青藏高原东部长江河流溶质载荷主要离子地球化学研究

作者于2000年和2002年对青藏高原东部长江河流溶质载荷进行了较为系统的野外取样工作,并对主要离子地球化学特征进行了分析研究。数据分析表明,长江水系TZ 高于世界河流1250μEq的平均值,主要介于2000~3000μEq之间,其次为1000~2000μEq。总体上,高原东部长江水系TZ 可以与世界上其它造山带相比较。高原东部长江水系主要阴离子的相对丰度和分布表现出HCO3->Si Cl- SO42-,河水富含HCO3-;阳离子主要表现为Ca2 >Mg2 Na K ,表明河水富含Ca离子特征。河水中富含HCO3-和Ca2 ,说明高原东部长江水系流域盆地中碳酸盐岩(主要是灰岩)应是河流中主要离子的风化源岩。     

青藏高原东部长江流域盆地陆地化学风化研究

长江河水主要离子由流域盆地碳酸盐岩的风化所控制,沱沱河和楚玛尔河受蒸发盐岩影响较为明显;河水溶质载荷Si,Si/TZ *,Si/(Na* K)等指标表明,长江流域盆地地表硅酸盐岩风化还是浅表层次的;金沙江地表化学剥蚀速率为1.74×103mol/yr.km2,雅砻江为1.69×103mol/yr.km2,大渡河为1.57×103mol/yr.km2,岷江为1.88×103mol/yr.km2,长江河源区楚玛尔河为2.32×103mol/yr.km2,沱沱河为1.37×103mol/yr.km2,流域地表化学剥蚀速率可与世界上其它造山带的河流进行对比。     

贵州喀斯特地区河流的研究--碳酸盐岩溶解控制的水文地球化学特征

测量了喀斯特地区乌江、沅江两大水系的河流枯水期的主元素、Sr2+离子浓度和Sr同位素比值。这些河流的化学组成代表了流经碳酸盐岩地层的河水的化学组成。这些河流及其支流有高的溶解盐,TZ+变化范围为：2.1～6.3 meq/L,高于全球河流的平均值(TZ+=0.725 meq/L)。河水含有较高的溶质浓度,河水水化学组成以Ca2+和HCO-3为主,其次为Mg2+和SO2-4,Na++K+和Cl-+Si分别只占阳离子和阴离子组成的5%～10%。 这些河流的化学和同位素组成主要受其自流盆地的地质特征控制。流经碳酸盐岩地层的乌江水系河流具有较高的Sr浓度（1.1～9.70 mol/L）和较低的87Sr/86Sr比值（0.7077～0.7110）,与流经碎屑岩地层的沅江水系的清水江河流中较高的87Sr/86Sr比值（0.7090～0.7145）及较低的Sr浓度（0.28～1.32 mol/L）形成鲜明的对比。 流域盆地的地理岩性控制了河水的化学组成和同位素组成。对河水的化学计量分析表明河水化学组成受碳酸盐岩溶解控制,而碳酸盐岩主要受碳酸和硫酸作用而溶解。乌江流域受硫酸作用特别明显,表明硫酸主要来源于燃煤或流域盆地硫化物矿物氧化而形成的大气输入。化学元素和同位素比值之间的相互关系表明3个主要来源为：石灰岩、白云岩和硅酸盐岩的风化。同时估计了碳酸盐岩和硅酸盐岩的化学风化速率,结果表明流域盆地的碳酸盐岩风化速率远远高于许多世界大河。岩石风化过程中硫酸的出现或土地的过度使用或土壤植被的退化等都可能是导致流域的碳酸盐岩风化速率如此高的原因。      

南水北调中线水源地河水地球化学特征与流域侵蚀

丹江口水库及其上游流域是南水北调中线工程的水源地,本文讨论了水源地河流水化学与锶同位素(87Sr/86Sr)组成变化特征,目的在于了解水源地流域河流地表水溶质的物质来源以及岩石风化侵蚀过程和人为活动的影响。流域内河流水化学组成以Ca2+、HCO3-为主,Mg2+和SO42-次之,反映了碳酸盐岩风化溶解起控制作用的典型特征。水化学分析表明水源地河水受到工农业活动等人为因素的影响;河流87Sr/86Sr同位素地球化学研究表明,流域岩石风化输入至少存在三个不同端员(硅酸岩、石灰岩和白云岩)之间的混合。水源地流域内硅酸岩和碳酸岩的风化侵蚀速率分别为38.6和4.4 t/km2.a,总岩石风化侵蚀速率高于全球河流平均值。     

