2011 Annual Report
1a.Objectives (from AD-416)
(a) Test several low-cost approaches to measure reduction of emissions from soil fumigation that could help guide air quality regulation.
(b) Obtain information needed to support the use of the new methodology.
(c) Compare results from low-cost approaches to the currently accepted large-scale field study approach.
1b.Approach (from AD-416)
The goal of this project is the development and demonstration of simple, low-cost, and accurate methodology that can be used in place of currently mandated approaches to obtain fumigant emissions estimates. Essentially, laboratory and modeling studies will be carried out using soils from the Buttonwillow, CA field site, and compated directly to the previously completed field experiments. As in the field experiment, the simplified methodologies will be applied to current fumigation practices and to new reduced-emission strategies. Additionally, a wide range of additional emission reduction strategies will also be assessed, with some of these experiments to be determined in collaboration with California ARB and stakeholder groups. A principle advantage to carrying out so many, differing, studies at a single site will be that our understanding of the important processes controlling fumigant fate and transport will not be clouded by inter-site differences, which has been a problem in previously conducted studies.
Progress was made on all three objectives, which fall under National Program 212, Component 1. Enable Improvements of Air Quality via Management and Mitigation of Emissions from Agricultural Operations. Research on this project focused on Problem Statement 1A: Understand, predict, and manage emissions from agricultural systems and relates to objective 1 of the parent project.
All proposed experiments were completed during FY2011 and most of the data analysis and mathematical modeling has been conducted. A draft of the final report is being written.
Numerous laboratory experiments and mathematical simulations were conducted to measure and predict volatilization of Telone®, 1,3-dichloropropene (1,3-D) alone or with chloropicrin, and methyl iodide after shank or drip application into agricultural soil.
Comparisons were made using existing measurement of fumigant volatilization rates and total emission losses from (a) field-scale experiments, (b) new laboratory measurements involving cylindrical and/or rectangular columns, and (c) mathematical models of a range of complexity (i.e., analytical solutions and multidimensional numerical models). The data were compared in terms of correspondence of peak emissions and total emissions.
Intermittent irrigation reduced total emissions of 1,3-D by approximately 50 % and conducting experiments in soil with high levels of organic material reduced total emissions by 80–85% compared to conventional fumigant applications. Use of VIF reduces emissions to less than 10% of the applied material. The laboratory and modeling results compared well to recent large-scale field studies.
Significant reduction in volatilization of 1,3-D are possible when virtually impermeable films were used as a emission barrier at the soil surface. For 1,3-D, repeated surface irrigation, deep injection and use of organic matter treatments also reduced emissions. A surface spray of ammonium thiosulfate with minimal water application was not as effective in reducing 1,3-D and chloropicrin emissions compared to applying ATS along with 1 cm irrigation water.
Repeated surface irrigations and use of high organic matter soils were largely ineffective in reducing emissions of methyl iodide. However, covering the soil surface with a VIF reduced emissions from 60–80 % to less than 10 %, if the film is removed after 14 days.
During the course of this research project, progress was monitored throughout the year from regular individual and group meetings, phone conversations, laboratory visits and email correspondence.