Antimony mobility and (bio)availability as reported from studies in derelict mines South Iberia

Antimony (Sb) is a semimetallic element, with important applications in modern industry. Europe as a whole, and Spain, Portugal and France have been important suppliers of this element. However, nowadays European production is almost null, except as a by-product of lead mining, always containing variables amounts of Sb. Due to these considerations, Sb is considered as a critical resource for Europe.

The ERA-MIN2 funded project AUREOLE (tArgeting eU cRitical mEtals (Sb, W) and predictibility of Sb-As-Hg envirOnmentaL issue) involves the French geological survey (BRGM), the Portuguese University of Porto, and the Spanish University of Castilla-La Mancha in the search of new criteria to prospect Sb mineralizations, as well as to assess the environmental possible consequences of the exploitation of Sb deposits.

This communication summarizes the main results obtained through the last three years of research based on the assessment of environmental concerns of the element, based on the surveying of Sb derelict mineralizations in South-Central Spain. In these, geochemical and biogeochemical surveys have been carried out, aimed to identify the main factors affecting the mobility and (bio) availability of the element and related ones (mainly Pb, but also Hg) in the nearby physicochemical. The diversity and structure of bacterial communities on a former mining site was investigated. Biogeochemical interactions will be discussed in the different mine environments (tailings, dump, polluted soil, sediments).

Geochemical and mineralogical soil characterization showed that most Sb remains as sulphide (≈99%), with a very small fraction bound to Fe and Mn oxy-hydroxides or organic matter, and a negligible proportions of leachable Sb. However, higher Sb mobility rates can be reached under oxidising conditions, with a long contact time between solids and water. The relationship between Sb concentrations in the soils and their measured enzymatic activity has yielded unclear results. Globally, results put forward that Sb mobility seems to be very low in semiarid climates, with also very low soil-to-plant transfer rates.