Thirteen soils collected from 11 provinces in eastern China were used to investigate the butachlor adsorption. The results indicated that the total organic carbon (TOC) content, clay content, amorphous Fe2O3 content, silt content, CEC, and pH had a combined effect on the butachlor sorption on soil. Combination of the data obtained from the 13 soils in the present study with other 23 soil samples reported by other researchers in the literature showed that Koc would be a poor predictive parameter for butachlor adsorption on soils with TOC content higher than 4.0% and lower than 0.2%. The soils with the ratio of clay content to TOC content (RCO) values less than 60 adsorbed butachlor mainly by the partition into soil organic matter matrix. The soils with RCO values higher than 60 apparently adsorbed butachlor by the combination of the partition into soil organic matter matrix and adsorption on clay surface. The relative importance of organic matter and clay in butachlor adsorption in soil will depend on the ratio of clay content to total organic carbon content.

Soils from Aveiro, Glasgow, Ljubljana, Sevilla and Torino have been investigated in view of their potential for translocation of potentially toxic elements (PTE) to the atmosphere. Soils were partitioned into five size fractions and Cr, Cu, Ni, Pb and Zn were measured in the fractions and the whole soil. All PTE concentrated in the <10 μm fraction. Cr and Ni concentrated also in the coarse fraction, indicating a lithogenic contribution. An accumulation factor (AF) was calculated for the <2 and <10 μm fraction. The AF values indicate that the accumulation in the finer fractions is higher where the overall contamination is lower. AF for Cr and Ni are particularly low in Glasgow and Torino. An inverse relationship was found between the AF of some metals and the percentage of <10 μm particles that could be of use in risk assessment or remediation practices.

Kinetic EDTA and citrate extractions were used to mimic metal mobilization in a soil contaminated by metallurgical fallout. Modeling of metal removal rates vs. time distinguished two metal pools: readily labile (QM1) and less labile (QM2). In citrate extractions, total extractability (QM1 + QM2) of Zn and Cd was proportionally higher than for Pb and Cu. Proportions of Pb and Cu extracted with EDTA were three times higher than when using citrate. We observed similar QM1/QM2 ratios for Zn and Cu regardless of the extractant, suggesting comparable binding energies to soil constituents. However, for Pb and Cd, more heterogeneous binding energies were hypothesized to explain different kinetic extraction behaviors. Proportions of citrate-labile metals were found consistent with their short-term, in-situ mobility assessed in the studied soil, i.e., metal amount released in the soil solution or extracted by cultivated plants. Kinetic EDTA extractions were hypothesized to be more predictive for long-term metal migration with depth. Kinetically defined metal fractions mimic mobility aspects of heavy metals.

This study reports the first data on the concentrations and distribution of phthalate esters (PAEs) in the agricultural soils from the peri-urban areas of Guangzhou city. Σ16PAEs concentrations ranged from 0.195 to 33.6 μg g−1-dry weight (dw). Elevated levels of PAEs were recorded in the vegetable fields located next to the urban districts, and a decreasing trend exists following the distance away from the urban center. Diisobutyl phthalate (DiBP), Di-n-butyl phthalate (DnBP), and Di(2-ethylhexyl) phthalate (DEHP) dominated the PAEs in the agricultural soils. Significant relationship (correlation coefficient R2 = 0.85, p < 0.01, n = 40) was present between the accumulation of PAEs and total organic carbons in agricultural soils. In addition, both pH and texture of soils are found to be important factors affecting the level of PAEs. This study shows that the agricultural soils in the peri-urban area of Guangzhou city were moderately polluted by PAEs. PAEs are determined in agricultural soils at high concentration levels, which imply a potential risk for the food chain.

