Transfer of heavy metals in topsoils, based on sequential extraction and statistical tools in Northeast Brazil

Abstract

Abstract Trace metals are associated with various organic and inorganic components, appearing in different chemical forms, which regulate their solubility, mobility, and availability to biological systems. Given this, it is necessary to know the chemical form in which these elements are found since this defines their potential for remobilization. Thus, this work aimed to evaluate the distribution and mobility of Pb, Cu, Cd, Cr, Ni, and Zn in eight types of soils from Northeast Brazil. The concentration in the fractions was determined through sequential extraction using the procedure outlined by the Community Bureau of Reference (BCR). Cu was extracted using oxidizing conditions and in the residual fraction. The Principal Component Analysis (PCA) and Pearson correlation matrix were used in fifty topsoil samples to investigate the relationship between metals and physical-chemical parameters. The results revealed that metals were prevalent in the residual fraction. Cd, Ni, and Zn were primarily detected in the mobile fraction. Cd and Pb were associated with Fe and Mn oxides, suggesting the mobility of these metals within the environment. The organic matter and texture influenced the mobility of metals in the soil. The PCA analysis shows that the pH correlates positively with Ni, Cu, and Cr and negatively with Zn, Cd, and Pb. The parameters analyzed showed significant variations across different soil classes, highlighting their diverse nature. The findings highlighted the significance of sequential metal extraction in soil and the utilization of PCA to predict changes in solubility and determine its availability to plants.