Ecological risk assessment and mobility of arsenic and heavy metals in soils and mine tailings from the Carmina mine site (Asturias, NW Spain)

Abstract

An evaluation of the pollution, distribution, and mobility of arsenic and heavy metals in spoil heaps and the soils surrounding the abandoned Carmina Pb–Zn mine (Asturias, Northern Spain), is carried out. Fractionation of As was performed by means of an As-specific sequential extraction method while heavy metals fractionations were assessed using the Bureau Community of Reference (BCR) protocol. As appeared predominantly associated with amorphous iron oxyhydroxides. Among the heavy metals, Pb and Zn showed high mobility since significant amounts were extracted in the non-residual fractions, whereas Cr, Cu and Ni showed very low mobility indicating its lithogenic origin. Results show that the extractability of heavy metals in soils is influenced mainly by the presence of Fe and Mn oxides as well as by pH and Eh. Multiple pollution indices were used to assess the soil pollution extent: Enrichment factor (EF), geoaccumulation index (Igeo), ecological risk index (Er) and potential ecological risk index (PERI). All of them showed that Pb was the key factor to cause the pollution and ecological risk in the studied area with significant contribution of Cu, Zn and As. Remarkably, the sites at higher risk coincided with those with higher mobility of As and heavy metals. This study provides an integrative approach as a powerful tool to evaluate the pollution status and potential threat to the local environment in abandoned mining areas which results useful for management decisions in these areas.