Knowledge Resource Center for Ecological Environment in Arid Area
| 黄河中游河水化学季节性变化及其控制因素 | |
| 其他题名 | Seasonal variation in river water chemistry of the middle reaches of the Yellow River and its controlling factors |
| 张茜茜 | |
| 出版年 | 2015 |
| 学位类型 | 硕士 |
| 导师 | 金章东 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 表生地球化学、元素地球化学循环一直以来是地球科学领域的研究重点之一，其中最关键的是地表化学风化过程。黄土具有高碳酸盐含量、结构松散、颗粒细小（即表面积大）、易剥蚀等特点，加之覆盖了约10%的全球大陆面积，其化学风化对地表水和沉积物的化学组成以及全球物质循环产生重要的影响。然而，有关黄土的现代风化过程的研究却十分薄弱。 我国黄土覆盖了黄河流域40%的面积，加之严重的水土流失使得黄河具有巨大的输沙量，因而黄土高原的风化必会对黄河水化学产生巨大的影响。黄河中游是流经黄土高原的主要河段，开展黄河中游河水化学的研究，可以帮助我们认识黄土现代化学风化过程及其控制因素。黄河中游具有的明显季节性气候特征，为我们利用河水化学变化示踪黄土风化如何影响水化学及其控制因素提供了一个良好的场所。目前，关于黄土风化对黄河水化学的影响过程及其控制因素，还未见详细的研究和报道。 本文选取黄河中游河水为研究对象，在龙门水文站对河水进行高时间分辨率的采集（每周一次，为期2013年全年），通过对水样品的主要阴阳离子的分析，并结合详细的水文气象资料，获得了黄河中游河水化学的季节性变化特征。利用forward model计算了雨水、人类活动、蒸发岩、硅酸盐、碳酸盐对河水化学的贡献，探讨了以黄土高原为主的流域季节性化学风化过程及其与气候、物理侵蚀之间的关系。 黄河中游2013年河水中主要的阴阳离子呈现显著的季节变化，反映了水化学来源及流域经历的化学风化过程。除NO3?，所有离子的含量从一月的最高值逐渐降低到雨季前的一个稳定值。在雨季期间，随着河水径流量的增加，Na+、Cl?、SO42?在稀释作用下，由雨季前稳定的含量降至全年最低值，在雨季最盛期回升后又降低回到雨季前的稳定值；同期，Ca2+、Mg2+、HCO3?的浓度在雨季早期和晚期均保持在相对稳定的水平，但早期的Ca2+和Mg2+浓度低于晚期，HCO3?则相反。雨季过后至年底，随着降雨的减少，所有离子浓度在河水的浓缩作用下又逐渐回升到年初水平。 Forward model计算结果显示，降雨、蒸发岩、硅酸盐、碳酸盐和人类活动的全年平均贡献率（范围）分别为6.5 +4.0/-3.5%（4.0 +2.5/-2.2 ~ 8.1 +5.0/-4.4%）、48.2 +18.2/-19.7%（38.1 +16.6/-15.6 ~ 60.3 +23.8/-25.8%）、20.4 +5.3/-11.7%（0.7 +6.3/-14.5% ~ 40.4 +5.6/-11.3%）、23.8 +23.4/-17.0%（12.1 +22.6/-11.2 ~ 33.0 +27.9/-17.7%）和5.1%（3.3 ~ 9.8%）。雨水和人类活动对河水化学贡献均值总和小于12%，且全年变化不大。在雨季之前，硅酸盐来源对河水化学有比较高的贡献比例，为29.1 +5.2/-11.0%，这段时期的硅酸盐风化速率与流量和物理侵蚀都显示出较好的相关性。此时，碳酸盐和蒸发盐的平均贡献率为20.4 +22.0/-12.5%和43.2 +13.1/-17.2%。我们认为雨季来临之前的河水主要来源于具有长时间水岩作用的河源水、土壤孔隙水和地下水。雨季及之后，碳酸盐的平均贡献率分别为25.0 +24.9/-19.5%和27.1 +24.8/-20.2%，蒸发岩的平均贡献率则分别为50.4 +20.9/-21.0%和52.0 +21.7/-21.2%，且随着流量的增高而升高。相应地，硅酸盐贡献的比例相应降低，雨季中、后的平均贡献率分别为16.3 +5.5/-12.4%和13.7 +5.5/-12.4%。这是因为降雨加速了高碳酸盐、蒸发岩含量的黄土的物理侵蚀。碳酸盐和硅酸盐来源相对比例的季节性变化，显示了不同季节河水的不同来源，以及黄土风化对季风水文过程的敏感响应。碳酸盐风化速率在2013年全年与流量和物理侵蚀都有很好的相关性，而硅酸盐风化速率在不同的季节时期与河水流量和物理侵蚀显示出不同的相关性，进一步地反映了河水中硅酸盐来源及黄土化学风化过程的季节性差异。 此次高时间分辨率的数据还捕捉到了两次水文事件对河水化学的巨大影响。在春季的融冰期（2013年3月16日至4月13日），大量的富含硅酸盐溶质的融水进入河流，导致此时硅酸盐风化对河水贡献的相对比率（32.6 +5.3/-11.2%）是雨季的两倍。而雨季期间出现的、50年一遇的暴雨（2013年7月22日至25日）则大大加速了黄土的物理侵蚀，从而触发了更多的碳酸盐和蒸发岩输入黄河。 本次研究初步揭示了处于半干旱区的黄河中游的河水化学季节性变化的控制因素以及黄土的现代化学风化过程，发现黄土风化主导了雨季黄河中游水化学组成，而河水流量和物理侵蚀为该流域风化速率的主要控制因素。 |
| 英文摘要 | The geochemistry of earth surface processes and element cycles has long been one of the key topics in the earth sciences, especially for chemical weathering. The loess, which covers 10% area of global continent, is characterized by high carbonates, loose structure, fine grains (i.e. large specific surface area) and easy denudation. The loess weathering would have a great impact on the chemical composition of surface water and sediment, even on the global mass cycle. However, the study of modern loess weathering process is deficiency at present. Since the loess covers 40% area of the Yellow River catchment and provides huge amount of sediment load to the river, the loess weathering would affect the river water chemistry greatly. Considering that the middle reaches of the Yellow River is the main channel flowing through the Chinese Loess Platuea (CLP), tracing river water chemistry in the middle reaches of the Yellow River will help us to better understanding loess weathering process and its controls. The contrast seasonal climate