2009 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. Documents Reimbursable Agreement with the California Air Resources Board. Log 37397
Movement of soil fumigants into the atmosphere have become a significant problem in many parts of the United States and has exposed the need for simple, low-cost, methods to accurately measure fumigant emissions. Several laboratory experiments were completed to study fate, movement and emissions of soil fumigants from 12 x 150 cm cylindrical columns. The effects of high density polyethylene (HDPE), virtually impermeable film (VIF), and surface irrigation with ammonium thiosulfate (ATS) solution on the behavior of 1,3-dichloropropene (1,3-D) and chloropicrin were determined. Shank application rates of 1,3-D and chloropicrin were the same as in the previous large-scale field studies. The emission fluxes, together with total cumulative fumigant losses for each of the treatments were obtained. Relative to the control, 1,3-D emissions were reduced 26.1 % by ATS spray, 1.0 % by deep injection, 0.01 % by HDPE, 94.2 % by VIF and 42.5 % by ATS irrigation. For chloropicrin, reductions of 41.6 % by ATS spray, 23.3 % by deep injection, 94.6 % by HDPE, 99.9 % by VIF and 87.5 % by ATS irrigation were observed. Virtually impermeable film gave the greatest reductions for both fumigants, whilst HDPE was very effective only for chloropicrin. Despite offering less significant emission reductions, the lower cost alternatives to tarping, particularly irrigation with ATS solution, yielded substantial emission reductions and it is considered that such methods may be useful when tarping is not economically viable. Comparison of cumulative emissions obtained from laboratory and field experiments demonstrate that simpler and less costly methods provide similar results. This research provides important information on obtaining emission estimates in a cost-effective manner.