Mapeamento geoquimico de solos contaminados por metais (Pb, Zn, As e Cu), Santo Amaro da Purificação, Bahia

Abstract

The urban area of Santo Amaro da Purificação is highly polluted by metals, especially lead, due to residues of lead smelter metallurgy during 33 years. The purpose of the study was to evaluate the amplitude of the soil contamination within the rural area around the city of Santo Amaro, and study the relationship with soil constituents. Forty-nine sampling locals were obtained from a regular 24 km x 24 km grid, and the soil was collected at 0-5 and 30-60 cm soil depth. The samples were air-dried, sieved at 2 mm and acid HNO3 digestions (method SW-846-3051 – USEPA, 1998) were performed to obtain the pseudo-total metal contents. Metal quantification was realized by ICP-OES. Concentrations were compared with those settled by CONAMA 344-04, and were used for constructing geochemical maps and pollution maps with gs+ 7, Surfer 8 and Arc Gis 9,3 softwares. The soils derived from the coarse to fine sandstones (with kaolinite) of the Barreiras geologic formation, showed the lower means for main soil chemical attributes at 0-5 cm soil depth, contrasting with soils formed from claystones and fine sandstones of the Santo Amaro group, where both lithogenic and anthropogenic origin were observed. Regarding the soil classes, the higher metal concentrations were found in the Vertisols and clay Oxisols, derived from Santo Amaro group. A whole contamination, moderate or higher, was identified in the sampled rural area.