阿特拉津和乙草胺对土壤酶的影响

【作者】 胡晓捷；

【导师】 刘维屏；

【作者基本信息】 浙江大学 ， 环境科学， 2004， 硕士

【摘要】 阿特拉津和乙草胺，是我国乃至世界上都应用很广泛的两种选择性除草剂，被广泛应用于玉米、大豆、高粱等的杂草控制。因为常年广泛地和大量地应用，由于它们所产生的水体、土壤等环境污染已经越来越引起人们的关注。 本文以这两种除草剂为研究对象，研究了他们对土壤酶的影响。其中选取被视为土壤生态系统的一种很好的感应器，能够及时、准确的反映出土壤生理-生态变化，预示出土壤肥力和土壤的健康状况的脱氢酶和过氧化氢酶作为研究的酶类。研究除草剂对这两种酶的影响，就脱氢酶而言，主要集中在研究阿特拉津和乙草胺在单用以及复配的情况下，对脱氢酶活性的影响。同时，土壤性质对酶活性的影响，在除草剂存在和不存在的情况下，是如何变化的；至于对过氧化氢酶影响的研究包括，调查阿特拉津和乙草胺对过氧化氢酶活性的影响。以及用动力学方法研究两种除草剂对酶是否具有抑制作用。 可以发现，阿特拉津和乙草胺的浓度变化对脱氢酶活性的变化起着重要作用，而且通过正交分析，除草剂的浓度就是本次试验研究因素中影响脱氢酶活性的主要因素。并且高浓度的阿特拉津和乙草胺(≥5μg／g soil)对土壤中脱氢酶的活性有强烈的激活效应(p≤0.01)。同时在整个观测的过程中，在同样浓度水平上两者并没有表现出对土壤脱氢酶活性影响有显著的差异(p≥0.05)。这可能说明这两种除草剂对脱氢酶活性的影响方式是一样的。但当两者加到一起时，它们对土壤脱氢酶的作用并不是独立的：由于施用了混合除草剂后，观测到的土壤脱氢酶活性值并不是两种除草剂单独作用后脱氢酶活性值的总和。当除草剂混合物中阿特拉津为高剂量时(即土壤中阿特拉津的浓度为10μg／g soil)，发现阿特拉津和乙草胺有协同作用，这可能跟阿特拉津在土壤环境中的半衰期相对较高有关系。同时在整个实验过程中没有发现结抗现象。 土壤性质对脱氧酶活性会产生影响。不过，是否有除草剂的参与，土壤性质对脱氢酶活性的影响趋势是不同。在没有除草剂存在的情况下，相对高温(30℃)和相对低湿度(40％MHC)会导致相对较低的脱氢酶活性。但是在有除草浙江大学硕士学位论文剂存在的情况下，结果正好相反。而且特别的是当土样中有高浓度的除草剂时，这种对激活效应的增强作用非常明显。 从活体实验，可以发现无论是阿特拉津还是乙草胺都对过氧化氢酶活性没有大的影响。过氧化氢酶对这两种除草剂并不敏感。但是当除草剂为高剂量时，还是表现出对过氧化氢酶有一定的激活作用。不过，这种激活效应并不强烈。 从动力学结果可以发现，阿特拉津和乙草胺可能会对过氧化氢酶产生抑制，这种抑制来自除草剂分子和酶一底物分子的结合。但是考虑到实际的情况，可以确定无论阿特拉津还是乙草胺都对过氧化氢酶没有明显的抑制，过氧化氢酶对这两种除草剂并不敏感，这和以前的实验结论还是相符的。至于高剂量的除草剂对过氧化氢酶活性有激活作用，这可能是因为这些除草剂可以被微生物作为碳源，刺激了微生物的活动，而表现出一定的激活效应。 总而言之，阿特拉津和乙草胺在推荐用量的范围内施用，对土壤脱氢酶和过氧化氢酶没有负效应，对土壤生态环境还是相对安全的。更多还原

【Abstract】 Atrazine and Acetochlor are two kinds of selective herbicides widely applied not only in China but also all over the world for control of weeds in corn, soybeans, and other row crops. As a result of these herbicides used widely and heavily for the last decades, the soil and water contamination by them is more and more of a public concern.The influence of these two herbicides to soil enzymes were chosen for this study. As good representative enzymes integrating the information form mibcrobial status and soil physico-chemical conidtion, which indicate the potential of soil to support biochemical processes and maintain fertility, soil dehydrogenase and catalse were selected. Regarding the dehydrogenase, this research was focused oil the influence of herbicide using and soil properties to its activity - how the enzyme activity responded to herbicide applied separately and jointly, and to the diverse soil conditions. As to the catalase, how it responded to atrazine and acetochlor, and whether it was inhibited by the two herbicides through kinetic measurement, are included in the research interests.From the results of the study, it was concluded that the concentration of herbicide plays an important role and it was the key factor that influences the enzyme activity most among the assessed factors. Atrazine and acetochlor of high concentration (> 5 ug/g soil) stimulated soil dehydrogenase activity significantly (p < 0,01) and intensely, and there was no significant (p >0.05) difference found between the effects of the two herbicides. However, when they were added together to a soil sample, they didn’t influence the enzyme activity independently - after applied the herbicide jointly, the value of enzyme activity observed was not equal to the sum of values accounted from the experiment of atrazine and acetochlor applied separately. When the atrazine among the herbicide compound was applied in high dose (the concentration of atrazine is 10 ug/g soil), synergism was observed. It probably resulted from the highhalf-life of atrazine. However, there was no antagonism observed. Despite the herbicides, soil properties could affect the activity of the enzyme as well. However, it is different in absence from presence of herbicide. In absence of herbicide, higher temperature (30C) and lower moisture content of soil (40%MHC) leaded to low dehydrogenase activity. However, Incorporated with herbicide, they worked conversely and potentiation was produced.As to the catalase, it was observed that the enzyme was not sensitive to atrazine or acetochlor. These two herbicides have little influence on the enzyme activity. However, when atrazine or acetochlor was applied in high dose (10 ug/g soil), they both could stimulate catalase activity. The stimulation was not strong and didn’t last for long time.From the kinetic measurement, atrazine and acetochlor was able to inhibit the enzyme activity as they could affect the active complex (Enzyme-Substrate). However, it is not convenient for these herbicides to do so in actual environment. Therefore, neither atrazine nor acetochlor will inhibit catalase and the enzyme was not sensitive to these herbicides. Thus was consistent with the results of experiment above. As for the explanation of the stimulation above, it possibly accounts for it that these two herbicides could be used as carbon resource by microbes and thus activated the organism and ultimately enhanced the enzyme activity.Generally speaking, atrazine and acetochlor, applied in recommend dose, didn’t have negative effects on soil dehydrogenase and catalase. These herbicides are friendly to environment of soil system.更多还原