Occurrence and toxicity of sediment-associated contaminants in Guangzhou College City and its adjacent areas: the relationship to urbanization.

Abstract

Guangzhou College City in the southeast of Guangzhou, China, became a home to 10 universities in 2003 after a largely agricultural past. The city has since experienced rapid urbanization with limited development of adjacent areas. Twenty-one sediment samples were collected in the city and its adjacent areas to evaluate the influence of urbanization in different functional zones on sediment quality in local waterways. Sediment toxicity was assessed by 10-day toxicity tests using two benthic invertebrates, Chironomus dilutus and Hyalella azteca. In addition, various organic contaminants-including current-use pesticides (pyrethroids and organophosphate insecticides) and polycyclic aromatic hydrocarbons-were analyzed, and a toxic unit (TU) approach was applied to identify possible toxicity contributors. In general, 38 and 4.8% of the sediments exhibited acute toxicity to C. dilutus and H. azteca, respectively, with 9.5% of the samples resulting in 100% mortality to C. dilutus. Distribution analysis showed that the rural industrial area, which is south of the city, had the greatest contaminant concentrations and greatest toxicity to both organisms compared with the other areas. Pyrethroids, especially cypermethrin, appeared to contribute the most to the observed toxicity, yet the lack of relationship between the toxicity and TU of pyrethroids may reflect toxicity associated with other contaminants.