代森联在几种典型土壤中的降解特性研究

Studies on the Degradation Characteristic of Metiram in Different Kinds of Soils

为了科学评价代森联在土壤环境中的生态安全性,在实验室条件下对比研究代森联在江西红壤、太湖水稻土、东北黑土等典型土壤中的降解特性,及其降解中间产物乙撑硫脲(ETU)的产生及消散状况。结果表明,代森联在各种土壤中的降解符合一级动力学方程,土壤的理化性质及水分条件对代森联的土壤降解周期影响明显:代森联在pH较大、有机质含量较高的太湖水稻土中降解最快,在pH较小、有机质含量偏低的江西红壤中降解最慢;积水厌气环境有利于代森联的降解;推测微生物作用是土壤中代森联降解的主要机制。在代森联土壤降解周期内,均可捕捉到ETU的存在;东北黑土中ETU变化趋势为先累积后降解,其余2种土壤中仅在降解初期中捕捉到。在原药降解至90%时,ETU残留量可降至0.05 mg/kg安全阈值以下。

In order to evaluate scientifically on the ecological safety of metiram in soil environment, the degradation characteristics of metiram in three typical soils, including black soil from northeast of China, and red soil from Jiangxi Province of China and also rice soil from Jiangsu Province of China, and emerging and dissipating of its ethylene thiourea（ETU） metabolite were both studied comparatively under laboratory conditions in the study. It was indicated that degradation of metiram in soil was accord with first order degradation kinetics, and physicochemical properties and moisture surrounding of tested soil had great effect on the degradation of metiram. Metiram was degraded the fastest in the rice soil of the highest pH and the most organic matter content, and it was degraded most slowly in the red soil of most acidity and least organic matter content from Jiangxi Province of China. Compared with aerobic condition, metiram was degraded faster under anaerobic condition. It was assumed that the biodegradation played a main role in the dissipation of metiram in these soils. The residues of metabolites ETU could be detected in all of the three soils during degradation of metiram. The content change of ETU in black soil from northeast China was accumulating first, and then being decreased little by little. However, it was decomposed too quickly in the other two tested soils to be detected later. ETU could be decreased to 0.05 mg/kg of safety threshold until 90% degradation of the raw pesticide.