Three methods for predicting element mobility in soils have been applied to an iron-rich soil, contaminated with arsenic, cadmium and zinc. Soils were collected from 0 to 30 cm, 30 to 70 cm and 70 to 100 cm depths in the field and soil pore water was collected at different depths from an adjacent 100 cm deep trench. Sequential extraction and a column leaching test in the laboratory were compared to element concentrations in pore water sampled directly from the field. Arsenic showed low extractability, low leachability and occurred at low concentrations in pore water samples. Cadmium and zinc were more labile and present in higher concentrations in pore water, increasing with soil depth. Pore water sampling gave the best indication of short term element mobility when field conditions were taken into account, but further extraction and leaching procedures produced a fuller picture of element dynamics, revealing highly labile Cd deep in the soil profile. Mobility of arsenic, cadmium and zinc in a polluted soil can be realistically interpreted by in-situ soil pore water sampling.

Effects of soil properties on the accumulation of metals to wood mice (Apodemus sylvaticus) were evaluated at two sites with different pH and organic matter content of the soil. pH and organic matter content significantly affected accumulation of Cd, Cu, Pb and Zn in earthworms and vegetation. For Cd, Cu and Zn these effects propagated through the food web to the wood mouse. Soil-to-kidney ratios differed between sites: Cd: 0.15 versus 3.52, Cu: 0.37 versus 1.30 and Zn: 0.33–0.83. This was confirmed in model calculations for Cd and Zn. Results indicate that total soil concentrations may be unsuitable indicators for risks that metals pose to wildlife. Furthermore, environmental managers may, unintentionally, change soil properties while taking specific environmental measures. In this way they may affect risks of metals to wildlife, even without changes in total soil concentrations. Soil properties significantly affect accumulation of heavy metals to wood mice so; risks cannot be based on total concentrations.

In this study, the ability of the organic fraction of municipal solid wastes (OFMSW) to enhance heavy metal uptake of maize shoots compared with ethylenediamine disuccinic acid (EDDS) was tested on soil contaminated with heavy metals. Soils treated with OFMSW and EDDS significantly increased the concentration of heavy metals in maize shoots (increments of 302%, 66%, 184%, 169%, and 23% for Cr, Cu, Ni, Zn, and Pb with respect to the control and increments of 933%, 482%, 928%, 428%, and 5551% for soils treated with OFMSW and EDDS, respectively). In soil treated with OFMSW, metal uptake was favored because of the high presence of dissolved organic matter (DOM) (41.6× than soil control) that exhibited ligand properties because of the high presence of carboxylic acids. Because of the toxic effect of EDDS on maize plants, soil treated with OFMSW achieved the highest extraction of total heavy metals.

The metabolite 2,6-dichlorobenzamide (BAM) is a frequent groundwater pollutant produced during degradation of the herbicide 2,6-dichlorobenzonitrile (dichlobenile). Spatial variability of BAM mineralisation is uncharacterized in surface soil, however, and factors controlling the heterogeneity remain unknown. We addressed these issues by sample-to-sample comparisons of BAM mineralisation rates and a range of soil characteristics at spatial scales ranging from meters to centimetres. For mineralisation assays nano-molar concentrations of labelled BAM were added to determine mineralisation rates under realistic conditions. We found a significant variability of BAM mineralisation which increased with decreasing spatial scale. BAM mineralisation rates were correlated to the density of BAM-degrading bacteria but not to water content, TOC, NH4+, NO3−, or pH. The genus Aminobacter, which contains the only BAM degraders known, was detected in MPN samples of BAM degraders by a specific PCR assay targeting the 16S rRNA gene, confirming a role of Aminobacter in BAM mineralisation. Density of degrader bacteria is the main factor in BAM mineralisation when considering realistic low concentrations in soil.

Soils contaminated with heavy metals can pose a major risk to freshwaters and food chains. In this study, the success of organic and inorganic intervention strategies to alleviate toxicity in a highly acidic soil heavily contaminated with As, Cu, Pb, and Zn was evaluated over 112 d in a mesocosm trial. Amelioration of metal toxicity was assessed by measuring changes in soil solution chemistry, metal leaching, plant growth, and foliar metal accumulation. Either green waste- or MSW-derived composts increased plant yield and rooting depth, reduced plant metal uptake, and raised the pH and nutrient status of the soil. We conclude that composts are well suited for promoting the re-vegetation of contaminated sites; however, care must be taken to ensure that very short-term leaching pulses of heavy metals induced by compost amendment are not of sufficient magnitude to cause contamination of the wider environment. Composts increase rooting depth and vegetation growth over inorganic amendment in an acidic, contaminated soil.

