Key Takeaways & Executive Findings
- •• • Total concentrations of seven rubber additives and 6PPD-Q in the Guangzhou section of the Pearl River ranged from 205 to 5400 ng·L−1 (mean 820±1100 ng·L−1), indicating substantial contamination levels that warrant monitoring and mitigation. • • DPG dominated both dissolved (99±1.9%) and particulate (66±13%) phases, underscoring its role as a primary pollutant and its potential for widespread aquatic transport. • • 6PPD-Q exhibited high ecological risk (RQ > 1) at all 29 sampling sites, while DPG showed moderate to high risk (RQ > 0.1) at most sites, necessitating priority action for these compounds. • • Source apportionment linked contamination to aquaculture, vessel navigation, agricultural land, and wastewater treatment plant discharges, providing actionable targets for pollution control strategies.
Abstract
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.
1. Introduction
The global rubber industry has expanded rapidly, with annual production of rubber additives in China increasing from 930,000 tons in 2013 to 1.37 million tons by 2020, accounting for approximately 75% of global output. These additives, including vulcanization accelerators like DPG and antioxidants such as PPDs, are essential for improving rubber processing and product durability. However, their release into aquatic environments, primarily through tire wear particles (TWPs), has raised concerns due to their persistence and toxicity. For instance, 6PPD-Q, an ozonation product of 6PPD, has been linked to acute mortality in coho salmon, while DPG exhibits allergenic and genotoxic potential. Despite increasing detection in rivers worldwide, comprehensive data on their distribution and ecological risks in Chinese river systems remain limited.
The Guangzhou section of the Pearl River, a major waterway in southern China, faces complex pollution sources, including urban runoff, industrial discharges, and intensive aquaculture. Previous studies have focused on legacy pollutants, leaving a gap in understanding the occurrence of rubber additives and their transformation products. This study addresses that gap by systematically analyzing 29 surface water samples for seven rubber additives and 6PPD-Q, employing risk quotient (RQ) assessment to evaluate ecological threats. The findings provide critical baseline data for regulatory frameworks and highlight the urgent need to manage these emerging contaminants in the Pearl River Basin.
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ZHANG Menghuan, CHEN Xiaoli, ZHONG Lixiang, LIN Mingfu, SONG Lisha, HUANG Yumei, WANG Jun (2026). Distribution Characteristics and Risk Assessment of Typical Rubber Additives and Their Transformation Products in the Guangzhou Section of the Pearl River, China. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025051404
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Frequently Asked Questions
What are the dominant rubber additives in the Guangzhou section of the Pearl River, and how do their phase distributions affect their environmental fate?
DPG was the most abundant compound, comprising 99±1.9% of dissolved phase and 66±13% of particulate phase concentrations. This indicates that DPG predominantly remains in the dissolved phase, enhancing its mobility and bioavailability. In contrast, 6PPD-Q showed a stronger affinity for particulate matter, which may influence its transport and sedimentation dynamics.
What are the ecological risk levels of the detected compounds, and which ones require immediate regulatory attention?
Risk quotient (RQ) analysis revealed that 6PPD-Q posed high ecological risk (RQ > 1) at all 29 sampling sites, while DPG exhibited moderate to high risk (RQ > 0.1) at most sites. In contrast, 6PPD, IPPD, CPPD, and DPPD showed low risk (RQ < 0.1). These findings necessitate priority monitoring and management for 6PPD-Q and DPG.
What are the likely sources of rubber additives in the Pearl River, and how can they be mitigated?
Source analysis suggests that aquaculture, vessel navigation, agricultural runoff, and wastewater treatment plant discharges are major contributors. Mitigation strategies could include improving wastewater treatment processes to remove these compounds, regulating rubber product use near waterways, and implementing best management practices for agricultural and aquaculture activities.
How do the concentrations of rubber additives in the Pearl River compare to other global rivers, and what are the implications for regional water quality?
The total concentrations (205–5400 ng·L−1) are comparable to or higher than those reported in other urban rivers, indicating significant contamination. This underscores the need for regional water quality standards and continuous monitoring to protect aquatic ecosystems and human health.
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