长江水系水文地球化学特征及主要离子的化学成因

在分析长江流域76个位点的水化学数据的基础上,运用吉布斯(Gibbs)图、三角图、主成分分析方法研究岩性对长江水系河水中离子化学特征的影响和流域的主要风化过程。结果表明,长江水系的主要离子化学特征受岩石风化作用的影响,其中碳酸盐和蒸发岩矿物对干流水系溶质的贡献率分别为43.6%和37.9%,而对支流水系溶质的贡献率分别为33.1%和39.1%。干流流域内主要的风化反应以白云石和方解石的溶解为主,而支流流域内Cl-/(Na++K+)接近1∶1,体现出蒸发岩风化的显著特性。Si/K比值较低,表明长江流域内的风化反应是在表生环境中进行的,且产物是富含阳离子的次生矿物。     

青藏高原东缘若尔盖盆地表层沉积物粘土矿物组成及其环境意义探讨

青藏高原东缘若尔盖盆地的古气候和物源研究一直备受关注,但现有指标研究尚不足以探讨若尔盖盆地物源、降水变化及流域化学风化特征.本研究选择若尔盖盆地表层沉积物和基岩为研究对象,以X射线衍射(XRD)分析为主,结合X荧光光谱(XRF)分析,系统获取了该盆地表层沉积物和基岩的粘土矿物组合、全岩地球化学元素组成变化特征,开展了不...     

金沙江河流悬浮物与沉积物的矿物学特征及其表生地球化学意义

为研究金沙江流域表生风化特征,系统采集了金沙江和岷江流域32件河流悬浮物和河床砂样品,对其进行了矿物组成分析。结果表明,不同江段河流悬浮物、沉积物的矿物组成大致相同,以石英、方解石、斜长石和粘土矿物为主,局部有白云石、钾长石和角闪石等;粘土矿物主要有伊利石、绿泥石、高岭石和蒙脱石。河床沉积物中非粘土矿物碎屑(岩屑)含量明显高于悬浮物。伊利石为铁镁质,Kubler指数在轻微变质范围内,主要来源于三叠系碎屑岩和砂板岩。金沙江、岷江的河流悬浮物矿物组成与流域内出露的碎屑岩、砂板岩、火成岩、碳酸盐岩等的分布有较好的对应关系。河流悬浮物和沉积物的矿物组成及伊利石结晶指数特征表明流域内以物理风化为主。     

珠江流域碳酸盐岩与硅酸盐岩风化对大气CO_2汇的效应

对珠江流域11个测站的河水1个水文年4次取样进行水化学和同位素测试分析,揭示无论是碳酸盐岩区还是硅酸盐岩区,岩石风化均使河流的离子成分以HCO3-、Ca2+、Mg2+为主,碳酸盐岩风化溶蚀速率和由碳酸盐岩风化溶蚀引起的大气CO2消耗量分别为27.60 mm/ka和540.21x103mol/(km2·a-1),是硅酸盐岩风化速率和由硅酸盐岩风化引起的大气CO2消耗量的10.8倍和6.7倍,说明碳酸盐岩风化是流域碳汇过程及效应的主体。由于有利的水热条件和高的碳酸盐岩面积比例,珠江流域平均岩石风化速率和由岩石风化作用引起的大气CO2消耗量分别为30.15mm/ka和620.36×103mol/(km2·a-1),为全球60条河流平均值的2.6倍。     

赤水河流域岩石化学风化及其对大气CO_2的消耗

岩石风化碳汇是全球碳汇的重要组成部分,通过对赤水河流域水体主要离子组成进行测定,分析赤水河流域河水水化学特征及其岩石风化过程对大气CO_2的消耗。结果表明:赤水河流域离子组成以Ca~(2+),Mg~(2+),HCO_3~-和SO_4~(2-)为主,河水总溶解性固体(TDS)含量均值为317.88 mg/L,高于全球流域均值(65 mg/L)。元素比值分析表明赤水河流域离子组成主要受岩石风化控制,其中碳酸盐岩风化为主导控制因素,碳酸盐岩、硅酸盐岩对河水溶质贡献率分别为70.77%和5.03%。人类活动和大气降水对流域河水溶质的贡献很小。流域岩石化学风化速率为126.716 t/(km~2·a),高于黄河、长江、乌江及世界河流均值。流域岩石化学风化对大气CO_2的消耗量为10.96×10~9mol/a,岩石风化对大气CO_2消耗速率为5.79×10~5mol/(km~2·a),与长江流域接近,高于黄河流域。     

流域化学风化过程的碳汇能力

通过对已有工作较为全面的分析,综述了流域化学风化过程对大气CO<,2>的吸收能力.陆地岩石的化学风化过程是联接地球各大碳库的关键环节.在地质时间尺度上陆地岩石的化学风化,尤其是硅酸盐岩的化学风化构成全球生物地球化学循环的重要碳汇,是调节地球气候性质使之相对稳定的关键表生地质过程.河流在陆地向海洋的物质输送中担任着重要角...     

