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.

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 2 km 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 1426.5 mg kg-1) and Zn (mean 4964.8 mg kg-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.

Toxicidade de águas e sedimentos em um rio afetado por atividades mineradoras pretéritas / Water and sediment toxicity in a river affected by formermining residues

bacia do Rio Ribeira de Iguape foi palco de intensa atividade de mineração de chumbo e, como resultado, estima-se que o rio Ribeira de Iguape tenha recebido a descarga de aproximadamente 5,5 t/mês de materiais ricos em As, Ba, Cd, Pb, Cu, Cr e Zn. No presente trabalho, foi analisada a toxicidade de sedimentos e águas coletados ao longo do rio com o intuito de avaliara qualidade ambiental, tendo sido realizadas 3 campanhas de coleta, entre 2009 e 2010. Os testes de toxicidade aguda foram conduzidos com o cladócero Daphnia similis, utilizando as amostras brutas de água e a exposição aos sedimentos pela interface sedimento-água. Os resultados indicaram, em geral, ausência de toxicidade, tanto para sedimentos quanto para águas, com efeitos tóxicos agudos registrados apenas episodicamente (toxicidade marginal). Tais resultados são coerentes com as baixas concentrações de metais em águas e sedimentos indicadas na literatura, porém diferem do monitoramento feito pela agência ambiental estadual, que tem registrado toxicidade crônica. Essa toxicidade aguda eventual indica, ainda, que embora a qualidade do Rio Ribeira de Iguape esteja sendo recuperada, as condições ainda não estão totalmente controladas.

The Ribeira de Iguape River basin received intense mining activities for lead exploiting and, as a result, the river received the discharges of estimated amounts of 5.5 tons/month of material rich in As, Ba, Cd, Pb, Cu, Cr and Zn. In this article, the toxicity of waters and sediments collected in Ribeira de Iguape River was assessed aiming to estimate environmental quality. Three sampling campaigns were conducted, from 2009 to 2010. Toxicity tests with the cladoceran Daphnia similis were done for water samples and for sediments, in this case using sediment-water interface exposure. Results showed in general absence of toxicity for sediments and waters, and only eventually were acute effects registered (marginal toxicity). Results are consistent with the conditions indicated by the literature, of low concentrations of metals in waters and sediments; however they differ from the monitoring made by the state environmental agency, which registered chronic toxicity. The occurrence of eventual acute toxicity indicates that although Ribeira de Iguape River quality is being restored, conditions still are not totally under control.