Elementos pontecialmente tóxicos e determinação de baselines geoquímicos no solo de Barcarena, Pará.

Abstract

The municipality of Barcarena, in the state of Pará, is home to a major industrial center, including mining and metallurgical activities, and has been the subject of debates about environmental impacts. Soil contamination by potentially toxic elements (PTEs) is a major concern, especially due to the lack of systematic information that can support public authorities' actions. The aim of this study was to assess the concentrations of arsenic (As), barium (Ba), cadmium (Cd), lead (Pb), cobalt (Co), copper (Cu), chromium (Cr), mercury (Hg), molybdenum (Mo), nickel (Ni), zinc (Zn), aluminum (Al) and iron (Fe) in the municipality's soils and to determine geochemical baseline values for these elements. Samples were collected at two depths (0-20 cm and 40-60 cm), and the concentrations were compared to the values established by Conama Resolution 420/2009. The analyses were carried out using inductively coupled plasma optical emission spectrometry (ICP-OES), except for Hg, which was determined using cold vapor atomic fluorescence spectrometry. The results showed that 8 samples exceeded the Prevention Values (PV) for Ba, 12 for Cu, 6 for Cr and 27 for Hg, while 2 samples exceeded the limit for Cd and Ni. In addition, the Investigation Values for Agricultural Areas (VIAgri) were exceeded in 2 samples for Cd and Cr, 1 for Cu and 10 for Hg, reinforcing the need to pay attention to these elements. For residential areas (VIRes), only 1 sample exceeded the limit for Cr, and no sample exceeded the criteria established for industrial areas (VIInd). The Mann-Whitney U test revealed statistically significant differences between the depths for As, Ba, Co, Cr, Hg, Mo, Ni, Pb, Zn, Al and Fe, and for all elements except Cd and Co, concentrations were higher in the 40-60 cm layer. Baseline values varied according to the methods used, with TIF and MAD being the most tolerant, while I2σ was the strictest. In addition, baseline values were higher for samples from the deepest layer, reflecting the influence of local geology and possible metal mobilization processes along the soil profile. These findings indicate that contamination can be associated with both anthropogenic sources and natural geochemical enrichment processes. In this way, it is hoped that this study will contribute to understanding the chemical quality of soils and provide subsidies for more effective environmental management strategies, promoting actions that minimize the impacts of contamination and guarantee the protection of the soil's ecological functions.