Atmospheric concentrations of DDTs and chlordanes measured from Shanghai, China to the Arctic Ocean during the Third China Arctic Research Expedition in 2008

In July to September 2008, air samples were collected aboard a research expedition icebreaker, Xuelong (Snow Dragon), under the support of the 2008 Chinese Arctic Research Expedition Program. DDTs and chlordanes were quantified in all samples. ∑DDTs concentrations over the whole cruise varied substantially, ranging from 2.0 to 110 pg m−3 with the average concentration of 36 ± 31 pg m−3. The fresh inputs of p,p′-DDT and o,p′-DDT indicated by DDT/DDE ratios and the relatively higher levels of p,p′-DDT and o,p′-DDT observed in East Asia and North Pacific Ocean may reflect direct transport of these compounds from the adjacent continent where continuing usage of DDT-related compounds is potentially occurring. In the Arctic, increase in sea ice melting in the summer of 2008 might result in the remobilization of DDT and enhance its atmospheric levels in this region. Air-borne pollutants arising from the fire occurring in the East Europe during the summer of 2008 might make a large contribution to higher levels of DDTs observed in the atmosphere of North Pacific Ocean and adjacent Arctic Ocean during our expedition. The ratios of o,p′-DDT/p,p′-DDT were higher than that in technical DDT but much lower than those observed in air samples from China, indicating the atmosphere during the present study was likely influenced by a mixture of DDT-containing products. The concentrations of ∑chlordanes varied between 1.8 and 11 pg m−3, with an average of 5.4 ± 2.6 pg m−3. Trans-chlordane (TC) and cis-chlordane (CC) were the most abundant among the chlordanes isomers, accounting for 40% and 39% of total chlordane for all samples. The TC/CC ratios measured in all samples were lower than in the technical mixture, reflecting the main influence by weathered chlordane. The sampling sites with low levels of TC and CC often have relatively low TC/CC ratios, and may be influenced by older air masses.

► DDTs and chlordanes were investigated over the MBL from China to the Arctic Ocean. ► The levels of DDTs and chlordanes over the whole cruise varied substantially. ► Increased sea ice loss enhanced atmospheric DDT levels in the Arctic Ocean. ► Biomass burning contributed to higher levels of DDTs. ► Trans-chlordane and cis-chlordane were the most abundant of the chlordanes isomers.