Photocatalytic films for soil fumigation: Control of dimethyl disulfide concentration after fumigation

• Optimization of dimethyldisulfide (DMDS) concentration for fumigation.
• Design of industrial photocatalytic virtually impermeable films.
• Determination of the optimal TiO2 content for efficient light absorption.
• Acetone and DMDS mineralization under UVA in closed chambers.

The photocatalytic oxidation of dimethyl disulfide (DMDS), a large spectrum and efficient fumigant, was studied with newly developed industrial Virtually Impermeable Films including a photocatalytic function. The aim was to define the optimal film composition to decrease DMDS concentration in the air space between the soil and the film at the end of the treatment while keeping an optimal DMDS concentration during the fumigation treatment. From the comparison between various films with different composition (polyethylene (PE) and polyamide (PA) layers together with a photocatalytic layer), number of layers, thickness and TiO2 concentration, it was concluded that for all the samples the light absorption was linearly correlated to TiO2 surface density. The optimal TiO2 content for efficient (98%) light absorption was determined.A first screening of the films was first carried out on the photocatalytic oxidation of acetone. Different diffusion rates of acetone and DMDS inside the PE matrix were deduced from the comparison of the results with the colored black and white films. Complete mineralization of acetone and less extensive mineralization of DMDS (due to formation of methanesulfonate together with sulfates) was observed with most of the studied films. Colored black and white films with suitable design were also efficient for DMDS degradation, but not for acetone mineralization.Since it is known that DMDS and its oxidation products are beneficial for plant growth, it was concluded that colored or uncolored gastight photocatalytic films could be successfully used for wide field fumigation with DMDS by optimizing its degradation rate in the air space for maximum nematicide, fungicide and herbicide efficiency, with decreased buffer zones (area of no fumigation) and maximum safety for neighborhood and workers at the end of the treatment.

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