Occurrence and partitioning of p-phenylenediamine antioxidants and their quinone derivatives in water and sediment

Abstract

p-Phenylenediamine antioxidants (PPDs) and PPDs-derived quinones (PPDQs) may pose a threat to the river ecosystem. However, the knowledge on the occurrence and environmental behaviors of PPDs and PPDQs in the natural river environment remains unknown. In this study, we collected paired water (n = 30) and sediment samples (n = 30) from Jiaojiang River, China and analyzed them for nine PPDs and seven PPDQs. Our results showed that target PPDs and PPDQs are frequently detected in water samples, with the dominance of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD; mean 12 ng/L, range 4.0–72 ng/L) and 6PPD-derived quinone (6PPDQ; 7.0 ng/L, <LOD–21 ng/L), respectively. In sediment samples, detected PPDs and PPDQs were also dominated by 6PPD (mean 31 ng/g, range 1.6–172 ng/g) and 6PPDQ (14 ng/g, <LOD–46 ng/g), respectively. This study first reports the field-based log-transformed sediment-water coefficients (log Koc) for PPDs and PPDQs. Among PPDs, N, N′-diphenyl-p-phenylenediamine (4.0 ± 0.55) had the highest mean log Koc value, followed by N-isopropyl-N′-phenyl-p-phenylenediamine (3.6 ± 0.26). The mean log Koc values of detected PPDQs ranged from 2.0 ± 0.49 to 3.3 ± 0.44. To our knowledge, this is the first study comprehensively investigating the occurrence of PPDs and PPDQs in paired freshwater and sediment. Results of this study provide new insights into their occurrence, spatial distribution, and behaviors in the freshwater environment.