Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2003
Publication Date: 5/1/2003
Citation: Guo, M., Papiernik, S.K., Zheng, W., Yates, S.R. 2003. Formation and extraction of fumigant residuess in soils. Environmental Science and Technology. 37(9):1844-1849. Interpretive Summary: Fumigants are biocides used to control weeds, pathogens, nematodes, and soil fungi. Fumigants have high vapor pressures at room temperature and quickly disperse in soils through gas-phase diffusion. The environmental fate of field-applied fumigants is of great concern because of their impacts on environmental quality and human health. Because of the high volatility, low sorptivity, and rapid degradation rate of fumigants in soils, persistent soil fumigant residues are usually considered insignificant, especially long after application. However, studies have shown that many fumigants persists in soils for a number of years following application. For instance, 1,3-dichloropropene, a methyl bromide replacement, has been detected in groundwater in many states and other fumigants such as ethylene dibromide, 1,2-dichloropropane, methyl bromide, and 1,2-dibromo-3-chloropropane have also been detected in groundwater. In this study, the effect of several environmental factors on the formation of persistent residues of three fumigants in three types of soils was investigated.
Technical Abstract: Fumigants are commonly thought to be short-lived in soil, but residues have been found in soils years following application. In this study, formation and extraction of persistent soil fumigant residues were investigated. Fumigants 1,3- dichloropropene (1,3-D), chloropicrin (CP), and methyl isothiocyanate (MITC) were spiked into Arlington, Glenelg, and Hagerstown soils and incubated for 30 d under controlled conditions. The incubated soils were evaporated for 20 h prior to extraction with a variety of organic solvents at different temperatures. Extraction with acetonitrile in sealed vials at 80 °C for 24 h was the most efficient method to recover persistent soil fumigant residues. At application rates of 1000-1700 mg (kg of soil)-1, persistent residues of 1,3-D, CP, and MITC in the three soils ranged from 5 to 67 mg kg-1. The residue content increased with application rate, correlated positively with soil silt content, decreased dramatically as indigenous organic matter (OM) was removed, and changed little with external OM addition. Adsorption to clay surfaces was not important in fumigant retention, while pulverization of soil aggregates significantly decreased persistent fumigant residues. The results suggest that persistent fumigant residues are retained in soil intra-aggregate micropores resulting from binding clay flocs and silt particles by humic substances.