Recently, Xu Xiangrong's team from the Key Laboratory of Tropical Marine Biological Resources and Ecology of the South China Sea Institute of Oceanography, Chinese Academy of Sciences made progress in ecological risk prevention and control of organic phosphorus flame retardants in the Pearl River Estuary based on the idea of land and sea integration. The relevant research results, titled Organophosphate flame retardants and their metabolites in the Pearl River Estuary: occurrence, influencing factors, and economic risk control strategies based on a mass balance model, were published in Environment International.

Plastic additives represented by organophosphorus flame retardants (OPFRs) are a new type of pollutant that has attracted much attention and has become one of the research hotspots in the field of offshore ecological environment. As these land-based pollutants enter the nearshore environment such as estuaries, they migrate under the action of hydrodynamic processes such as runoff and tides, redistribute through processes such as adsorption, sedimentation, and suspension, undergo transformation under the effects of photodegradation and biodegradation, and accumulate and even transfer between different organisms in the food chain, thereby posing a pollution stress effect on the entire nearshore ecosystem. However, current research on new pollutants such as OPFRs in nearshore environments such as estuaries is mostly limited to environmental occurrence, spatiotemporal distribution, and source identification. There are cognitive bottlenecks in their source sink patterns and ecological risk prevention and control in nearshore ecosystems.

Through seasonal monitoring, this study revealed the temporal and spatial distribution and influencing factors of OPFRs and their metabolites in the water and sediment of the the Pearl River Estuary. The study found that OPFRs and their metabolites showed obvious land sea transfer characteristics in the the Pearl River Estuary, and showed significant seasonal differences; However, there was no significant seasonal difference observed in the sediment, indicating that OPFRs may be in a state of input-output balance in the sediment. Further, the horizontal and vertical migration fluxes of OPFRs and the inventory of water and sediment were studied and calculated. It was found that the horizontal migration of OPFRs was the main trend in the the Pearl River Estuary. Inventory assessment indicates that both water bodies and sediments are important storage facilities. Based on the improved mass balance model, the study clarifies the seasonal source sink pattern of OPFRs in the estuarine environment for the first time. It is found that river input is the main way for OPFRs to enter the the Pearl River Estuary, and the fluxes in the normal season, dry season and wet season are 1.55 × 105, 6.28 × 104 and 9.00 × 104 kg/yr respectively, while a large number of OPFRs in the the Pearl River Estuary will eventually migrate to the open sea. The the Pearl River Estuary plays a limited role in the ecological barrier of OPFRs in the process of land sea transfer, and tends to be the source of offshore OPFRs.

This work found through risk assessment based on marine ecosystems that one type of OPFRs (EHDPHP) exhibits moderate ecological risk in water bodies, while the marine ecological risk of other target compounds is relatively low. In combination with the established mass balance model, the study uses the multi scenario numerical simulation of controllable factors to find that the ecological risk of EHDPHP in the the Pearl River Estuary can be effectively reduced by limiting the concentration of EHDPHP in the estuary section of the the Pearl River Estuary. Based on the PNEC value of EHDPHP in the the Pearl River River Estuary area, the theoretical control objective of EHDPHP pollution in the Pearl River Estuary in normal, dry and wet seasons was proposed. This achievement provides a reference for the risk control of new pollutants in land sea coordination, but due to limited data, there is a certain degree of uncertainty in risk assessment models and environmental models. Future research still needs to further demonstrate the proposed regulatory objectives, optimize research results on the premise of obtaining more toxicity data and field investigation data, in order to serve marine and watershed environmental management.

The research work has received support from the National Natural Science Foundation of China, the Guangzhou Science and Technology Program, and the Guangdong Provincial Key Laboratory of Applied Marine Biology.