Mercury accumulation and speciation in plants and soils from abandoned cinnabar mines

Abstract

This study examines total Hg, free Hg(0), matrix-bound Hg and MeHg contents in soils and plant tissues from two old cinnabar mining sites (La Soterraña and Los Rueldos) in Asturias (Spain), as well as Hg transfer and translocation from soils to plants. The studied soils from both mines accumulated moderate to very high total Hg concentrations (36–1709mg·kg−1) but quite low available Hg contents (0.005–3.062mg·kg−1) which resulted in relatively low transfer factor values. Matrix-bound Hg was the prevalent Hg form in soils from both mining sites representing 67–88% of total Hg content. Significant Hg(0) concentrations were found in soils as a consequence of atmospheric deposition. Appreciable MeHg concentrations were found in soils from La Soterraña mining site while non-detectable MeHg could be found in soils from Los Rueldos. All the studied plants can be considered as excluders. Hg(0) is practically absent in roots indicating that this Hg form is not uptaken from soils. Hg(0) contents found in aboveground tissues evidenced that foliar uptake of atmospheric Hg occurs. Significant MeHg contents were found in the aerial parts for all studied plants. However, MeHg contents in roots were extremely low in La Soterraña plants and non-detectable in those from Los Rueldos.