Sewage discharge and organic matter affect the partitioning behaviors of different polycyclic aromatic hydrocarbons in a river surface sediment-pore water system

The partitioning behaviors of persistent organic pollutants (POPs) between sediments and water are significant for their transport and fate in aquatic environments; however, an in-depth understanding is still required. Herein, we studied partitioning coefficients, fugacity fractions (ff), and influencing factors of parent, nitrated, and oxygenated polycyclic aromatic hydrocarbons (PPAHs, NPAHs, and OPAHs, respectively), which are typical POPs composed of multiple aromatic rings, in the surface sediment-pore water system of the Haihe River. The logarithmic organic carbon normalized partitioning coefficient (lgKOC) of PPAHs (4.04 ± 0.80) was evidently greater than those of NPAHs (2.64 ± 1.30) and OPAHs (2.69 ± 0.77). Owing to the effects of the polar groups in NPAHs and OPAHs, their partitioning behaviors were different from that of PPAHs. ff values showed that most PAH species approached dynamic equilibrium. As an important source of riverine PAHs, sewage discharge affected PAHs partitioning, whereas dam interception exerted less impact in this study. lgKOC and ff were negatively correlated with sediment organic matter, represented by particulate organic carbon (POC) and n-alkanes, and positively correlated with the sand fraction in surface sediments. In addition, positive correlations of lgKOC and ff with pH and salinity were observed in pore waters. The results indicate appreciable impacts of sewage discharge and organic matter on the partitioning processes of different PAHs.