Extractable copper, arsenic and antimony by EDTA solution from agricultural Chilean soils and its transfer to alfalfa plants (Medicago sativa L.)

Abstract

Following our research on copper, arsenic and antimony in Chilean ecosystems, a study to understand the mobility and transport of these elements from soil to plants was carried out. So, the aim of this study, which follows on from the previous work, was to demonstrate if the total concentrations of these elements or their fractions extracted by 0.05 M EDTA pH 7 from different Chilean soils correlate with the respective total concentrations in the edible tissue of alfalfa plants collected simultaneously from 20 different sites affected or unaffected by mining activities. The highest copper fractions extracted by EDTA solutions were obtained in contaminated soils from the central region (41–69%); however the northern soils presented the highest extractable fractions of arsenic (9–34%). The antimony fraction was low in all soils (0.4–8.0%). Alfalfa plants from all contaminated sites presented high copper, arsenic and antimony concentrations (19–126 mg kg⁻¹, 5.7–16.3 mg kg⁻¹ and 0.16–1.7 mg kg⁻¹, respectively). Statistically significant correlations were obtained between the total contents of copper and arsenic and their respective extractable fractions in soils. Good correlations were found between elements in alfalfa plants. Correlations were also obtained between the total concentrations of three elements in soils and in alfalfa plants. However, excepting for antimony in the northern samples, higher correlation coefficients were evaluated when the extractable fractions were considered. Samples from the north region presented the highest copper transfer factor and the lowest for arsenic, in spite of the high concentration of this metalloid extracted by EDTA solution in these soils. There was not a clear trend on the transfer factor for antimony, probably due to the low content of this element in alfalfa plants and/or the low recovery obtained for this element by EDTA.