Effect of co-formulation of 1,3-dichloropropene and chloropicrin on evaporative emissions from soil

Authors: ASHWORTH, DANIEL - University Of California; Yates, Scott; VAN WESENBEECK, IAN - Dow Agrosciences; STANGHELLINI, MIKE - Trical Inc

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2014
Publication Date: 12/22/2014
Citation: Ashworth, D.J., Yates, S.R., Van Wesenbeeck, I.J., Stanghellini, M. 2014. Effect of co-formulation of 1,3-dichloropropene and chloropicrin on evaporative emissions from soil. Journal of Agricultural and Food Chemistry. doi: 10.1021/jf506010b.

Interpretive Summary: Agricultural fumigants are an air quality concern since large evaporative emissions from the soil to the atmosphere may occur. The fumigants 1,3-dichloropropene (1,3-D) and chloropicrin (CP) are often applied to soils together for the control of plant pests. These co-formulations are available in various ratios of 1,3-D:CP and it has been previously noted that when the amount of CP in a co-formulation is low, a very low proportion of the total CP applied is emitted from the soil. However, this has not been previously studied in a scientific manner. We used soil columns, to which co-formulations with various 1,3-D:CP ratios were applied, to measure the emission losses of these fumigants from the soil surface. A strong positive relationship between CP emissions and CP percentage in the formulation was observed. Further, strong positive relationships between CP degradation half-life and CP percentage in the formulation, and between CP degradation half-life and total column emissions, suggested that the lower emissions were due to faster CP degradation when the CP percentage (and hence initial application mass) in the formulation was low. It is concluded that co-formulation of 1,3-D and CP was itself not a significant factor affecting CP emissions; rather, in co-formulations with a low level of CP, the CP was more rapidly degraded in the soil and therefore not available for emission to the air. This research would be of interest to scientists, regulators, cooperative extension personnel and grower groups.

Technical Abstract: Co-formulations of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) are commonly used for pre-plant fumigation in the production of high value crops. Various ratios of 1,3-D to CP are available in these co-formulations. Collation of previous field data suggested that when the two fumigants were co-applied, the emissions of CP were significantly lower than when CP was applied singly. However, none of these previous studies had a control treatment with CP applied alone, alongside a treatment where CP was co-applied with 1,3-D under the exact same climatic and edaphic conditions. In this work, we aimed to address this issue by measuring emission fluxes from soil columns maintained under controlled conditions in which 1,3-D and CP were applied alone, and as four commercial co-formulations with varying 1,3-D:CP ratios. A strong positive relationship between CP emissions and CP percentage in the formulation was observed. Further, strong positive relationships between CP degradation half-life and CP percentage in the formulation, and between CP degradation half-life and total column emissions, suggested that the lower emissions were due to faster CP degradation when the CP percentage (and hence initial application mass) in the formulation was low. The presence of 1,3-D did not significantly affect the degradation rate of CP, and, therefore, it is hypothesized that co-application was, in itself, not a significant factor in emission losses from the columns. The findings have implications for the accurate modeling of CP since the effect of initial mass applied on CP degradation rate is not usually considered.