Quantitative source-oriented, bioaccumulation and toxicity of organic pollutants in a formerly mining area

Persistent organic pollutants (POPs) are a significant class of environmental hazards in the atmosphere, posing substantial risks to human health and to various components of forest ecosystems. This research focused on assessing contamination levels and sources of 14 polychlorinated biphenyls (PCBs) and on potential toxicity associated with seven low-molecular-weight (Σ7 LMW) and eight high-molecular-weight (Σ8 HMW) polycyclic aromatic hydrocarbons (PAHs). Here, leaves of several tree species (the native Quercus robur L., Fagus sylvatica L., Pinus sylvestris L., and Taxus baccata L.; the introduced Chamaecyparis lawsoniana (A. Murray bis) Parl.), litter and soil samples (10‒15 and 30‒40-cm depths) were analyzed in the formerly mining center of Baia Sprie, NW Romania. The content of Ʃ7 LMW PAHs decreased from litter to deeper soils (287, 9.07 ng g^-1), also for Ʃ8 HMW PAHs (447.53, 13.11 ng g^-1), and had an opposite pattern for Ʃ14 PCBs (61.76, 92.67 ng g^-1). In C. lawsoniana and Q. robur, the Ʃ15 PAHs and Ʃ14 PCBs contents were the highest, demonstrating their ability to accumulate organic pollutants. Based on the source diagnostic ratio analysis and statistical analyses, the origins of PAHs are attributed to a combination of petrogenic and pyrogenic combustion in mining and residential activities. The toxic equivalency factor shows that Ʃ8 HMW induces a moderate to high risk (10.45 ng g^-1) in Q. robur leaves, primarily due to the significant contribution of carcinogenic BaA, BbF, and BaP, whereas the risk is even higher in litter with levels of 71.55 ng g^-1. Q. robur leaves are recommended as suitable bioindicators in the assessment of ecosystem health. We underscore the necessity for future monitoring and engagement to implement more stringent regulatory measures of POPs, strategies for air pollution reduction, and sustainable practices aimed at risk mitigation.