Assessment of the mobility, bioaccessibility, and ecological risk of Pb and Zn on a dirt road located in a former mining area-Ribeira Valley-Brazil.

Abstract

The inadequate transportation of foundry slags during the construction of a mining waste landfill accounted for the presence of slags in the dirt road that connects the working district of Vila Mota to the city of Adrianópolis. The objectives of this work were to assess the lead (Pb) and zinc (Zn) contamination of the dirt. Three samples separated by 2km were collected along a dirt road (samples: Adrianópolis, Deposit, and Plant). The conducted assays were physico-chemical parameters, pseudototal concentration, three sequential extraction procedures, and bioaccessibility assay. The laboratory data was used as input in the calculation of contamination indices risk assessment code (RAC) and potential ecological risk (Eri). The dirt road presented high concentrations of Pb (mean 1426.5mgkg-1) and Zn (mean 4964.8mgkg-1). The BCR SEP (Bureau Community of Reference Sequential Extraction Procedure) method was more adequate in extracting the soluble-exchangeable fraction, and this fraction was correlated with the gastric phase. The bioaccessible fraction is mainly present in the stomach fraction and is transported to the intestinal phase. Using BCR SEP method to calculate the contamination indices, sample Deposit yielded very high risk when calculating RAC and Eri for Pb (72.9% and 639.5, respectively). For Zn, high risk was obtained with RAC and very high risk for Eri (42.5% and 344.2, respectively). The high content of Pb and Zn on the dirt road presents a risk to the population that uses this road, since the soil particles are easily transported, deposited on the dermis, and inhaled.