| Glaciers are indicators of climate change,and glacial rivers are an important part of the global water cycle,which is of great significance to the earth's hydrochemical cycle and sediment transport.The transport characteristics of various substances in the basin can reflect the erosion process and the interaction mechanism among hydrology,topography,climate and glaciers in the area.Rongbuk Glacier River in the Qinghai-Tibet Plateau and the Keqikar Glacier River in the arid area of the northwest were selected as the research objects to explore the denudation characteristics of glacial rivers under different natural geographical backgrounds.The hydrochemical characteristics of the two glacial rivers and their influencing factors,main ion sources and weathering process,water-sediment relationship,and sediment transport characteristics were analyzed through field observation,water sample monitoring and statistical analysis,and then the total denudation rate of the Rongbu River and the Keqikar River was estimated,and the influence of lithology,climate,topography and glaciers on the denudation rate was discussed at the same time.The main conclusions are as follows:(1)The water bodies of Rongbu River and Keqikar River are weakly alkaline.HCO3-and Ca2+in the water body are the dominant ions in anions and cations respectively,and the water chemistry type is HCO3--SO42--Ca2+type water.The water chemical ion concentration has a significant seasonal feature,and has a certain"dilution effect"during the intense ablation period.Rock weathering is the main controlling factor of water chemical ions,followed by the influence of human activities and atmospheric precipitation.The ions of the Rongbuk River water body mainly come from the hydrolysis of carbonate rocks,silicates and evaporites,followed by the hydrolysis of fluorine-containing ore and pollution caused by local human activities.The water ions of the Kochikar River mainly come from the oxidation of sulfur-containing minerals and the mineral hydrolysis promoted by this process,followed by the carbonation of calcium salts.(2)During the ablation period,the runoff of the Rongbu River and the Keqikar River increased first and then decreased,and the runoff modulus were 7.36×105m3/(km2?yr)and 6.82×105 m3/(km2?yr),respectively.The average sediment content of the two rivers during the ablation period was 316.51±182.34 mg/L and1217.51±1189.92 mg/L,respectively.Analyzing the water-sediment relationship between the two glacial rivers,the results show that the regression effect is significantly improved after the runoff is divided into two stages:rising and falling,and the resulting sediment transport volume is 55.85×103 t and 97.95×103 t,respectively,and the sediment transport modulus is 200 t/(km2?yr)and 890 t/(km2?yr).(3)The chemical erosion rate,mechanical erosion rate and total erosion rate of the Rongbuk River are 22 t/(km2?yr),200 t/(km2?yr)and 222 t/(km2?yr),respectively.They are 51 t/(km2?yr),890 t/(km2?yr)and 941 t/(km2?yr)respectively.The mechanical denudation rates of the two accounted for 90.0%and94.58%of the total erosion rate respectively,and there was a significant correlation between the chemical denudation rate and the mechanical denudation rate(r=0.676,P=0.006),and the chemical erosion rate increased with the increase of the mechanical erosion rate.The chemical erosion rate is calculated by the mechanical erosion rate,and the results are 51 t/(km2?yr)and 153 t/(km2?yr),both of which are greater than the actual value.The ratio of mechanical erosion rate to chemical erosion rate(P/C)of the two is larger(9.09 and 17.45,respectively).Factors such as lithology,climate,topography and glacier coverage are the main factors that cause the difference in denudation rates. |
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