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基于多示踪剂的农业小流域暴雨径流水源初步解析
Alternative TitlePreliminary interpretation of water sources in an agricultural watershed during rainstorm events based on Multi-tracer approach
Language中文
王芮
Thesis Advisor唐家良
2016
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name硕士
Degree Discipline土壤学
Keyword紫色土丘陵区 农业小流域 径流分割 暴雨径流过程 水文示踪
Other Abstract

紫色土丘陵区雨季暴雨径流冲刷加剧了氮磷等污染物流失,下游水质已出现富营养化等环境问题。小流域尺度径流产生过程的水源分析可以为认识该区域农业面源污染成因提供依据,对于紫色土丘陵区水资源评价和合理开发利用水资源,保护地下水、控制农业面源污染物质排放等方面具有重要意义。本研究通过对紫色土丘陵区嵌套式农业小流域典型暴雨过程多尺度(从3-1236公顷)连续监测,分别研究了苏荣小流域(3.2公顷)、截流小流域(35公顷)、大兴小流域(480公顷)、万安小流域(1236公顷)暴雨径流过程及水化学特征、水源特征、基于氢氧同位素示踪和水化学示踪不同小流域暴雨径流水文路径的研究。其中重点研究了基于氢氧同位素和无机水化学离子示踪分割径流水文途径,分析了不同无机水化学离子的示踪潜力,并试图说明多水文示踪剂的选择,从而最终解析径流中不同水源的贡献。主要结果和结论如下:(1)紫色土丘陵区农业嵌套式小流域中较小尺度流域径流峰值对降雨峰值有较快响应,随着流域面积的增大,径流峰值出现明显滞后和平坦化。暴雨雨强、降雨量、降雨历时、降雨前期土壤湿度对不同尺度小流域产流有一定影响。相同雨型事件中,前期较湿润的土壤条件可使径流峰值明显提前。暴雨事件使硝态氮(NO3--N)及无机水化学离子(K+、Na+、Ca2+、Mg2+、Cl-、SO42-、EC、DOC)大量流失,且浓度曲线与降雨过程并不一一对应,出现多峰现象,其中NO3--N、DOC、Ca2+流失主要来源扰动后的表层土壤。流失。小流域集镇污水出口(苏荣小流域)径流中硝态氮浓度最高,万安小流域出口处硝态氮浓度最低。退水过程中来自坡地壤中流的补给致使径流中硝态氮多次出现浓度峰值。(2)紫色土丘陵区农业小流域水源中水化学性质总体特征为:土壤水中各水化学指标值(K+、Na+、Ca2+、Mg2+、SO42-、Cl-、NO3--N、EC、DOC)最高,井水次之,雨水最低。不同土地利用方式下土壤水的水化学特征值有较大差异,来自于林地的土壤水比来自于耕地的土壤水的各项水化学指标特征值偏低。盐亭县嵌套式农业小流域内不同位置地下水化学性质有差异较大。受人为活动干扰较大的地下水中各水化学离子浓度均较高、其中Ca2+和EC指标的变异性最大。受不同水汽来源及温度等影响,不同时间降雨雨水中氢氧同位素有着显著差异,呈现出夏低冬高的特征。土壤水、地下水是非本次降雨事件水混合的结果。本研究区域中土壤水与地下水联系紧密,二者在水化学性质上有时会比较接近。因此在复杂农业小流域,应注意区分土壤水和地下水化学特征,减少对径流示踪结果准确性的影响。(3)无机水化学离子(K+、Na+、Ca2+、Mg2+、SO42-、Cl-、NO3--N、EC、DOC)均具有示踪潜力,与氢氧同位素一样都能在一定程度上示踪径流过程中土壤水比例的变化。在进行两水源分析时,18O与NO3--N均能示踪紫色土丘陵区农业小流域径流消退期壤中流补给过程,但密集居住区高含氮污水导致基于NO3-N示踪法的苏荣子流域出现土壤水比例过高的偏差;NO3--N、Ca2+、EC作为水文示踪剂的应用需尽量排除生活污水等输入源干扰。三水源的分析至少需要两种示踪剂,此时可根据主成分分析法来选定合适的无机水化学示踪剂组合。研究表明,EC-DOC、O18—NO3--N/SO42-/Ca2+/Na+/Cl-、Na+/(Na++Ca2+)—NO3--N、Ca2+—SO42-水化学示踪剂组合能较好的示踪降雨产流过程中小流域径流土壤水比例的变化。单一示踪剂可能带来偶然性结果,因此作者建议复杂农业小流域进行水文过程模拟时应采用多示踪剂校核的方法。(4)紫色土丘陵区农业小流域内暴雨径流主要由雨水、土壤水、地下水三种水源混合组成。降雨初期小流域径流以雨水贡献为主(60%),径流消退期以林地为主的大兴、万安小流域暴雨径流中地下水、土壤水补给比例增大,小流域出口万安暴雨径流中地下水比例达到50%以上。前期土壤条件越湿润,面积较小的流域(苏荣、截流小流域)暴雨径流中地下水的贡献率就越高。暴雨径流中土壤水比例出现多次上升使得径流中NO3--N浓度也出现多峰值波动,流域面积越大(大兴、万安小流域)该现象越明显。本研究结果为区域农业面源污染防控提供了重要的科学依据。

