Risk management for arsenic in agricultural soil-water systems: lessons learned from case studies in Europe.

Chronic exposure to arsenic may be detrimental to health. We investigated the behaviour, remediation and risk management of arsenic in Freiberg, Germany, characterized by past mining activities, and near Verdun in France, where World War I ammunition was destroyed. The main results included: (1) pot experiments using a biologically synthesized adsorbent (sorpP) with spring barley reduced the mobility of arsenic, (2) the Omega-3 Index ecotoxicological tests verified that sorpP reduced the uptake and toxicity of arsenic in plants, (3) reverse osmosis membrane systems provided 99.5% removal efficiency of arsenic from surface water, (4) the sustainability assessment revealed that adsorption and coagulation-filtration processes were the most feasible options for the treatment of surface waters with significant arsenic concentrations, and (5) a model was developed for assessing health risk due to arsenic exposure. Risk management is the main option for extensive areas, while remediation options that directly treat the soil can only be considered in small areas subject to sensitive use. We recommend the risk management procedure developed in Germany for other parts of the world where both geogenic and anthropogenic arsenic is present in agricultural soil and water. Risk management measures have been successful both in Freiberg and in Verdun.

Linking cellulose fiber sediment methyl mercury levels to organic matter decay and major element composition.

Methylation of mercury (Hg) to highly toxic methyl Hg (MeHg), a process known to occur when organic matter (OM) decomposition leads to anoxia, is considered a worldwide threat to aquatic ecosystems and human health. We measured temporal and spatial variations in sediment MeHg, total Hg (THg), and major elements in a freshwater lagoon in Sweden polluted with Hg-laden cellulose fibers. Fiber decomposition, confined to a narrow surface layer, resulted in loss of carbon (C), uptake of nitrogen (N), phosphorus (P), and sulfur (S), and increased MeHg levels. Notably, fiber decomposition and subsequent erosion of fiber residues will cause buried contaminants to gradually come closer to the sediment-water interface. At an adjacent site where decomposed fiber accumulated, there was a gain in C and a loss of S when MeHg increased. As evidenced by correlation patterns and vertical chemical profiles, reduced S may have fueled C-fixation and Hg methylation at this site.