Partition of Polycyclic Aromatic Hydrocarbons between the River Water and Sediments at Downstream Locations of Rivers in Kanazawa, Japan

Abstract

The fate of hydrophobic pollutants in rivers depends on the partition of pollutants between river water and sediments. Understanding the partition of pollutants in a sediment-water system is important for the environmental quality management of a water environment. The concentration of polycyclic aromatic hydrocarbons (PAHs) in water and sediment was monitored at downstream locations of the two main rivers of Kanazawa City, the Asano and Sai Rivers. Sediments were classified into three different particle size fractions. The estimated sediment-water partition coefficient, K_d was found to be correlated with the organic carbon contents of the sediment. The organic carbon normalized partition coefficient K_oc was calculated as K_d/f_oc, where f_oc is the content of sedimentary organic carbon values. No apparent relation was found between the K_oc and sediment particle size. The K_oc and K_ow values of PAHs except for Benzo[k]fluoranthene were fitted to the linear free energy relationship logK_oc = alogK_ow + b. Value of a = 0.562 and b = 3.55 for the Asano River and a = 0.814 and b = 2.19 for the Sai River were obtained. These results suggest that the organic carbon content, not the particle size, controls the sediment-water partition coefficient.