IMHE OpenIR  > 山地表生过程与生态调控重点实验室
3,5,6-三氯-2-吡啶醇在紫色土耕地中的迁移行为与模拟研究
Alternative TitleExperimental and modelling study on transport of 3,5,6-trichloro-2-pyridinol in cultivated purple soils
Language中文
雷文娟
Thesis Advisor唐翔宇
2015
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name博士
Degree Discipline土壤学
Keyword3 5 6-三氯-2-吡啶醇 紫色土 耕作类型 对流弥散方程 传递函数模型 最大熵原理
Abstract3,5,6-三氯-2-吡啶醇(TCP)是广谱杀虫剂毒死蜱的主要降解产物。和毒死蜱相比,TCP 的水溶性较大(49.1 g/L,25℃),与土壤、沉积物等结合能力相对较弱,抗降解能力较强,能够在环境中长期存在,更易迁移,且毒性相当,对土壤和水环境都具有潜在的污染风险。但当前对农药污染的研究主要侧重于农药母体,而对其降解产物的关注相对较少。紫色土是长江上游地区最主要的耕作土壤资源,其典型特征是有机质含量低、孔隙度高、饱和导水率高、团粒结构水稳性差、颗粒分散性强。这些特征将导致TCP对水环境的污染风险在紫色土广泛分布的区域显著增加。因此,研究农药降解产物TCP在紫色土中的迁移特征,并采用模型模拟其动态过程,找到或建立精度高、参数简单的模型来预测TCP在紫色土中的迁移,对于揭示其对地表、地下水体和土壤的污染风险特别是加强长江上游地区农业面源污染防治具有重要的参考意义。 依据紫色土的典型耕作类型,在中国科学院盐亭紫色土农业生态试验站采集3种耕地土壤:旱地(主要采用小麦-玉米轮作)、水田(主要采用水稻-油菜轮作)和菜地(四季种植各种蔬菜)。测定土壤的基本理化性质、土壤水分特征曲线,估算土壤水力学参数。通过批量平衡法实验,获取紫色土对TCP 的吸附特征,并采用填装和原状土柱在饱和稳定流场下进行易混合置换试验,研究TCP 的动态迁移过程。随后,采用三种模型对TCP迁移动态进行模拟:首先,采用基于对流弥散机理的物理模型进行模拟,如可动不可动模型,双孔隙两点吸附模型;而后,为简化物理模型模拟过程中参数测定的不足,采用传递函数模型对TCP迁移进行了模拟;最后,以信息熵理论为基础,以溶质运移过程中的已知信息为约束条件,最大熵原理为目标函数,建立并求解TCP迁移的模型,并验证了模型的精度。通过以上实验与模型模拟研究特别是新模型的建立,得出主要结论如下: (1)线性模型能够较好的描述紫色土对TCP的吸附特征。旱地、水田和菜地3种紫色土耕地土壤对TCP的等温吸附常数Kd分别为1.94 L/ kg、1.22 L/ kg和1.02L/ kg,即旱地>水田>菜地的特征。分析土壤的物理性质表明,黏粒含量和矿物组成(蒙脱石和高岭石)是影响3组供试紫色土样品对TCP的吸附常数Kd的主要因素。 (2)TCP迁移性较强,淋溶量大,对深层土壤及浅层地下水或地表水的污染风险较高。TCP在填装土柱中穿透曲线表明,平衡浓度分别为初始浓度的77%(旱地)、84%(水田)和92%(菜地),所需的平衡时间分别对应于2.88PV、4PV 和6.5PV(孔隙体积,PV)。原状土柱实验中的峰值浓度分别为80%、90%和70%,所对应的出峰时间依次为2.7PV、1.35PV和3.5PV。 (3)TCP在原状土柱中迁移的优先流作用明显。分析示踪剂Br-穿透曲线的偏度值、峰度值和斜率表明:曲线存在明显的不对称性和拖尾性,即优先流存在的穿透曲线的特征。当Br-穿透曲线相对浓度为0.5时,所对应的孔隙体积V/V0值分别为0.75(旱地)、0.28(水田)和0.86(菜地)。V/V0均小于1,也从另一个方面证实原状土柱中存在优先流现象。 (4)基于对流弥散机理的物理模型能够较好的模拟TCP的迁移动态,拟合的R2≥0.83,MSE<0.15,所获得的参数可解释其迁移机理。填装土柱:TCP迁移主要受化学非平衡影响,物理非平衡影响较小;水动力弥散系数D是影响穿透曲线峰值出现时间的主要原因;吸附常数Kd是影响穿透曲线峰值高低的主要原因;旱地、水田和菜地耕地紫色土壤中TCP的瞬时吸附在迁移过程中比例均较高,且旱地(83%)>水田(77%)>菜地(60%);TCP迁移过程中一阶动力学系数表现为旱地(0.28h-1)<水田(0.34 h-1)<菜地(0.38 h-1)。原状土柱:TCP迁移同时受化学非平衡和物理非平衡影响显著;TCP在紫色土可动水区中的吸附较小,低于7.15%;TCP在可动-不可动两区之间交换的质量和在可动水中的一阶动力学吸附也较小,同时瞬时吸附与动力学吸附之间的交换也较小。 (5)以对数正态分布概率密度函数为基础的传递函数模型,模拟填装和原状土柱的TCP迁移过程,R2达到0.76以上。和物理模型相比,尽管参数明显减少,但其精度有所下降。最大熵原理将穿透曲线划分为两个阶段:溶质浓度增加阶段和溶质浓度减小阶段,并将其看作是缩放后的概率分布函数;以已知信息为约束条件(通常出流溶质浓度均值已知),以浓度最大时的体积为边界条件,未知信息假设服从最大熵分布,通过建立拉格朗日函数,求解拉格朗日条件极值来获取概率密度函数,积分后得到穿透曲线。基于最大熵原理的模型能够很好的对TCP迁移过程进行模拟,R2≥0.97,MSE≤0.07。最后以相关系数(R2)、均方根误差(RMSE)、赤池信息量准则(AIC)和Nash-Suttcliffe系数(E)对3种模型的模拟结果对比分析,表明基于对流弥散机理的模型和基于最大熵原理的溶质运移模型都具有较高的精度,前者能更好的解释各物理和化学现象,后者具有更好的适应性、输入参数少、精度高的优点,可以作为快速和流域尺度预测的重要补充。 本研究探讨了紫色土不同耕作类型下的土壤对TCP的动态迁移特征,揭示出TCP在紫色土中易于迁移,在原状土柱中优先流作用明显,使其对水体的污染风险较大;物理化学机制分析表明TCP的动态迁移在原状土壤中受化学非平衡和物理非平衡影响均较显著;熵理论将溶质迁移的宏观态和微观态统一起来,模型的精度高、适应性更广,且参数更简单。这些结论可为长江上游紫色土地区农药面源污染风险评估,提供重要的理论依据和模型方法。
Other Abstract3,5,6-trichloro-2-pyridinol (TCP), the main degradation product of pesticide chlorpyrifos, exhibits strong anti-degradation ability, high water solubility at high proability. However, most studies on pesticide comtaniant pay more attention to the maternal pesticide and little to its degradation products. Purple soil is the main cultivated soil in upper reaches of the Yangte River, with the typical characteristics of low organic matter, high prosisy, high saturated hydraulic conductivity, heavy particle dispersibility and much water loss and soil erosion. These hydraculic and physical characteristics wold lead