Distribution Characteristics and Risk Assessment of Typical Rubber Additives and Their Transformation Products in the Guangzhou Section of the Pearl River, China
Rubber additives, such as 1,3-diphenylguanidine (DPG) and p-phenylenediamine antioxidants (PPDs), are widely used in the rubber industry and have been increasingly detected in aquatic environments. This study investigated the distribution characteristics and potential sources of seven typical rubber additives (DPG, 6PPD, IPPD, DPPD, CPPD, DNPD, and 77PD) and the transformation product 6PPD-Q in surface water of the Guangzhou section of the Pearl River, China. A total of 29 sampling sites were analyzed. Total concentrations of the target compounds ranged from 205 to 5400 ng·L−1, with a mean of (820±1100) ng·L−1. DPG was the dominant compound in both dissolved and particle phases, accounting for (99±1.9)% and (66±13)% of the total concentrations, respectively. Source analysis indicated that aquaculture, vessel navigation, agricultural runoff, and wastewater treatment plant discharges likely influence the occurrence of rubber additives in this river section. Risk quotient (RQ) assessment revealed that 6PPD-Q posed high ecological risk at all sampling sites (RQ > 1), while DPG exhibited moderate to high risk at most sites (RQ > 0.1). In contrast, 6PPD, IPPD, CPPD, and DPPD showed low ecological risk. These findings highlight the need for heightened attention to the ecological risks posed by 6PPD-Q and DPG in the Pearl River Basin and provide scientific data for pollution prevention and risk management.