利用环境示踪剂研究黄土坡地土壤水深层渗漏及其变化

发布时间：2018-02-10 17:13

  本文关键词： 黄土高原 坡地 土地利用 环境示踪剂 深层渗漏量　出处：《西北农林科技大学》2016年硕士论文　论文类型：学位论文

【摘要】：黄土高原地处我国西北内陆地区,气候干旱,降水稀少,土壤水分成为该地区植物生长的主要限制因子。1999年退耕还林还草生态工程的实施,有效的改善了局部生态环境,减少了水土流失,但同时也引发了土壤干燥化和地下水位下降等一系列生态水文问题,并直接威胁生态建设的可持续性和稳定性。尽管黄土塬区不同土地利用类型下,深剖面土壤水分的研究已经取得了很多进展,但对黄土坡面土壤深剖面土壤水分及其对地下水补给的研究还很少,阻碍了全面回答该区退耕还林还草生态工程和地下水资源利用是否可持续这一重大科学问题。本文利用环境示踪剂研究黄土高原分布面积较广的坡地不同坡位的深层渗漏,以陕西长武王东沟为例,研究其不同坡位不同土地利用类型下土壤水分及水同位素特征,研究黄土坡地不同土地利用类型下的耗水情况,估测不同坡位深层渗漏量及其变化,进而探讨黄土坡地深层土壤水的补给方式。取得的主要研究结果如下:(1)黄土塬面和坡面不同土地利用类型的耗水特点。通过对塬面和坡面不同土地利用深剖面土壤水分对比分析可知,由于受不同生长年限、林地管理水平、根系空间分布状况的影响,相比于浅根植物(荒草、玉米),深根植物均有不同程度的水分亏缺,其中塬面盛果期17年苹果,亏缺深度达15 m;其次上坡位23年苹果,由于管理水平低下以及苹果龄期较大,产量较低,其亏缺量有限,根系耗水深度可达22.6 m;最后,中下坡位杏树,耗水深度达6-7 m。(2)黄土坡地林-草土壤水分平均入渗速率和深层渗漏量。草地黄土坡地上、中、下三个剖面有比较清晰完整的铃形氚峰,说明非饱和区土壤水主要以活塞流的形式运移,且存在不同程度的弥散作用。通过氚峰值示踪法估算得到草地三个坡位的深层渗漏量分别为20 mm y-1、22 mm y-1、27 mm y-1,约占多年平均降水量的3%-5%。中、下坡位的深层渗漏量较上坡位分别大10%和35%,这主要由于该地区6-9月的集中降雨产生的地面径流导致,中、下坡位上方集水面积较大,能够接受较多径流,从而产生较大的深层渗漏量。改进的氯质量平衡法估算黄土坡面草地深层渗漏量:上坡位为19-23 mm y-1,中坡位为23-29 mm y-1,下坡位为37-45 mm y-1,其深层渗漏量约占多年平均降水的3.3%-7.7%。总体来说,氯质量平衡法较氚峰值示踪法的估测量偏大,尤其下坡位两者的差异较大,这主要是由于下坡位地势最低,上方来水最多,容易产生更多入渗量;其次与降水中氯离子空间变异及土壤孔隙水中氯离子的阴离子排斥效应有关。林地不同坡位也存在清晰的峰值,3H剖面波动较大,平均入渗速率为6.0 cm y-1、7.8 cm y-1、10.0 cm y-1;该峰值深度与入渗速率均比草地相同坡位的峰值深度与入渗速率分别偏浅、偏慢,这主要由深根植物的根系不断向下生长及耗水,阻滞了土壤水分向下运移造成的。(3)应用环境示踪剂研究深层土壤水补给规律。通过分析黄土坡面草地氢氧同位素剖面的变化特征发现,受土壤蒸发、降水入渗补给的影响,浅层土壤水同位素出现贫化峰值,深层土壤水同位素基本不发生变化,并结合相应坡位的3H剖面分布,可知草地的深层土壤水主要以活塞流的形式进行入渗补给。通过对比分析林-草土壤水的氢氧同位素剖面变化特征,可知林地深层土壤水在不同土层出现不同程度的贫化现象,其中上坡位氯离子受到“稀释”,且氚的波动较大,认为林地深层根系不断生长、衰败的生理现象,导致土壤根系区密集孔隙的出现,使得降水可以快速均匀流的方式入渗补给到深层土壤。
[Abstract]:The Loess Plateau is located in the northwest inland region, China's dry climate, scarce rainfall, soil moisture has become the main limiting factor of.1999 in the area of plant growth in returning farmland to forest and grass ecological engineering implementation, effectively improve the local ecological environment, reduce soil erosion, but also caused the soil desiccation and underground water level after a series of eco hydrological problems, and a direct threat to the sustainability and stability of ecological construction in Loess Plateau. Despite the different land use types, research on deep soil moisture has been made a lot of progress, but on the loess slope soil deep soil moisture and Study on groundwater recharge is very few, hindered the full answer to this area of returning farmland to forest ecological engineering and sustainable use of groundwater resources is an important scientific problem. In this paper, using environmental tracers to study the distribution area of Loess Plateau Wide slope slope seepage in Shaanxi Changwu Wang Donggou as an example to study the different slope under different land use types of water and water isotope