Occurrence of chlorinated and brominated polycyclic aromatic hydrocarbons in surface sediments in Shenzhen, South China and its relationship to urbanization

One hundred and fourteen surface sediments were collected from the Maozhou River Watershed in Shenzhen, China from December 2009 to January 2010. Three individual chlorinated polycyclic aromatic hydrocarbons (ClPAHs), six individual brominated polycyclic aromatic hydrocarbons (BrPAHs), and five corresponding parent polycyclic aromatic hydrocarbons (PAHs) were determined. The concentration of 9-chlorophenanthrene was the highest ranging from 0.51-289 ng g(-1) (average, 16.5 ng g(-1)). For BrPAHs, the concentration of 2-bromofluorene was the highest ranging from 0.31-266 ng g(-1) (average, 35.3 ng g(-1)). No correlation was observed between the concentrations of ClPAHs and parent PAHs in surface sediments. In addition, there was no correlation between 1-bromopyrene, 7-bromobenz(a) anthracene and 9,10-dibromoanthracene, and corresponding parent PAHs. However, a significant correlation was found between 9-bromophenanthrene and phenanthrene (p < 0.01), between 9-bromoanthracene and anthracene (p < 0.05), and between 2-bromofluorene and fluorene (p < 0.05). Six fly ash samples collected from one of the municipal domestic waste incineration plants in Shenzhen were also analyzed for source identification. The concentration of 7-bromobenz(a) anthracene was the highest, ranging from 3.21-4.08 ng g(-1). In addition, 2-bromofluorene was not detected in all the fly ash samples. No correlation was found between the concentrations of Cl-/BrPAHs and corresponding parent PAHs in fly ashes. We also examined the relationship between the levels of Cl-/BrPAHs in surface sediments and the urbanization process. Our results suggested the levels of individual Cl-/BrPAHs congeners presented a similar increasing trend with the increasing urbanization level.