Multisource attribution and transfer dynamics of PTEs in soil–rice systems in Southwestern China

Contamination by potentially toxic elements (PTEs) in soil–rice systems poses serious threats to food safety and human health. A total of 225 soil samples and 90 rice samples were collected from typical rice-growing areas in Chongqing, Southwestern China, to investigate PTE sources and transfer in the soil–rice system. The concentrations of 11 PTEs (As, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Se, and Zn) were determined, and their sources and migration behaviors were investigated using a Positive Matrix Factorization (PMF) model combined with enrichment and transfer indices. Results showed that Zn and Mn dominated in soils, while As, Cd, and Hg exhibited pronounced spatial heterogeneity and signals of exogenous disturbance. PMF identified five pollution sources in soils: geological background (39.5%), agricultural sources (34.8%), light industrial activities & sewage irrigation (17.8%), arsenic-enriched urban disturbance mixed source (5.7%), and industrial emissions & atmospheric deposition (2.2%). Within rice plants, Cd, As, and Se were notably enriched in roots (BCF > 2.6), while grain translocation was limited, indicating a protective barrier. PMF source analysis for rice identified industrial activities & traffic (40.8%), agriculture & irrigation water (34.5%), and coal combustion & waste disposal (24.7%) as major contributors. Transfer coefficient patterns suggested element-specific translocation within rice plants, with Cd showing relatively stronger upward movement, Zn preferentially enriched in stems, and grain accumulation remaining low for most elements. This study provides insights into PTE source-associated patterns and transfer dynamics in soil–rice systems, providing a theoretical basis for paddy soil remediation and agricultural product safety management.