An Approach for Estimating the Permeability of Agricultural Films

Abstract

Plastic tarps currently used during soil fumigation to control emissions have been shown to be permeable to fumigant vapors, resulting in appreciable losses to the atmosphere. New low-permeability films are being developed to reduce fumigant emissions and increase efficacy. A rapid, reliable, and sensitive method is required to measure the permeability of various films that may be used in new management practices. This manuscript presents an approach for estimating the mass transfer coefficient (h) of fumigant compounds across agricultural 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. This method uses static sealed cells; fumigant vapor is spiked to one side of the film and the concentrations on both sides of the film are monitored until equilibrium. An analytical model is fitted to the data to obtain h. This model relies on a mass balance approach and includes sorption to and diffusion across the film membrane. The method was tested using two polyethylene films and a very low-permeability film and showed that the method produces a sensitive and reproducible measure of film permeability.

Evaluation of permeation rates of soil fumigants through plastic films by the cup method

“…This proposed approach has several advantages over previously reported procedures 17,[19][20][21] to measure the permeation of fumigant compounds through agricultural films. Permeability cells of this type are easy to construct and simple to use to determine mass transfer coefficients under steady state conditions.…”

“…It is assumed to occur by the fumigant dissolving into the surface of the film, with subsequent diffusion through the film and evaporation from the opposite film surface into the atmosphere; however, for physicochemical properties such as low vapor pressures and strong sorbability of fumigants, it is generally difficult to measure gas-permeability rates of fumigants accurately; therefore, only a little information about the gas permeability of fumigants exists. To date, several methods for measuring gas-permeability rates of plastic films have been proposed, [17][18][19][20][21] but these methods necessitate gas chromatography equipment and specialized apparatus.…”

“…[19][20][21] Because of the high dilution of the receiving chamber, these methods would probably not be useful for gas-barrier films. These methods produce variable and insensitive measures of permeability, rendering them useful only for films with high permeability.…”

The Effect of Two Types of Biochars on the Efficacy, Emission, Degradation, and Adsorption of the Fumigant Methyl Isothiocyanate

“…The columns were constructed of two open stainless steel columns (each 6.0 cm high with 15 cm internal diameter) [31]; one was used as a soil column, while the other was used as a chamber to collect the emitted gas. MITC emissions were measured after MITC was injected into soil columns at 6.0 cm depth and the application of BC-1 or BC-2 to the surface soil (1.5 cm depth).…”

Isomeric Effects on Volatilization of 1,3-Dichloropropene Fumigant in Soil

“…In an effort to reduce the environmental effects of fumigation, especially the atmospheric emission of fumigants, various improvements to the existing application methods have been proposed 7,8) . The movement of a fumigant in the soil is mainly a result of diffusion in the vapor phase.…”