Geochemistry of the headwaters of the Yangtze River, Tongtian He and Jinsha Jiang: Silicate weathering and CO2 consumption

Water and sediment samples were collected from the headwaters of the Yangtze River, Tongtian He and Jinsha Jiang (upstream of the Yangtze River which flows on the eastern Qinghai-Tibet Plateau). A detailed geochemical study of the river system was carried out to determine: (i) temporal and spatial variations of the major ions and their implications; (ii) contribution of carbonate, silicate and evaporite to the river dissolved load and (iii) CO₂ consumption via silicate weathering. Results show that cations derived from evaporite dissolution account for 44.7–82.8% of the total cations in the headwaters of the Yangtze River and increasing from SE to NW of the drainage basin. The contribution from silicate weathering gradually increases from the headwaters due to exposure of intrusive rocks and volcanic rocks in the Jinsha Jiang suture belt. Proportion of cations derived from silicate weathering to the total cations in river waters reaches a maximum at Panzhihua City, which is consistent with the abundant exposure of Cenozoic granitoids and Precambrian high-grade metamorphic rocks around Panzhihua. The Jinsha Jiang basin has higher silicate weathering rates but lower carbonate weathering rates than the middle and lower reaches of the Yangtze River. The calculated enrichment factors of potentially harmful metals in the river sediments are within the range of 0.33–2.59, indicative of level 1 or 2 contamination. The highest enrichment factor for Co, Cr and V is found in Panzhihua City, indicating that it has been influenced by anthropogenic sources.     

Chemical weathering of carbonates and silicates in the Han River basin,South Korea

A detailed investigation of the fluvial geochemistry of the Han River system allows to estimate the rates of chemical weathering and the consumption of CO₂. The Han River drains approximately 26,000 km² and is the largest river system in South Korea in terms of both water discharge and total river length. It consists of two major tributaries: the North Han River (NHR) and the South Han River (SHR). Distinct differences in basin lithology (silicate vs. carbonate) between the NHR and SHR provide a good natural laboratory in which to examine weathering processes and the influence of basin geology on water quality. The concentrations of major elements and the Sr isotopic compositions were obtained from 58 samples collected in both summer and winter along the Han River system in both 2000 and 2006. The concentrations of dissolved loads differed considerably between the NHR and SHR; compared with the SHR, the NHR had much lower total dissolved solids (TDS), Sr, and major ion concentrations but a higher Si concentration and ⁸⁷Sr/⁸⁶Sr ratio. A forward model showed that the dissolved loads in the NHR came primarily from silicate weathering (55 ± 11%), with a relatively small portion from carbonates (30 ± 14%), whereas the main contribution to the dissolved loads in the SHR was carbonate weathering (82 ± 3%), with only 11 ± 4% from silicates. These results are consistent with the different lithologies of the two drainage basins: silicate rocks in the NHR versus carbonate rocks in the SHR. Sulfuric acid derived from sulfide dissolution in coal-containing sedimentary strata has played an important role in carbonate weathering in the SHR basin, unlike in the NHR basin. The silicate weathering rate (SWR) was similar between the NHR and SHR basins, but the rate of CO₂ consumption in the SHR basin was lower than in the NHR basin due to an important role of sulfuric acid derived from pyrite oxidation.     

Chemical processes affecting alkalis and alkaline earths during continental weathering

The alkali and alkaline earth concentrations in the Toorongo Granodiorite weathering profile are controlled by two competing processes; leaching of cations from primary minerals during their degradation to clays; fixation, by exchange and adsorption, of the same cations onto the secondary clay minerals. Degradation and leaching dominate the early weathering stages whereas during the advanced stages, exchange and adsorption onto clays are of most influence.The alkali and alkaline earth compositional changes in the Toorongo Granodiorite weathering profile are typical of changes occurring during weathering of the continents, consequently the following generalizations apply to continental weathering. Ca, Sr and Na are most rapidly and most strongly removed (as dissolved species) during weathering of fresh continental rocks. Although large quantities of Mg are transported to the marine environment as dissolved species, appreciable amounts remain (fixed in secondary clay minerals) at the weathering site to be removed during mass wasting of continental weathering profiles. Large quantities of Rb, Cs and Ba, fixed in continental weathering profiles by exchange and adsorption onto secondary clays, are transported from the continents only during mass wasting of the continents.     

