Study on the Hydrolysis Kinetics of Dimethyl Disulfide

Han, Dawei; Yan, Dongdong; Cao, Aocheng; Fang, Wensheng; Wang, Xianli; Song, Zhaoxin; Li, Yuan; Ouyang, Canbin; Guo, Meixia; Wang, Qiuxia

Study on the Hydrolysis Kinetics of Dimethyl Disulfide

2017

Dimethyl disulfide (DMDS) is a new soil fumigant that is considered a good alternative to methyl bromide due to its high activity toward soil-borne pests, with no ozone-depleting potential. The correlative literature for the study of DMDS and its environmental fate is limited. The hydrolysis kinetics of DMDS were studied in buffered aqueous solutions within a pH of 5, 7, and 9, temperature at 15, 25, 45, and 65 °C, and in natural water samples at an ambient temperature of 25 °C. The results showed that DMDS hydrolysis rates were accelerated by increases in pH and temperature. The calculated half-lives of DMDS hydrolysis in the solutions of pH 5, 7, and 9 were 13.91, 10.81, and 10.52 days, respectively at 25 °C, and the trend showed that DMDS hydrolyzed faster in neutral or mild alkali conditions than in acidic solutions at the same temperature. The calculated half-lives of DMDS hydrolysis in the solutions at 15, 25, 45, and 65 °C were 15.78, 10.81, 9.78, and 7.72 days at pH = 7, respectively. There existed no obvious correlations between the activation energies of DMDS hydrolysis and temperatures. However, the activation entropy absolute values of DMDS hydrolysis increased with increasing temperatures, suggesting that the hydrolysis of DMDS in aqueous solutions was driven by activation entropy. The hydrolysis rates of DMDS in natural water samples are as follows: rice paddy field water > Grand Canal water > tap water. Sterilization of three kinds of natural water samples showed that biodegradation accounted for 4.08, 21.52, and 8.82% in tap water, paddy field water, and Grand Canal water, respectively. This research result has important implications in the scientific evaluation of DMDS.

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