Basalt weathering in Central Siberia under permafrost conditions   总被引：2，自引：0，他引：2  

O.S. Pokrovsky  J. Schott  B. Dupré 《Geochimica et cosmochimica acta》2005,69(24):5659-5680

Chemical weathering of basalts in the Putorana Plateau, Central Siberia, has been studied by combining chemical and mineralogical analysis of solids (rocks, soils, river sediments, and suspended matter) and fluid solution chemistry. Altogether, 70 large and small rivers, 30 soil pore waters and groundwaters and over 30 solids were sampled during July to August 2001. Analysis of multiannual data on discharge and chemical composition of several rivers of the region available from the Russian Hydrological Survey allowed rigorous estimation of mean annual major element concentrations, and dissolved and suspended fluxes associated with basalt weathering. For the rivers Tembenchi and Taimura that drain monolithologic basic volcanic rocks, the mean multiannual flux of total dissolved cations (TDS_c = Ca + Mg + Na + K) corrected for atmospheric input is 5.7 ± 0.5 t/km²/yr. For the largest river Nizhniya Tunguska—draining essentially basic rocks—the TDS_c is 6.1 ± 1.5 t/km²/yr. The overall CO₂ consumption flux associated with basalt weathering in the studied region (∼700,000 km²) achieves 0.08 × 10¹² mol/yr, which represents only 2.6% of the total CO₂ consumption associated with basalt weathering at the Earth’s surface. The fluxes of suspended matter were estimated as 3.1 ± 0.5, 9.0 ± 0.8, and 6.5 ± 2.0 t/km²/yr for rivers Taimura, Eratchimo, and Nizhniya Tunguska, respectively. Based on chemical analyses of river solutes and suspended matter, the relative dissolved versus particulate annual transport of major components is C_inorg ≥ C_org > Na + K > Ca > Mg > Si > Fe ≥ Mn ≥ Ti ≥ Al which reflects the usual order of element mobility during weathering.According to chemical and mineralogical soil and sediment analyses, alteration of basalt consists of (1) replacement of the original basaltic glass by Si-Al-Fe rich amorphous material, (2) mechanical desegregation and grinding of parent rocks, leading to accumulation of “primary” hydrothermal trioctahedral smectite, and (3) transformation of these trioctahedral (oxy)smectites and mixed-layer chlorite-smectite, into secondary dioctahedral smectite accompanied by removal of Ca, Mg, and Fe, and enrichment in Al. No vertical chemical differentiation of fluid and solid phases within the soil profile was identified. All sampled soil pore waters and groundwaters were found to be close to equilibrium with respect to chalcedony, gibbsite, halloysite, and allophanes, but strongly supersaturated with respect to goethite, nontronite, and montmorillonite.Over the annual cycle, the contribution of atmospheric precipitation, permafrost melting, underground reservoirs, litter degradation, and rock and soil mineral weathering for the overall TDS_c transport in the largest river of the region (Nizhniya Tunguska) is 9.3 ± 3, 10 ± 5, 10.5 ± 5, 25 ± 20, and 45 ± 30%, respectively. In the summertime, direct contribution of rocks and soil mineral weathering via solid/fluid interaction does not exceed 20%. The main unknown factors of element mobilization from basalt to the river is litter degradation in the upper soil horizon and parameters of element turnover in the vegetation.  相似文献   

Rate controls on the chemical weathering of natural polymineralic material. I. Dissolution behaviour of polymineralic assemblages determined using batch and unsaturated column experiments     

《Applied Geochemistry》2006,21(2):352-376

Chemical weathering rates for a mudstone obtained from a mining environment were investigated using a combination of batch reactors and hydrologically unsaturated column experiments. Results of tracer tests were combined with relationships between solute concentrations, mass fluxes, flow rates and residence times, and used to calculate element release rates and infer rate-controlling mechanisms for the two different experimental environments.Elements that eluted from column experiments exhibited either:

• (1)concentrations independent of flow rate and column length coupled with mass flux increasing with flow rate, or
• (2)an inverse relationship between concentration and flow rate coupled with mass flux increasing with both column length and flow rate.