in the the middle reaches of the Yellow River provides a good opportunity to trace the loess weathering. However, little is known about the influences by loess weathering on the river chemistry and the controlling factors. In this thesis, the seasonal river water in the middle reaches of the Yellow River was chosen as the object of this study. The river water samples were collected weekly from the Longmen hydrological station over the whole year of 2013 and were measured major cation and anion compositions. These water chemical data, combined with synchronous hydrological data, were used to reveal the seasonal variations of river water chemistry. A forward model was used to calculate the contributions of rain, evaporite, silicate, carbonate, and anthropogenic inputs and discuss the seasonal chemical weathering of the catchment in CLP and its relation with hydro-climate and physical erorion rate (PER). The major ionic compositions of the dissolved load in the middle reaches of the Yellow River exhibited distinct seasonal variability over the whole year of 2013, reflecting various sources and weathering reactions within the catchment. All of the major ions, except for NO3?, declined gradually from the highest values in January and reached stable levels until the beginning of the monsoon season. During the monsoon season, with the increasing Q, Na+, Cl?, and SO42- dropped from their stable levels to a lowest value owing to a dilution, then increased in the peak of monsoon and returned to the levels of the monsoon beginning. Meanwhile, the concentrations of Ca2+, Mg2+ and HCO3? kept stable levels in the early and late monsoon seasons. The concentrations of Ca2+ and Mg2+ in the early monsoon were lower than those in the late monsoon, but HCO3? was contrary. After the monsoon season, all these major ions gradually rose to the pre-monsoon level until the end of this year, again resulting from the dominated input of the base flow when the Q was low. The calculation result of the forward model showed that the annual average contributions of rain, evaporite, silicate, carbonate, and anthropogenic inputs were 6.5 +4.0/-3.5% (4.0 +2.5/-2.2 – 8.1 +5.0/-4.4%), 48.2 +18.2/-19.7% (38.1 +16.6/-15.6 – 60.3 +23.8/-25.8%), 20.4 +5.3/-11.7% (0.7 +6.3/-14.5% – 40.4 +5.6/-11.3%), 23.8 +23.4/-17.0% (12.1 +22.6/-11.2 – 33.0 +27.9/-17.7%), and 5.1% (3.3 – 9.8%), respectively. The contributions of both rain and anthropogenic sources to the middle Yellow River were less than ~12% in average, with little seasonal variations in 2013. The silicate input during the pre-monsoon seasons was 29.1 +5.2/-11.0%, with strong correlations versus Q and PER. In the same period, the average contributions of carbonate and evaporite were 20.4 +22.0/-12.5% and 43.2 +13.1/-17.2%, respectively. We suggested that the river water in the pre-monsoon was potentially derived from plateau headstream, soil pore and ground water, which had the long |
| 中文关键词 | 黄河 ; 水化学 ; 季节性变化 ; 水文事件 ; 黄土风化 |
| 英文关键词 | the Yellow River water chemistry seasonal variation hydrological event loess weathering |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 环境科学 |
| 来源机构 | 中国科学院地球环境研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287498 |
| 推荐引用方式 GB/T 7714 | 张茜茜. 黄河中游河水化学季节性变化及其控制因素[D]. 中国科学院大学,2015. |
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