【作者】 李晶莹；

【导师】 张经；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2003， 博士

【摘要】 岩石的风化剥蚀作用是研究物质地球化学循环和全球气候变化的重要环节之一。论文的主要研究内容包括3大部分，其一通过数理统计方法利用河水主要化学组成去追溯流域发生的化学风化反应，探讨不同岩性、大气降水、人类活动因素、大气CO₂等因素对河水中溶解质的相对贡献率，进而估算流域盆地的化学风化率及岩石化学风化所消耗的大气CO₂量；其二通过河流沉积物主要元素组成来探讨流域岩石的化学风化强度，揭示流域盆地中碳酸盐类、硅酸盐类化学风化的相对强度，并根据质量平衡原理估算机械剥蚀率；其三从宏观上利用离子径流模数与化学风化率、输沙模数与机械剥蚀率之间的关系汇总了中国主要流域盆地的化学风化率和机械剥蚀率，结合流域盆地的综合岩性、气候、地貌、植被、人文活动等相关影响因子的量化数值，建立中国主要河流的输沙模式，阐述自然因素及人为活动诱因对中国主要流域盆地风化剥蚀率的影响程度，最后对定量化结果进行了客观分析与评价。 1 河水化学、化学风化率和岩石风化的大气CO₂消耗量 利用Gibbs图分析得到趋于“大气降水控制”类型的河流-东江和赣江。利用大气降水的控制面积和流域的蒸发蒸腾F因子，计算得到大气降水对东江河水中Cl^-的最大输送量，将Cl^-作为参照元素，通过海盐校正方法估算得到大气降水对东江、赣江河水溶解质载荷的总贡献率分别为4.94％和5.09％，由此对于受大气降水影响较为显著的东江和赣江，大气降水对河水溶解质的总贡献率仅为5.0％左右，中国绝大多数河流矿化度很高，大气降水对河水溶解质的相对贡献率更低，可忽略不计。初步探讨了长江干流人类活动对河水中溶解质的输入贡献率，发现河水离子中仅SO₄^2-表现出20-40％人为来源的输入率，占长江干流河水溶解质总量的约2-3％，与长江流域广泛发生的酸雨密切相关。 黄河流域蒸发盐类和碳酸盐类风化溶解较强，对河水的贡献率均很高且平分秋色，而硅酸盐类化学风化对黄河河水的贡献很微弱。长江干流主要发生了碳酸盐类的化学风化尤其是白云岩的溶解，碳酸盐类对河水溶解质的贡献率占主导地位（达到近50％），蒸发盐类和硅酸盐类风化的贡献率较弱。珠江流域3条主要支流的化学风化过程存在明显差异，西江和北江流基本以碳酸盐类溶解为主，而东江河水扣除大气降水的来源外，溶解质基本出自硅酸盐类的风化。总体而言，中国主要流域盆地大部分以碳酸盐类的风化溶解为主，其对河水溶解质的平均贡献率介于30-60％之间，而硅酸盐类和蒸发盐类风化通常较微弱，对河水溶解质中国土要流域盆地的风化剥蚀作用与人气CO:的消耗及其影响因子研究的贡献率分别为。一20%和10一30%，大气CO:对河水溶解质载荷的总体贡献率约占30%。 扣除大气降水、人类活动、大气CO:等非岩石风化来源的物质后得到了中国17个主要流域盆地较为准确的化学风化率数值。对这17个主要流域盆地的化学风化率与其离子径流模数的相关统计发现两者之间存在着非常显著的正相关关系，且两者之间的平均比值为1.40，反映了河水中共计约30%的溶解载荷来自于大气CO:或降水等非岩石风化来源，这与对中国主要河流溶解质载荷来源分析得到大气CO:对河水溶解质的平均贡献率在30%左右完全吻合，由此利用离子径流模数除以140近似地估算得到了中国所有主要流域盆地较为准确的化学风化率数据，其化学风化率值分布在10.65一168.0t/k mZ.yr范围。 中国主要流域盆地岩石化学风化的年均大气CO:消耗量1375.91x109mol（占世界岩石风化年均消耗co:总量的6.55%）、转移的碳量为1.65又107t碳，其中碳酸盐和硅酸盐类化学风化消耗的大气CO:量分别占85%和15%。中国主要流域盆地岩石化学风化的大气CO:消耗率通常较高，而且中国主要流域盆地整体上碳酸盐类的风化溶解对河水化学的影响程度明显强于硅酸盐类，这是中国主要流域盆地较为突出的特征。2沉积物地球化学与化学风化进程和机械剥蚀率 化学风化指数与化学风化率属于表征化学风化作用意义不同的函数，前者为相对概念反映流域岩石在原岩基础上己发生淋溶作用的深度，主要受到了气候因子的深刻影响（中国流域沉积物化学风化指数由北到南呈有规则的递增序列，气候因子对风化进程的影响掩盖了岩性的巨大差异），而化学风化率含义是指单位流域面积岩石风化淋溶产生的离子绝对总量。但2者又紧密联系，文中引入综合岩性和岩石化学风化响应度的概念，反映出流域岩石整体对岩石风化的反应和敏感程度。研究发现综合岩性整体上控制了中国主要流域盆地化学风化率的大小，但化学风化率一定程度上也受制于流域岩石的化学风化进程。 西江和北江沉积物中易溶元素风化淋溶强烈，Ca消耗最为强烈，流域内碳酸盐类化学风化程度较之硅酸盐类强烈。西江和北江流域岩石的相对化学风化指数分别达到了1.71和1.91，且沉积物中Al加a摩尔丰度平均比值分别为黄河的2.10倍和长江的5.92倍。相比而言，西江和北江流域岩石的整体化学风化进程、2大类岩性的化学风化程度均较之长江、黄河流域强烈的多。3条支流的硅酸盐类化学风化作用已达到了?更多还原

