Pb, Cd, Zn, Cr, Cu and Ni contamination assessment in the topsoil collected in a former mining waste deposition area - Adrianópolis, PR (Brazil)
Mariana Consiglio Kasemodel1; Joel Barbujiani Sígolo2; Valéria Guimarães Silvestre Rodrigues1
1 Escola de Engenharia de São Carlos - Universidade de São Paulo; 2 Instituto de Geociências - Universidade de São Paulo
Baixar PDF doi:10.20906/CPS/CB-05-0058
Resumo
From 1991 to 1995 mining waste (slag and tailing) enriched in potentially toxic metals was disposed directly on the soil of the rural area of Adrianópolis city (Paraná, Brazil). The waste was exposed to weathering for 18 years before it was spread in the form of waste cells and covered with thin layer of heterogeneous uncompressed residual soil from Eldorado Paulista (São Paulo, Brazil). In many spots the waste is still exposed due to the characteristics of the soil used in the coverage and the technique in which the coverage was conducted, making the waste susceptible to leaching and exposed to animals. The main objective of this study was to evaluate the geological and geotechnical properties of the topsoil of the deposit and determine whether these properties are assisting in the retention of the potentially toxic metals present in the waste. For this study, 9 soil profiles were collected from the deposit; 4 soil samples in the north-south (NS) direction (NS1, NS2, NS3 and NS4) and 5 in the east-west (EW) direction (EW1, EW2, EW3, EW4 and EW5). Soil samples were collected at 0-20 cm depth with an auger (Dutch model). The performed analysis were: particle size distribution, cation exchange capacity - CEC, specific surface - SS, clay activity (Ta), soil organic matter - SOM, delta pH - ΔpH, potential redox - Eh, x-ray fluorescence - XRF and total concentration of metals. Statistical treatment was obtained using the Pearson correlation index (R²). To assess the contamination the enrichment factor (EF) and the Nemero Quality Index (NQI) were calculated. The topsoil constitution is mainly of sand, in NS samples considerable quantities of silt and loam were also found. Medium CEC and SS values obtained for the NS samples were higher than those found for EW samples, indicating that NS samples has a greater content of fines and greater ability to retain cations. Activity clay varied from 18.9-75.6 cmol.kg-1 and SOM content was obtained in the interval of 0.40-3.30 %. Medium soil pH was neutral (7.0) with little v
Palavras-chave: potentially toxic metals; enrichment factor; pollution index; Ribeira Valley