Prioritizing alkylated and oxygenated PAHs over PAHs in freshwater organisms: Evidence from a Chinese freshwater lake

Although the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) has been extensively studied, there is no consensus on their trophic transfer in freshwater food webs. More importantly, data on bioaccumulation and trophic transfer of PAH derivatives remain scarce. To fill this knowledge gap, 79 polycyclic aromatic compounds (PACs), including PAHs, alkylated PAHs (Alk-PAHs), oxygenated PAHs (OPAHs), and heterocyclic aromatic hydrocarbons (HAHs), were quantified in 19 aquatic species from Lake Chaohu, China. Total concentrations of PACs ranged from 2.2 to 47 ng g^-1 wet weight (median: 15 ng g^-1). Notably, unlike lake sediments, Alk-PAHs replaced PAHs as the predominant component in organisms, demonstrating their strong bioaccumulation. Biota-sediment accumulation factor (BSAF) further indicated that methylation likely enhances the bioavailability and bioaccumulation of anthracene, phenanthrene, benzo[a]anthracene, and benzo[c]phenanthrene. In addition, ontogenetic shifts in diet and metabolism during growth also appeared to affect Alk-PAHs burdens in C. alburnus, H. molitrix, and C. carpio. Trophic magnification factors (TMFs) for PACs varied from 0.50 to 2.1. A comparison with data from a 2010 survey revealed a shift in trophic transfer of priority PAHs, from dominated-biodilution toward more frequent occurrences of TMFs > 1. Importantly, several PAH derivatives, including dibenzothiophene, 2-methylnaphthalene, 1,4-dimethylnaphthalene, 1,5-dimethylnaphthalene, 2-methylbenzo[c]phenanthrene, 9,10-anthraquinone, 9-fluorenone, and 6,8-dimethylbenzo[a]anthracene displayed higher TMFs than their corresponding parent PAHs or analogs, highlighting the necessity of enhancing the priority of their monitoring.