Atmospheric Polychlorinated Naphthalenes in a Tropical Megalopolis of Vietnam: Concentrations, Potential Sources, and Health Risk

In this study, 75 congeners of polychlorinated naphthalenes (PCNs-the new persistent organic pollutants under the Stockholm Convention) were firstly analyzed in ambient air samples collected at five sites in Vietnam. Results indicated that the concentration of total PCNs ranged from 56.8 to 263 (pg m^–3) in the dry season and 12.9 to 208 (pg m^–3) in the rainy season. Gaseous PCNs dominated in both seasons, however, the contribution of particulate PCNs increased in the rainy season. Two typical homologue profiles were found in ambient air samples, including low-chlorinated PCNs (monoCNs > diCNs > triCNs) and medium-chlorinated PCNs (tetraCNs > triCNs). Principal component analysis indicated that atmospheric PCNs might be derived from three typical sources including evaporation from products containing PCNs (42.7%), primary emission from combustion-related sources (20.8%), and flue gas after treatment (11.9%). Cluster analysis and diagnostic ratios of typical PCNs indicated that PCNs in each sample might be contributed by different sources with varying magnitudes. The results of the health risk assessment reveal that low risk is associated with atmospheric PCNs in Ho Chi Minh City, Vietnam. This study provides useful information on the characteristics of PCNs in Vietnam, thereby bridging the knowledge divide regarding the pollution of new POPs in developing countries.