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Cycle 6 (2017 Deadline)
Field-scale application of vetiver grass to mitigate dioxin contaminated soil at Bien Hoa Airbase
PI: Ngo Thi Thuy Huong, ngothithuyhuong@gmail.com, Phenikaa University, in cooperation with the Research Institute of Disaster and Environment (RIDES), and co-PI Nguyen Hung Minh, Center for Environmental Monitoring
U.S. Partner: James Landmeyer, U.S. Geological Survey
Project Dates: December 2017 - February 2023
Project Overview
Vietnam is one of the worst dioxin-contaminated areas in the world as a result of extensive use of the herbicide “Agent Orange” (AO) during the war (1961–1971). The worst contaminated sites in Vietnam are located at airbases where large quantities of AO were stored/handled. These areas still pose serious environmental and health risks. To date, no low-cost, effective phytoremediation technology has been developed to stabilize, mitigate, and remediate soils with low to moderate levels of dioxin contamination over large areas. Initial studies with vetiver grass (Chrysopogon zizanioides L.) indicate that it is a very promising candidate for providing such an alternative. This PEER project will (1) assess the use of vetiver grass for the phytoremediation and phytostabilization of dioxin-contaminated soils on a field scale at Bien Hoa Airbase and (2) deepen our understanding of the mechanisms of dioxin uptake and degradation pathways of Vetiver grass. The Monto genotype–a known, noninvasive type of vetiver grass (hereafter “Monto”)—will be used in the two proposed experiments. The indoor experiment will help address and clarify the remaining issues in phytostabilization and phytoremediation from a previous project completed by the PI. The field experiment will help reevaluate the results from the indoor experiment, and the potential use of vetiver in phytostabilization of dioxin-contaminated sites will be assessed.
The project will benefit about 135,000 people in the vicinity of the airbase, particularly the personnel of the 935th Air Regiment, by helping to reduce the potential health risks associated with dioxin. Furthermore, the results of the proposed project should significantly contribute to advances in phytoremediation technology that can be applied elsewhere in Vietnam and worldwide. The practical measures to be developed and tested will also help local, regional, and national policy makers and NGO-sponsored programs develop and evaluate short- and long-term mitigation and remediation alternatives and ultimately implement remedial actions effectively. Through workshops with local people, potential adverse health-related, environmental, and social issues will be addressed to help raise community awareness of dioxin-related issues and solutions. By providing funding support for PhD and MSc students, the project is also expected to foster a new generation of environmentalists interested in phytoremediation technology.
Final Summary of Project Activities
 | | Dr. Huong and participants in the project kick-off meeting, March 2018 (photo courtesy of Dr. Huong). |
After more than a year of preparatory work devoted to close coordination with the relevant military authorities and detailed site selection survey work, this project involved more than three years of field experiments at the Pacer Ivy site on the Bien Hoa Airbase. Despite the challenges of the COVID pandemic, including lockdowns that made even domestic travel temporarily impossible, members of the project team traveled to the airbase every few months to maintain the field site, monitor the growth of the Vetiver plants being used in their phytoremediation experiment, and collect soil, water, and vegetation samples. Project co-PI Dr. Nguyen Hung Minh and his colleagues analyzed the samples at their laboratory and the PI Dr. Ngo Thi Thuy Huong and her team subsequently evaluated the data.
The experiment was divided into two groups, an experimental group with Vetiver and a control group without Vetiver, with each group being repeated three times over a 100 m2 area. Vetiver grass (Chrysopogon zizanioides L.) was chosen for this study because it had previously been used successfully in similar studies in Australia and many other countries, and the PI and her team wanted to see how results under Vietnamese conditions would compare. Their results show that Vetiver grass effectively reduces soil erosion and contaminant runoff compared to the control group, confirming previous research on Vetiver’s ability to stabilize dioxins in soil in contaminated areas. A comparison of the dioxin content in the plant roots versus that in the shoots suggests a clear biodegradation of dioxin by plants, with very little dioxin being transferred to the shoots. According to the PI, the findings of this study confirmed the effectiveness and suitability of Vetiver grass in stabilizing dioxins in soil structure and preventing their flow into the surrounding environment, as well as treating dioxin contamination in soil by plants in areas with moderate dioxin contamination.
The final dissemination workshop for this PEER project was held February 9-12, 2023 in Quy Nhon, Binh Dinh, Vietnam, with more than 40 participants and 10 speakers. As of May 2023, the researchers had published two papers in Vietnamese journals, with one more due for presentation at The Seventh International Conference on Vetiver (ICV-7) to be held in Thailand later that month. That paper, entitled “Using Vetiver Phytoremediation Technology to Mitigate Dioxin–Contaminated Soils at Bien Hoa Airbase, Dong Nai, Vietnam,” has been awarded the King of Thailand Vetiver Award 2023 for Outstanding Research in the Field of Non-Agricultural Applications. Further publications are planned, and Dr. Huong indicates that she intends to transfer this technology to government organizations and other stakeholders that are interested in working in this field. In the future, she and her team hope to learn more about the mechanisms behind phytoremediation and how they can be combined with other approaches to make it an even more powerful tool for cleaning up polluted environments, not just those tainted with dioxins. Thanks to the increased visibility provided by the PEER project, Dr. Huong reports that faculty from Hanoi National University, Hanoi University of Mining and Geology, Hanoi Open University, and Naresuan University (Thailand) are interested in collaboration, as are Ecofarm Mekong (a private company) and the Vietnam Vetiver Network (a non-governmental organization). On the education side, the project resulted in two PhD students, four MSc students, and five undergraduate students receiving training in soil sampling methods for dioxins, enzyme, microbial, and soil physical structure samples, as well as sample processing and preparation and vetiver transplanting. In addition, knowledge of planting and using Vetiver for wastewater and contaminated soil treatment has been transferred to Nam Sach High School in Hung Yen Province, and 1000 Vetiver tillers have been donated to the school as well.
To support her continued research efforts, Dr. Huong and her colleagues have been awarded one Vietnamese and seven international grants totaling approximately $3 million just in the period from 2020 to mid-2023.
Publications
Ngo Thi Thuy Huong, Nguyen Quoc Dinh, Nguyen Thi Thanh Thao and Vu Thi Lan Anh. 2023. Using Vetiver phytoremediation technology to mitigate dioxin-contaminated soils at Bien Hoa Airbase, Dong Nai, Vietnam. The Seventh International Conference on Vetiver (ICV-7), Chiang Mai, Thailand, held May 29 – June 1, 2023.
Nguyễn Thị Thanh Thảo, Ngô Thị Thúy Hường, Quách Đức Tín, Nguyễn Thị Lợi, Đặng Thị Huyền (accepted December 2022). Mối liên hệ giữa thành phần khoáng vật và sự tồn lưu dioxin trong môi trường đất tại sân bay quân sự biên Hòa tỉnh Đồng Nai. Tạp chí Địa chất (Series A). [in English: The relationship between mineral composition and dioxin retention in the soil environment at the airport border military in Dong Nai Province. Journal of Geology (Series A).]
Phạm Thị Huệ, Ngô Thị Thúy Hường, Nguyễn Quốc Định, Nguyễn Kim Nữ Thảo, Nguyễn Hồng Minh. 2022. Carbazole degrading of microbial consortium er07 enriched from dioxin-contaminated soil at Bien Hoa airport (in Vietnamese: Phân giải carbazole của mẫu làm giàu ER07 từ đất nhiễm dioxin tại sân bay Biên Hòa). Tạp chí Khoa học và Công nghệ, Trường Đại học Khoa học, ĐH Huế. Tập 21 (2).
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