旱改水对土壤中氯嘧磺隆生物有效性的影响及其调控研究

As an important commercial grain base, the Sanjiang Plain is also the key area of "the project of increasing yield by 50 billion kilos". Changing upland fields to paddy fields is an effective way of increasing yield. However, residual of chlorimuron-ethyl in upland field restricts the changing process. Chlorimuron-ethyl is a kind of herbicide widely used in soybean (Glycine max) fields, and its residual in soil poses great phytotoxicity to rotational rice (Oryza sativa). The bioavailability of pollutants is more suitable for an index of the assessment of remendiation and ecotoxicology. In the proposal, a method of chemical analysis estimating chlorimuron-ethyl bioavailability, which uses rice (Oryza sativa) as model plant, is developed based on Sequential Extraction, Solid Phase Extraction and High Performance Liquid Chromatography analysis. The degradation process and bioavaibility variation of chlorimuron-ethyl in paddy field is analyzed. Straw returning and optimizing of water management have great potentialities in lowering the bioavaibility of pollutants in soils. Straw returning could increase the adsorption of pollutants on soils, which reduces the concentration of pollutants in soil solutions. And wetting-drying cycles would be establised through the optmizing of water management, which have great capacity in reducing bioavailability through changing the conformation of soil organic matter and other physicochemical properties of soil. Furthermore, these two ways are of low cost. Hence the influence of straw returning and water management on chlorimuron-ethyl bioavailability will be studied comprehensively to gain more knowledge on the mechanism of reducing bioavaibility. Based on a clear understanding of influence factors, regulation of chlorimuron-ethyl bioavaibility aiming to reduce phytotoxicity on rice (Oryza sativa) will be suggested. The implementing of the proposal would be helpful in solving the problem of chlorimuron-ethyl residual in paddy fields, technologically supporting the construction of national commercial grain base.

三江平原是我国重要的商品粮基地，也是"增产1000亿斤工程"的核心区域。旱改水是重要的增产措施之一。氯嘧磺隆是旱田(大豆)施用的主要除草剂，旱田改为水田后其残留对水稻有严重药害，是旱改水的主要限制因素之一。污染物生物有效性较总量更适宜作为衡量污染修复效果和生态毒理的指标。本项目拟从氯嘧磺隆的生物有效性入手，以水稻为供试植物，借助梯度溶剂提取技术、固相萃取技术及高效液相色谱分析技术，建立土壤中氯嘧磺隆生物有效性分析方法；研究氯嘧磺隆在水田中降解过程及生物有效性变化过程，分析秸秆还田方式、田间水分管理措施等对氯嘧磺隆生物有效性的影响，明确水田中氯嘧磺隆生物有效性主要控制因素；在此基础上，确立氯嘧磺隆生物有效性调控方案，通过降低氯嘧磺隆生物有效性实现消除其对水稻药害的目的，解决三江平原地区旱改水顺利进行的土壤氯嘧磺隆残留问题，为国家商品粮基地建设提供科学技术支持。

氯嘧磺隆生物有效性化学分析是本项目的核心。项目执行过程中，我以潮土、黑土和红壤为供试土壤，采用梯度溶剂法区分氯嘧磺隆和土壤颗粒的结合程度，结合不同土壤中植物毒理学数据，建立了氯嘧磺隆生物有效性化学分析方法。在系统的分析了氯嘧磺隆在不同土壤以及不同土壤组分中的吸附解吸特征的基础上，我们采用优化肥料种类和施肥量等方式对氯嘧磺隆生物有效性进行了调控。.三种土壤中，SOD和POD活性均随氯嘧磺隆的浓度升高而增加。当潮土、黑土和红壤中氯嘧磺隆浓度为1.0 mg/kg时，SOD活性分别提高了217 %，28 %和54 %， POD活性分别提高了321%，61 %和61 %。随氯嘧磺隆浓度升高，CAT的活性呈下降趋势。当土壤中氯嘧磺隆浓度为1.0 mg/kg时，三种土壤中CAT活性分别降低了77 %，34 %和50 %。POD活性对氯嘧磺隆胁迫的响应更为灵敏，线性关系也更佳，更适宜作为评价氯嘧磺隆生物有效性的指标。.我们分别采用0.01 M CaCl2溶液以及不同比例水与甲醇的混合液土壤中的氯嘧磺隆，分析其赋存形态。不同土壤中POD比活性和CaCl2溶液提取浓度的斜率并不一致，CaCl2提取低估了黑土和红壤中氯嘧磺隆生物有效性。将不同提取形态氯嘧磺隆浓度加权求和后作为氯嘧磺隆有效浓度并将其和POD比活性做线性回归，相关系数R2=0.92-0.96，斜率k=4.14-4.30，三条回归曲线基本重合较好的解决梯度溶剂提取中提取溶液选择困难的难题。.氯嘧磺隆在黑土、红壤和潮土中吸附的Kd值分别为0.468，0.623和0.038 L/kg。Freundlich模型可以更好的描述氯嘧磺隆在三种土壤中的吸附-解吸特征。腐植酸对氯嘧磺隆的吸附能力和膨润土相当，稍低于蒙脱土。氯嘧磺隆在各种蒙脱土上的吸附量几乎相同，与可交换离子无关，而膨润土则表现出较大差异。氯嘧磺隆在腐植酸上的吸附几乎随着pH的升高而呈直线下降趋势。.NH4Cl对土壤吸附氯嘧磺隆的影响与土壤类型有关。NH4Cl的施用对了氯嘧磺隆在黑土中的吸附起轻微的促进作用，对其在红壤中的吸附作用不大，但却显著降低了潮土对氯嘧磺隆的吸附能力。不同浓度的NaNO3对土壤吸附氯嘧磺隆的影响在3种土壤中存在较大的差异。NaNO3的施用对氯嘧磺隆在黑土和红壤中的吸附特性影响不大，但显著降低了其在潮土中的吸附量，提高了其生物有效性。