presence of extracellular biopolymers. This study aims at investigating the effect of ultrasonic, microwave and combined microwave–ultrasonic treatment on biogas production, solids removal and dewaterability of anaerobically digested sludge. A comparison was made between the three pretreatment techniques conducting the digestion tests under similar conditions on the same synthetic sludge sample inoculated by digested sewage sludge. The experimental results depict that the combined microwave–ultrasonic treatment (2,450-MHz, 800-W and 3-min microwave treatment followed by 0.4-W/ml and 10-min ultrasonication) resulted in better digester performance than ultrasonic or microwave treatment. Mesophilic digestion of combined microwave–ultrasonic-pretreated sludge produced a significantly higher amount of methane (147 ml) after a sludge retention time of 17 days, whereas the ultrasonic- and microwave-treated sludge samples produced 30 and 16 ml of methane, respectively. The combined microwave–ultrasonic treatment resulted in total solids reduction of 56.8 % and volatile solid removal of 66.8 %. Furthermore, this combined treatment improved dewaterability of the digested sludge by reducing the capillary suction time (CST) down to 92 s, as compared to CST of 331 s for microwave-treated and 285 s for ultrasonically treated digested sludge samples. Optimisation tests were also carried out to determine the best combination.

In Asturias (north of Spain), mercury mining has been identified as a potential source of trace elements such as As, Sb, Pb, and Hg. In particular, at Los Rueldos mine site, some of these contaminants are dissolved in acidic mine drainage (AMD). Here we treated this leachate by means of nanofiltration to remove some of its pollutants. In order to improve our understanding of the geochemical factors involved in nanofiltration, we analyzed sediment geochemistry and the origin of acidic waters. In coherence with the observation of similar behaviors of As, Fe, and Al in the nanofiltration tests, a clear geochemical association between As, Sb, S, and Fe both in sediments and in the occurrence of AMD was detected. The FILMTEC™ NF-2540 membrane used in this study proved to be highly suitable for the treatment and concentration of the metallic and semimetallic contaminants in the acidic water, even at low pH and moderate pressures.

Dual-effects of adsorption and photodegradation over titania, silica embedded titania, silica and commercial Degussa P-25 samples were studied for the decolourization of methylene blue in aqueous medium. Silica embedded titania and silica were prepared using inexpensive polymeric version of ethyl silicate as a source of silica. Catalysts were characterized by X-ray diffraction, scanning electron microscopy, UV-Vis spectroscopy and low temperature (77 K) nitrogen adsorption measurements. Among all the catalysts, silica embedded titania has exhibited faster decolourization of methylene blue solution on account of the enhancement of adsorption followed by degradation. An amount of the catalyst and the initial dye concentration of MB solution were found to influence the decolourization activity. Compared to titania catalyst, silica embedded titania and Degussa P-25 have shown the red shift in their UV-Vis spectrum. The experimental data of the reaction fitted well to the pseudo first order kinetic model. In present studies, the adsorption mechanism for the decolourization of MB solution was found to be applicable for an intra particle diffusion model. © 2013 Springer Science+Business Media Dordrecht.