Characteristics of PCDD/Fs in soil and sediment samples collected from A-So former airbase in Central Vietnam

Le Thi Hai Le; Nguyen Duy Dat; Nguyen Hung Minh; Kim-Anh Nguyen

doi:10.1016/j.scitotenv.2019.01.163

Characteristics of PCDD/Fs in soil and sediment samples collected from A-So former airbase in Central Vietnam

Sci Total Environ. 2019 Apr 15:661:27-34. doi: 10.1016/j.scitotenv.2019.01.163. Epub 2019 Jan 15.

Authors

Le Thi Hai Le¹, Nguyen Duy Dat², Nguyen Hung Minh³, Kim-Anh Nguyen⁴

Affiliations

¹ Hanoi University of Natural Resources and Environment, Phu Dien, North-Tu Liem, Hanoi 10000, Viet Nam. Electronic address: drlhaile@gmail.com.
² Graduate Institute of Environmental Engineering, National Central University (NCU), Zhongli, Taoyuan 32001, Taiwan, ROC; Faculty of Chemical & Food Technology, Ho Chi Minh City University of Technology and Education, Thu Duc, Ho Chi Minh 700000, Viet Nam. Electronic address: nguyenduydat.hcmute@gmail.com.
³ Vietnam Environment Administration, Nguyen Van Cu, Long Bien District, Hanoi 10000, Viet Nam.
⁴ Center for Space and Remote Sensing Research, National Central University (NCU), Zhongli, Taoyuan 32001, Taiwan, ROC; Institute of Geography, Vietnam Academy of Science and Technology, 18-Hoang Quoc Viet, Hanoi 10000, Viet Nam.

PMID: 30665129
DOI: 10.1016/j.scitotenv.2019.01.163

Abstract

A-So airbase, located in A-Luoi Valley - Central Vietnam, is a former military base occupied by US Special Forces between 1963 and 1966. The storage of Agent Orange in A-So airbase during the Vietnam War now poses a high potential for PCDD/F contamination in soils and sediments. In order to evaluate the occurrence and characteristics of PCDD/Fs in A-So former airbase, which has been reserved for a long time and suffered almost no significant anthropogenic impacts, soil and sediment samples were collected from 40 sites of two adjacent zones A and B in an area of 160,000 m². Seventeen 2,3,7,8-substituted PCDD/Fs were analyzed using HRCG/HRMS (US EPA method 1613). Results indicate that concentrations of PCDD/Fs measured in zone A ranged from 95.0 to 4534 ng kg_dw^-1 (4.58 to 746 ng TEQ kg_dw^-1), while those in zone B were in the range of 80.8-4150 ng kg_dw^-1 (2.70-89.0 ng TEQ kg_dw^-1). The concentrations of PCDD/Fs observed in zone A are higher than those in zone B, suggesting that PCDD/Fs could be transported from zone A to zone B through surface soil erosion and runoff events. The main contributor to the total TEQ concentration was 2,3,7,8-TCDD, which was the indicator of Agent Orange contamination, accounting for 91 ± 9% and 72 ± 17% of the total TEQ concentrations measured in zones A and B, respectively. Comparison of PCDD/F concentrations in different soil layers reveals that the topsoil layer (at depth < 1 m) contributed 81-95% to the total PCDD/Fs in the study area, indicating that future remediation projects should focus on this topsoil layer. Since PCDD/F contamination in A-So airbase has not significantly improved for the last 20 years, remediation projects are urgently needed in order to mitigate the negative impacts of PCDD/F contamination on human health and wellbeing.

Keywords: Agent Orange; Contamination; Dioxin; Distribution; Sediment; Subsurface soil.