Occurrence of azaarenes in sediments of the Danshuei River, Taiwan: the use of azaarenes as indicator of anthropogenic source to the estuarine system.

Azaarenes belong to the newly identified classes of anthropogenic pollutants. To our knowledge, this study presents the first result of pollution history of azaarenes and their controlling factors in estuary. To understand the transport mechanisms, surface sediment samples were collected from 18 sites of the Danshuei River during the summer and the winter of 2005. The highest concentrations of azaarene, 21.9 ng g(-1) for 2-ring, 9.89 ng g(-1) for 3-ring, and 9.17 ng g(-1) for 4-ring, were observed in midstream surface sediments near the Shi-Zi-Tou waste water pumping station. Therefore, this waste water pumping station not only provides a good sediment accumulation environment but also discharges small particle size sediments, which contain mass amounts of azaarenes into the Danshuei River. This research also finds highly significant covariations among 3-ring and 4-ring azaarenes, which suggests similar source strengths and transport mechanisms for these compounds. Additionally, core samples were collected from two sites of the Danshuei River and analyzed to determine the pollution history. Values found in the core sediments correspond to pollution events in recent history. Contaminant inputs via in situ burning of dumping field and wastewater discharge for the periods of 1975-1985 and 2004-2005, respectively, were two major sources of azaarenes to the Danshuei River.