Identification of volatile/semivolatile products derived from chemical remediation of cis-1,3-dichloropropene by thiosulfate

Authors: ZHENG, WEI - UNIV. OF CA-RIVERSIDE; GAN, JAY - UNIV. OF CA-RIVERSIDE; Schneider, Sharon; Yates, Scott

Submitted to: Journal of Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2007
Publication Date: 8/15/2007
Citation: Zheng, W., Gan, J., Papiernik, S.K., Yates, S.R. 2007. Identification of volatile/semivolatile products derived from chemical remediation of cis-1,3-dichloropropene by thiosulfate. Journal of Environmental Science and Technology. 41(18):6454-6459.

Interpretive Summary: Soil fumigants are used to control weeds, insects, and diseases in high-cash-value crops. Fumigants are volatile compounds and their application to soil can result in air contamination in some agricultural regions. Our previous research showed that application of thiosulfate fertilizers at the soil surface can reduce emissions of soil fumigants into the air. Decomposition of the reaction product of the fumigant 1,3-dichloropropene and thiosulfate can result in the production of compounds with strong, unpleasant odors. This study investigated the stability of the reaction product in soil and water. We identified some secondary reaction products (several organic sulfur compounds) that have a low-smell threshold. We determined the conditions that favor their formation in soil and water. The environmental fate and effects of these compounds needs to be considered in the application of thiosulfate and other sulfur-containing fertilizers in fumigated fields. This information can be used by regulators to develop a management tool to direct the correct use of thiosulfate compounds to reduce air contamination by soil fumigants.

Technical Abstract: The prevalent use of soil fumigants resulted in air pollution in some agricultural regions. Our previous research showed that application of thiosulfate fertilizers at the soil surface may offer an effective and economical approach to reduce the emission of halogenated fumigants via a chemical remediation process. In this fumigant emission-reduction strategy, volatile 1,3-dichloropropene (1,3-D) reacts with thiosulfate to generate a nonvolatile Bunte salt (thiosulfate derivative of 1,3-D). However, the decomposition of the Bunte salt may be associated with the production of perceptible odors. This study investigated the stability of this reaction product in different environmental media. Hydrolysis experiments demonstrated that the thiosulfate derivative was relatively stable in neutral and moderately acidic aqueous solutions. In contrast, the thiosulfate derivative was readily converted to a dialkyl disulfide via a base hydrolysis process in pH 10 buffer solution. In a strongly acidic solution, a mercaptan and a dialkyl disulfide compound were detected as two primary hydrolysis products. In soil, this initial reaction product underwent a series of biotic conversions to generate several volatile or semivolatile organic sulfur compounds. The formation and distribution of four volatile/semivolatile products in the air and soil were detected in different soils treated with the thiosulfate derivative of 1,3-D. This study indicated that odors occurring in soil treated with halogenated fumigants and thiosulfate fertilizers might arise from the generation and release of these and other volatile/semivolatile organic sulfur products. The environmental fate and effects of such volatile/semivolatile sulfur compounds should be considered in the application of sulfur-containing fertilizers in fumigated fields.