Spatial distribution of polychlorinated naphthalenes in the atmosphere across North China based on gridded field observations

Polychlorinated naphthalenes (PCNs) belong to a group of dioxin-like pollutants; however little information is available on PCNs in North China. In this study, gridded field observations by passive air sampling at 90 sites were undertaken to determine the levels, spatial distributions, and sources of PCNs in the atmosphere of North China. A median concentration of 48 pg m−3 (range: 10–2460 pg m−3) for ∑29PCNs indicated heavy PCN pollution. The compositional profile indicated that nearly 90% of PCNs observed were from thermal processes rather than from commercial mixtures. Regarding the source type, a quantitative apportionment suggested that local non-point emissions contributed two-thirds of the total PCNs observed in the study, whereas a point source of electronic-waste recycling site contributed a quarter of total PCNs. The estimated toxic equivalent quantity for dioxin-like PCNs ranged from 0.97 to 687 fg TEQ m−3, with the electronic-waste recycling site with the highest risk. -- Highlights: •Gridded atmospheric concentrations of PCNs were measured across North China. •Relatively high levels of PCNs were observed in the atmosphere of North China. •Thermal processes were the major source of PCNs based on the compositional profile. •Source apportionment was performed between point and non-point sources. •Significant dioxin-like toxicity of PCNs was found particularly at an e-waste site. -- High levels of PCNs were observed in the atmosphere of North China, which were mainly from thermal processes