Behaviour of lithium and its isotopes during weathering in the Mackenzie Basin, Canada

We report Li isotopic compositions, for river waters and suspended sediments, of about 40 rivers sampled within the Mackenzie River Basin in northwestern Canada. The aim of this study is to characterize the behaviour of Li and its isotopes during weathering at the scale of a large mixed lithology basin. The Mackenzie River waters display systematically heavier Li isotopic compositions relative to source rocks and suspended sediments. The range in δ⁷Li is larger in dissolved load (from +9.3‰ to +29.0‰) compared to suspended sediments (from −1.7‰ to +3.2‰), which are not significantly different from δ⁷Li values in bedrocks. Our study shows that dissolved Li is essentially derived from the weathering of silicates and that its isotopic composition in the dissolved load is inversely correlated with its relative mobility when compared to Na. The highest enrichment of ⁷Li in the dissolved load is reported when Li is not or poorly incorporated in secondary phases after its release into solution by mineral dissolution. This counterintuitive observation is interpreted by the mixing of water types derived from two different weathering regimes producing different Li isotopic compositions within the Mackenzie River Basin. The incipient weathering regime characterizing the Rocky Mountains and the Shield areas produces ⁷Li enrichment in the fluid phase that is most simply explained by the precipitation of oxyhydroxide phases fractionating Li isotopes. The second weathering regime is found in the lowland area and produces the lower δ⁷Li waters (but still enriched in ⁷Li compared to bedrocks) and the most Li-depleted waters (compared to Na). Fractionation factors suggest that the incorporation of Li in clay minerals is the mechanism that explains the isotopic composition of the lowland rivers. The correlation of boron and lithium concentrations found in the dissolved load of the Mackenzie Rivers suggests that precipitation of clay minerals is favoured by the relatively high residence time of water in groundwater. In the Shield and Rocky Mountains, Li isotopes suggest that clay minerals are not forming and that secondary minerals with stronger affinity for ⁷Li appear.Although the weathering mechanisms operating in the Mackenzie Basin need to be characterized more precisely, the Li isotope data reported here clearly show the control of Li isotopes by the weathering intensity. The spatial diversity of weathering regimes, resulting from a complex combination of factors such as topography, geology, climate and hydrology explains, in fine, the spatial distribution of Li isotopic ratios in the large drainage basin of the Mackenzie River. There is no simple relationship between Li isotopic composition and chemical denudation fluxes in the Mackenzie River Basin.     

南黄海北部晚更新世以来常量元素记录的化学风化作用

以南黄海北部高沉积速率柱状样DLC70-3孔作为研究对象,对沉积物的黏土矿物和常量元素地球化学组成进行了综合分析。结果显示,DLC70-3孔沉积物中黏土矿物组合以伊利石为主,其次为蒙皂石,绿泥石和高岭石含量较低;绝大部分样品中伊利石与蒙皂石含量的比值<6,表明沉积物主要来源于黄河物质的输送。研究认为DLC70-3孔沉积物的化学风化指标CIA值受到海平面变化和源区气候变化共同控制,其中源区的气候变化为主要控制因素,而海平面变化造成的机械沉积分异作用主要影响27.80~38.00 m（MIS 4）层位沉积物的CIA值。CIA值显示在MIS 5和MIS 3期大陆化学风化作用较强,与内陆黄土高原地区夏季风和化学风化指标的变化趋势一致,尤其是在MIS 3早期（40~60 ka）记录的化学风化作用非常强,反映了黄河流域地区出现强夏季风降雨过程。     

Geochemistry of large river suspended sediments: silicate weathering or recycling tracer?