The former is attributed to equilibrium-controlled release of particular elements (Si, Al), while the latter is ascribed to transport-controlled release of others (Mg, Mn, Ca, Na, K, S). Tracer tests using NaBr solutions revealed that some elements were also affected by ion exchange (Mg, Mn, Ca, Na), but these effects were temporary and did not mask underlying dissolution rate-controlling mechanisms. Analysis of characteristic diffusive lengths was used to distinguish between transport rates limited by the transfer of solutes between immobile and mobile water within the columns, and rates limited by slow diffusion across partially reacted mineral layers. The analysis suggests that transfer between immobile and mobile water limited the element release rates, with diffusion hindered by low diffusion coefficients within the unsaturated medium, and by low interfacial areas between mobile and immobile fluids. Results of the batch experiments showed different characteristics. Element concentrations either rose to a plateau or increased linearly with time. Rate-controlling mechanisms associated with these characteristics were equilibrium (Fe) and surface kinetic reactions (Si, Mg, Mn, Ca, K, S), respectively. Surface area-normalized element release rates for Mg, Mn, Ca and S are consistently a factor of 4 higher than those from the column experiments. This is a significant difference and cannot be attributed to differences in mineral preparation or to factors influencing individual minerals. It must, therefore, reflect the difference in the rate-controlling mechanism, that is, transport vs. surface-kinetic control.These results suggest that some proportion of the commonly recorded discrepancy between laboratory and field weathering rates is due to hydrological differences between the two environments, and that hydrological characterization of weathering environments is, therefore, as important as physical–geochemical characterization of reacting solids. An important practical implication of the work is that substantial reservoirs of solutes are held in immobile water in the unsaturated environment, and that these could be released by soil disturbance or flooding.  相似文献   

The major-element chemistry of suspended particles in the north basin of windermere     

Edward R. Sholkovitz  David Copland 《Geochimica et cosmochimica acta》1982,46(10):1921-1930

Detailed vertical profiles were taken in the north basin of lake Windermere between July and November 1980. Measurements were made of temperature, dissolved oxygen, pH, total suspended load and the major-element composition (organic C, Al, Fe, Mn, Si, S, P, Ca, Mg, Ba and K) of suspended particles.Excess concentrations (those reactive phases not supported by detrital phases) of particulate S, P, Ca, Mg, Ba and K are highest in the epilimnion due to their incorporation into the growing phytoplankton. These elements are associated with planktonic organic matter and are rapidly recycled in the upper 25 m of this 60 m oxic lake. This is documented by the decrease with depth of both excess concentrations of S, P, Ca, Mg, Ba and K and their ratios to POC. Large concentrations of excess particulate Si occur in the hypolimnion as the result of the settling out of diatom skeletal matter produced near the surface during the spring bloom. These siliceous particles do not contain significant quantities of excess particulate S, P, Ca, Mg, Ba and K. This observation supports the conclusion that organic matter is the important recycling matrix for these inorganic elements.Elevated concentrations of excess particulate Mn at depth indicate that there is a Mn-redox cycle operating in the lake.  相似文献   

Effects of volcanic eruptions on the CO₂ content of the atmosphere and the oceans: the 1996 eruption and flood within the Vatnajökull Glacier, Iceland     

S. R. Gí  slason    . Snorrason  H. K. Kristmannsd  ttir    . E. Sveinbj  rnsd  ttir  P. Torsander  J.   lafsson  S. Castet  B. Dupr 《Chemical Geology》2002,190(1-4):181-205

