Soil Properties Regulate the Fate and Accumulation of Atmospherically Deposited Trace Metals in Rice across Six Major Growing Regions of China

Atmospheric deposition is a pathway of trace metal contamination in agroecosystems, yet how divergent soils regulate the behavior and crop uptake of newly deposited trace metals remains incompletely understood. Here, we combined a field soil-transplantation experiment and a greenhouse pot experiment that separately imposed foliar and root exposure using six paddy soils from six major growing regions of China. Results showed that soil properties governed the speciation, mobility, and rice accumulation of deposited metals. Copper (Cu), lead (Pb), and zinc (Zn) exhibited greater solubility and grain accumulation in lower-pH, lower-sorption, and southern-provenance soils, whereas arsenic (As) was more mobile and accumulated preferentially in higher-pH, SOM-rich northern-provenance soils with finer texture. The pot experiment indicated that foliar exposure dominated trace metal enrichment in leaves and husks, whereas root exposure contributed more strongly to grain As in several soils. Elemental mapping of the flag leaf-node junction measured by LA-ICP-MS revealed distinct tissue-association patterns under the two pathways. Soil redox fluctuations further differentiated metal behavior: Cu increased after drainage, whereas As peaked under flooding. These findings show that element- and soil-property-specific responses shape food-safety risks posed by atmospheric deposition and support region-specific soil and emission management.