Distribution of polycyclic aromatic hydrocarbons (PAHs) in the bottom sediments of a dam reservoir, their interaction with organic matter and risk to benthic fauna

Purpose The aims of the study were to investigate the interaction between fractions of organic matter and polycyclic aromatic hydrocarbons (PAHs) in bottom sediments and to use mussels as passive biomonitors and consensus-based sediment quality guidelines for ecological risk assessment in sediments. Methods Bottom sediment samples were taken from 46 points located in the Rożnów reservoir (Poland). The sediment organic matter (SOM) characteristics included total carbon (TC), total organic carbon (TOC), humic acid carbon (Cha), fulvic acid carbon (Cfa), non-hydrolysing carbon (Cnh), and dissolved organic carbon (DOC). The extraction procedure was carried out in bottom sediments as well as in freeze-dried mussel tissue samples to directly determine the accumulation potential of PAHs to the living organisms in their natural environment. Results The content of organic matter fractions was in the following order: Cfa (fulvic acid) > Cnh (non-hydrolysing carbon) > Cha (humic acid) > DOC (dissolved organic carbon). The mean ∑16PAHs (μg kg−1) concentration was 1755.2 ± 724 (total) and 256 ± 254 (bioavailable) in sediments and 1740 ± 72.2 in the mussel tissues. A significant positive correlation was found between the concentration of PAHs in the mussel tissues and the total and bioavailable concentration of PAHs in bottom sediments. Conclusion The PAH concentration in bottom sediments depended on the stabile carbon forms Cnh. Principal component analysis (PCA) suggests that the fine fraction can significantly increase the bioavailability of PAHs and can be an important factor in the distribution of PAHs in the sediments.