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Long-term application of nitrogen fertilizer, coupled with the runoff scouring, aggravated the nitrate nitrogen leaching and loss from hilly area of purple soil. Water quality of downstream water has been severely eutrophicated and nitrate accumulation in groundwater raised serious environmental threats to the safety of local residents' drinking water. Identification of water sources and pathways of runoff is key to catchment hydrology. A good understanding of the mechanism of runoff formation was helpful for the cause of agricultural non-point pollution, assessment and development of water resources, the construction of hydrological models.This study was conducted in the typical agricultural watershed which included comprehensive monitoring during typical rainstorm events at multiple scales (from 3 to 1236 hectares) in hilly area of purple soil. Streamwater hydrograph and chemograph in catchments of Surong(3.2ha), Jieliu(35ha), Daxing(480ha), Wanan(1236ha),water sources’ chemical characteristics (Rainwaters, soil waters, groundwaters, irrigation waters), identification of hydrological pathways based on different tracers are studied respectively. The tracers include hydrogen and oxygen isotope, and main inorganic ions. The potential of different inorganic tracers were validated based on EMMA assumptions and then the selection of appropriate hydrological tracers helped quantification of the contributions from different water sources in the nested agricultural watersheds. There search results were as follows.(1)In the smaller watersheds, stream runoff has faster response to the rainfall runoff peak. With the increase of catchment area, the runoff peak appeared obvious lag and smoothed phenomenon. Under the same type of rain events, the more moist soil conditions favored early peak runoff. The town sewage outlet (Surong watershed) led to the highest NO3--N concentrations in runoff during heavy rain events, with lowest concentration reaching the Wanan watershed which is the outlet of the whole nested agricultural watershed. The NO3--N concentrations decrease can be attributed to the dilution of forest subwatershed water in larger scale. The hydrochemistry indicators (K+、Na+、Ca2+、Mg2+、Cl-、SO42-、NO3--N、DOC) were significantly transported out with runoff during storm events and appeared several peaks. During the recession of the streamflow, nitrate nitrogen derived from the interflow on farmed hillslope caused multiple peak concentrations.(2)Investigated water chemical characteristics within the nested watershed are as follows: the concentrations of hydrochemistry ions (K+、Na+、Ca2+、Mg2+、Cl-、SO42-、NO3--N、EC、DOC) in the precipitation are lowest, groundwater are higher,soil waters are the highest. The hydrochemistry characteristic values of the soil water in the forest lands are lower than cultivated lands. Moreover, the groundwater chemical properties within Wanan watershed in different positions are also different. Compared with spring water,the chemical index of wells water are higher. The wells with greater human disturbance are higher in all hydrochemistry ions, with Ca2+ and EC index variation being the largest. Influenced by different sources of water vapor and temperature, hydrogen and oxygen isotope in different rainfall water has a significant difference, presenting lower values in summer and higher values in winter. In addition, hydrogen and oxygen isotopes differed greatly in different water sources. The soil water, groundwater are the mixed waters of diferent ages old water. (3)We found that the dissolved inorganic elements (K+、Na+、Ca2+、Mg2+、Cl-、SO42-、NO3--N、EC、DOC) all have the potential of hydrologic tracers, as well as stable isotopes hydrogen and oxygen which can trace the rise of soil water percentage in flow process in many places.The EMMA model analysis results of the 4 storm events show that: For the two end-members mixing model, 18O and nitrate nitrogen can both trace the process of subsurface interflow supply in the runoff recession period. High nitrogen sewage of the dense residential resulted in inaccuracy to nitrate tracer results at Surong watershed. According to the PCA (dimension reduction method), tappropriate inorganic hydrochemical tracer could be selected to better represent the water mixing processes by the different water sources. The situation for the three end- member mixing model is different. The tracing accuracy of nitrate nitrogen is better proved by other tracers. Nitrate nitrogen acts not only as an indicator of water environment but also behave as the hydrologic tracer, but its application needs to get rid of sewage influences. In order to avoid with the bias by single tracer, the author suggests that using mutiple tracers methods combined with integrated hydrological monitoring would be best approach in interpretation of hydrological process in complex agricultural watershed.We found that EC-DOC、O18—NO3--N/ SO42-/Ca2+/Na+/Cl-、Na+/Na++Ca2+—NO3--N、Ca2+—SO42- can trace soil water contribution during storm events. (4)Streamflow during rainy season is mainly composed of rainwater, soil water, groundwater in the agricultural watershed in the hilly area of purple soil. Daxing and Wanan watershed streamflows are mainly affected by groundwater and soil water supply, with proportion even up to 50%. Subsurface interflow release from farmed hillslope with the soil water contribution led to NO3--N peaks of the chemograph. The basin area is bigger (Daxing, Wanan watershed), the phenomenon of soil water flushing is more obvious.

Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/18864
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
王芮. 基于多示踪剂的农业小流域暴雨径流水源初步解析[D]. 北京. 中国科学院大学,2016.
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