Occurrence, Ecological Risks, and Potential Influencing Factors of Typical PPDs and PPDQs in Urban River Sediments from the Hinterland of the Yellow River Delta in China

Surface sediments from 9 rivers in the hinterland of the Yellow River Delta in China were analyzed for five p-phenylenediamines (PPDs) and their quinones (PPDQs). PPDs and PPDQs were widely detected, with ΣPPDs and ΣPPDQs ranging from 0.02 to 31.7 ng/g dry weight (dw) and 0.03 to 72.8 ng/g dw, respectively. N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) was the dominant PPD, accounting for 42.96% of ΣPPDs, whereas N,N′-diphenyl-p-phenylenediamine quinone (DPPDQ) was the predominant PPDQ, contributing 59.3% of ΣPPDQs. ΣPPDs and ΣPPDQs concentrations differed significantly among rivers, with marked variation within the same basin. Significant differences in ΣPPDs and ΣPPDQs were observed among the economic level–road exposure groups. Most site-specific ΣRQ values (92.0%) were below the screening threshold of 1, with a median ΣRQ of 0.124. DPPDQ contributed the most to ΣRQ (39.32%), followed by 6PPD-quinone (6PPDQ) (24.14%) and N-cyclohexyl-N′-phenyl-p-phenylenediamine quinone (CPPDQ) (8.71%). The findings provided insights into the environmental behavior and monitoring of tire-derived contaminants in urban rivers.