Dynamics of polycyclic aromatic hydrocarbons (PAHs) in water column of Pearl River estuary (China): Seasonal pattern, environmental fate and source implication

Based on a monthly sampling effort in 2011, >62 polycyclic aromatic hydrocarbons (PAHs) in different environmental phases were detected in the Pearl River estuary, China. The study aimed to investigate seasonal variation in PAH concentration and composition, potential risk source, depth profile and environmental correlation and to provide a non-deterministic insight into the PAH behavior. The total PAHs varied widely throughout the 12 months of the study period, ranging from 25.99 ng/l to 522.26 ng/l in seawater and from 7.37 μg/g to 167.44 μg/g in suspended sediment (SPM). The 16 Environmental Protection Agency (EPA) priority PAHs ranged from 12.70 ng/l to 160.15 ng/l in seawater and from 2.82 μg/g to 112.32 μg/g in SPM. Low molecular weight (LMW) PAHs (2- and 3-ring) were the most abundant, responsible for 81% in seawater and 73% in SPM. Moreover, it appeared that SPM and ambient water temperature were the determining factors controlling the transport and distribution of PAHs in the water column. A higher concentration of SPM contributed to a higher content of PAHs due to adsorption and low solubility. The PAHs were more significantly associated with particles than were dissolved in seawater. In addition, petroleum emissions, vehicle emissions, and wood combustion were considered a potential risk of PAHs via statistically-based methods of principal component analysis (PCA) and diagnostic ratios. The findings are useful for understanding the dynamics of estuarine PAHs, which exert significant influence on coastal ecosystems.