Strong Evidence of Organophosphite Antioxidant Transformation as an Important Source of High-Risk Novel Organophosphate Esters in River Water

Organophosphate esters (OPEs) are widely detected in various environmental media, but the indirect source from the transformation of organophosphite antioxidants (OPAs) is usually neglected. This study identified 12 novel OPEs (NOPEs) in water from the upper reaches of the Yellow River, China. The total concentrations of dissolved OPEs in water ranged from 51 to 1575 ng/L, while the suspended particulate matter associated with the OPEs were 84–8009 ng/g dw, both dominated by four suspected transformation products of the OPAs. Among them, bis(2,4-ditert-butylphenyl) pentaerythritol phosphate phosphite (AO626=O) was first reported in environmental matrices. Interestingly, the concentrations of NOPEs were higher in rural areas than in urban areas, which might be attributed to the extensive application of OPAs in industrial and agricultural activities in rural areas. The significant correlation between the concentrations of bis(2,4-ditert-butylphenyl) pentaerythritol diphosphite (AO626) and AO626=O in water, principal component analysis, and simulated photolysis experiments confirmed that transformation of the OPAs made a great contribution to the total OPEs in the surface water of the Yellow River. Based on the Toxicological Priority Index scheme, four OPA transformation products were identified as high priority. This study provides new insights into the great contribution from the transformation of OPAs to the contamination and environmental risk of OPEs in aquatic environments.