【Abstract】 The atmospheric CO₂ consumed by rock weathering is long been recognized as providing a major loss of carbon and decreasing atmospheric CO₂. The 0.28xl0^<sub>9t carbon derived from atmospheric CO₂ is transferred from atmosphere and biosphere to the ocean by surface rock weathering processes. In order to monitor the quality of the river, it is also important to understand the natural flux of dissolved ions. So far, most studies on water chemistry in China had focused on water quality and dissolved flux, scarce literatures could be used to understand the sources of solute load and CO₂ consumption budget in China. However, many scholars had attempted to fill in the gap in our knowledge of atmospheric CO₂ wastage by rock weathering and tried to link water chemistry with weathering reactions in the major world watersheds.In fact, as a very important part of material geochemistry cycle, chemical weathering and mechanical denudation plays a crucial role in affecting and changing the surface continent deeply. The global rivers transported the dissolved loads of about 4.0X10⁹t and solid fluxes of 15.5X10⁹t mainly derived from chemical weathering and mechanical denudation into the ocean yearly. In addition, the water and soil lost correlative with weathering and erosion had threatened seriously the production and living along the valleys at present.In this paper, newly compiled data on the major rivers of China were used to calculate the relative contribution rates of precipitation, main lithologies and atmospheric CO₂ according to the dissolved loads by principal components and correlative analysis. New estimates of carbonate and silicate weathering fluxes and associated with CO₂ consumption budget were given in the major drainage basins of China where previous information was indeed limited. An attempt was also made to calculate chemical weathering rates of silicates and carbonates per unit area. The paper focused on consumption of atmospheric CO₂ through rock weathering and weathering reactions what were attributable for dissolved loads in the major basins ofChina.Generally, dissolved loads were preferentially considered to evaluate chemical weathering relative to river-borne particulate/sediment because they are directly from source rock weathering. However, local differences in lithlology and human activities or precipitation might participate in and disturb the processes. Many studies had attempted to characterize chemical weathering process by focusing on geochemisty of river particulate and sediment.The sediment geochemistry may reflect and compare with the carbonates and silicates weathering degree by introducing the chemical index of alteration （CIA） and new sediment index of variation （SIV） and elemental molar abundance ratio of the sediment. The one main objective of this study would provide and compare the relative weathering intensities of silicates and carbonates with the different basins. For the mass balance equations, the average mechanical denudation rates would be estimated based on chemical weathering rates for the major basins of China.Finally, the first detailed compilation on fluvial transport model of solid was established based on data from a variety of sources for the typical major rivers of China. The relationship between the chemical weathering and physical denudation rates and possible controlling parameters were also explored. A combined effect of climate, relief, integrated lithology, vegetation and cultivated area seemed to explain the variability of modern chemical weathering and mechanical denudation rates.Samples and analysis methodsHundreds of water samples from the upper reaches to lower reaches of the rivers were collected and stored in acid-washed polypropylene bottles from 1997 to 2001 in major watersheds of China. After collection, all samples were filtered in time through 0.45 um acetate fibrous filters. The analytical procedure for water analysis included conventional flame atomic absorption spectrophotometry （AAS） for Ca,更多还原