IMHE OpenIR  > 山地表生过程与生态调控重点实验室
紫色土坡耕地径流水源的同位素示踪研究
Alternative TitleTracing Water Source on Sloping Farmland of Purple Soil by Hydrogen and Oxygen Isotopes
Language中文
王超
Thesis Advisor高美荣 ; 赵培
2013
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name硕士
Degree Discipline土壤学
Keyword紫色土丘陵区 氢氧同位素 坡地径流 产流机制
Abstract紫色土丘陵区是我国西南地区重要的农业产区,坡耕地是本地区主要的土地利用方式,密集的农业生产和特殊的土壤、水文特征是造成该地区水土流失和农田非点源污染主要原因之一。坡地径流不但是区域水文过程的重要组成部分,同时也是土壤侵蚀、面源污染和其它污染物迁移的重要影响因素。本文通过对降雨-径流过程中水文特征与各水体中氢氧同位素监测,利用同位素示踪技术与传统土壤学、水文学的研究方法,分析了本地区降雨同位素特征、降雨入渗和坡地产流机制,取得了以下研究结果: (1)初步建立盐亭地区区域大气降水线(LMWL):δD = 8.3δ18O + 18.3。与全球大气降雨线相比(δD = 8.0δ18O + 10),降雨δD和δ18O关系线斜率与截距均偏大,说明本区域内陆性水汽相比全球水平占有更重要的作用。本地区降雨同位素存在明显的降雨量效应和温度效应。全年氘盈余呈夏低冬高,说明本地区雨季降雨水汽来源于海洋,冬季水汽来源于大陆区域水循环。次降雨过程中δD和δ18O存在强烈的时间变异,玉米截留对降雨同位素分馏作用不明显。 (2)降雨主要通过活塞流的形式补给土壤水,降雨补给土壤水效率主要取决于降雨量、降雨强度和前期土壤含水量。在前期土壤含水量较高、低雨强情况下,降雨更容易替换土壤水。用陶土管法与真空提取法采集到的土壤水δD和δ18O有较大差异,说明土壤中的活动水和不动水并没有完全混合。 (3)在玉米生长期,紫色土坡地径流以地面下径流为主。在大雨强下产生少量的地表径流,其水源主要来自产流时的降雨;前期土壤水是壤中流与地下径流的主要水源,当前期土壤含水量高并且降雨强度较大时,前期土壤水在径流初期所占的比例较小;而在前期土壤含水量较小或雨强较低情况下,前期土壤水在产流初期径流所占比例较高。在整个径流过程中,前期土壤水在径流过程中所占比例与流量呈负相关关系,峰值流量时前期土壤水在径流中所占比例处于低值,说明降雨强度较大时存在降雨对径流的优先流补给途径。在前期土壤含水量和降雨量较大的情况下,壤中流与地下径流的产流机制不相同:壤中流的产生与降雨强度相关,当降雨强度大于某层土壤入渗率时即在该层之上产流,随径流发育壤中流发生层降低;地下径流是表层土壤水与降雨混合后,通过优先流的孔隙和缝隙到达岩层,产生地下径流。 (4)地面下径流是NO3--N输出坡耕地的主要途径,径流迁移的NO3--N与前期土壤水对径流贡献率存在显著的正相关关系。实现土壤水资源的高效利用,可能对养分流失起到有效的控制作用。
Other AbstractHilly area of purple soil is an important agricultural area in southwest of China. There are a large number of sloping farmlands. The irrational and intensive agricultural activities on sloping farmland were the main reason for soil erosion and non-point source pollution. Hillslope runoff is not only an important part of the regional hydrological processes, but also is the important factor of soil erosion, non-point source pollution and other contaminants mitigation. To understand the mechanism of runoff generation, the hydrological characteristics of the rainfall-runoff processes were monitored during three storms. The hydrogen and oxygen isotopes in precipitation, soil water and runoff were monitored continuously. This paper aimed at analyzing the hydrological processes of runoff based on isotopes technologies combined with soil physical and hydrological experiment. The preliminary results were shown as follows: (1) Initially establishment of the Yanting regional Local Meteoric Water Line (LMWL): δD = 8.3δ18O + 18.3. Compared with the global Meteoric Water Line (GMWL), it had bigger slope and intercept which meant that the local vapor is an important source for the precipitation compared with the global average level. Temperature and rainfall was the main control factors of δD and δ18O in precipitation. In this year, the deuterium excess (d) was low in summer and high in winter, indicating that the local water vapor was the main source of precipitation in dry season and the sea vapor was the main source of precipitation. (2) Rainfall mainly recharged soil moisture by piston flow. The efficiency of rainfall recharging the soil mainly depends on rainfall amount, rainfall intensity and antecedent soil moisture. In the case of higher antecedent soil moisture and low rainfall intensity, the soil water was easier to be replaced by rain water. Between the collected suction pipes and cryogenic vacuum distillation of soil water, δD and δ18O was different indicated that the mobile soil water was not well mixed with stationary soil water. (3) The subsurface flow was the mainly form of runoff on the sloping farmlands of purple soil. A small amount of surface runoff occurred when the rainfall intensity was enough high. Its water source was mainly from the precipitation. Antecedent soil water was the main water source of the interflow and underground flow. In the case of higher antecedent soil moisture and high rainfall intensity, antecedent soil water occupied a small proportion of the early runoff; In the case of higher antecedent soil moisture or heavy rainfall intensity, antecedent soil water had a larger proportion of the early runoff. In the entire rainfall–runoff processes, antecedent soil water in the proportion of runoff had a negative correlation with flow rate. Soil water had the smallest proportion in the flow peak, indicating that there were the preferential flow channels that rainfall can quickly appear to runoff during the heavy rainfall intensity. In the case of higher antecedent soil moisture and high rainfall intensity, the interflow and underground flow had different generation mechanism: Interflow generation was mainly dependent on the rainfall intensity. When the rainfall intensity was higher than soil infiltration rate of the soils, the interflow was generated in the layer of soil and gradually decreased in runoff process; Rain water mixed with surface soil water and rainfall moved vertically through the macropores or cracks to reach the rock generated the preferential flow. (4) Subsurface flow was the main pathway of NO3--N loss in the sloping farmland. NO3--N concentration and antecedent soil water proportion had a significantly positive relationship. Efficient usage of soil water would benefit the non-point pollution control.
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/6977
Collection山地表生过程与生态调控重点实验室
Recommended Citation
GB/T 7714
王超. 紫色土坡耕地径流水源的同位素示踪研究[D]. 北京. 中国科学院研究生院,2013.
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