Sampling and Analysis of Atmospheric Pcdd/fs in South China Sea and Background Area in Vietnam

During the Vietnam conflict, United States (US) forces sprayed a greater volume of defoliant (Agent Orange) with higher PCDD/F content in central Vietnam. The Vietnamese have been exposed to these levels during spraying primarily through contact with former US military infrastructure. In this study, the concentrations of atmospheric PCDD/Fs observed at three background stations (Fig. 1) at Dongsha Island (Sites A) in South China Sea, Da Nang (Site B) city and Son La (Site C) in central and northern Vietnam, respectively, to further understand the PCDD/F contamination in Vietnam. The Measurements indicated that the atmospheric PCDD/F concentrations at Sites A, B and C were 1.66~10.8, 23.4~146 and 11.1~59.5 fg I-TEQ/m3, respectively, during the spring season in 2010 and 2011. The significantly lower PCDD/F concentrations and contents in suspended particles (23.7~33.9 pg I-TEQ/g-TSP) measured at Site A in the South China Sea can be attributed to the lack of any combustion sources within almost 300 km of this island. However, the significantly higher PCDD/F contents in suspended particles (270~300 pg I-TEQ/g-TSP) were measured at Site B in central Vietnam. In addition, Fig. 2 shows that the distribution of PCDD/F congeners measured at Da Nang station was quite different from those measured at other station with high PCDD distribution (>85%) especially in OCDD (>70%). We consider that the high fraction of PCDDs observed at Da Nang probably originated as anthropogenic emission from specific source in Vietnam.