Penetration of methyl bromide, sulfuryl fluoride, ethanedinitrile and phosphine into timber blocks and the sorption rate of the fumigants

Abstract

To evaluate timber fumigants alternative to the ozone-depleting methyl bromide (MB), pinewood (Oregon, Pseudotsuga menziesii) blocks (10 cm × 10 cm × 30 cm) were fumigated in a stainless steel chamber (30.0 L). The timber blocks were fumigated at 48 mg L −1 of MB, sulfuryl fluoride (SF) and ethanedinitrile (C 2N 2) and 1 mg L −1 of phosphine (PH 3) for 48 h. During fumigation, 70% MB, 35% SF, 63% C 2N 2 and 25% PH 3 were absorbed by the timber block. At 6-h exposure, the concentrations of SF, PH 3 and C 2N 2 in the headspace of the chamber were stable. Each fumigant penetrated to all parts of the block, but the speed and extent of penetration were different. The fumigants that most rapidly achieved an even concentration throughout the block and chamber were PH 3 and C 2N 2. The maximum variation of MB, SF, C 2N 2 and PH 3 concentration between the chamber and gas port (15 cm) was 81.3, 11.8, 1.5 and 9.3% at 24-h exposure and 76.8, 9.3, 0.5 and 1.1% at 48-h exposure respectively. Possible alternative fumigants to MB need to penetrate timber at least as well as MB; SF, PH 3 and C 2N 2 met this criterion.