Knowledge Resource Center for Ecological Environment in Arid Area
| 天山南坡科其喀尔冰川作用区水化学过程研究 | |
| 其他题名 | Geochemical Denudation and Hydrograph Separation in Koxkar Glacierised Region at the South Slope of Mt. Tuomuer, West China |
| 王建 | |
| 出版年 | 2009 |
| 学位类型 | 博士 |
| 导师 | 丁永建 |
| 学位授予单位 | 中国科学院寒区旱区环境与工程研究所 |
| 中文摘要 | 由于化学侵蚀率较高和人类活动影响较小，冰川作用区是研究水圈和岩石圈交互作用的理想环境系统，详细研究冰雪融水水质的变化对评估区域化学侵蚀、生物地球化学循环及河水来源组成具有重要意义。托木尔峰地区是天山最大的冰川作用中心，也是塔里木盆地重要的水资源形成区，对我国西部干旱区具有重要作用。本文在对2004年6月～2005年9月科其喀尔冰川作用区地下水、冰川冰（融水）、冰面径流、大气降水和河水的野外样品采集和室内测试分析的基础上，主要得出以下几点认识与结论：\n（1）科其喀尔冰川区降水中可溶性离子的特征及来源\n根据实际观测资料，重点分析研究区降水中可溶性离子的组成、变化特征以及溶质来源。区域降水属于（ HCO3-－SO42-）—Ca2+型，可溶性离子浓度顺序遵循：阳离子：Ca2+＞Na+＞Mg2+＞K+；阴离子：HCO3-＞SO42-＞Cl-＞NO3-。浓度主要受降水量影响，随降水量的增加而减小。不同形式的降水中可溶性离子总浓度：雨水>雪>冰雹。溶质主要来源于区域性粉尘物质的大气气溶胶，其次是来源于海洋或周围咸水湖及海相沉积物的粉尘。\n（2）科其喀尔冰川区河水中可溶性离子的特征及来源\n科其喀尔冰川作用区水文断面处河水中阳、阴离子浓度总体遵循Ca2+＞Na+＞Mg2+＞K+ ；HCO3-＞SO42-＞Cl-＞NO3-，且季节性差异显著。通过离子间相关性和EOF分析，河水中的溶质主要源于区域水化学作用，降水中溶质补给贡献较小。Na+ 、K+ 和Mg2+源于肉红色的碱长花岗岩侵入灰白色的二长花岗岩中的钠长石和钾长石的水解；SO42-主要来源于硫化物的氧化；Ca2+正电荷总和与HCO3 −负电荷总和比值为0.96，表明二者可能具有相同的离子来源，即钙盐的碳酸化作用所致。NO3-浓度最小，仅占溶质总通量的1.18%，是冰下细菌数目维持的主要控制因素之一，主要是通过干湿沉降、气液界面交换及降水作用，到达地面补给到河水中。\n（3）科其喀尔冰川区不同水体中可溶性离子的浓度差异\n分析冰面径流、冰川冰融水、大气降水和河水中可溶性离子浓度，表明不同水体中溶质浓度差异明显，总浓度顺序为：河水>冰面径流>大气降水>冰川冰。其中，冰川冰和冰面径流中可溶性离子浓度随海拔降低浓度整体呈现增大趋势，但冰面径流中离子从海拔3900m区域到冰川末端，浓度增大过程中，表现出一定的“振荡性”，这种“振荡性”的出现是由于冰川表面表碛物不连续性，水岩作用不均一所致。\n（4）冰川消融季节（2004-6-21～9-10），流域物理（机械）、化学侵蚀量估算\n利用物质平衡原理估算流域水化学侵蚀量，并分析区域侵蚀过程中暂时没收大气CO2量。冰川消融季节，河水中溶质来源于大气降水的补给为60.7kg•km-2d-1（5.72×105kg），占流域总溶质通量的7.7%；冰川冰融水中溶质补给为60.2 kg•km-2d-1（5.77×105kg），占7.6%。因此，科其喀尔冰川流域水化学侵蚀补给占84.7％，是溶质的主要来源，为670.3kg•km-2d-1（6.43×106kg）。其中，HCO3-侵蚀量最大，为308.9 kg•km-2d-1（2.96×106kg），源于硫化物氧化作用导致碳酸盐水解和暂时性没收大气CO2引起的碳酸化作用补给。暂时性没收大气CO2质量为81.0 kg•km-2d-1（7.77×105kg）。另外，通过对断面河水中悬移质测定，流域机械（物理）侵蚀量为43.25×104t，日平均侵蚀模数约为：4.50×104kg•d-1km-2。侵蚀动力主要取决于冰川融水，其次是大气降水。因此，机械侵蚀评估中，不仅需要考虑降水，同时还需要考虑气温（气温是冰川融水侵蚀的源动力）。\n（5）科其喀尔冰川作用区各种水体中的δ18O变化\n分析表明，流域大气降水中δ18O不仅存在显著的“降水效应”和“温度效应”，与湿度之间也存在明显的负相关关系。河水中δ18O日内变化过程中随流量增加而减小，主要是因为冰川冰消融加剧稀释了河水中18O含量；而日变化过程中，因季节性积雪消融及季节性冻土中土壤水释放，引起河水中降水、地下水和冰川冰融水比例发生变化，导致δ18O波动剧烈，尤其是季节性积雪消融期间（2005-4-20～6-17）。总体上，各种水体中的δ18O值遵循：地下水＞大气降水＞河水＞冰川冰。\n（6）科其喀尔冰川作用区河水径流组成\n利用水质的变化划分径流的组成是水化学研究的焦点之一，研究最初集中于利用变化的融水水质模拟冰下水文系统。本文在此基础上，借鉴3－水源概念性物理模型，以δ18O和电导率（EC）变化为划分依据，对流域流量过程线进行划分。流域年径流过程中，冰川冰融水补给占支配地位，为72.11％，其次是地下水补给，占16.38％，大气降水（雪）补给最少，为11.51％。暖季冰川消融期间（2004-6-21～2004-9-20），各补给源对河水通量贡献分别占77.63％、14.93％和7.44％。 |
| 英文摘要 | Glacierised areas present an ideal environment to study water-rock interaction, since chemical weathering rates are high and anthropogenic impacts are often minimal. Detailed investigations of ice-snow meltwater quality variations have suggested the importance of these environments in estimates of terrestrial chemical erosion and global biogeochemical cycles. Mt. Toumuer, located in western Mt.Tienshan, China, is the largest glacierised area of Tienshan. It is the main water resource area of Tarim, which is very important to the arid and semi-arid basins of western China. In this paper, the samples of groundwater, ice meltwater, glacier surface runoff, rainfall and river from Koxkar basin were used for analysis. It was concluded as following. \n1) Change characteristics and source of dissoluble Ion concentrations in Koxkar glacier \nEmphasizing to analysis of ionic component，change characteristics and its provenances using observed hydrochemical data. Precipitation component in this region belongs to (HCO3--SO42-)-Ca2+ type, and ion in concentration order follow: cationic Ca2+＞Na+＞Mg2+＞K+, anionic HCO3-＞SO42-＞Cl-＞NO3-. Major ion concentrations were heavily affected by precipitation amount, and would decrease due to precipitation increasing. The ion concentrations of the precipitation are different among the types, which follows: rainfall > snow > hailstone. Aerosol from the atmospheric dusts were the mainly suppliers of the precipitation solute, and next is dust of marine, nearby saline lakes and marine sediment. The K+ and pH of precipitation were rarely correlative with other chemical indices, maybe be affected by muti- provenances (e.g. territorial dusts, dust of marine, nearby saline lakes and marine sediment).