The October 1996 eruption within the Vatnajökull Glacier, Iceland, provides a unique opportunity to study the net effect of volcanic eruptions on atmospheric and oceanic CO₂. Volatile elements dissolved in the meltwater that enclosed the eruption site were eventually discharged into the ocean in a dramatic flood 35 days after the beginning of the eruption, enabling measurement of 50 dissolved element fluxes. The minimum concentration of exsolved CO₂ in the 1×10¹² kg of erupted magma was 516 mg/kg, S was 98 mg/kg, Cl was 14 mg/kg, and F was 2 mg/kg. The pH of the meltwater at the eruption site ranged from about 3 to 8. Volatile and dissolved element release to the meltwater in less than 35 days amounted to more than one million tonnes, equal to 0.1% of the mass of erupted magma. The total dissolved solid concentration in the floodwater was close to 500 mg/kg, pH ranged from 6.88 to 7.95, and suspended solid concentration ranged from 1% to 10%. According to H, O, C and S isotopes, most of the water was meteoric whereas the C and S were of magmatic origin. Both C and S went through isotopic fractionation due to precipitation at the eruption site, creating “short cuts” in their global cycles. The dissolved fluxes of C, Ca, Na, Si, S and Mg were greatest ranging from 1.4×10¹⁰ to 1.4×10⁹ mol. The dissolved C flux equaled 0.6 million tonnes of CO₂. The heavy metals Ni, Mn, Cu, Pb and Zn were relatively mobile during condensation and water–rock interactions at the eruption site. About half of the measured total carbon flood flux from the 1996 Vatnajökull eruption will be added to the long-term CO₂ budget of the oceans and the atmosphere. The other half will eventually precipitate with the Ca and Mg released. Thus, for eruptions on the ocean floor, one can expect a net long-term C release to the ocean of less than half that of the exsolved gas. This is a considerably higher net C release than suggested for the oceanic crust by Staudigel et al. [Geochim. Cosmochim. Acta, 53 (1989) 3091]. In fact, they suggested a net loss of C. Therefore, magma degassed at the ocean floor contributes more C to the oceans and the atmosphere than magma degassed deep in the oceanic crust. The results of this study show that subglacial eruptions affecting the surface layer of the ocean where either Mn, Fe, Si or Cu are rate-determining for the growth of oceanic biomass have a potential for a transient net CO₂ removal from the ocean and the atmosphere. For eruptions at high latitudes, timing is crucial for the effect of oceanic biota. Eruptions occurring in the wintertime when light is rate-determining for the growth of biota have much less potential for bringing about a transient net negative CO₂ flux from the ocean atmosphere reservoir.  相似文献   

The chemistry of suspended matter in Esthwaite Water,a biologically productive lake with seasonally anoxic hypolimnion   总被引：1，自引：0，他引：1  

Edward R. Sholkovitz  David Copland 《Geochimica et cosmochimica acta》1982,46(3):393-410

Ten detailed vertical water column profiles were taken between April and November, 1979, in Esthwaite Water (English Lake district), a lake with high biological productivity and a seasonally anoxic hypolimnion. Measurements of the major-element particle composition (organic C, P, S, Si, Al, Ti, K, Mg, Ca, Fe, Mn, and Ba) and hydrochemical constituents (temperature, pH, dissolved oxygen, total suspended load, dissolved Fe, Mn, P, and Ba) were carried out. These have revealed new information about the mechanisms and kinetics of biogeochemical cycles in a lake.Pronounced seasonal cycles exist in which large excess concentrations (those unsupported by detrital components) of particulate organic C, Fe, Mn, P, S, Mg, K, Ba, and Ca are being generated and lost in situ in the water column (15m deep). In the epilimnion these elements (excepting Fe and Mn) are incorporated into the organic components of growing phytoplankton during the spring and summer. Simultaneously, in the hypolimnion there is a build-up and then a decrease in the excess concentrations of particulate C, P, S, Mg, K, Ba and Ca; this cycle is due to the indirect involvement of these elements with the iron redox cycle. As the hypolimnion becomes anoxic, dissolved ferrous Fe is released from the sediments and large concentrations of excess particulate iron (III) oxides accumulate; these oxides act as adsorbing substrates for the above mentioned elements. As conditions become more reducing, these same elements are solubilized as the iron (III) oxide particles are reduced to dissolved ferrous iron.Adsorption equations are derived from the field data which relate the concentration of excess particulate Fe to those of POC, P, S, Ca, Mg, Ba, and K. At the last stages of anoxia (before the lake overturns) large populations of bacteria and the formation of iron sulfide particles control the concentrations of excess particulate C, S, P, Mg, K, and Ca.  相似文献   

Hydrogeochemical Processes in the Kafue River upstream from the Copperbelt Mining Area, Zambia     

Ulf T. Pettersson  Johan Ingri  Per S. Andersson 《Aquatic Geochemistry》2000,6(4):385-411

Frequent sampling during an annual cycle of dissolved(<0.45 m) and suspended (>0.45 m) elementshas been conducted in the Kafue River at Raglan'sFarm, upstream from the mining activities within theCopperbelt Province, Zambia. Additional sampling ofsediment and interstitial pore water was conductedduring low water discharge. The presence of carbonateswithin the drainage basin naturally gives rise to highelement concentrations in the dissolved phase(Ca = 626, Mg = 494, Na = 360 and K = 24 mmol l^-1).During the rainy season the relative composition ofthe dissolved elements indicated a wash out ofaccumulated weathering products and mineralisedorganic material from the unsaturated zone of the soilprofile. High concentrations of dissolved Al, Fe andMn were measured during high water discharge. At lowwater discharge the sediment was a major source of Fe,Mn and associated Co and Cu to the water column.Enhanced concentrations of dissolved and suspended S,Co and Cu during the rainy season indicated thatatmospheric deposited particles from the mining areawere washed out into the river. Autochthonousformation of particles rich in Si indicated diatomproduction during low water discharge.  相似文献   

