Toxic effects of complex mixed organic compounds in aerosols on <i>Skeletonema costatum</i>

Considering the complexity of organic components in aerosols, this study aimed to compare the toxic effects of mixed PAHs and the highly toxic benzo[a]pyrene on Skeletonema costatum (S. costatum). To achieve this, weakly polar organic compounds containing PAHs (TSP-PAHs) were extracted from winter aerosols collected in Qingdao, China. The study then assessed and compared the toxicity of TSP-PAHs (the exposure concentrations were set at 0.15 - 1 μg/L) and a single PAH (1 μg/L benzo[a]pyrene) on S. costatum. Results showed that both TSP-PAHs and benzo[a]pyrene inhibited S. costatum growth, with TSP-PAHs exhibiting a stronger dose-dependent inhibitory effect. On the fourth day, growth inhibition in TSP-PAHs groups ranged from 58.8% to 96%, while benzo[a]pyrene caused only 15% inhibition. This suggests that mixed PAHs impose greater toxicity than a single PAH, likely due to synergistic effects and oxidative stress mechanisms.