Pollution Levels, Ecological Risks, and Potential Sources of Toxic Elements in Farmland Soils of the Ibinur Lake Basin, China

Potentially toxic elements (PTEs) are one of the most concerning pollutant types in the surface environment. In this study, a total of 115 farmland soils from the 0–20 cm layer were collected from the Ibinur Lake Basin (ILB) in northwest China to investigate the concentration characteristics, pollution status, potential ecological risks, and possible sources of seven PTEs (As, Cd, Cu, Ni, Pb, Hg, and Zn). The pollution load index (PLI) method was applied to quantify soil pollution status, while the potential ecological risk index (RI) was adopted to evaluate PTE-induced ecological risks. Multivariate statistical approaches were further implemented to trace the potential sources of these PTEs. The obtained results revealed that the average concentrations of As, Cd, Ni, Pb, and Zn present in farmland soil surpass the corresponding background values by factors of 2.41, 1.99, 1.15, 1.18, and 5.60, respectively. Single-factor pollution assessment indicated heavy Zn pollution, moderate As pollution, low-level Cd, Pb, and Ni pollution, and slight Cu pollution across farmland soils in the ILB, whereas no Hg pollution was detected. PTEs in farmland soil show a low pollution level, with an average PLI value of 1.31. Obvious spatial heterogeneity was observed in the distribution of all seven PTEs. The comprehensive potential ecological risk of PTEs remained low, with an average RI of 23.87; among all target PTEs, As and Cd contributed the largest share of ecological risks. Source apportionment demonstrated that Cd, Cu, Ni, Pb, and Zn were potentially derived from combined natural and anthropogenic inputs, Hg was likely associated with lithogenic natural sources, and As was potentially derived from agricultural anthropogenic activities. Collectively, As and Cd were identified as the priority pollutants posing pollution and ecological risks in this basin. This study improves the systematic understanding of PTE pollution risks in arid agricultural soils and the results suggest that regular long-term monitoring should be implemented for local soils.