Project at a Glance
Title: Reducing emissions of volatile organic compounds (VOCs) from agricultural soil fumigation : comparing emission estimates using simplified methodology
Principal Investigator / Author(s): Yates, Scott
Contractor: United States Department of Agriculture
Contract Number: 07-332
Topic Areas: Agriculture, Monitoring, Toxic Air Contaminants
Laboratory experiments and mathematical simulations were conducted to measure and predict volatilization of the 1,3-dichloropropene (Telone®), chloropicrin and methyl iodide after shank or drip application into agricultural soil.
The goals of this study were to (a) evaluate the effectiveness of several emission-reduction methods, including: sprinkler irrigation, organic amendment, deep injection, agricultural films, and fertilizer amendment on the volatilization of 1,3-dichloropropene, chloropicrin, and methyl iodide into the atmosphere; (b) determine if simplified data collection methods (i.e., laboratory systems and modeling) could be used to obtain total emission estimates that adequately represent large-scale systems.
Comparisons were made using existing measurement of fumigant volatilization rates and total emission losses from field scale experiments, new laboratory measurements involving cylindrical and/or rectangular columns, and mathematical models of a range of complexity (i.e., analytical solutions and multidimensional numerical models). This data were compared in terms of correspondence of peak emissions and total emissions.
For 1,3-dichloropropene, intermittent irrigation reduced total emissions by approximately 50 % and conducting experiments in soil with high levels of organic material (composted municipal green waste) reduced total emissions by 80–85 % compared to conventional fumigant applications. Use of a virtually impermeable film (VIF) reduced total emissions to less than 5 % of the applied material. Applying ammonium thiosulfate (ATS) to the soil surface as a low water-volume spray reduced emissions in laboratory experiments by 26 % and when applied in irrigation water reduced emissions by 43 %. In general, the laboratory and modeling results compare well to recent large-scale field studies.
Significant reductions in total emission of chloropicrin were possible when a virtually impermeable film ( < 0.1 % of applied) or a high-density polyethylene (HDPE) film ( < 2 % of applied) was used as an emission barrier at the soil surface. For chloropicrin, deep injection reduced emissions by 23 % relative to the control; applying ammonium thiosulfate to the soil surface as a low volume spray reduced emissions by 42 % and applying ammonium thiosulfate in irrigation water reduced emissions by nearly 88 %.
In laboratory experiments and modeling studies (computer programs: Hydrus 1D and Solute 1D), repeated surface irrigations and use of high organic matter soils were largely ineffective in reducing emissions of methyl iodide (MeI), with total emissions exceeding 60 %. However, covering the soil surface with a virtually impermeable film reduced emissions from > 60 % to less than 1 %, if the film is removed after 14 days.
For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893
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