Atmospheric PCDD/F concentration and source apportionment in typical rural, Agent Orange hotspots, and industrial areas in Vietnam

- This is the very first studies about atmospheric PCDD/Fs in Vietnam's ambient air.
- PCDD/F concentrations in Vietnam (21.3-139 fg I-TEQ/m3) related with urbanization.
- Biomass burning and open burning are the major sources of PCDD/Fs in rural areas.
- PCDD/Fs in urban areas are mostly influenced by industrial emission.
- The trace of Agent Orange still remains in Agent Orange hotspot areas.

Vietnam has a double burden of dioxin from both industrial sources and historical sources. To evaluate the concentration of PCDD/Fs in ambient air in different areas of Vietnam and their possible sources, atmospheric samples were collected from three areas namely Son La (rural area) and Da Nang (harbor - Agent Orange hotspot area), and Ho Chi Minh City (metropolitan - industrial city). Vapor and solid phases of PCDD/Fs were collected and analyzed following the TO-9A sampling method. Principal Component Analysis and Positive Matrix Factorization model were applied to characterize the possible source. The average concentrations of PCDD/Fs were found to be 21.3 ± 13 fg I-TEQ/m3 in Son La (n = 32), 65.2 ± 34 fg I-TEQ/m3 in Da Nang (n = 16) and 139 ± 84 fg I-TEQ/m3 in Ho Chi Minh City (n = 8). The findings of this study targeted open burning (42%) and biomass burning (51%) as the major emission sources of PCDD/Fs in ambient air of Son La, Vietnam. Major possible sources of PCDD/Fs in Da Nang could be transportation activities (64%), however, the other factor (36%) was suspected to be contaminated with 2,3,7,8-TeCDD from Agent Orange. Most of PCDD/Fs emitted in Ho Chi Minh City related to industrial activities (93%).

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