Phyto-Fenton remediation of a dichloro-diphenyl-trichloroethane contaminated site in Ha Tinh Province, Vietnam.

A field trial was conducted at a site in Cam Binh commune, Ha Tinh province, Vietnam, highly contaminated with organo-pesticides. The phyto-Fenton process was applied to remove pesticide residues in soils. In addition to magnetite (Fe3O4) materials added to the soils, fertilizers and elicitors for oxidative burst were also added in the different experimental treatments. Dichloro-diphenyl-trichloroethane (DDT) and isomers were removed in all experimental lots. The removal efficiency was highest in lot B1, a site where only iron materials were added. The removal efficiency and the final content of DDTs in B1 were 98.4% and 0.009 mg kg-1, respectively. In the presence of elicitors, the conversion of DDT to dichloro-diphenyl-dichloroethylene was more favorable. Analysis of soil properties indicated that the phyto-Fenton process can occur at neutral soil pH, and when there are only small changes in soil organic carbon content and cation exchange capacities. Shifts in the composition of the microbial communities were observed. Further studies on the interactions between materials added to soil, plants, and the soil microbiome are needed to understand the mechanism of action of the phyto-Fenton process during soil remediation.

Accelerated remediation of organochlorine pesticide-contaminated soils with phyto-Fenton approach: a field study.

Phytoremediation and advanced oxidation processes are among the most promising techniques for removing organic pollutants from soils. A field trial was performed for six months to evaluate the effect of nano-Fe3O4 on the degradation of organochlorine pesticide residues including Lindane, p,p'-dichlorodiphenyltrichloroethane (DDT), p,p'-dichlorodiphenyldichloroethylene (DDE), and p,p'-dichlorodiphenyldichloroethane (DDD) in pesticide-contaminated soils in the presence of vetiver in Bac Giang province, Vietnam. Vetiver was planted in three zones with different nano-Fe3O4 concentrations. Soil samples from each zone were periodically collected to determine the remaining concentrations of selected organochlorine pesticides via gas chromatography-electron capture detector. Results indicated that the total DDT concentrations in the examined soil were 1.9-13 times higher than the permissible threshold level (10 µg g-1) established by the national technical regulation on pesticide residues in soil. The (p,p'-DDE + p,p'-DDD)/p,p'-DDT ratios ranged from 13.5 to 114, indicating the absence of recent inputs of technical DDTs at the study area. DDT dechlorination mainly occurred under aerobic pathways to form DDE. Furthermore, DDE degradation in soil was adequately described by the pseudo-first-order kinetics model (R2 > 0.892). In the presence of vetiver, the rate constants of DDE degradation were 0.264, 0.350, and 0.434 month-1 with 0, 25, and 100 mg kg-1 of added nano-Fe3O4, respectively, indicating that the degradation of DDE correlated positively with Fe3O4 concentration in the soil. Additionally, the presence of vetiver and nano-Fe3O4 in the soil increased DDT removal rates, which might be linked to the involvement of Fenton/Fenton-like reactions.