Characterization of atmospheric cadmium deposition and its simulated combined toxicological effects on wheat (Triticum aestivum L.) seedlings with sulfamethoxazole in soil.

Cadmium (Cd) accumulation caused by atmospheric deposition and combined Cd-sulfonamides stress via different input pathways in agricultural ecosystems warrants more attention. Based on a 2-year (2019-2020) observation of atmospheric Cd deposition, the effects of varying simulated Cd fluxes, different soil sulfamethoxazole (SMX) contents and their joint exposure on wheat (Triticum aestivum L.) seedlings were systematically investigated. Atmospheric Cd deposition was prominent in the region during the winter-to-spring and autumn-to-winter transitions (5 months, accounting for nearly 60 % of the annual total), and driven by human activities (most enrichment factors (EFs) were >1000). According to pot bioassays, response thresholds to simulated Cd deposition were: 5.0 mg m-2 yr-1 (early warning) and 25.0 mg m-2 yr-1 (irreversible damage). Roots physiological responses to Cd deposition were more sensitive than aerial parts, probably due to organ-specific coping mechanisms and spatial enrichment of Cd in topsoil. An integrated biomarker response (IBR) assessment on combined stress suggested that high-intensity Cd deposition affected seedlings more than high-concentration SMX, which could be explained by dual mechanism of Cd invasion upon its deposition. Evaluation on compound toxic effect and analyses on translocation factors of Cd revealed an antagonistic influence of two pollutants, further indicating that the application of manure fertilizer in autumn might be more reasonable.