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Title: Effect of surface application of ammonium thiosulfate on field-scale emissions of 1,3-dichloropropene

Author
item Yates, Scott
item ASHWORTH, DANIEL - University Of California - Cooperative Extension Service
item Zhang, Qiaoping

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2016
Publication Date: 12/21/2016
Citation: Yates, S.R., Ashworth, D.J., Zhang, Q. 2016. Effect of surface application of ammonium thiosulfate on field-scale emissions of 1,3-dichloropropene. Science of the Total Environment. 580:316-323. doi: 10.1016/j.scitotenv.2016.11.121.

Interpretive Summary: Soil fumigant chemicals are used to prepare soil for planting and help to increase crop production and improve produce 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 1,3-dichloropropene emissions after fumigation. For this experiment, the soil surface was sprayed with ammonium thiosulfate fertilizer. Five methods were used to measure the volatilization rate. The results from the field study show that approximately 12 to 26% of the total applied 1,3-dichloropropene was released to the atmosphere. Applying ammonium thiosulfate to the soil surface reduced emissions from 3 to 29%, depending on which method to calculate emissions is considered. Using a mathematical model to predict the emissions for bare soil with, and without, using ammonium thiosulfate spray, it was revealed that emissions may be reduced by 21%. This study also provides a baseline on emissions of 1,3-dichloropropene after application of a reactive chemical (ammonium thiosulfate)to the soil surface prior to fumigation. 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: Soil fumigation is important for food production but has the potential to discharge toxic chemicals into the environment, which may adversely affect human and ecosystem health. A field experiment was conducted to evaluate the effect of applying ammonium thiosulfate fertilizer to the soil surface prior to fumigating with 1,3-dichloropropene (1,3-D). The ammonium thiosulfate solution was applied as a spray with minimal water to minimize the effect on emissions from saturating (e.g. sealing) the soil pores with water. Two independent data sets were collected for determining the emission rate. One data set was used with three micrometeorological approaches: aerodynamic, integrated horizontal flux and theoretical profile shape; the other dataset with two indirect, back calculation methods that used the CALPUFF and ISCST3 dispersion models. Using the five methodologies, the 1,3-D emission rate was obtained for 16 days. The maximum emission rates ranged from 7 to 20 micrograms per square meter per second, the maximum 24-hour averaged emission rates ranged from 5 to 13 micrograms per square meter per second, and the total 1,3-D emissions ranged from 12 to 26%. Comparing to fumigation without ammonium thiosulfate spray revealed that emissions were reduced from 3% (CALPUFF) to 29% (ADM). Using a simulation model, ammonium thiosulfate spray would be expected to reduce emissions by almost 21%. These data provide evidence that emissions of 1,3-D can be reduced by spraying ammonium thiosulfate fertilizer on the soil surface prior to soil fumigation.