Biogeochemical controls on the mobility and bioavailability of metals in soils and groundwater
Numerous trace metals have been identified as essential micronutrients for plants and/or microorganisms (including iron, zinc, copper, selenium, and nickel) and as electron acceptors or donors in metabolic processes. At elevated concentrations, however, many of these same metals exhibit significant toxicity and trace metal pollution in soils and groundwater remains one of the most pressing issues in modern environmental science. Arsenic contamination of drinking water, cadmium, copper, lead, and zinc pollution in soils, the transport of radio nuclides over long time scales, and the cycling of mercury are a few examples of important research areas in this context. As a result of their multifaceted biological functions, the significance of metals in the environment will depend on the concentration at which they occur and on environmental factors that control their mobility and bioavailability. The biogeochemical processes that control metal mobility and bioavailability include sorption on mineral and plant surfaces, dissolution, (bio-)mineralization, redox processes, complexation by biogenic or non-biogenic ligands, and biological uptake and derivatization. A wide range of experimental approaches has been used in trace metal related environmental research. It is therefore imperative to foster the discussion of these fundamental processes and approaches among researchers from various fields including plant nutrition, environmental chemistry and microbiology, environmental engineering, agricultural sciences, geochemistry, mineral surface chemistry, and soil chemistry and biology.