|Qin, Ruijun - UC DAVIS|
|Ajwa, Husein - UC DAVIS|
Submitted to: Proceedings of International Research Conference on Methyl Bromide Alternatives
Publication Type: Proceedings
Publication Acceptance Date: September 1, 2006
Publication Date: November 6, 2006
Citation: Qin, R., Mcdonald, J.A., Gao, S., Hanson, B.D., Trout, T.J., Ajwa, H. 2006. The Effect of Ammonium Thiosulfate on Reducing Fumigant concenteration Under Tarp. 2006 Proceedings of International Research Conference on Methyl Bromide Alternatives, pages 124-1 - 124-4, Orlando, Florida. Technical Abstract: Surface barriers, especially plastic films with low permeability (e.g., virtually impermeable film) are effective to reduce fumigant emissions by retaining fumigants under the tarp. Fumigants accumulated under the tarp, however, can be released into the air when the barrier is removed or planting holes are cut. This poses risks to workers and the environment. This study was conducted to determine the effectiveness of ammonium thiosulfate (ATS) on the degradation of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) in sealed soil columns. Dripping ATS solution to soil surface greatly enhanced the degradation of 1,3-D and CP in the gas phase below barrier as well as within the soil. Under the ATS treatments, the degradation of 1,3-D and CP showed first order degradation kinetics with the highest degradation rate in the highest amount of ATS (2:1 ATS:fumigant ratio) treatment and the lowest rate in the control (without ATS application). The differences in 1,3-D degradation rates between the treatments decreased with time indicating that the effect of ATS on fumigant degradation was greater at the initial application period of time than later. The degradation of CP was much faster rate than 1,3-D and was not detectable after 4 days. Residual 1,3-D and CP extracted from soil samples also supported the effect of ATS on fumigant degradations. Results of the study indicated that application of ATS to surface soils can reduce fumigant concentrations effectively to minimum environmental risks. Field tests are necessary to determine the effective quantity and application frequencies of ATS after fumigation.