Recent insights into the dissolved and particulate fluxes from the Himalayan tributaries to the Ganga River     

Md Maroof Azam  Monika Kumari  Chinmaya Maharana  Abhay K. Singh  Jayant K. Tripathi 《Environmental Earth Sciences》2018,77(8):313

The Ganga River plays a major role in the transfer of materials from the Indian sub-continent to the Bay of Bengal, both in dissolved and particulate forms. To understand the present elemental dynamics of the Ganga River system, it is important to assess the hydrogeochemical contribution of its tributaries. In this paper, we present an updated database on dissolved and particulate fluxes and denudation rates of the Himalayan tributaries of the Ganga River (Ramganga, Ghaghara, Gandak and Kosi). Dissolved trace element concentrations, their fluxes and suspended sediment-associated elemental fluxes of the Himalayan tributaries have been reported for the first time. Total dissolved flux of the Ramganga, Ghaghara, Gandak and Kosi was estimated as 4, 19.1, 10.3 and 8.8 million tons year^?1 accounting for ~?5.7, ~?27.3, ~?14.7 and ~?12.6%, respectively, of the total annual dissolved load carried by the Ganga River. The total particulate flux of the Ramganga, Ghaghara, Gandak and Kosi was computed as 8.2, 81.6, 30.9 and 19.5 million tons year^?1, respectively. Compared to earlier studies, we have found a significant increase in the total dissolved flux and chemical denudation rate of the studied tributaries. The estimated particulate fluxes were found to be low in comparison to the previous studies. We suggest that a significant increase in the dissolved fluxes and a decrease in the particulate fluxes are an indication of the increasing anthropogenic disturbances in the catchment of these tributaries.  相似文献   

Hydrogeochemistry and sensitivity to acidification of streamwaters in crystalline areas of northern Fennoscandia     

Pertti W. Lahermo 《Environmental Geology》1991,18(1):57-69

About 6,400 water samples were collected from small catchments in northern Finland and Norway above 66° N latitude as a part of the Nordkalott Project carried out jointly by the Geological Surveys of Finland, Norway, and Sweden. Electrical conductivity (EC) was measured in situ and Ca, Mg, Sr, Ba, Na, K, Si, Fe, Mn, Al, and Zn concentrations were determined from filtered and acidified samples by the ICAP method. The relative abundance of mafic, ultramafic, and carbonate rock components in the catchments is the most influential factor controlling the EC values and the main cation concentrations (Ca, Mg, Sr). These components also determine the HCO₃ alkalinity or acid-neutralizing capacity (ANC) of streamwater. In the northern coastal belt, Na is derived largely from airborne sea salts, but in the southwestern corner of the research area it may be derived partly from relict sea salts in sediments. The concentrations of Na, K, and Si do not depend solely on the lithological environment. Fe and, to a lesser extent, Mn and Al occur in the highest abundances in the low-lying, intensely paludified southern part of the area, suggesting that these metals tend to go into solution and are transported in complexed forms with dissolved and colloidic humic matter. The areal distribution patterns of the main cations (Ca, Mg, Sr) and of some heavy metals (Fe, Mn) in streamwater are fairly consistent with those of till and minerogenic stream sediments, although, in a statistical approach, only a few significant correlation coefficients were established.  相似文献   

An experimental study of crystalline basalt dissolution from 2 ? pH ? 11 and temperatures from 5 to 75 °C     

Snorri Gudbrandsson  Domenik Wolff-Boenisch  Eric H. Oelkers 《Geochimica et cosmochimica acta》2011,75(19):5496-5525

