|Allen, Leon - Hartwell|
Submitted to: Journal of Environmental Science and Health
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/5/2008
Publication Date: 1/6/2008
Citation: Ou, L., Thomas, J.E., Allen Jr, L.H., Vu, J.C., Dickson, D.W. 2008. Comparison of surface emissions and subsurface distribution of cis- and trans-1,3-dichloropropene and chloropicrin in sandy field beds covered with four different plastic films. Journal of Environmental Science and Health. 43:376-381. Interpretive Summary: Methyl bromide (MBr) in agriculture will be phased out due to its ozone depletion potential. Chloropicrin (CP) and cis- and trans-dichloropropene (1,3-D) are considered to be potential alternatives to MBr as preplant soil fumigants. Previous field studies on surface emissions and subsurface distribution of these fumigants have been conducted without replications, and the conclusions therefore are still in dispute. To reevaluate this aspect, USDA-ARS and University of Florida scientists in this study measured subsurface distribution and surface volatilization of cis-1,3-D, trans-1,3-D and CP in 16 raised beds injected with Telone C35 and covered with 4 different plastic films, 4 beds for each film. The results show that surface emissions and subsurface distribution of the 3 compounds in beds covered with 4 different plastic films with 4 replications were not statistically different. This indicates that the results from similar studies conducted previously at the same field site without replications were also valid. This study also shows that sunlight may have an influence on initial upward diffusion and volatilization of these 3 compounds, as their subsurface concentrations and volatilization were greater in plastic-covered beds on the east side than those on the west side of the field.
Technical Abstract: Experiment was conducted at a Florida sandy soil field site to study surface emissions and subsurface distribution of cis- and trans-1,3-dichloropropene (1,3-D) and chloropicrin (CP). Sixteen raised beds were applied with Telone C35 by chisel injection and covered with 4 different plastic films (black, blue and metallic polyethylene, and black virtually impermeable film). Each bed was installed along its length with five 20-cm long soil pore air probes for soil pore air sampling, and a collection pan for surface air sampling. Concentrations of the compounds at 20-cm depth among the beds covered with different plastic films were not different. Among beds covered with the same plastic film, concentrations of the compounds were different only in metallic film beds at 5 and 24 hours after injection. Volatilization of the compounds among beds covered with different plastic films, with exception of CP at 48 hours after injection, was not different. Sunlight appeared to have an influence on initial upward diffusion and volatilization of the compounds, as their initial subsurface concentrations and volatilization flux, especially cis-1,3-D, were greater in beds on east side than those on west side of the field. The possible impact of sunlight on fumigant efficacy remains to be determined.