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Chinese Geology University (Beijing) (2003)

Occurrence And Movement Of Water And Salt In Aeration Zone In Arid Regions And Their Effect On The Ecologic Environment

吴胜军;Sheng Jun

Titre : Occurrence and Movement of Water and Salt in Aeration Zone in Arid Regions and Their Effect on the Ecologic Environment

Auteur : 吴胜军;Sheng Jun

Grade : Master’s Theses 2003

Université : Chinese Geology University (Beijing)

Résumé
The Heihe River Valley in the Hexi Corridor, located in the northwest of China , is an arid and semi-arid region and one of the largest endorheisms in China. With the development of agriculture and industry and the enlargement of man’s activity , the demand of water supply has increased in the region over the past decades .In the backward areas along the Heihe River, there are a lot of ecological environmental problems such as lake dried up, sustainable, lowering of ground water level , water pollution , soil salinization and desertification, degradation of natural oasis and grassland , as well as sand storm.The plants growing on the land surface can be affected by the occurrence and movement of water and salt in the aeration zone . In order to understand the characteristics of occurrence of water and salt in the aeration zone ,we installed three tensionmeter systems .which includes 35 ceramic cups , in the soil of Ejnqi Oasis on the downstream of Heihe River in Inner Mongolia Province. The moisture potential distribution in aeration zone was observed, and the samples of water and soil were collected along the Heihe River. The chemical components of salt in the soil and ground water were examinated. The distribution and movement of water in the aeration zone of the arid region were discussed based on the matrix potential of soil water and the contents of salt in the soil.Some conclusions have been drawn in this thesis. In the arid and semi-arid region, matrix potential of soil water diversifys intensively in aeration zone, so there is good environment for zero flux potentials to develop. There are several zero flux potentials in aeration zone and the types of the zero flux potentials are different. For example, in He3, there are three zero flux potentials in aeration zone, they are different and exist at depths of 1 m,1.7 m,2.3 m below the land surface. Changes in climate can affect the water-salt interaction by the roots of plants, can also affect the values of the matrix potential of soil water, and the distribution and movement of water in the aeration. In the course of intensive evaporation, the convergent zero flux potentials may occur at depths where the main roots of most plants develop. What’s more, the capacity of flowing water at the depth is not zero , and it equals to the water absorbed by the root of the plants.The movement of the water in aeration zone is different at different depth, if the Zero flux potentials exist in the aeration zone. In the region of investigation, the water in the soil is upward and under the evaporation condition in the first zone, where intensive evaporation occurs ; the matrix potential of soil water is downward so that the water is downward in the second zone.Sometime the matrix potential of soil water, moisture capacity and the total content of salt capacity in the soil have the same trends of change with depth. In the profile of aeration zone, the matrix potential of soil water and salt capacity in the soil can be affected by the lithology. For example, the salt capacity in the soil decreases with the increase of depth, while the lithology is the same in the aeration zone.We can draw some conclusions below by analyzing the salt capacity in the soil in the Ejnqi Oasis in the direction from east to west and from south to north, which is that in the horizonal direction, the total salt capacity in the soil become more and more higher withthe longer distance far from the center of the oasis and in the vertical direction the salt capacity differs evidently with depth.In the aeration zone, Ca2+ and CI-, K++Na+ and SO42+ have the same rules with the depth. The salts consisting up of Ca2+ K++Na+ and Cl- SO42- are throught to be alkalescent and the combination of salts in aeration zone. The different TDS of groundwater and hydro-chemical types differ in different environment.

Mots clés : zero flux potential; matrix potential of soil water; tensiometer; aeration zone; ecologic environment; Heihe River Region;

Présentation (CNKI)

Page publiée le 19 avril 2013, mise à jour le 13 septembre 2017