Steady-state element release rates from crystalline basalt dissolution at far-from-equilibrium were measured at pH from 2 to 11 and temperatures from 5 to 75 °C in mixed-flow reactors. Steady-state Si and Ca release rates exhibit a U-shaped variation with pH where rates decrease with increasing pH at acid condition but increase with increasing pH at alkaline conditions. Silicon release rates from crystalline basalt are comparable to Si release rates from basaltic glass of the same chemical composition at low pH and temperatures ?25 °C but slower at alkaline pH and temperatures ?50 °C. In contrast, Mg and Fe release rates decrease continuously with increasing pH at all temperatures. This behaviour is interpreted to stem from the contrasting dissolution behaviours of the three major minerals comprising the basalt: plagioclase, pyroxene, and olivine. Calcium is primarily present in plagioclase, which exhibits a U-shaped dissolution rate dependence on pH. In contrast, Mg and Fe are contained in pyroxene and olivine, minerals whose dissolution rates decrease monotonically with pH. As a result, crystalline basalt preferentially releases Mg and Fe relative to Ca at acidic conditions. The injection of acidic CO₂-charged fluids into crystalline basaltic terrain may, therefore, favour the formation of Mg and Fe carbonates rather than calcite. Element release rates estimated from the sum of the volume fraction normalized dissolution rates of plagioclase, pyroxene, and olivine are within one order of magnitude of those measured in this study.  相似文献   

Absorbed complex of riverine solid substances and its role in geochemical balance of the ocean     

A. V. Savenko  V. S. Savenko 《Lithology and Mineral Resources》2016,51(1):13-37

Data on the composition of the absorbed complex of riverine solid substances and its transformation in marine environments obtained from field observations and experimental investigations are systematized and generalized. Average values of the specific surface of the riverine suspended particulates (~20 m²/g) and the total exchange capacity of solid substances of the continental runoff (~28 mg-equiv/100 g or 280 g-equiv/t of the transported terrigenous material) are determined. It is shown that the composition of the absorbed complex in the riverine suspended particulates, as well as bottom sediments of rivers and inland water bodies differs principally from that of bottom sediments in oceans and seas: Ca dominates in the first case; Na, in the second case. When the riverine terrigenous material enters oceans and seas, the composition of the absorbed complex is subjected to the ion-exchange transformation reflected in the replacement of exchange Ca (~80%) mainly by Na and also by K and Mg of seawater. This process is responsible for the influx of 45.5 Mt/yr of dissolved Ca to ocean and the removal of 37.3, 12.8, and 3.9 Mt/yr of Na, K, and Mg, respectively. The relative transport of Ca, Na, K, and Mg to ocean with the river runoff is +7.5,–12.3,–22.4, and–2.6%, respectively.  相似文献   

长江水系河水主要离子化学特征   总被引：14，自引：2，他引：12  

夏学齐  杨忠芳  王亚平  季峻峰  李文明  袁旭音 《地学前缘》2008,15(5):194

2007年夏季采集了长江从上游沱沱河至入海口的干流原水样品36个,长江各主要支流水样品40个,分析了江水Ca2+、Mg2+、Na+、K+、HCO3-、SO42-、Cl-离子含量及溶解性SiO2等溶质成分。结果显示,长江流域水系离子化学组成主要受碳酸盐和蒸发岩风化控制,长江上游水离子化学呈现阳离子以K+和Na+为主,阴离子以Cl-和SO42-为主的蒸发岩类风化控制特征,但随着采样点位下移,离子含量逐渐呈现阳离子以Ca2+为主,阴离子以HCO3-为主的逐渐向碳酸盐风化过渡的特征;从时间变化上看,与20世纪50年代至1990年长江水离子化学数据相比,以Na+、K+、SO42-和Cl-为代表的所有阴阳离子均有明显增加;从通量上看,洞庭湖和鄱阳湖是长江离子两个最大的输入源,除洞庭湖和鄱阳湖外的其他长江各大支流中,岷江是长江Na+、K+、Ca2+、Mg2+、F-和HCO3-的最大输入源,嘉陵江是SO24-和溶解性SiO2的最大输入源;在几大世界河流中,长江是对海洋Mg2+、SO24-和Cl-的输入通量最大的河流,Ca2+和HCO3-通量仅次于亚马逊河。  相似文献   

How important is it to integrate riverine suspended sediment chemical composition with depth? Clues from Amazon River depth-profiles   总被引：1，自引：0，他引：1  

Julien Bouchez  Maarten Lupker  Christian France-Lanord 《Geochimica et cosmochimica acta》2011,75(22):6955-6970

