Location: Water Management ResearchTitle: Emission and distribution of fumigants as affected by soil moistures in three different textured soils Author
Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2012
Publication Date: 1/1/2013
Citation: Qin, R., Gao, S., Husein, A. 2013. Emission and distribution of fumigants as affected by soil moistures in three different textured soils. Chemosphere. 90(2):866-872. Interpretive Summary: Water application is known as a low-cost method for fumigant emission control and is applicable for a wide range of commodity groups. However, the effect of soil moisture on reducing fumigant emissions in various textured soils has not been defined. Through lab column studies under very well controlled conditions, the emission and distribution of 1,3-dichloropropene and chloropicrin were evaluated in three different textured soils (sand, sandy loam, loam) with a range of soil moistures. When soil moisture increased from 30% of field capacity (FC) to 100% FC, peak emission fluxes and cumulative emission losses were reduced dramatically in sandy loam and loam soils. However, little changes occurred in the sandy soil when soil moisture increased from 60% to 200% FC. Higher fumigant concentrations observed in soils with higher water content imply that fumigation efficacy may be maintained even at FC level for the soils studied. A positive and linear correlation between air-filled porosity and cumulative emission loss was found across all soil types suggesting that the air-filled porosity could serve as a simple indicator for estimating emissions. The research findings can be further tested under field conditions to conclude proper irrigation schedule for specific type of soil to achieve optimum soil moisture conditions before fumigant application to minimize fumigant emissions and ensure pest control efficacy.
Technical Abstract: Stringent environmental regulations are being developed to control the emission of soil fumigants to reduce air pollution. Water application is a low-cost strategy for fumigant emission control and applicable for a wide range of commodity groups, especially those with low profit margins. Although it is known that an increase in soil moisture reduces emissions, the range of soil moisture for minimizing emissions without risking pest control, is not well defined for various types of soils. The objective of this study was to determine the effect of different soil moisture levels on emission and distribution of 1,3-dichloropropene and chloropicrin in three different textured soils (Delhi sand, Hanford sandy loam, and Madera loam). Soil columns were used under well controlled moisture conditions. Results on sandy loam and loam soils showed that by increasing soil moisture from 30% of field capacity (FC) to 100% FC, emission peak fluxes were lowered by 77-88% and their occurrences were delayed 5-15 hours, and cumulative emissions were reduced 24-49%. For the sandy soil, the emission fluxes and the cumulative emissions were not significantly different when soil moisture increased from 60% to 200% FC. Compared to drier soils, the wetter soils have consistently higher fumigant concentrations, suggesting efficacy may not be impacted by increasing soil water content to FC level in these soils. The air-filled porosity was found to positively and linearly correlate with the cumulative emission loss across all soil types indicating that the air-filled porosity may serve as a good indicator for estimating emissions. The laboratory findings can be further tested under field conditions to conclude what irrigation regime should be used for increasing soil water content prior to fumigant application that can achieve maximum emission reduction while achieving uniform fumigant distribution with high exposure index values.