Resumo

ROCA, NURIA. HEAVY METAL BACKGROUND LEVELS IN RURAL SOILS: A CASE STUDY IN PAMPEAN SOILS (ARGENTINA). Cienc. suelo [online]. 2015, vol.33, n.2. ISSN 1850-2067.

Azul, an agricultural county at the center of Buenos Aires province, Argentina, was proposed as a reference for heavy metal background levels. These levels will be used to identify and assess soil pollution processes at the regional level. Forty-two top soils were sampled and heavy metals contents were analysed for seven elements (Cd, Co, Cr, Cu, Ni, Pb, and Zn) with an inductively coupled plasma-mass spectrometer (ICP-MS) after acid digestion. Considering the need to find a simple and robust statistical test, three methods (4o-outlier test, iterative 2o-outlier test and calculated distribution function) were used. The upper limits of the background ranges were expressed in mg kg^-1: Cd 0.15, Co 10.8, Cr 22.1, Cu 39.2, Ni 13.7, Pb 11.8 and Zn 133.9. Once the background upper limits were established, a few points with anthropic signatures were observed. Cd was the heavy metal which showed the greatest number of samples with enrichment anomalies. The greatest enrichment anomalies in Cd, Cr, Cu, Ni, Pb and Zn were detected in grassland top soils due to an unauthorized rubbish dump. The slight anomalies in crop lands could be due to an incipient anthropic contamination.

Palavras-chave : Background, trace elements, soil pollution, anthropic sources.

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