The Characterization Of Hydrochemistry And Isotopic In The Natural Water Of The Yarlung Tsangpo Lhasa-Nyingchi

Based on the point of hydrological geochemistry and environmental isotopes to study the natural water of chemical and isotopic characteristics, and reaching the following conclusions:(1) By the reseach main physical and chemical characteristics of natural water (pH, temperature, water chemical type, ionic composition and salinity, hardness and corrosion resistance) and its characteristics on study area. On study area, different types and different regions of natural water, mainly by the supply of natural water types and the different human activities.①The study area basin (a tributary of the Yarlung Tsangpo and the Lhasa River, Niyang River) the pH value of greater range, pH value in the 6.9-8.23 range, average 7.69; study area tributary river of the pH value of 7.03 -8.68 range, average 7.67; the study area the pH value of the local spring water is stable in the range 7.08-8.43, average 7.92; hot spring water pH value of the differences are significant, and well water pH value is more stable. Major rivers and tributary water, with the HCO₃^- content increase, pH content increased, when HCO₃^- content more than 70-100mg/L time, with HCO₃^- content increases the pH decrease; other types of natural water (hot springs, springs and well water) changed little. With the increase of longitude (along the lower reaches of the river) and pH continue to lower, rainfall downstream growing, well-developed vegetation, biological and other factors continue to increase, may be leading to continue to lower the pH. Glacier melt water supply as the main source of water body weak acid, with little corrosion resistance. Showed weak alkaline hot springs, other types of natural water pH value is high, the water element is not conducive to migration of suspended particles is the main element of the existence and migration patterns.②The study area has very small annual range of water temperature, water temperature and the temperature has a very close relationship, the annual average temperature is higher than the annual average temperature. Annual temperature is lower in the study area, direct the water temperature is low, and different types of supplies also affect the river water temperature; high altitude and low air pressure caused by the relatively low concentration of dissolved oxygen, biochemical slowly. The water temperature is low, the annual range is small, the study area is to control the dissolution rate of natural mineral water and water main biochemical factors.③The chemical types of natural water, based on CⅡC a,CⅢCa , are mainly calcium bicarbonate water, a small number of the chemical type of natural water are CⅠC a, the chemical type of hot spring water to the main are SⅠN a, portion are CⅠN a. The main types of natural water chemistry in the first phase, the silicate-carbonate water phase, the chemical type of hot spring water district is the third phase, the chloride-sulfate phase, which relative to the accumulation of its features SO₄²-. At this stage, there may be SiO₂, CaCO₃^, MgCO₃^, CaSO₄^, and a certain amount of Na2SO₄ precipitation.④The major rivers and major ions mainly influenced by salinity changes in the type of supply and followed by human activities. The measured increase in conductivity and TDS with the longitude (to the river downstream) did not change significantly, only in Millin-Nyingchi with import snowmelt caused the sections of the main basin and tributary basin where the measured conductivity and TDS decreased significantly. Natural water conductivity and TDS measured about rules to follow: spring> springs, wells> rivers> tributary water, mainly in the Yarlung Tsangpo > Lhasa River> Niyang.⑤According to natural water hardness classification, the region most major and tributary basin of water, are mostly soft water, cold springs, hot springs, wells and more for the medium hard water. The paragraph Niyang and some tributary water appears very soft water, part of the tributary water can moderate hardness water in Langxian, spring water appears extremely hard water, hardness of the general negative samples in hot spring water, some of communication have a negative hardness of water may associated with the import of hot water.⑥The erosion CO₂ of natural water content in the large, but follow the erosion CO₂ river water> tributary water> springs, wells> springs, while the erosion CO₂ content is generally less than the erosion of 15mg / L, only paragraph in the Niyang there erosion CO₂ 15.40mg/L. (2) The solute of natural water sources, sinks and control factors were analyzed, combined with water chemistry triangle diagram and the Gibbs diagram to illustrate the main study area is the origin of the river ions weathering of rocks, evaporation - crystallization of a secondary role, while enter the atmosphere is very weak. A simple analysis of the region while the natural river water and the solute and the geographical relationship between the geological conditions to determine the main chemical characteristics of river water is the precipitation process of the composition of the atmosphere and surface material of the leaching process, the main tributary of the mixing junction, SS adsorption and resolution process, and deterioration caused by evaporation and other processes, but also by lithology and structure and other factors.(3) The study area and major tributary rivers upstream to downstream water stable isotopeδD andδ¹⁸O gradual increase in the overall trend.δD andδ¹⁸O precipitation line graph to compare with the southwest, the natural water were landed near the southwest line of precipitation, showing the main supply of natural water recharge precipitation type;δD andδ¹⁸O showed obvious in the plane partition, theδ¹⁸O of hot springs also performed at the obvious drift;δD andδ¹⁸O region showed significant effects of altitude effect and the mainland, with the elevation and moisture away from the source,δD andδ¹⁸O decreased, in view of the unique natural and geographical characteristics of the region, the actual effect on the regional and continental comprehensive reflection of altitude effect.(4) Key areas of the Lhasa area is located in the Qinghai-Tibet Plateau in the southern Bay of Bengal and the abduction of water vapor, to the region has brought abundant summer rainfall, the rainy season from June in Lhasa, has been continued until September, the rainy season precipitation accounted for 90% of annual precipitation. Select GNIP Lahsa station, from June 1986 to December 1992, a total of 41 data, study show Lhasa precipitationδ¹⁸O amount effect was to cover up the temperature on the precipitationδ¹⁸O role. The deuterium excess parameter (d) of Lhasa station, basic mountain fluctuations in the average value of 10‰, but in the dry and wet seasons at the obvious differences in liquidity, reflecting the different sources of water vapor effect on precipitation.