Using benzo[a]pyrene in willow leaves as an indicator for assessing the toxic equivalent concentration of PAHs in a coking industrial area.

Abstract

Polycyclic aromatic hydrocarbons (PAHs), typical persistent organic pollutants, are ubiquitous around coking plants and pose potential ecological and human health risks. This study used readily available willow leaves collected from areas surrounding a coking plant as a passive sampling medium to investigate PAH accumulation characteristics and evaluate their feasibility as bioindicators. The results showed that PAH concentrations in willow leaves were relatively high, indicating a strong accumulation capacity for atmospheric PAHs. A significant positive correlation was observed between the logarithm of the leaf-air partition coefficient (KLA) and the logarithm of the octanol-air partition coefficient (KOA) (R2 = 0.6170, p < 0.001). Further analysis of concentration correlations and toxic effects revealed that, among individual PAHs, naphthalene exhibited the strongest correlation with total PAH concentration (R2 = 0.6375), although it was insufficient to represent the overall PAH pollution level. Toxic equivalency analysis indicated a strong relationship between the toxic equivalent concentration of benzo[a]pyrene (TECBaP) and the total toxic equivalent concentration (TTEC) (R2 = 0.9387). Leave-one-out cross-validation (LOOCV) further demonstrated good internal robustness of the model (RMSE = 0.157). Overall, under the specific meteorological and source conditions during the sampling period of this study, BaP can serve as a surrogate indicator for the rapid estimation of the total toxic equivalent concentration of PAHs in willow leaves. However, the applicability of this indicator is source-dependent and should be further validated under different plant species, meteorological conditions, and emission source scenarios before broader application.