characteristics of soil, water consumption under different land use types on loess slope, estimation of different slope deep percolation and its changes, and to explore the deep soil of loess slope the water supply mode. The main results are as follows: (1) the water consumption characteristics of different land use types in Loess Plateau and the slope. The slope Tableland and different land use of deep soil moisture analysis can know, due to different growth years, the management level of forest land, influence spatial distribution of root system. Compared to shallow rooted plants (grass, corn), deep root plants have different degree of water deficit, the tableland full fruit period 17 years Apple deficit depth of 15 m; the second top 23 years due to apple. The management level is low and the apple age bigger, lower yield, the deficit is limited, water consumption depth of up to 22.6 m; finally, the lower slope position apricot, water consumption depth of 6-7 M. (2) loess slope forest grass average soil moisture infiltration rate and deep percolation. Grassland on the loess slope. In the three section has clear bell shaped tritium peak, non saturated soil water is the main form of transport to the piston flow, and there are different degrees of dispersion. The tritium peak tracer estimated by deep percolation three grassland slopes were 20 mm y-1,22 mm y-1,27 mm Y-1. About the average annual precipitation of 3%-5%. in deep percolation is a downhill uphill respectively 10% and 35%, this is mainly due to the surface runoff in the region concentrated rainfall caused by the 6-9 month, in the downhill, above the catchment area is larger, can receive a multipath flow from Due to a large amount of deep percolation. Estimation of grassland on Loess Slope deep percolation chloride mass balance method improved: upper slope is 19-23 mm Y-1, middle slope is 23-29 mm Y-1, the downhill is 37-45 mm Y-1, the deep leakage accounted for annual precipitation 3.3%-7.7%. overall, quantitative estimation of the chloride mass balance method a tritium peak tracer method is too large, especially a large difference between the downhill, this is mainly due to the downhill is the lowest, the most easy to produce more upslope runoff and infiltration; secondly and chloride ions in precipitation and soil spatial variability in pore water of chloride anion exclusion effect. There are also clear forest in different slope positions the peak of 3H profile fluctuations, average infiltration rate of 6 cm y-1,7.8 cm y-1,10.0 cm Y-1; the peak depth and infiltration rate of grassland with same peak slope and depth of infiltration rate was low, slow, 杩欎富瑕佺敱娣辨牴妞嶇墿鐨勬牴绯讳笉鏂�鍚戜笅鐢熼暱鍙婅�楁按,闃绘粸浜嗗湡澹ゆ按鍒嗗悜涓嬭繍绉婚，

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