Tin distribution in soils and plants, Cistus ladanifer L., in Neves Corvo mining area

Abstract

The Neves Corvo mining area includes the Mina de Neves Corvo (MNC) that started exploitation in 1988 for Cu and Sn and six abandoned Mn and Cu mines.

The Volcano Sedimentary Complex (VSC) which hosts the massive sulphide deposits and the Flysch formations of schist and greywacke dominates the regional geology.

The aim of this study was to evaluate tin distribution in soils as well as the capacity to absorb and translocate this element for plants (Cistus ladanifer L.) growing in the MNC area. Samples were collected in two campaigns: the first, for soils, in 1971-72 before MNC existence; and the second campaign (1998), 10 years after mining exploitation began in MNC, for soils and plants in the same places sampled in the first campaign. Soil and plant samples were digested with four acids for total elements extraction and analysed by ICP-AES.

The soils developed from Flysch formations have the same average Sn concentrations in both campaigns (2.9 mg kg ^-1). In contrast, the Sn concentration in soils developed on VSC in the second campaign were twice those (10.4 mg kg^-1) from soils of the first campaign (4.5 mg kg^-1), reflecting mining. However, tin content in soils developed on both lithologies was considered as a background concentration. Generally, plant roots have higher Sn concentrations than leaves. C. ladanifer plants presented highest Sn concentration than soils suggesting tin accumulation by these plants.

The soil pH and solid phases where tin was present were determinant factors for tin uptake and translocation from roots to shoots in C. ladanifer plants.