Distribuição de elementos traço em solos do município de Salvador

Abstract

Population agglomeration, combined with intense human activity in the capital of Bahia, generates a large amount of waste that tends to reach the various ecosystems, altering them continuously. Of these, the terrestrial ecosystem deserves to be highlighted, whose soil matrix, object of study in this work, can be a vehicle for human exposure to elements present in these residues. Despite the possible human impacts on the soil, the main source of information related to its physicochemical characteristics is present in the soil map, which does not always meet the real characteristics. Therefore, the relevant data are associated with the original composition of the matrix rock and not with the effects of urbanization. So, in order to expand the information in the database on soils in the municipality of Salvador-Ba, this work aims to characterize its soils, collected in areas with high circulation of people and vehicles. For this purpose, the physical-chemical characterization of the samples was carried out by determining the following parameters: pH, organic matter content, granulometry, presence of organic and inorganic compounds, and mineralogical composition. In addition, the contents of 24 elements were determined (Al, As, Ca, Cd, Pb, Co, Cr, Cu, S, Sb, Sn, Sr, Fe, P, Li, Mg, Mn, Mo, Ni, K , Se, Na, V and Zn) using ICP-OES. Of the elements selected to be quantified, 12 were detected (Al, Ca, Cr, Pb, Cu, Sr, Fe, Mg, Mn, K, V and Zn). The concentrations of these elements are found with values below the guiding limits according to Resolution No. 420 of December 28, 2009 of the National Council for the Environment (CONAMA), for elements with established limits. However, when confronted with assessments of the Pollution Index (PI), Geoaccumulation Index (Igeo) and Enrichment Factor (EF), it is clear that their values fall into a situation of environmental care, as they indicate significant contamination due to the accumulation of same. These data were most prominent for Al, V and Sr, elements of wide application in items such as car construction and everyday objects such as pots, aluminum foil, cutlery etc. These data were evaluated using two partial extraction methods, one involving pseudo-total extraction and the other of phytoavailable elements. Comparing the data from both methods, a favoring of the elements in the phytoavailable fraction can be seen, that is, a prevalence of the elements preferentially in the ionic form, where it is more available for carrying out mass exchanges in the rhizosphere region. Therefore, in the phytoavailable fraction, the PI, Igeo and FE for some elements (Cu, Sr and Pb) have higher values than expected in relation to the pseudo-total fraction. From all the information obtained, it is concluded that the soils collected in the city Salvador-Ba are in a situation of environmental care and are not in agreement with the information contained in the soil map of Brazil.