Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2003
Publication Date: 10/20/2003
Citation: Guo, M., Yates, S.R., Zheng, W., Papiernik, S.K. 2003. Leaching potential of persistent soil fumigant residues. Environmental Science and Technology. 37:5181-5185.
Interpretive Summary: Chemical fumigants are widely used in agricultural production to control soil-borne pests and pathogens. After soil treatment, fumigants dissipate rapidly through volatilization and degradation. Even so, fumigants such as 1,3-dichloropropene (1,3-D), chloropicrin (CP), dibromoethane, 1,2,3-trichloropropane, and 1,2-dibromo-3-chloropropane have been detected in groundwater in many states. Dissolved organic matter is an important constituent of soil water and may promote the movement of persistent fumigant residues in soil. It has been proposed that ammonium thiosulfate be used to rapidly degrade halogenated fumigants, at the soil surface, and reduce atmospheric volatilization of fumigants. The utility of adding ammonium thiosulfate to soil to eliminate persistent fumigant residues deserves further testing. The objectives of this study were to investigate the release of persistent fumigant residues 1,3-D, CP and methyl isothiocyanate from soil into water with batch extraction methods, to evaluate the leaching potential of the fumigant residues using packed soil columns, and to examine the effect of dissolved organic matter and the application of ammonium thiosulfate on the mobility of persistent fumigant residues in soil. The information obtained from this study could be used to develop fumigation methods that are efficacious and environmentally safe.
Technical Abstract: Persistent fumigant residues in soil resulting from agricultural pest-control practices may be released into water and leached to groundwater. In this study, the leaching potential of persistent soil fumigant residues was evaluated, and the effect of dissolved organic matter (DOM) and ammonium thiosulfate (ATS) amendment was investigated. A silt loam soil was incubated separately with the fumigants 1,3-dicholoropropene (1,3-D), chloropicrin (CP) and methyl isothiocyanate (MITC) at 240-990 mg/kg for 35 d, followed by 48 h of evaporation. The soil was packed into stainless steel columns (1.5 cm × 10 cm) and leached with water, 5 mM ATS and DOM solution (DOC 250 mg/L) by gravity. Residues of 1,3-D, CP and MITC in the evaporated soil were 5.61, 11.38 and 1.83 mg/kg, respectively. Concentrations of 1,3-D, CP and MITC in column effluents ranged from 0.05 to 0.73, 0.16 to 0.81 and 0.05 to 0.27 mg/L, respectively, when the soil was leached with 10 pore volumes of water. DOM did not promote the leaching of persistent fumigant residues, and ATS markedly reduced the amount of 1,3-D and CP yet notably increased MITC recovered in the effluents. The results suggest that leaching of persistent fumigant residues through soil to water is significant, and movement of persistent fumigant residues in soil is not associated with DOM. Amending soil with ATS is an effective method to remove persistent residues of halogenated fumigants. To reduce groundwater pollution risks posed by fumigation, persistent soil fumigant residues have to be considered.