磺酰脲除草剂在饮用水处理过程中的去除研究

发布时间：2018-05-13 22:01

本文选题：磺酰脲除草剂 + 饮用水处理　；参考：《南京农业大学》2014年硕士论文

【摘要】：磺酰脲除草剂可以有效除去杂草,因其具有高效低量、施药时间范围宽等特点在世界范围内得到广泛应用。但这类除草剂不易挥发、不易光解且选择性强,对不同作物的敏感性差异很大,会毒害后茬作物。进入环境中的磺酰脲除草剂会通过各种途径迁移进入天然水体,如果受污染水体作为饮用水水源,这些农药将有可能直接暴露给人体。然而常规饮用水处理过程能否有效去除此类除草剂尚不清楚。本研究采用实验室模拟常规饮用水处理工艺,选取氯磺隆、甲磺隆、氯嘧磺隆、氯吡嘧磺隆和氟胺磺隆5种长残效磺酰脲除草剂作为研究对象,研究它们在4个典型的饮用水处理单元(包括混凝、活性炭吸附、氯化消毒和臭氧消毒)中的去除情况。结果发现,只有不到10%的磺酰脲除草剂可通过混凝沉降过程去除；活性炭吸附较为有效,此单元中这些除草剂的去除率随着活性炭投加量的增大而增大,去除率为50%-70%,但即使投加量增至20 mg·L-1时,仍不能达到完全去除；臭氧消毒对磺酰脲除草剂的去除非常有限；加氯消毒对此类除草剂的去除率最高,但也不能完全去除,此单元中不同种类除草剂的降解表现迥异,氯磺隆和甲磺隆更易被去除。从实际情况出发,本研究还考察了饮用水处理过程(即混凝-沉淀-过滤-加氯消毒连续处理)对5种磺酰脲除草剂的去除效果。对比单独氯化的结果发现,该过程可以大幅提高这些农药的去除率。其中,对去离子水配制的样品中的除草剂得到完全去除,但成分更加复杂的天然水样中仍有部分除草剂残留。当在加氯消毒前增设活性炭吸附单元,结果发现此措施可显著提升天然水样的去除率,使之达到100%去除。虽然整个饮用水处理过程可以完全去除磺酰脲除草剂,而且加氯消毒单元的去除率最高,但对这些除草剂的氯化反应进行深入研究发现,这一过程中它们都生成了结构稳定的产物。在加氯量足够的情况下,产物生成量取决于除草剂的初始浓度；而且这些产物也不随加氯量和时间的增加而进一步降解；另外,通过质谱分析证明,它们和磺酰脲分子中的杂环结构(如三嗪结构等)相关,可能具有生态毒性。总而言之,磺酰脲除草剂母体虽然可以在常规饮用水处理过程中被完全去除,但氯化过程中生成的产物并不能被完全降解,依旧具有危害人体的潜在风险。所以,本研究可为全面、准确评价这类农药的生态风险以及对人体的可能暴露水平提供依据。
[Abstract]:Sulfonylurea herbicides are widely used in the world because of their high efficiency and low quantity and wide application time. However, these herbicides are not volatile, easy to photolysis and highly selective. The sensitivity of these herbicides to different crops is very different, which will poison the next crop. Sulfonylurea herbicides that enter the environment will migrate into natural water bodies through various channels. If polluted water is used as a source of drinking water, these pesticides may be directly exposed to human body. However, it is not clear whether conventional drinking water treatment can effectively remove such herbicides. In this study, the conventional drinking water treatment process was simulated in laboratory. Five long residual sulfonylurea herbicides, chlorsulfuron, mesulfuron, chlorosulfuron, clopimuron and flurazuron, were selected as the research objects. Their removal from four typical drinking water treatment units, including coagulation, activated carbon adsorption, chlorination and ozone disinfection, was studied. The results showed that less than 10% of the sulfonylurea herbicides could be removed by coagulation and sedimentation, and the adsorption of activated carbon was more effective. The removal rate of these herbicides in this unit increased with the increase of the amount of activated carbon. The removal rate was between 50 and 70, but even when the dosage was increased to 20 mg L-1, it could not be completely removed; the removal of sulfonylurea herbicides by ozone disinfection was very limited; and chlorine disinfection had the highest removal rate of such herbicides, but it could not be completely removed. The degradation of different herbicides in this unit is very different, and chlorsulfuron and mesulfuron are more easily removed. The removal effect of five sulfonylurea herbicides by the process of drinking water treatment (i.e. coagulation-precipitation-filtration and chlorination disinfection continuous treatment) was also investigated. Compared with the results of chlorination alone, this process can significantly improve the removal rate of these pesticides. The herbicides in the samples prepared by deionized water were completely removed, but some herbicide residues were still found in the natural water samples with more complex composition. When activated carbon adsorption unit was added before chlorination, it was found that the removal rate of natural water samples could be significantly improved by this measure, and the removal rate of natural water samples could reach 100%. Although sulfonylurea herbicides can be completely removed during the whole process of drinking water treatment, and the removal rate of chlorinated disinfection units is the highest, the chlorination reaction of these herbicides has been studied in depth. In this process they all produce products of structural stability. When chlorine is sufficient, the amount of the product is determined by the initial concentration of the herbicide, and these products do not degrade further with the amount and time of chlorine added; in addition, mass spectrometry shows that, They are related to heterocyclic structures in sulfonylurea molecules (such as triazine) and may be ecotoxic. In a word, although the parent of sulfonylurea herbicides can be completely removed during the treatment of conventional drinking water, the products produced in the chlorination process can not be completely degraded, which still has the potential risk of harming the human body. Therefore, this study can provide a basis for comprehensive and accurate assessment of ecological risks of these pesticides and possible exposure to human body.
【学位授予单位】：南京农业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU991.2;X592

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