Antimony in the environment: Lessons from geochemical mapping

Abstract

Abstract The distribution of Sb in a variety of sample materials, including soils, plants and surface water, was studied at different scales, from continental to local, combining published data sets with the aim of delineating the impact and relative importance of geogenic vs. anthropogenic Sb sources. Geochemical mapping demonstrates that variation is high at all scales – from the detailed scale with sample densities of many sites per km 2 to the continental-scale with densities of 1 site per 5000 km 2 . Different processes govern the Sb distribution at different scales. A high sample density of several samples per km 2 is needed to reliably detect mineralisation or contamination in soil samples. Median concentrations are so low for Sb in most sample materials (below 1 mg/kg in rocks and soils, below 0.1 mg/kg in plants, below 0.1 μg/L in surface water) that contamination is easier to detect than for many other elements. Distribution patterns on the sub-continental to continental-scale are, however, still dominated by natural variation. Given that the geochemical background is characterised by a high variation at all scales, it appears impossible to establish a reliable single value for “good soil quality” or a “natural background concentration” for Sb for any sizeable area, e.g., for Europe. For such a differentiation, geochemical maps at a variety of scales are needed. Different sample materials can reflect different geochemical sources and processes, even when collected from the same survey area. Weathering (soil formation) leads to an increased Sb concentration in soils compared to rocks. Organic soils are highly enriched (factor 5–10 compared to mineral soils) in Sb. Soils and stream sediments return comparable median Sb concentrations. Plants are usually well protected against Sb uptake. There exist, however, plant species that can accumulate Sb to values of more than 1000 mg/kg. Antimony concentrations in the marine environment are not sufficiently well-documented. High Sb concentrations, related to hydrothermal and volcanic processes may have been previously underestimated.