Polluted Soils

Smelting activities are one of the most common sources of trace elements in the environment. The aim of this study was to determine the lead distribution in upper horizons (0–5 and 5–10 cm) of acidic soils in the vicinity of a lead-acid battery recycling plant in northern France. The combination of chemical methods (sequential extractions), physical methods (Raman microspectroscopy and scanning electron microscopy with an energy dis-persive spectrometer) and multi-surface complexation modelling enabled an assessment of the behaviour of Pb. Regardless of the studied soil, none of the Pb-bearing phases commonly identified in similarly polluted environments (e.g., anglesite) were observed. Lead was mainly associated with organic matter and manganese oxides. The association of Pb with these soil constituents can be interpreted as evidence of Pb redistribution in the studied soils following smelter particle deposition.

A laboratory experiment was carried on the same initial soil and at the same time than a windrow treatment in order to compare results at field and laboratory scales for a soil mainly contaminated with PAHs. After 6 months, laboratory experiments gave similar but less scattered results than those obtained in the field indicating that the field biotreatment was well optimised. The total amount of PAHs degraded after 6 months was ca. 90% and degradation rates followed a negative exponential trend. Relative degradation rates of 3-and 4-ring PAHs were about 32 and 7.2 times greater than those of 5-and 6-ring PAHs, respectively. With respect to the bacterial community, bacteria belonging to Gamma-proteobacteria persisted whereas Beta-proteobacteria appeared after three months of biotreatment when PAH concentration was low enough to render the soil non-ecotoxic.

In this study we have examinated the results of two experiments on the uptake and distribution of arsenic (As) in roots, shoots, and grain of wheat grown in As-polluted soils and in an unpolluted soil irrigated with As-contaminated water in absence or presence of phosphorus (P) fertilization. Arsenic concentrations in wheat samples of the two experiments are higher than those in the plants grown on uncontaminated soil. In the experiments showed in this work, it is highlighted the role of P fertilization in preventing As uptake and translocation in wheat plants. These findings could have important implications to reduce the potential risk posed to human health by As entering the food-chain.