The vertical variability in mineralogical, chemical and isotopic compositions observed in large river suspended sediments calls for a depth-integration of this variability to accurately determine riverine geochemical fluxes. In this paper, we present a method to determine depth-integrated chemical particulate fluxes of large rivers, based on river sampling along depth-profiles, and applied to the Amazon Basin lowland tributaries. The suspended particulate matter (SPM) concentration data from depth-profiles is modeled for a number of individual grain size fractions using the Rouse model, which allows to predict the grain size distribution of suspended sediment throughout the whole river cross-section. Then, using (1) the relationship between grain size distribution and the Al/Si ratio (2) relationships between the Al/Si ratio and the chemical concentrations, the chemical composition of river sediment is predicted throughout the river cross-section, and integrated to yield the depth-integrated chemical particulate flux for a number of chemical elements (e.g. Si, Al, Fe, Na, REEs, …). For elements such as Al, Fe, REEs, Th, the depth-integrated flux is around twice as high as the one calculated from river surface sample characteristics. For Na and Si, the depth-integrated flux is three times higher than the “surface” estimate, due to the enrichment of albite and quartz at the bottom of the river. Depth-integrated ⁸⁷Sr/⁸⁶Sr composition of suspended sediment, also predictable using this method, differs by more than 10⁻³ from the surface sample composition.Finally, potential implications of depth-integrated estimates of Amazon sediment chemistry are explored. Depth-integration of particulate ⁸⁷Sr/⁸⁶Sr isotopic ratios is necessary for a reliable use of Sr isotopes as a provenance tracer. The concept of steady-state weathering of a large river basin is revisited using depth-integrated sediment composition. This analysis shows that, in the Amazon Basin river, the previously observed discrepancy between (1) weathering intensities of channel surface sediment and (2) silicate-derived dissolved fluxes is only slightly accounted for by the vertical variability of suspended sediment weathering intensities. This observation confirms that most large rivers basins are not eroding at steady-state.  相似文献   

Evidence for extensive diagenesis,Madagascar Basin,Deep Sea Drilling Site 245     

Joris M. Gieskes  Miriam Kastner  Theodore B. Warner 《Geochimica et cosmochimica acta》1975,39(10):1385-1393

Deep Sea Drilling Hole 245 (31°32′S, 52° 18′E) in the southwest Indian Ocean shows pronounced linear concentration-depth gradients in interstitial dissolved Ca, Mg and Sr. Electrical conductivity tests enable us to make the estimate of a constant diffusion coefficient with depth of about 2 × 10^?6 cm²/sec. The shapes of the concentration-depth gradients suggest that the major reaction sites in this hole are situated in the basal sediments and/or underlying basalts. It is proposed that observed interstitial water concentration changes in Ca and Mg are related to alteration of basaltic material, whereas those in Sr are due to calcium carbonate recrystallization processes. Support for the basaltic material alteration hypothesis comes from petrochemical and mineralogical data. Geochemical data also indicate that the high contents in Fe and Mn of the basal sediments can be related to low temperature alteration of basaltic glass and not necessarily to ‘hydrothermal’ activity.  相似文献   

Environmental geochemistry of Damodar River basin, east coast of India   总被引：1，自引：0，他引：1  

A. K. Singh  S. I. Hasnain 《Environmental Geology》1999,37(1-2):124-136

 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  相似文献   

Dissolution kinetics of a lunar glass simulant at 25 degrees C: the effect of pH and organic acids     

Eick MJ  Grossl PR  Golden DC  Sparks DL  Ming DW 《Geochimica et cosmochimica acta》1996,60(1):157-170

The dissolution kinetics of a simulated lunar glass were examined at pH 3, 5, and 7. Additionally, the pH 7 experiments were conducted in the presence of citric and oxalic acid at concentrations of 2 and 20 mM. The organic acids were buffered at pH 7 to examine the effect of each molecule in their dissociated form. At pH 3, 5, and 7, the dissolution of the synthetic lunar glass was observed to proceed via a two-stage process. The first stage involved the parabolic release of Ca, Mg, Al, and Fe, and the linear release of Si. Dissolution was incongruent, creating a leached layer rich in Si and Ti which was verified by transmission electron microscopy (TEM). During the second stage the release of Ca, Mg, Al, and Fe was linear. A coupled diffusion/surface dissolution model was proposed for dissolution of the simulated lunar glass at pH 3, 5, and 7. During the first stage the initial release of mobile cations (i.e., Ca, Mg, Al, Fe) was limited by diffusion through the surface leached layer of the glass (parabolic release), while Si release was controlled by the hydrolysis of the Si-O-Al bonds at the glass surface (linear release). As dissolution continued, the mobile cations diffused from greater depths within the glass surface. A steady-state was then reached where the diffusion rate across the increased path lengths equalled the Si release rate from the surface. In the presence of the organic acids, the dissolution of the synthetic lunar glass proceeded by a one stage process. The release of Ca, Mg, Al, and Fe followed a parabolic relationship, while the release of Si was linear. The relative reactivity of the organic acids used in the experiments was citrate > oxalate. A thinner leached layer rich in Si/Ti, as compared to the pH experiments, was observed using TEM. Rate data suggest that the chemisorption of the organic anion to the surface silanol groups was responsible for enhanced dissolution in the presence of the organic acids. It is proposed that the increased rate of Si release is responsible for the one stage parabolic release of mobile cations and the relatively thin leached layer compared to experiments at pH 3 and 5.  相似文献   

