Influences of Particulate Organic Carbon and Black Carbon on the Transport of Persistent Organic Pollutants in Estuarine and Coastal Water

Terrestrial inputs resulted from anthropogenic activities strongly influenced on the estuaries and coastal areas, where are the significant sink of global organic carbon (OC) mainly from river runoff. Black carbon (BC) is derived from the incomplete combustion of biomass and fossil fuels, has recently received increasing attention due to its potential importance on regional/global climate change, carbon cycle, air quality, and public health. Because pyrogenic compounds of polycyclic aromatic hydrocarbons (PAHs) are part of BC, their links have aroused many attentions, meanwhile BC is involved in affecting the overall behavior of organic pollutants (such as organochlorine pesticide, OCPs; perfluoroalkyl substances, PFASs) partially due to its porous nature in the environments. Persistent organic pollutants (POPs) strongly bind to BC particles through the occlusion into the carbon condensed structure, conditioning their transport to that of BC particles. To study the potential influence of particulate OC and BC on the transport of POPs from river to coastal area, Jiulong River Estuary (JRE), a subtropical river in China was chosen. The concentrations, compositions and spatial distribution of OC, BC, and POPs (PAHs, OCPs and PFASs) were investigated. In the estuary, BC showed a significant correlation with OC in SPM, reflecting a general hydrodynamic controls and/or their similar initial input pathways (e.g., land-based provenance). The land-source markers (long-chain n-alkanes and perylene) were significantly correlated with OC and BC, further indicating that the source of organic matter was mainly related to the terrestrial inputs. Significant positive relationships were found between OC, BC and POPs (PAHs, OCPs, and PFASs) in the estuarine waters, inferring that sorption of POPs in water is more significantly controlled by terrestrial organic matter resulted in human activities. In the coastal area, significant positive relationships were found between BC and PAHs (especially low rings) in the coastal waters. Furthermore, the relationships between soot-BC and PAHs were stronger than that between char-BC and PAHs, which might be related to the terrestrial fluvial inputs and atmospheric deposition. Our findings provide new knowledge on the behavior of POPs in the estuarine and coastal areas.