Diffusion of polycyclic aromatic hydrocarbons between water and sediment and their ecological risks in Wuhu city, Yangtze River Delta urban agglomerations, China

Abstract

To understand how black carbon (BC) might affect the nature of polycyclic aromatic hydrocarbons (PAHs) diffusion at the water–sediment interface and how their diffusion process and ecological risks vary in different functional areas due to strong heterogeneity of urban system. 24 pairs of samples (water and sediment) were collected across the watery landscape of Wuhu, China in four functional areas. The results suggested that PAHs concentrations ranged between 6.95 and 43.2 ng/L, with a mean value of 19.8 ng/L in water, and were from 32.8 to 3790 ng/g averaging 690 ng/g in sediment. The primary sources of the PAHs might be coal combustion and biomass combustion as was revealed by Positive Matrix Factorization model. BC can absorb PAHs, especially high-molecular-weight (HMW) PAHs with strong lipophilic properties, into sediment and affect their diffusion trend at water-sediment interface in different functional areas. The coexistence of BC and PAHs will affect the associated risks in aquatic environments. The water has a higher risk in the education and residential area, which was polluted by low-molecular-weight (LMW) PAHs. The sediment risk was mainly manifested in industrial areas, which are contaminated by HMW PAHs that was caused by the presence of BC. These results indicate that it is very significant for ecological risk assessment to understand the pollution status of PAHs in different functional areas and their relationship with BC.