Seasonal discharge and chemical flux variations of rivers flowing into the Bayhead canal of Durban Harbour,South Africa     

Kavandren Moodley  Srinivasan Pillay  Keshia Pather  Hari Ballabh 《中国地球化学学报》2016,35(4):340-353

The u Mhlatuzana, u Mbilo and a Manzimnyama river catchments located on the eastern seaboard of the Kwa Zulu-Natal province, South Africa, form the core of urbanization and industrialization, contributing the only natural freshwater inflows to the Bayhead Canal portion of the Durban Harbour. In this study, seasonal discharges and physico–chemical water properties were used to quantitatively determine the material mass transport capacity of the river systems on the basis of hydrographic inputs and chemical loading from the surrounding land use sectors.The mass transport of the total dissolved solids（TDS）,ammonia（NH₄）, phosphorous（P）, aluminum（Al）, calcium（Ca）, copper（Cu）, chromium（Cr）, mercury（Hg）, potassium（K）, magnesium（Mg）, sodium（Na）, nickel（Ni）, lead（Pb）, sulphur（S） and vanadium（V） was determined for each river. Results indicated that land use, seasonality and river flow were significant determinants for the material loading in the rivers and the receiving port waters. The spatio-temporal distribution patterns of chemical fluxes indicated that industrial activity associated with the a Manzimnyama canal contributed the most, with regards to TDS, NH₄, Ca, K, Mg, Na, S and V, loading in both wet and dry seasons, as well as Al, Cu, Hg and Pb during the dry season. Similarly, industrial activity associated with the u Mbilo/u Mhlatuzana Canal at the lower reaches accounted for the highest P, Al, Cu and Pb fluxes in the wet season alone. Fluxes of these parameters are used to explain theobserved elemental concentrations and patterns of the receiving port waters of the Bayhead Canal.  相似文献   

Impact of trace mineral phases on the total solute flux from andesitic volcanics     

《Applied Geochemistry》2015

Recent work on the weathering of high standing islands (HSI’s) of New Zealand (Goldsmith et al., 2008), Dominica (Goldsmith et al., 2010) Martinique and Guadeloupe (Rad et al., 2006) and portions of the Philippines (Schopka et al., 2011) shows weathering rates based on stream water chemistry for areas draining andesitic terrains are comparable to weathering rates determined for basaltic terrains, indicating that andesite weathering might be much more important in drawing down atmospheric CO₂ than previously recognized. While an easily erodible parent material has been largely attributed to sustaining rates at these locations, little is known to known regarding its associated reaction kinetics. We conducted a series of batch dissolution experiments on andesitic material collected from ∼10,000 year old tephra deposits from Dominica to determine the dissolution rate of major and trace mineral phases to better understand geochemical processes controlling weathering flux from these areas. Dissolution experiments were conducted over a range of pH (4 and 7) on bulk samples and mineral separates.The dissolution rates based on Si release from the Dominica tephra bulk samples were similar, and ranged from 0.04 to 0.13 μmole Si/g-day in water, and ∼0.14 to 0.27 μmole Si/g-day in dilute acid (initial pH ∼4). Although the bulk of the ash is predominately composed of vesicular felsic (Na–Al–Si) volcanic glass, reaction rates and stoichiometry indicate ash dissolution is dominated by the reactivity of trace Mg or Ca-bearing silicate phases (olivine, pyroxene or amphiboles) and Ca–phosphate phases (apatite), especially under slightly acidic conditions. Analysis of reacted phases by SEM shows little evidence of alteration of glassy material, whereas surfaces of Ca–Mg inosilicates, olivine and apatite show etched features indicative of dissolution. Results of the dissolution experiments suggest that, although these phases are relatively minor components of the ash, they contribute disproportionately to the overall weathering flux, and their reactivity may be particularly important in areas where physical weathering and erosion are constantly exposing new fresh surfaces available for chemical reaction.  相似文献   

