Enantioselective accumulation and trophodynamics of p-phenylenediamine antioxidants and their quinones in the mangrove ecosystem.

p-Phenylenediamines (PPDs) and their quinones (PPDQs) are contaminants of emerging concern. Nevertheless, scarce information exists on their bioaccumulation and biomagnification in food web. Moreover, chiral signatures of 6PPD and its quinone (6PPDQ) have not been studied in the field. Herein, the distribution, bioaccumulation, trophodynamics and enantiomeric compositions of PPDs and PPDQs were explored in the Qi'ao Island mangrove wetland of China. Concentrations of ΣPPDs and ΣPPDQs in mangrove biota ranged from not detected (nd)-352 and nd-49.4 ng/g lipid weight. Mangrove terrestrial birds had higher concentrations of ΣPPDs than aquatic biota. The enantiomeric compositions of 6PPD and 6PPDQ were assessed in the field for the first time. A notable enrichment of (+)-6PPD was detected in crab and fish, while a preferential accumulation of (-)-6PPD was seen in birds. Nonracemic signatures were also found for 6PPDQ in mangrove biota, with the preference accumulation of (+)-6PPDQ. IPPD, DPPD, DTPD and DPPDQ presented significant trophic magnification in the mangrove food web, while no clear trophodynamics trend was found for other target PPDs and PPDQs. Further investigation is necessary to explore the factors affecting the trophodynamics of PPDs and PPDQs and the mechanisms underlying the enantioselective bioaccumulation of 6PPD and 6PPDQ.