J Environ Qual. 2013 Sep;42(5):1555-64. doi: 10.2134/jeq2013.03.0072.
Methyl isothiocyanate (MITC) generators, such as metam sodium (Met-Na), are used for soil fumigation of agricultural land. The ban on the fumigant methyl bromide has resulted in greater use of MITC generators. To understand the efficacy of MITC, it is necessary to assess its generation and disappearance kinetics when Met-Na is applied to soil. This study evaluated the movement of water and distribution and dissipation of MITC in soil after application of Met-Na through surface drip irrigation systems. The effects of varying water application volume (25, 50, and 75 mm) and rate (1.9, 5.0, and 7.5 L h m) were evaluated in a sandy loam soil. Good fumigant distribution within the sandy loam soil was observed under medium water application amount (50 mm) with slow to intermediate drip application rates (1.9-5.0 L h m). Low water application amount (25 mm) or high application rate (7.5 L h m) did not provide adequate MITC distribution throughout the soil bed width and rooting depth. Dissipation patterns of MITC in soil in all water application amounts and rates followed first-order kinetics, with a rate constant of 0.025 ± 0.004 h and a half-life of 27 ± 3 h. Simulated water distribution through the soil profile using HYDRUS 2D/3D fitted measured field data well, and the model accurately simulated MITC fumigant distribution in the soil.
甲基异硫氰酸酯（MITC）发生器，如威百亩（Met-Na），被用于农业土地的土壤熏蒸。熏蒸剂甲基溴的禁用导致了 MITC 发生器的更大使用。为了了解 MITC 的效果，有必要评估 Met-Na 施用于土壤时的生成和消失动力学。本研究通过地表滴灌系统评估了威百亩施用后水的运移以及 MITC 在土壤中的分布和消散。在砂壤土中评估了不同施水量（25、50 和 75mm）和施水率（1.9、5.0 和 7.5L h m）的影响。在中等施水量（50mm）和慢到中等滴灌施水率（1.9-5.0L h m）下，观察到威百亩在砂壤土中具有良好的熏蒸剂分布。低施水量（25mm）或高施水率（7.5L h m）不能在整个土壤床宽度和根系深度内提供足够的 MITC 分布。在所有施水量和施水率下，MITC 在土壤中的消散模式均遵循一级动力学，速率常数为 0.025±0.004h，半衰期为 27±3h。HYDRUS 2D/3D 通过土壤剖面模拟的水分布很好地拟合了实测田间数据，并且该模型准确地模拟了 MITC 熏蒸剂在土壤中的分布。
