Fate, transport, and plant uptake of ricinine in soils amended with castor cake organic fertilizer

The toxic alkaloid ricinine in castor cake organic fertilizers poses significant risks to groundwater and crop safety due to its potential for downward transport and plant uptake following land application. However, its environmental behavior remains insufficiently studied. To address this gap, a modified QuEChERS-based method coupled with LC-QTOF/MS was developed and validated, achieving recovery rates of 74.0-93.3 % and detection limits of 0.01-0.32 µg kg-1 for ricinine in castor cake, soils, and lettuce. Soil pot experiments investigated the fate, transport, and plant uptake of ricinine using two loam soils amended with castor cake fertilizers. Pot leaching experiments demonstrated ricinine's high mobility, with ricinine either leaching directly into water or converting to metabolites like N-demethyl-ricinine before transport. Ricinine concentrations in leachate, soil pore water, and soil solid phases decreased over time, with 5.1-40.6 % of the initial ricinine remaining after 14 days. Pot-cultivation experiments confirmed lettuce uptake of ricinine and its metabolite, with accumulation increasing at higher castor cake application rates, reaching up to 7.6 µg and 10.0 µg, respectively, and higher concentrations in shoots than roots. These results highlight ricinine's potential to contaminate agroecosystems, stressing the need for regulatory measures and effective management strategies to ensure food safety.