Analysis of Soil Parameters in Almadenejos. Behavior of Mercury in Soil-Plant System

This scientific-technical report is the result of the stay of Rocio Fernandez Flores practices in the Research Unit soil degradation of the Department of Environment CIEMAT. The aim of this study is to determine the behaviour of mercury in soil of Almadenejos (Almaden, Ciudad Real, Espana) by using a six-step sequential extraction procedure and evaluate the transfer of this pollutant to Marrubium vulgare L., predominant in the area and studied for years due to its ability to accumulate large amounts of mercury without visual symptoms of toxicity. Furthermore, the results will be useful in order to determine if this plant specie could be used as phyto extractor in the recovery mercury contaminated soils. The results show that total mercury concentrations in soil ranged from 709 mg kg-1 to 22,616 mg kg-1. Regarding mercury distribution among different soil fractions, this heavy metal is mainly found in the fraction assigned in the fi nal insoluble residues, the oxidizable fraction and in the crystalline Fe-Mn oxydroxides, on the other hand, barely 1% or lower is readily available to plants However, Marrubium vulgare is able to accumulate high amount of mercury (3.5 - 373.5 mg kg-1). Regarding the mercury distribution inside the plant, mercury concentration in the root was higher than in the aerial part. Within the aerial part the maximum mercury concentration was generally found in leaves. According to the obtained results, Marrubium vulgare L. could be considered as a (hyper)accumulator plant. (Author) 57 refs.