We studied the effectiveness of remediation on microbial endpoints, namely microbial biomass and activity, microbial and plant species richness, of an As-contaminated mine spoil, amended with compost (C) alone and in combination with beringite (B) or zerovalent iron grit (Z), to increase organic matter content and reduce trace elements mobility, and to allow Holcus lanatus and Pinus pinaster growth. Untreated spoil showed the lowest microbial biomass and activity and hydrolase activities, and H. lanatus as sole plant species, whereas the presented aided phytostabilisation option, especially CBZ treatment, significantly increased microbial biomass and activity and allowed colonisation by several plant species, comparable to those of an uncontaminated sandy soil. Microbial species richness was only increased in spoils amended with C alone. No clear correlation occurred between trace element mobility and microbial parameters and plant species richness. Our results indicate that the choice of indicators of soil remediation practices is a bottleneck. Organo-mineral amendment and revegetation of a gold mine spoil increased microbial activity but did not increase microbial species richness.

This paper contributes to increase the knowledge of the contents and sources of heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) to agricultural soils in Castellón province (Spain), a representative area of the European Mediterranean region. The surface horizons of 77 agricultural soils under vegetable crops were sampled and heavy metals were analysed by atomic absorption spectroscopy (AAS) after microwave extraction using the USEPA 3051A method. Mean heavy metal contents were similar to those obtained in other areas of this region. However, heavy metal contents (e.g. Cr, Pb) in some soils were above the maximum limit set in the 86/278/CEE Directive. Multivariate analysis (correlation analysis and principal component analysis - PCA) was performed so as to identify the sources of heavy metals to soils. Co, Fe and Ni were highly correlated amongst them (r > 0.800; p < 0.01), whereas Cr and Mn were less correlated with Co, Fe and Ni (r > 0.500; p < 0.01). Other relationships among heavy metals (i.e. Cu, Pb and Zn) were also identified, although correlation coefficients were not so high as those among Co, Fe and Ni (r < 0.500; p < 0.01). Contents of Co, Fe, Mn and Ni were interpreted to be mainly associated with parent rocks corresponding to the first principal component (PC1). On the other hand, Cd, Cu, Pb and Zn were interpreted to be mainly related to anthropogenic activities and comprised the second (Pb and Zn) and the third (Cd and Cu) principal components (PC2 and PC3, respectively), designated as anthropogenic components. Remarkably, Cr appears to be related in the study area to both the lithogenic and the anthropogenic components. Lithogenic elements were highly correlated with soil properties. Positive relationships with CEC (r > 0.200; p < 0.05) and clay (r > 0.400; p < 0.01), and negative relationships with carbonates (r > -0.400; p < 0.01) and sand (r > -0.300; p < 0.01) were observed. Anthropogenic elements were less correlated with soils properties, since these elements are generally more mobile because they form more soluble chemical species associated to anthropogenic sources. Particularly, no correlation was found between Cd and Zn and soil properties. These findings extend results achieved in other parts of the region, highlighting the need to set soil quality standards in order to declare soils affected by anthropogenic pollution, particularly in the case of anthropogenic metals such as Cd, Cu and Pb, and also Cr and Zn in some areas. Further knowledge from other areas in this region would improve the basis for proposing such standards at regional level, which is a priority objective in Europe according to the European Thematic Strategy for Soil Protection.

Agrichemical spills and discharges to soil can cause point-source contamination of surface and ground waters. When high contaminant concentrations inhibit natural attenuation in soils, chemical treatments can be used to promote degradation and allow application of treated soils to agricultural lands. This approach was used to remediate soil containing >650 mg atrazine, >170 mg metolachlor and >18,000 mg nitrate kg⁻¹. Results indicated a decrease in metolachlor concentration to <1 mg kg⁻¹ within 95 days of chemical treatment with zerovalent iron (Fe⁰, 5% w/w) and aluminum sulfate (Al₂(SO₄)₃, 2% w/w) but after one year >150 mg atrazine and >7000 mg nitrate kg⁻¹ remained. Laboratory experiments confirmed that subsequent additions of sucrose (table sugar) to the chemically pretreated soil promoted further reductions in atrazine and nitrate concentrations. Field-scale results showed that adding 5% (w/w) sucrose to windrowed and pretreated soil significantly reduced atrazine (<38 mg kg⁻¹) and nitrate (<2,100 mg kg⁻¹) concentrations and allowed for land application of the treated soil. These results provide evidence that zerovalent iron in combination with Al₂(SO₄)₃ and sucrose can be used for on-site, field-scale treatment of pesticide- and nitrate-contaminated soil.

