Spatiotemporal Differentiation and Degradation Analysis of Polybrominated Diphenyl Ethers in Sediments of Shanmei Reservoir and Its Inflowing River, Quanzhou, China

Abstract

To investigate the spatiotemporal differentiation of polybrominated diphenyl ethers (PBDEs) in urban water-source reservoirs and degradation sources of BDE homologues and their contributions, we analyzed the contents, pollution degrees, spatial distributions, hydrological period changes, inventories, profiles, and degradation source contributions of PBDEs in the surface sediments of Shanmei Reservoir and its inflowing river, Quanzhou, China. The results showed that the median ∑PBDEs (1072.1 ng ·g-1) in the inflowing river sediment was 6.7 times than that of the reservoir (160.4 ng ·g-1) and the total amount of ∑PBDEs in sediments per unit area (80.3 kg ·km-2) was 6.3 times than that of Taihu Lake and 188 times than that of the Great Lakes in North America. The pollution degrees of PBDEs in Shanmei Reservoir were more severe than those of most lakes and reservoirs at home and abroad, which was dominated by BDE-209 (84.5%-99.2%). Most of the sampling sites in the reservoir (r 0.564-0.994, P<0.034) and the inflowing river (r 0.953-1.0, P<0.000) had high similarity in the composition of PBDEs. Significantly positive correlations (r 0.779-0.964, P<0.005) were observed between the reservoir entry area and river sampling sites, which were stronger than the other functional areas, indicating that the inflowing river was a major pollution source of PBDEs in the Shanmei Reservoir. The tail region of the reservoir had low correlations with the inflowing river (r 0.454-0.915, P≤0.128), and was relatively much more affected by Jiudu Town. The changes in hydrological period of the ∑PBDEs were relatively consistent at each sampling site (r 0.617-0.714, P≤0.077), but the impact of the changes in the hydrological period on the ∑PBDEs was not statistically significant (P=0.178, Two-Way ANOVA). However, the site changes had a significant influence on the ∑PBDEs (P=0.0001), and significant or nearly differences were observed between the reservoir entry area and other functional areas (P 0.019-0.061), indicating that the spatial distribution variations of the PBDEs in reservoir sediments were greater than the changes in hydrological period. The natural degradation of the PBDEs gradually increased from the river to the reservoir entry area and then to the central reservoir area. The reductive debromination rates varied at different brominated levels, and some BDE homologues accumulated due to their slowly continued degradation velocities. Research on abundance ratios indicated that the lower brominated BDE homologues were mainly derived from the natural degradation of decabromodiphenyl ether by stepwise reductive debromination. Approximately 70% of Nona-BDE produced by Deca-BDE degradation could rapidly be degraded to form Octa-BDE. Approximately 85% of BDE-208 was derived from the degradation of BDE-209. During the degradation process from Octa-BDE to Penta-BDE, some Octa-BDE and Hexa-BDE homologues accumulated due to relatively slower degradation velocities, and the degradation rates of Penta-BDE to Tri-BDE were above 70%.