Risk classification and zoning management of heavy metal pollution in paddy soils: A model coupling soil health and...

To improve management and refined control of soil contamination, the positive matrix factorization (PMF) model was integrated with the global and local Moran's index (Moran's I) to quantitatively identify the sources of heavy metal contamination. Furthermore, an assessment of soil health was conducted, taking into account heavy metal concentrations, soil fertility, and buffering capacity. A new methodology was proposed, integrating pollution source contribution analysis with soil health evaluation to systematically classify and delineate risk zones for soil heavy metal contamination. A total of 209 soil samples were collected from the rice-growing areas in Deyang region. The research findings on heavy metal pollution in this region indicated that Cd and Pb (1.81 mg/kg and 136.11 mg/kg, respectively) are the primary control elements. These values are 4.17 and 4.28 times the background values in the study area, respectively. Five source factors were identified through the PMF model, and combined with the Moran's I, it was indicated that Cd mainly originated from industrial activities (13.06 %), while Pb mainly came from road traffic (accounting for 22.96 %). The results of the soil health index implied that approximately 40 % of the area in the study region exhibits unhealthy soil conditions. The integrated grading and zoning model, incorporating the interaction of pollution source contributions and soil health, demonstrated that roughly 25 % of the study area is at medium-to-high risk. The areas prioritized for control are predominantly distributed within a circular zone with a radius of 750 m, centered around the industrial enterprises along the Shiting River. The findings present a viable strategy for mitigating soil heavy metal contamination at point sources, thereby diminishing total remediation expenses.