Spatiotemporal distribution of tetrabromobisphenol A and hexabromocyclododecane in mangrove sediments from the Pearl River Estuary

Surface sediments were collected from Tantou Mangrove Nature Reserve in Nansha, Guangzhou; Futian Mangrove National Nature Reserve in Shenzhen; and Qi'ao Island Mangrove Provincial Nature Reserve in Zhuhai in 2024 to investigate the distribution, composition, and spatial distribution of tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD), and temporal trends of TBBPA and HBCD were also discussed combining with the historical data. The results showed that concentrations of TBBPA in mangrove sediments were significantly lower than those of HBCD. Significant differences in levels and compositions of TBBPA and HBCD were found in sediments of the three mangrove wetlands from the Pearl River Estuary. The Futian mangrove wetland in Shenzhen had relative higher levels of TBBPA, and the Tantou mangrove wetland in Guangzhou had higher concentrations of HBCD. γ-HBCD and α-HBCD were the dominant HBCD in sediments form the Tantou mangrove wetland in Guangzhou and Futian mangrove wetland in Shenzhen, respectively. Sediments from Qi’ao Island mangrove wetland in Zhuhai had similar proportions of α-HBCD and γ-HBCD. Compared with the composition of HBCD industrial products, the proportions of α-HBCD in sediments of the three mangrove welands from the Pearl River Estuary increased significantly and the fractions of γ-HBCD decreased obviously. The concentrations of TBBPA in the mangrove wetlands of the Pearl River Estuary showed a decreasing trend, indicating that the use of TBBPA in the Pearl River Delta region is decreasing. The concentrations of HBCD in the mangrove wetlands is still increasing.