铁岭市东部山区野生经济植物榛子营养元素地球化学特征   总被引：1，自引：1，他引：0  

张春晖  丁秋红  商翎  陈树旺  邢德和  卞雄飞  张志斌  高飞  郑月娟 《地质与资源》2006,15(4):299-303

对辽宁省铁岭市东部山区野生经济植物榛子样品中的常量营养元素P、K、Ca、Na、Mg、S,14种营养微量元素和稀土元素含量进行了分析.结果表明,本区的榛子样品其主量元素化学特征属K > P > Ca型,其中Na元素含量变异系数最大,为44.27.微量元素含量水平均在植物元素含量正常值变化范围内,由高到低,元素含量排列顺序为;Mn > Si > Fe > Zn > B > Cu > Ni > F > Cr > Mo > Co > Se > I > V.其中,V元素变异系数最大,为93.18.稀土元素总量∑REE（平均值）为29.66×10^-9,属低含量.元素相关性分析表明,元素K与Na、Mg,S与Mg、Ca,P与K、Na、Mg、Ca,Fe与Mn,Co与Mn,Cu与Zn之间,在0.01水平都表现出极显著的正相关,反映这些元素之间的吸收积累有很好的协同作用.  相似文献   

Alteration of basaltic glass: Mechanisms and significance for the oceanic crust-seawater budget   总被引：1，自引：0，他引：1  

Hubert Staudigel  Stanley R. Hart 《Geochimica et cosmochimica acta》1983,47(3):337-350

Alteration of basaltic glass to palagonite is characterized by a nearly isomolar exchange of SiO₂, Al₂O₃, MnO, MgO, CaO, Na₂O, P₂O₅, Zn, Cu, Ni, Cr, Hf, Sc, Co and REE for H₂O and K₂O, whilst TiO₂ and FeO are passively accumulated during removal of the remaining cations. The network forming cations Al and Si are removed from the glass in proportion to the gain in Ti and Fe, whilst the other cations do not show a significant relationship to the amount of Ti and Fe accumulation. Sr isotopic data show that during palagonite formation approximately 85% of the basaltic Sr is lost to the hydrous solutions and 40% of seawater Sr is added to the glass, yielding an average loss of the same order of magnitude as of the network forming cations. Losses and gains of oxides yield an average increase of +105% TiO₂.K, Rb, and Cs show high increases, but $\text{K}\text{Rb}$ and $\text{K}\text{Cs}$ ratios indicate two different alteration processes: (1) formation of palagonite involves a drastic decrease in these ratios, indicating structural similarities between palagonite and smectite; (2) surface alteration of glass is characterized by an increase in $\text{K}\text{Rb}$ and $\text{K}\text{Cs}$ ratios, probably best interpreted as sorption of alkalies in ratios approximating those of seawater.The total fluxes involved in alteration of glass in the upper portion of the oceanic crust are estimated from the modal abundance of palagonite in the oceanic crust and the abundance of the vein materials smectite and carbonate. Smectite and carbonates act as a sink for a significant portion of the elements liberated up during alteration of basaltic glass except for Na and Al, which are probably taken up by zeolites and/or albite, possibly hidden in the macroscopic estimate of carbonate. Formation of the observed quantity of secondary phases requires additional sources for Si, Fe. Ca and K. K is provided in excess from the inflowing seawater at reasonable water/rock ratios. The remaining excess Ca, Si and Fe required may be derived by alteration of interstitial glass and breakdown of anorthite rich plagioclase and titano-magnetite, and/or by supply of deeper seated metamorphic reactions.  相似文献   

洞庭湖区沉积物物源推断的地球化学指标与应用     

魏军才  张建新  邢旭东  鲁江 《大地构造与成矿学》2010,34(3)

在对洞庭湖区钻孔岩心进行地球化学采样分析的基础上,研究总结了不同物源沉积物元素及其组合的地球化学特征,认为长江物源与四水(湘、资、沅、澧)相比,以富Fe、Na、Ca和Mg、贫Si、高CaO/MgO、Cr/Th、Ca/Cd、Ti/Si、TC/N,低K/Na等为特征,通过散点图和因子分析筛选出Cr/Th等8个指标,构建物质来源地球化学推断的判别方程,利用多目标区域地球化学调查数据,绘制湖区表层沉积物的判别得分图,划分出了长江和四水物源的两个沉积区。  相似文献