|Qin, Ruijun - VISITING SCIENTIST|
|Ajwa, Husein - UC, DAVIS|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 2009
Publication Date: April 1, 2009
Citation: Qin, R., S. Gao, D. Wang, B.D. Hanson, T.J. Trout, and H. Ajwa. 2009. Relative effect of soil moisture on emissions and distribution of 1,3-dichloropropene and chloropicrin in soil columns. Atmospheric Environment. 43:2449–2455. Interpretive Summary: Emissions of the soil fumigants are regulated to protect air quality in California. Irrigation to increase soil water content can reduce fumigant emissions at relatively low costs; however, the optimum range of soil water content that reduces emissions without reducing efficacy is not clearly defined. This study tested various soil water content (30-100% field capacity of a sandy loam on the emission and distribution of fumigants 1,3-dichloropropene and chloropicrin in soil columns. As soil water content increased, the emission peak flux of the fumigants was reduced and occurrence was delayed. So increasing soil water content will reduce the risk of acute fumigant exposure to workers and bystanders. The cumulative emission loss over a longer period of time, however, did not appear to be reduced until soil water content reached 100% field capacity. Increasing soil water content in the tested range did not reduce fumigant concentrations in soil air indicating that pest control efficacy may not be affected. This research illustrated the relationship between soil water content and fumigant emissions. The information helps development of practices using irrigation to minimize negative environmental impact from soil fumigation.
Technical Abstract: Emissions of the soil fumigants are regulated to protect air quality in California. Irrigation prior to fumigation can reduce fumigant emissions at relatively low costs; however, the optimum range of soil water content that reduces emissions without reducing efficacy is not clearly defined. The objective of this study was to determine the effects of soil water content [at 30, 45, 60, 75, 90 and 100% field capacity (FC)] on the emission and distribution of fumigants 1,3-dichloropropene (1,3-D) and chloropicrin (CP) in columns packed with a sandy loam soil. After injecting equal amounts of cis-1,3-D, trans-1,3-D, and CP, the experiment was conducted for 14 days. Emissions of all three compounds showed similar response to soil water content except that CP emissions were lower than both isomers of 1,3-D. The emission peak flux was highest and occurred earliest in the driest soil while it was reduced and delayed as soil water content increased. After the peak, emission flux decreased rapidly in the dry soil but more slowly in higher water treatments. Initially, higher soil water content resulted in substantially lower cumulative emissions among the treatments, but as time progressed, the differences in cumulative emissions decreased or even disappeared. These trends were most likely due to the closed-bottom effect of the soil columns which allowed fumigants to move upward only and contribute to emission. Higher fumigant concentrations in the soil-gas phase were observed in high soil water content treatments, due to more fumigant retained in soil and less emission loss.