This study focuses on the major and trace element composition of suspended sediments transported by the world’s largest rivers. Its main purpose is to answer the following question: is the degree of weathering of modern river-borne particles consistent with the estimated river dissolved loads derived from silicate weathering?In agreement with the well known mobility of elements during weathering of continental rocks, we confirm that river sediments are systematically depleted in Na, K, Ba with respect to the Upper Continental Crust. For each of these mobile elements, a systematics of weathering indexes of river-borne solids is attempted. A global consistency is found between all these indexes. Important variations in weathering intensities exist. A clear dependence of weathering intensities with climate is observed for the rivers draining mostly lowlands. However, no global correlation exists between weathering intensities and climatic or relief parameters because the trend observed for lowlands is obscured by rivers draining orogenic zones. An inverse correlation between weathering intensities and suspended sediment concentrations is observed showing that the regions having the highest rates of physical denudation produce the least weathered sediments. Finally, chemical and physical weathering are compared through the use of a simple steady state model. We show that the weathering intensities of large river suspended sediments can only be reconciled with the (silicate-derived) dissolved load of rivers, by admitting that most of the continental rocks submitted to weathering in large river basins have already suffered previous weathering cycles. A simple graphical method is proposed for calculating the proportion of sedimentary recycling in large river basins. Finally, even if orogenic zones produce weakly weathered sediments, we emphasize the fact that silicate chemical weathering rates (and hence CO₂ consumption rates by silicate weathering) are greatly enhanced in mountains simply because the sediment yields in orogenic drainage basins are higher. Hence, the parameters that control chemical weathering rates would be those that control physical denudation rates.     

Environmental geochemistry of Damodar River basin, east coast of India

 Water and bed sediment samples collected from the Damodar River and its tributaries were analysed to study elemental chemistry and suspended load characteristics of the river basin. Na and Ca are the dominant cations and HCO₃ is the dominant anion. The water chemistry of the Damodar River basin strongly reflects the dominance of continental weathering aided by atmospheric and anthropogenic activities in the catchment area. High concentrations of SO₄ and PO₄ at some sites indicate the mining and anthropogenic impact on water quality. The high concentration of dissolved silica, relatively high (Na+K)/TZ⁺ ratio (0.2–0.4) and low equivalent ratio of (Ca+Mg)/(Na+K) indicate that dissolved ions contribute significantly to the weathering of aluminosilicate minerals of crystalline rocks. The seasonal data show a minimum ionic concentration in the monsoon season, reflecting the influence of atmospheric precipitation on total dissolved solids contents. The suspended sediments show a positive correlation with discharge and both discharge and suspended load reach their maximum value during the monsoon season. Kaolinite is the mineral that is possibly in equilibrium with the water. This implies that the chemistry of the Damodar River water favours kaolinite formation. The concentration of heavy metals in the finer size fraction (<37 μ m) is significantly higher than the bulk composition. The geoaccumulation index values calculated for Fe, Mn, Zn, Ni and Cr are well below zero, suggesting that there is no pollution from these metals in Damodar River sediments. Received: 21 January 1998 · Accepted: 4 May 1998     

广西桂林石灰土元素迁移特征及影响因素 ——以会仙峰丛谷地石灰土为例

碳酸盐岩的化学风化是岩溶关键带各圈层相互作用的主要形式,风化壳中蕴含重要气候环境和物质循环信息.通过对广西桂林会仙峰丛谷地石灰土的化学风化强度及元素迁移特征的研究,并与滇黔湘和青藏高原的岩溶风化壳的对比分析,结果表明:(1)会仙石灰土化学蚀变指数(CIA)均值为92.14,与贵州兴义岩溶风化壳相当,反映炎热潮湿气候下的...     

青藏高原东部长江流域盆地地表化学剥蚀通量剥蚀速率大气CO2净消耗率研究

2000-2002年期间,笔者对青藏高原东部长江流域溶质载荷分别进行了取样分析并对流域盆地化学剥蚀通量、剥蚀速率和大气CO2净消耗率进行了计算。结果表明,流域盆地化学剥蚀速率以河源区楚玛尔河最高为2.34×10^6mol/a/km^2,沱沱河最低为1.40×10^6mol/a/km^2,四大支流雅砻江为1.69×10^6mol/a/km^2,金沙江为1.74×10^6mol/a/km^2,大渡河为1.57×10^6mol/a/km^2,岷江为1.88×10^6mol/a/km^2;流域盆地ФCO2估算结果以大渡河最高为101.81×10^3mol/a/km^2,楚玛尔河最低为7.55×10^3mol/a/km^2,金沙江为44.38×10^3mol/a/km^2,雅砻江为69.64×10^3mol/a/km^2,岷江为81.90×10^3mol/a/km^2,沱沱河为21.90×10^3mol/a/km2^。并对长江流域地表化学剥蚀速率主要控制因素进行了讨论。