Substituted polycyclic aromatic hydrocarbons( SPAHs) can be emitted to the environment not only through the incomplete combustion,but also through the transformation from parent polycyclic aromatic hydrocarbons( PAHs) by photo chemical and biological processes. The toxicities of some SPAHs are higher than their corresponding PAHs. Samples were collected from the wastewater treatment plants in Beijing. Three types of SPAHs,including oxy-PAHs( OPAHs),methyl-PAHs( MPAHs) and nitro-PAHs( NPAHs),as well as 16 PA...