to a higher risk on water environment pollution in purple soil with slope cultivated land. Therefore, it is necessary to study the transportation characteristics of TCP in the purple soil distributed region, simulate the dynamic process to reveal the risk to surface water, underground water and soil enviroment, and find a simple and reliable model to simulate and forcast the TCP for the special soil. The results would provide an important reference value to prevent typical pesticide pollution in upstream region of Yangtze River. Three group of soil columns were sampled according to the typical cultivating type of purple soil in Yanting Agro-ecological Experimental Station of Purple Soil, including to rainfed cropland, a paddy field and a vegetable field sample close to the residential areas, corresponding to the crop rotation of wheat-corn, rice-rape and radish-cabbage, respectively. Fisrtly, physicochemical property, soil water characteristic curve and some inversed its soil hydraulic parameters were measured, including particle-size fraction, organic matter content, bulk density, pH value and content of clay minerals (montmorillonite and kaolinite), soil water characteristic curve and inversed its soil hydraulic parameter. Then, the batch equilibrium method was used to determine the liquid - solid partition coefficient of the TCP to reveal the absorbing characteristics of these purple soil samples to TCP; meanwhile, miscible displacement experiment was carried out under steady-state flow condition with Br- as a conservative tracer, from which dispersion coefficient for TCP transport could be estimated by inverse simulation. Finally, we simulated TCP transportation process. The physical model based on convection-dispersion mechanism was adopted to simulate TCP mobility and reveal its transported mechanism, followed by transfer function model to simplify parameters compared to convection-dispersion model. An entropy theory based model was used to simulate solute transportion with the contraints of known information. Through the above experiments, model simulation and established new model to simplidied the parameters, the conclusion are as follow. (1)The Linear equation could describe adsorption feature of the purple soil on TCP. The isothermal adsorption parameter Kd in rainfed cropland, paddy field and vegetably field was 1.94L/kg, 1.22 L/kg, 1.02 L/kg repectively. Clay content and mineral compositition (montmorillonite and kaolinite) were main factors effecting the parameter Kd . (2) A high pollution risk to deep soil and water environment due to the high mobility and much leaching loss of TCP. The breakthrough curve of disturbed soil column manifested that the equilibrium concentration of TCP were 77% (rainfed cropland), 84% (paddy field) and 92% (vegetably field) respectively. The time of equilibrium concentration was at 2.88PV, 4PV, 6.5PV respectively. The peak concentration in undisturbed soil column were about 80%, 90% and 70%, correspong to time was at 2.7PV, 13.5PV and 3.5PV respectively. (3)The preferential flow was obvious in undisturbed soil column according to the breakthrough curve. The skewness, kurtosis and slope of breakthrough curve of tracer Br- was analyzed, the results demostrated the curves exhibiting asymmetry and trailing feature. Meawhile, the