\n（2）Ion concentrations variation and its provenances at headwater Koxkar river\nGenerally, cation and anion concentrations of river water in Koxkar basin shown the disciplinarian of Ca2+＞Na+＞Mg2+＞K+, HCO3-＞SO42-＞Cl-＞NO3-, respectively. And the concentration varies with seasons. In the winter, river runoff is small and with a low velocity of flow, since the water mostly be replenished by groundwater and subglacial meltwater. It resulted in the strong water-rock interaction. Conversely, in the summer, water-rock interaction is not strong due to the large river runoff which affected by the rapid ice melting. Analysis of correlation between the ion concentrations and EOF (Emipirical Orthogonal Function), indicate water-rock interaction were main resource of river water solutes. Na+, K+ and Mg2+ came from hydrolyzing of albite and potassium feldspar SO42- should mainly be contributed by sulphates oxidation coupled with limestone/dolomite dissolution. Ca2+ and HCO3 – might have the same source that is carbonation of carbonates (limestone and dolomite), since the ratio of Ca2+ and HCO3 – charges was 0.96, which implied their same sources, i.e. carbonation of carbonates (limestone and dolomite). NO3- with the smallest concentration, accounting for the 1.18% of the total solutes, which is one of the main bacterial population control factors in subglacier, is through dry and wet deposition, air-water interaction and precipitation into river.\n（3）Differences among the ion concentrations of different water in Koxkar basin\nDissoluble ion concentrations of ice meltwater, supraglacial runoff, precipitation and bulk meltwater show remarkable differences. General sequence is ordered as bulk meltwater > supraglacial stream > precipitation > ice melt-water. Moreover, dissoluble ion concentrations of ice melt-water, supraglacial stream increased with altitude descending. However, these of supraglacial stream from 3900m in altitude to glacier terminal at the Koxkar glacier region did not show linear increasing but the oscillating, which would result from the asymmetric distributing of debris and the nonuniform water-rock interaction.\n(4) Assessment of chemical denudation and physical erosion in Koxkar basin during the melt season (from June 21st to September 10th in 2004)\nIn general, the concept of chemically- and physically-limited erosion regimes may be useful in reappraising the voracity of chemical erosion processes in glacial systems relative to other environments. Chemically-limited systems are those where mechanical erosion exceeds chemical erosion. The latter is highly selective, and dependent on mineral-specific reaction rates. Thus, the most reactive minerals (e.g. calcite) contribute to solute fluxes disproportionately to their abundance, and are selectively leached. Conversely, in physically-limited systems mechanical erosion is less intense, and the most reactive mineral phases have been depleted from accessible rock and sediment surfaces. Here, chemical weathering is no longer dependent on mineral reaction kinetics but on fluid transport. Here, we took advantage of law of conservation of