TRANSPORT OF FUMIGANT COMPOUNDS THROUGH HDPE AND VIRTUALLY IMPERMEABLE FILMS

Volatilization of soil-applied fumigants is dependent on many factors, including climatic variables, soil conditions, the method of fumigation, and surface cover. Low-density or high-density polyethylene films (LDPE or HDPE) are most commonly used in fumigation of soil with methyl bromide, but these films are reportedly permeable to methyl bromide (MeBr) and other soil fumigants. To be useful in field applications, films must maintain their integrity through application and throughout the cover period under a wide variety of environmental conditions. To reduce emissions, they must also maintain their impermeability to fumigant vapors under field conditions. In these experiments, we used static sealed permeability cells (1) to determine the mass transfer coefficient (h) of fumigant compounds through HDPE and other films. The h is a measure of the resistance to diffusion which, unlike other measures of permeability, is a property of the film-chemical combination and independent of the concentration gradient across the film (2). The impact of environmental conditions on the h of fumigants across HDPE was determined; th