Spatiotemporal toxicity assessment of suspended particulate matter (SPM)–bound polycyclic aromatic hydrocarbons (PAHs) in Lake Chaohu, China: Application of a source-based quantitative method

Abstract

The spatiotemporal associations between the emissions and environmental toxicities of polycyclic aromatic hydrocarbons (PAHs) in lake still remain an issue. Here, we focused on the suspended particulate matter (SPM)–bound PAHs in Lake Chaohu, China to quantitatively estimate their spatiotemporal toxicities from different sources. A source–based quantitative method, positive matrix factorization (PMF)–benzo[a]pyrene–based toxic equivalency (TEQBaP) model, was applied. Firstly, we investigated the spatiotemporal characteristics of SPM–bound PAHs. The concentrations of Σ21 PAHs ranged from 1646 to 19267 ng·g−1. Low–ring PAHs were found to have the highest fractions. T–distributed stochastic neighbor embedding (t–SNE)–partitioning around medoid (PAM) technic revealed significantly spatiotemporal variation characteristics of SPM–bound PAHs in Lake Chaohu. Season, location (west or east lake zone), and sample classification (estuary or lake) together governed the patterns. Then, their potential sources were apportioned. Our results found that diagnostic ratios did not work perfectly. However, 3 factors were separated by PMF model. Unburned petroleum (F1), biomass, coal and gasoline combustion (F2), and diesel, straw combustion (F3) were the main sources of PAHs, accounting for 36.16%, 48.96% and 14.88%, respectively. The patterns of the source profiles were season–dependent. Finally, the toxicity of SPM–bound PAHs from different sources were predicted by PMF–TEQBaP model, and the model predictions were satisfactorily acceptable. Overall, predicted Σ19 TEQBaP of SPM–bound PAHs in Lake Chaohu ranged from 20.8 to 947.9 ng·g−1. Benzo[e]pyrene (BeP), benzo[a]pyrene (BaP) and benzo[b]fluoranthene (BbF) were the main toxic species. Temporally, PAH toxicity posed significantly seasonal differences. F3 had primary contributions to Σ19 TEQBaP. Cutting the diesel consumption and using cleaner energy substitutes were suggested to reduce the PAH toxicity in Lake Chaohu. Overall, we expected this study could give new insights into the spatiotemporal associations between the sources and toxicities of SPM–bound PAHs in lake ecosystem.