Spatiotemporal variations of halogenated polycyclic aromatic hydrocarbons in sediments of Pearl River Estuary: Occurrence, sources, and potential ecological risks.

Halogenated polycyclic aromatic hydrocarbons (HPAHs) as a group of emerging environmental contaminants have attracted considerable attention. The occurrence, sources, and potential ecological risks of HPAHs in the human-impacted estuaries still need to be continually examined. Here, surface sediments were collected from the Pearl River Estuary (PRE) and analyzed to understand the spatiotemporal variations of HPAHs (8 chlorinated PAHs and 9 brominated PAHs). The total concentrations of 17 HPAHs in the PRE sediments were significantly higher in the wet season (6.41-17.1 ng/g) than in the dry season (0.46-5.35 ng/g). Among all HPAHs, 2,7-dibromofluorene was most abundant in both wet and dry seasons, accounting for 21.5 % and 42.0 % of the total HPAHs, respectively. Positive matrix factorization (PMF) demonstrated that industrial processes, fuel combustion and waste incineration were the primary anthropogenic sources of HPAHs in the PRE. Individual HPAHs in the PRE sediments were estimated to be no or low risks to aquatic organisms. However, the combined ecological risks of all HPAHs detected in the PRE sediments reached the low or moderate levels in the wet season. Our results suggest that synergistic exposure to multiple HPAHs with seasonal elevation can lead to significant risks to the estuary ecosystem.