Accumulation of antimony and other potentially toxic elements in plants around a former antimony mine located in the Ribes Valley (Eastern Pyrenees)

Abstract

Soil contamination by Sb is of increasing environmental concern due to the use of this amphoterous p-block element in many industrial applications. However, still little is known about the response of plants to Sb. Here we report on the accumulation of Sb and other potentially toxic elements (mainly As, Pb and Cu) in plants growing around a former Sb mine in the Ribes Valley located in the Eastern Pyrenees. Soil and plant samples were taken at six locations with different concentrations of Sb, As, and polymetallic contamination. Aqua regia and EDTA extractable chemical elements from sites with low (sites 1 and 2), moderate (site 3 and 4) and high (sites 5 and 6) pollutant burdens were analyzed. While sites 1 to 4 had alkaline soil pH (7.4–8.7), sites 5 and 6 were acidic with values of 6 and 4.6, respectively. Different herbaceous plant species (Poa annua L., Echium vulgare (L.), Sonchus asper (L.) Hill, Barbera verna (Mill.) Asch.) at the low and moderately polluted sites were able to efficiently restrict Sb and As transport to the shoots showing average concentration ranges between 5.5 and 23mgkg−1 As and 1.21mgkg−1 and 4.9mgkg−1 Sb. However, at the highly polluted acidic sites (5 and 6) only Agrostis capillaris L. was found. This grass was able to withstand up to 240mg/kg As and 68mg/kg Sb in the shoots. Antimony tolerance in this A. capillaris ecotype was due to efficient exclusion, yet under lab conditions commercial, non-resistant A. capillaris plants sown into a 50% mixture of sand with this highly polluted soil showed severe toxicity symptoms and a shoot Sb concentration of 230mg/kg Sb. In the original mine spoil soil (100% without sand) from the highly polluted sites the commercial A. capillaris was unable to grow. The mechanism of Sb resistance in the mine spoil ecotype of A. capillaris deserves further investigation.