An integrated approach for quantifying trace metal sources in surface soils of a typical farmland in the three rivers plain, China

The presence of trace metals (TMs) in agricultural soil has garnered considerable attention due to their potential migration into crops, posing a significant risk to human health. In this study, we examined the concentrations of eight trace metals (Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) in the soil and investigated various soil physicochemical characteristics in the Three Rivers Plain region, China. The assessment of the geoaccumulation index (Igeo) for the mean concentration of all trace metals indicated that the soils were generally free from significant TM pollution. However, a noteworthy finding emerged in relation to Hg, where the maximum Igeo value suggested moderate pollution levels. Kriging prediction results further indicated that approximately 1.55% of the study area might be impacted by Hg pollution. Moreover, it is prudent to direct attention towards Cd, Cr, Cu, Mn, and Ni, as their Igeo values revealed that the region with the highest concentrations of these metals ranged from unpolluted to moderately polluted. This study employed a comprehensive approach, utilizing the Self-Organizing Map (SOM), Kriging spatial distribution, and the Positive Matrix Factorization (PMF) model to identify the sources of TMs in agricultural soil. The results unveiled that the primary contributors to TM presence were the natural parental materials, alongside industrial activities such as coal mining and coal plant operations, as well as agricultural practices. These findings provide foundational insights for future management strategies in the Three Rivers Plain, aiming to enhance agricultural productivity and promote sustainability.