To reveal the degradation capacity of bacteria in PAH polluted soil and rhizosphere we combined bacterial extradiol ring-cleavage dioxygenase and 16S rRNA analysis in Betula pubescens rhizoremediation. Characterisation of the functional bacterial community by RFLP revealed novel environmental dioxygenases, and their putative hosts were studied by 16S rRNA amplification. Plant rhizosphere and PAH amendment effects were detected by the RFLP/T-RFLP analysis. Functional species richness increased in the birch rhizosphere and PAH amendment impacted the compositional diversity of the dioxygenases and the structural 16S rRNA community. A shift from an Acidobacteria and Verrucomicrobia dominated to an Alpha- and Betaproteobacteria dominated community structure was detected in polluted soil. Clone sequence analysis indicated catabolic significance of Burkholderia in PAH polluted soil. These results advance our understanding of rhizoremediation and unveil the extent of uncharacterized functional bacteria to benefit bioremediation by facilitating the development of the molecular tool box to monitor bacterial populations in biodegradation.

Activated carbon (AC) can help overcome toxicity of pollutants to microbes and facilitate soil bioremediation. We used this approach to treat a Histosol and an Alluvial soil historically contaminated with PCB (4190 and 1585 mg kg−1, respectively; primarily tri-, tetra- and pentachlorinated congeners). Results confirmed PCB persistence; reductions in PCB extractable from control and AC-amended soils were mostly due to a decrease in tri- and to some extent tetrachlorinated congeners as well as formation of a bound fraction. Mechanisms of PCB binding by soil and AC were different. In addition to microbial degradation of less chlorinated congeners, we postulate AC catalyzed dechlorination of higher chlorinated congeners. A large decrease in bioavailable PCB in AC-amended soils was demonstrated by greater clover germination and biomass. Phytotoxicity was low in treated soils but remained high in untreated soils for the duration of a 39-month experiment. These observations indicate the utility of AC for remediation of soils historically contaminated with PCB. Activated carbon promotes remediation of soils historically contaminated with PCB.

The transfer of Cd and Zn from soils amended with sewage sludge was followed through a food chain consisting of wheat, aphids and the predator Coccinella septempunctata. Multiple regression models were generated to predict the concentrations of Cd and Zn in C. septempunctata. No significant model could be generated for Cd, indicting that the concentration of this metal was maintained within relatively narrow limits. A model predicting 64% of the variability in the Zn concentration of C. septempunctata was generated from of the concentration of Zn in the diet, time and rate of Zn consumption. The results suggest that decreasing the rate of food consumption is an effective mechanism to prevent the accumulation of Zn and that the availability of Zn in the aphid prey increased with the concentration in the aphids. The results emphasise the importance of using ecologically relevant food chains and exposure pathways during ecotoxicological studies. Arthropod predators can regulate trace metal body burden through physiological and behavioural mechanisms.

The impact of residual PAHs (2250 ± 71 μg total PAHs g−1) following enhanced natural attenuation (ENA) of creosote-contaminated soil (7767 ± 1286 μg total PAHs g−1) was assessed using a variety of ecological assays. Microtox™ results for aqueous soil extracts indicated that there was no significant difference in EC50 values for uncontaminated, pre- and post-remediated soil. However, in studies conducted with Eisenia fetida, PAH bioaccumulation was reduced by up to 6.5-fold as a result of ENA. Similarly, Beta vulgaris L. biomass yields were increased 2.1-fold following ENA of creosote-contaminated soil. While earthworm and plant assays indicated that PAH bioavailability was reduced following ENA, the residual PAH fraction still exerted toxicological impacts on both receptors. Results from this study highlight that residual PAHs following ENA (presumably non-bioavailable to bioremediation) may still be bioavailable to important receptor organisms such as earthworms and plants. Residual PAHs in creosote-contaminated soil following enhanced natural attenuation impacted negatively on ecological receptors.

A Pb-mine site situated on acidic soil, but comprising of Ca-enriched islands around derelict buildings was used to study the spatial pattern of genetic diversity in Lumbricus rubellus. Two distinct genetic lineages (‘A’ and ‘B’), differentiated at both the mitochondrial (mtDNA COII) and nuclear level (AFLPs) were revealed with a mean inter-lineage mtDNA sequence divergence of approximately 13%, indicative of a cryptic species complex. AFLP analysis indicates that lineage A individuals within one central ‘ecological island’ site are uniquely clustered, with little genetic overlap with lineage A individuals at the two peripheral sites. FTIR microspectroscopy of Pb-sequestering chloragocytes revealed different phosphate profiles in residents of adjacent acidic and calcareous islands. Bioinformatics found over-representation of Ca pathway genes in ESTPb libraries. Subsequent sequencing of a Ca-transport gene, SERCA, revealed mutations in the protein's cytosolic domain. We recommend the mandatory genotyping of all individuals prior to field-based ecotoxicological assays, particularly those using discriminating genomic technologies. Landscapes punctuated by Pb-polluted islands have engendered local genetic differentiation in resident earthworms.