Depleting Methyl Bromide Residues in Soil by Reaction with Bases

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• 作者：Richeng Xuan ; Daniel J. Ashworth ; Lifang Luo ; Haizhen Wang ; Scott R. Yates
• 刊名：Environmental Science & Technology
• 出版年：2010
• 出版时间：December 1, 2010
• 年：2010
• 卷：44
• 期：23
• 页码：9080-9085
• 全文大小：158K
• 年卷期：v.44,no.23(December 1, 2010)
• ISSN：1520-5851

文摘

Despite generally being considered the most effective soil fumigant, methyl bromide (MeBr) use is being phased out because its emissions from soil can lead to stratospheric ozone depletion. However, a large amount is still currently used due to Critical Use Exemptions. As strategies for reducing the postfumigation emissions of MeBr from soil, Ca(OH)₂, K₂CO₃, and NH₃ were assessed as means of promoting MeBr degradation. Ammonia aqueous solution (NH₄OH) was the most effective, because MeBr can be degraded by both hydrolysis and ammonolysis. At 20 °C, the half-lives (t_1/2) of MeBr were 18.0, 2.5, and 1.3 h in 0.1, 1.0, and 2.0 M NH₄OH, respectively. In 1.0 M NH₄OH, increasing the solution temperature to 40 °C reduced the half-life of MeBr to 0.23 h. Ammonia amendment to moist soil also promoted MeBr transformation, and the MeBr degradation rate increased with increasing soil temperature. NH₄OH (30%, 16 M) very effectively reacted with MeBr that was contained under plastic film. Under Hytibar (a virtually impermeable film, VIF), over 99.5% of the MeBr could be destroyed by 30% NH₄OH in 8 h at 20 °C. On the basis of these results, good management practices (i.e., VIF plus NH₄OH) could be developed for continued use of MeBr as a soil fumigant under Critical Use Exemptions, without significant emissions.