Fumigants are used to control nematodes, insects and disease organisms in the soil. Upon the application into the soil, fumigants transform into the gas phase and disperse in the soil through air-filled pores. Volatilized fumigants can move from the soil into ambient air resulting in human exposure through inhalation. The Department of Pesticide Regulation (DPR) has employed emission data from field studies and implemented mitigation measures to minimize potential exposure to bystanders. However, the number of these initial field studies are limited.<br/>Fate of fumigants in the soil - which includes processes such as absorption to soil particles, degradation, diffusion, and volatilization - clearly interact with environmental conditions such as soil moisture profile, temperature, porosity, and organic content; atmospheric evaporative demand; and fumigant physiochemical properties in a complex manner that cannot easily be resolved with ‘experience’ or field experimentation alone. An additional approach to better understand this complexity is employment of mathematical and physical models that utilize first principles of soil physics, water and solute movement in soils, and processes included in fate of fumigants in the soil. DPR combines computer modeling (i.e., HYDRUS) with field studies to expand its ability to estimate the emission of fumigants for different application methods and under different environmental conditions.  In this study, we evaluate the effect of different environmental conditions such as soil moisture profile, temperature regime, soil organic content, and atmospheric evaporative demand on fumigant emission. We also investigate the effect of tarpaulins with different permeability and post irrigation on reducing the fumigant emission. We specifically focus on temporal degradation of tarp (increase in permeability) and effect of post irrigation on both soil temperature and moisture profile and the resulting effect on fumigant emission.

Environmental effects on fumigant emission from soil surface: Modeling perspective

2019 Fall National Meeting

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