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Cycle 9 (2020 Deadline)

Developing a framework for the identification of soil limiting factors for bioremediation of dioxin compounds in contaminated soils of Vietnam

PI: Nguyen Khoi Nghia (, Can Tho University
U.S. Partner: M. Scott Demyan, The Ohio State University
Project Dates: April 2021 - April 2024

Project Overview:
9-554_Nghia pic
´╗┐Dr. Nghia in his lab with a new fume hood purchased with PEER funds. Photo credit: Dr. Nghia
In Vietnam, soil contaminated with dioxin has been detected in many areas, especially in and immediately surrounding the Bien Hoa, Da Nang, and Phu Cat air bases. Although dioxin concentration in these soil is much lower than before, there are still significant impacts on the environment and ecosystem health. The goal of this project is to develop a framework for site-specific, synergistic bioremediation approaches to decontaminate soils containing low concentrations of dioxin (between 20-1000 ppt) in Vietnam. It aims to accomplish this through investigation and identification of soil limiting factors regulating and preventing successful remediation of dioxins and test biostimulation and biosurfactant strategies to alleviate site-specific limiting factors. Project researchers will collect samples from expected low-level dioxin contaminated soil sites at Phu Cat, Da Nang, and Bien Hoa, with sampling points selected based on previous site history and current vegetative cover. Samples will be analyzed for dioxin congener concentration and bioaccessibility. Soil pH, texture, organic carbon, nitrogen, microbial biomass, particulate organic matter, and biosurfactant synthesizing microorganisms will be determined by using infrared reflectance spectroscopy to identify factors limiting dioxin degradation. Infrared spectra and reference data from the planned analyses will be used to develop models to predict unknown samples as a rapid assessment technique. Biostimulation, organic amendments (sawdust), biosurfactants (rhamnolipids), dioxin-degrading bacteria, and mineral fertilizers will be applied in various combinations in soil microcosms in the lab. The most beneficial treatments will be further tested in three field experiments.

The anticipated outcome of this project is to find out the most limiting factors of soil for dioxin bioremediation and an innovative synergistic approach for in situ dioxin bioremediation. The results of the proposed research will benefit local and regional populations. The success of bioremediation strategies to be developed under this project will provide the local communities and national government agencies with further information on both the soil dioxin levels and bioavailability in the vicinity of Phu Cat, Da Nang, and Bien Hoa air bases, as well as further strategies for managing these soils. These strategies will help to improve this major environmental health issue for local stakeholders by means of soil and water quality improvement, giving the local people the opportunity to use the bio-remediated soils for beneficial uses such as crops, livestock, and forests and eventually increase their income. The data collected from this project will also advance the body of research about the limiting factors of bioremediation strategies of soil dioxin and will be helpful for developing a framework for site-specific bioremediation approaches of biostimulation and biosurfactants.

Summary of Recent Activities

IIn the third quarter of 2022, Dr. Nghia and his team isolated 77 strains from 9 bacterial communities that had the ability to degrade dibenzofuran (DF) to varying extents. At the same time, from 9 bacterial communities they isolated 14 strains that are able to produce biosurfactant in dioxin-contaminated soil. These selected biosurfactant-producing bacteria have been analyzed for hemolytic activity and subjected to other lab tests.

The PI overcame procurement delays to get all the new equipment that had been budgeted under the project, including a gas chromatograph, high-performance liquid chromatograph, centrifuge, gel electrophoresis system, and fluorometer. As of October 2022, he and his colleagues were still having difficulty obtaining access to the Bien Hoa Airbase site where they need to collect soil samples. USAID staff in Vietnam are assisting with obtaining the necessary approvals.

In the remainder of 2022 and first quarter of 2023, the PI and his group will continue evaluating the ability of their bacterial strains to synthesize biosurfactants and identifying the DF degradation rate of the selected isolates. In addition, they expect to submit a second paper on their results. After receiving permission to access the airbase, they will conduct the site sampling and will take their first planned life evaluation survey of local residents, including household economy activity, household income, impressions of changes in living standards, health, education, and personal activities.


Thanh H. V. Luong, Thao H. T. Nguyen, Binh V. Nguyen, Nghia K. Nguyen, Thanh Q. C. Nguyen, and Giao H. Dang. 2022. Efficient degradation of methyl orange and methylene blue in aqueous solution using a novel Fenton-like catalyst of CuCo-ZIFs. Green Processing and Synthesis 11:71-83.

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