title: Vertical distribution of dioxins in soil of Bien Hoa airbase, Vietnam.
abstract: Bien Hoa airbase is a known dioxin-contaminated hotspot in Vietnam. The contamination occurred during the Vietnam War at the site where dioxins were transported, stored, sprayed, and spilled in the area. Dioxins, which are cancer inducing substances, may transfer from the soil to food crops and finally to human beings living around the area. Many surveys of dioxins in soil, water, organisms, and human have been carried out in this study area since 2002. In this paper vertical distribution of dioxins in undisturbed soil cores were examined. Twelve soil samples from three drilled cores were collected to analyze dioxin levels according to the standard Japanese analytical method. The results showed that the toxicity equivalency quantity (TEQ) in one soil sample at a depth of 2.6 m reached 3,300 pg-TEQ/g-dw. High TEQs were also observed in the clay layer. This anomaly of dioxin concentrations could be attributed to the affinity of dioxins for the clay layer. The isomer patterns in the soils were different from those in the soil of Hokkaido in that 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TCDD) was the most dominant in the soil sample. This indicates that the dioxins originate from a defoliant Agent Orange disposed at the site after the Vietnam War.
authors.affiliation: Geo-Environment Department, Faculty of Geology and Petroleum Engineering, Ho Chi Minh City University of Technology, 168 Ly Thuong Kiet, Dist. 10, Ho Chi Minh City, Vietnam.
authors.forename: Dang Thuong
authors.identifier: 0000-0002-7844-1573
authors.initials: DT
authors.lastname: Huyen
authors.affiliation: Faculty of Engineering, Hokkaido University, Kita-ku, Sapporo City, 060-8628 Hokkaido Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Igarashi
authors.affiliation: Yagai-Kagaku Co., Ltd., Higashi-ku, Sapporo City, 065-0043 Hokkaido Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Shiraiwa
keywords: Bien Hoa airbase; Dioxins; Dominant isomer; Soil; TEQ; Vertical distribution