mass to evaluate chemical denudation fluxes and to calculate transient carbon dioxide drawdown. During the melt season (from June 21st to September 10th in 2004), there were 60.7 kg•km-2d-1（5.72×105kg）and 60.2 kg•km-2d-1（5.77×105kg）supplied by precipitation and ice melt-water respectively which accounts for about 7.7% and 7.6% of the total solutes of bulk river water. Consequently, the rate of chemical denudation derived from the crustal flux during melt season was 670.3kg•km-2d-1 or 6.43× 106kg. Carbonation weathering was 308.9 kg•km-2d-1or 2.96×106kg, heavier than the other chemical denudations. The crustal concentration of bicarbonates (HCO3-) is attributed chiefly to the carbonation of carbonates (limestone and dolomite) and aluminosilicates/silicates. A further important source of bicarbonates and sulphates is pyrite oxidation coupled with limestone/dolomite dissolution. Utilizing proportion of dissoluble ion chemical reaction, we might obtain that transient carbon dioxide drawdown was 81.0 kg•km-2d-1 or 7.77×105kg from June 21st to September 10th in 2004. \nWe also investigated sediment flux of suspended load at level table during the melt season (from June 21st to September 10th in 2004), showed that fluxes of mechanical erosion were 4.50×104kg•d-1km-2 or 43.25×104t. \n(5) Variation of δ18O in different water in Koxkar glacier region \nThe δ18O in precipitation in Koxkar basin was influenced by precipitation amount, air temperature, air humidity and wind speed., the hourly δ18O in river water is decreased with discharge increase during 8：00 July 13～7：00 July 14 in 2004, because that increasing river discharge diluted the 18O concentration. However, daily δ18O processes in river water from June in 2004 to September in 2005 showed dramatically variational, especially in early melt season, because seasonal snow and frozen soil released some water which led proportion of precipitation, groundwater and ice-meltwater to total flow fluxes to change. As a whole, average δ18O in the different water followed: groundwater＞precipitation ＞river water＞ice meltwater.\n(6) Hydrograph separation \nOne of focus of meltwater quality investigations is to attempt to differentiate runoff components and hydrological pathways through glacierised basins utilizing variations in water quality. These studies initially focused upon the modelling of subglacial hydrological systems using bulk meltwater quality variations, based on the application of simple two-component conservative chemical mixing models imported from the temperate fluvial literature. In this research, bulk discharge of Koxkar glacier would be separated into three hydrological components with parameters of δ18O rate and electrical conductivity (EC). The results showed that ice meltwater component dominantly contributed to the total discharge, accounting for 72.11% of the total river runoff from June 21st in 2004 to June 20th in 2005 and 77.63% from June 21st to September 10th in 2004, respectively. Groundwater was the secondly important component, which accounted for about 16.38% and 14.93% from June 21st in 2004 to June 20th in 2005 and 77.63% from June 21st to September 10th in 2004, respectively. Precipitation component was the least, accounting for about 11.51% and 7.44% of total discharge. |
| 中文关键词 | 可溶性离子 ; δ18O ; 化学侵蚀 ; 流量过程线划分 ; 科其喀尔冰川作用区 |
| 英文关键词 | dissoluble ion δ18O geochemical denudation hydrograph separation Koxkar glacier |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286770 |
| 推荐引用方式 GB/T 7714 | 王建. 天山南坡科其喀尔冰川作用区水化学过程研究[D]. 中国科学院寒区旱区环境与工程研究所,2009. |
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