PV was 0.75, 0.28 and 0.86 when relative concentrative equaled to 0.5. PV, less than 1 also meaned prefertial flow phenomenon esisting. (4)The physical model based on convection-dispersion mechanism could simulate TCP transported process well, the R2≥0.83, MSE<0.15, and its parmaters could reveal mechanism of transportation. For disturbed soil column, TCP transportioned was mainly effected by chemical non-equilibrium instead of physical non-equilibrium. Hydrodynamic dispersion D was the main factor effecting the time of peak vuale and Kd controlling the peak value chiefly; the instantaneous adsorption proportion of TCP transportion in rainfed cropland, paddy field and vegetable field were at high level, with 83%, 77% and 60% respectively; the parameter of first order dynamic adsorption were 0.28h-1, 0.34 h-1and 0.38 h-1 correspond to rainfed cropland, paddy field and vegetable field respectively. For undisturbed soil column, TCP transportion were affected by both chemical and physical non-equilibrium process; the adsorption proportion in mobile zone were all less than 7.15%; the exchange quality between mobile zone and immobile zone was at a low level, as well as exchange between instantaneous and dynamic adsorption. (5)The transfer function model, based on lognormal distribution proability density function, was used to simulate TCP transportion in both disturbed and undisturbed soil colums, and the results showed the R2≥0.76. Compared with physical model, the precision decreased although the advantage of less parameters was obvious. The solute transportion model based on principle of maximum entropy divided lognormal distribution into two phases, solute concentration increasing and decreasing process; known information as constraint condition, the outflow volume at equilibrium state as boundary conditions, unknown information obey to maximum entropy distribution, established lagrangian function to obtain breakthrough curve. The result showed a good simulation to TCP transportion, with R2≥0.97 and MSE≤0.05. (6)Correlation coefficient, root mean square error, Akaike information criterion and Nash-Suttcliffe effeicnt coefficient were used to evaluate the performance of the three models above. Which manifest the model based on maximum entropy exhibited the best performation. Less imput parameters and high precision, which reflect entropy unified statistics and physics. This study revealed the adsorption feature of purple soil to TCP under different cultivation, and also showed high risk to water environment, especially intensified by preferential flow in undisturbed soil colum. The physical model revealed that transportion of TCP was mostly affected by both chemical and physical non-equilibrium. Solute transported model based on maximum entropy exhibited both high precision and simple parameters. These results and conclusions colud provide important theoretical reference and technological support to typical pollution prevention in upsteam regions of Yangze River as well as the regions of Three Gorges Reservoir.
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/15061
Collection山地表生过程与生态调控重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
雷文娟. 3,5,6-三氯-2-吡啶醇在紫色土耕地中的迁移行为与模拟研究[D]. 北京. 中国科学院大学,2015.
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