Source Identification and Apportionment of HeavyMetals in Tobacco Farmland Soils via PositiveMatrix Factorization and Geochemical Indices

Abstract

Soil heavy metal contamination in tobacco-growing areas poses a significant threat to ecosystem health and agricultural product safety. Precise identification of pollution sources and assessment of ecological risks are crucial for developing targeted environmental management strategies in such typical agricultural regions. This study conducted a systematic evaluation of pollution levels, ecological risks, and sources of heavy metals in the soils of Zhangping County, a key tobacco-producing region in Fujian Province, China. We collected 70 surface soil samples and analyzed the concentrations of Cd, Hg, As, Pb, Cr, Cu, and Zn. A comprehensive methodology was employed, including the Single-factor Pollution Index (P<sub>i</sub>), Nemerow Integrated Pollution Index (P<sub>n</sub>), Potential Ecological Risk Index (RI), and Geo-accumulation Index (Igeo) for contamination and risk assessment, coupled with Principal Component Analysis (PCA) and Positive Matrix Factorization (PMF) for quantitative source apportionment. Results revealed that Cd and Hg were the primary pollutants, showing significant enrichment compared to the Fujian background values. Ecological risk assessment identified Cd and Hg as the major risk drivers, elevating the study area to a moderate-to-considerable ecological risk level. Igeo values confirmed the predominance of anthropogenic inputs for Cd and Hg. Source apportionment quantitatively resolved three main sources: industrial-traffic emissions (43.1%, contributing primarily to Pb, Cu, Zn, and Cd), a mixed source of natural pedogenesis and historical agricultural activities (48.6%, contributing predominantly to Cr, As, and Hg), and a specific agricultural source (8.3%, contributing notably to Cd and Hg). Although the total concentrations of heavy metals did not exceed national risk thresholds, inputs of highly toxic elements (particularly Cd and Hg) from agricultural and industrial activities have induced significant potential ecological risks. The synergistic application of PCA and PMF effectively elucidated the complex pollution sources. This study underscores the necessity of prioritizing the control of anthropogenic heavy metal inputs (especially Cd and Hg) in intensive agricultural areas and provides a scientific basis for formulating precise and differentiated soil pollution control strategies.

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