Eight soils from the Gulf of Kalloni in Lesvos Island, Greece, most of which were of low clay and low organic matter content, were used in a series of leaching experiments. The aim was to investigate the role of sewage sludge on Zn leaching and determine the soil properties that affect it. It was found that sludge addition at a low application rate (10 t ha⁻¹) decreased Zn leaching significantly by 30%. From a regression analysis it was found that eluted Zn was reduced with increasing Fe oxides content, probably due to Zn adsorption onto them, and that Zn transport increased with clay content. This indicates that Zn leaching was facilitated by the downward movement of clay particles, which was also suggested by the erratic Zn breakthrough observed in many soils. This was further confirmed by the fact that colloid concentrations increased with clay content in the soils (R = 0.85, P < 0.05). The results show that the addition of sewage sludge to low organic matter and clay content soils at moderate application rates enhances soil organic carbon and increases metal retention capacity.

Temporal changes in microbial community function (enzymatic activities) and structure (phospholipid fatty acids) were studied in a post-mining chronosequence of coal discard sites of different rehabilitation ages. The objective was to determine whether temporal changes in microbial community function and structure were related to rehabilitation age or management practices. No trends consistent with the rehabilitation ages (1 to 11 years) of the respective sites were observed. A canonical correspondence analysis showed that sites clustered according to the time of sampling irrespective of their individual rehabilitation ages. Sites sampled in 2002 clustered together, while sites sampled in 2004 and 2005 clustered separately from the 2002 sites. This corresponded with a change in management practices applied after 2002. Dehydrogenase, β-glucosidase, acid phosphatase, and alkaline phosphatase activities for all sites were higher after 2002. Urease activities were lower after 2002, with the exception of Site 3 (4 years old in 2002). Phospholipid fatty acid data showed significant (p < 0.05) differences between sites of different rehabilitation ages over the study period. There was a decrease in microbial biomass in all sites from 2002 to 2004 but an increase in 2005. Fungal to bacterial abundance ratios for all sites decreased over the study period. The proportion of the total microbial community comprised of Gram positive bacteria increased from 2002 to 2005. These data show the value of microbial community function and structure to elucidate management effects that may not be apparent through traditional assessments of rehabilitation status such as aboveground indicators.

The enrichment factor, multivariate analysis and metal speciation studies were used to identify degree, source and dispersal of metal contamination in Khli Ti watershed, Thailand. Topsoil samples were collected throughout the watershed, analyzed for total metal concentration. Sequential extraction was also carried out to determine geochemical phases of metals which were identified as exchangeable and bound to carbonates, Fe–Mn oxides, organic matter and residuals. Soil characteristics including pH, total organic carbon, redox potential, cation exchange capacity and texture were also analyzed. Principal component analysis yielded three metal groups which explained 83% of the variance. The concentrations of metals which were derived from lithogenic origin, such as Co, Cr, Fe, Ni and V were in natural background levels and were mostly bound to the residual phase. The remaining elements (i.e. Ba, Cd, Cu, Pb, Sb and Zn) were associated with the contamination from previous activities of the Pb-ore concentrator and Zn–Pb mining. Anthropogenic contamination mainly increased Pb and Zn bound to Fe–Mn oxides at the expense of residual fraction. Even though low exchangeable Pb contents in Khli Ti soils indicated low availability to plants, Pb bound to Fe–Mn oxides fraction might increase its mobility under reducing conditions.