Polychlorinated naphthalenes in sewage sludge from wastewater treatment plants in China

Polychlorinated naphthalenes (PCNs) were nominated as persistent organic pollutants candidate in the Stockholm Convention in 2011. In this study, the profiles, concentrations and spatial distributions of PCNs were analyzed in 30 sewage sludge samples from wastewater treatment plants (WWTPs) in China. Concentrations of Sigma(75)PCNs in sludge samples were in the range of 1.05-10.9 ng/g dry weight (dw) with a mean value of 3.98 ng/g dw. The predominant homologues in the sludgewere mono-to tetra-CNs, accounting for approximately 85% of total PCNs. The total toxic equivalent quantities (TEQs) of dioxin-like PCNcongeners ranged from0.04 to 2.28 pg/g dw with amean value of 0.36 pg/g dw, whichwere lower than the maximumpermissible TEQ concentrations in sludge for land application in China. Levels of PCNs and TEQs in sludge were relatively higher in samples from highly industrialized and developed cities in eastern China, implying a possible link between PCN contamination and the local economic development, but more studies are warranted to corroborate this. Industrial sources might be important contributors of PCNs to sewage sludge in China. (C) 2014 Elsevier B.V. All rights reserved.