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Title: Effect of deep injection on field-scale emissions of 1,3-dichloropropene and chloropicrin from bare soil

Author
item Yates, Scott
item ASHWORTH, DANIEL - University Of California
item ZHENG, WEI - University Of California
item KNUTESON, JAMES - Dow Agrosciences
item VAN WESENBEECK, IAN - Dow Agrosciences

Submitted to: Atmospheric Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2016
Publication Date: 4/26/2016
Citation: Yates, S.R., Ashworth, D.J., Zheng, W., Knuteson, J., van Wesenbeeck, I.J. 2016. Effect of deep injection on field-scale emissions of 1,3-dichloropropene and chloropicrin from bare soil. Atmospheric Environment. 137:135-145. doi: 10.1016/j.atmosenv.2016.04.042.

Interpretive Summary: Soil fumigant chemicals are used to prepare soil for planting and help to increase crop production and improve product quality. However, soil fumigants are highly volatile which can lead to the release and accumulation of toxic chemicals in the environment. To assess the risks to ecosystem and human health from the effects of fumigant emissions, accurate measurement of volatilization rates and total emissions are critical. A field experiment was conducted to measure Telone C-35 (i.e., 1,3-dichloropropene and chloropicrin) emissions after deep injection (i.e., 61 cm injection depth). Five methods were used to measure the volatilization rate. The results from the field study show that approximately 15 to 27% of the total applied 1,3-dichloropropene, and less than 2% of the chloropicrin applied during the experiment were released to the atmosphere. Deep injection reduced emissions up to 24%. Using a mathematical model to predict the emissions for deep-injection, it was revealed that emissions should be reduced by 21%. This study also provides a baseline on emissions of 1,3-dichloropropene and chloropicrin after deep injection. This research will help growers meet future regulations on toxic and VOC emissions and will provide valuable information for determining reasonable buffer zone sizes.

Technical Abstract: Fumigating soil is important for the production of many high-value vegetable, fruit, and tree crops, but fumigants are toxic and highly volatile which can lead to significant atmospheric emissions. A field experiment was conducted to measure emissions and subsurface diffusion of a mixture of 1,3-dichloropropene (1,3-D) and chloropicrin after shank injection to bare soil at 61 cm depth (i.e., deep injection). Three on-field methods, aerodynamic (ADM), integrated horizontal flux (IHF), and theoretical profile shape (TPS) methods, were used to obtain fumigant flux density and cumulative emission values. Two air dispersion models (CALPUF and ISCST3) were also used to back-calculate the flux density using air concentration measurements surrounding the fumigated field. Emissions were continuously measured for 16 days and the daily peak emission rates for the five methods ranged from 13 to 33 ug/( m^2 s) for 1,3-D and 0.22 to 3.2 ug/( m^2 s) for chloropicrin. Total 1,3-D mass lost to the atmosphere was approximately 23-41 kg/ha, or 15-27% of the applied active ingredient. Based on the five methods, deep injection reduced total emissions by approximately 2–24% compared to standard fumigation practices where fumigant injection is at 46 cm depth. Given the relatively wide range in emission-reduction percentages, a fumigant diffusion model was used to predict the percentage reduction in emissions by injecting at 61 cm, which was a 21% reduction. Significant reductions in volatilization of 1,3-D and chloropicrin are possible by injecting these fumigants deeper in soil.