Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 13, 2010
Publication Date: August 24, 2011
Citation: Wang, D., Yates, S.R., Gao, S. 2011. Chloropicrin emissions after shank injection: Two-dimensional analytical and numerical model simulations of different source methods and field measurements. Journal of Environmental Quality. 40:1443-1449. Interpretive Summary: By comparing with direct field emission measurements, the modeling study clearly showed that shank injected soil fumigants such as chloropicrin (CP) behaved more like a vertical rectangle source than a point source. This is attributed to the creation and persistence of soil fractures generated by the physical passage of shank knives in the soil and slight compaction when the metal knives were pulled across the field. The study also showed that the effect of rectangle source on CP emissions was more pronounced for deep injections than shallow injections. Compared to “true” point sources, the effect of rectangle sources on fumigant emissions was also exhibited as increased total and peak emissions and accelerated occurrence of peak emissions. The modeling study also demonstrated and validated the accuracy of the analytical solutions for predicting cumulative fumigant emissions.
Technical Abstract: Understanding the control mechanisms of fumigant movement in soil is a fundamental step for developing management strategies to reduce atmospheric emissions. Most soil fumigants including chloropicrin (CP) are applied by shank injection and the application process often leaves vertical soil fractures that would potentially cause preferential fumigant movement and increased emissions. This potential transport pathway was evaluated using analytical and numerical model predictions by comparing simulated emissions and soil air concentrations, after assuming either point and rectangle sources for the injected CP, with direct field measurements. Results clearly showed that shank injected CP, when treated as vertical rectangle sources produced cumulative emission losses similar to the field measurements. Treating the shanked CP as point sources caused approximately 50% under prediction than the field measurements. The study also demonstrated that fumigant cumulative emissions can be predicted, with reasonable accuracy, using either analytical or numerical simulations.