Spatial patterns of groundwater‐lake exchange – implications for acid neutralization processes in an acid mine lake     

Christiane Neumann  Julia Beer  Christian Blodau  Stefan Peiffer  Jan H. Fleckenstein 《水文研究》2013,27(22):3240-3253

Exchange of groundwater and lake water with typically quite different chemical composition is an important driver for biogeochemical processes at the groundwater‐lake interface, which can affect the water quality of lakes. This is of particular relevance in mine lakes where anoxic and slightly acidic groundwater mixes with oxic and acidic lake water (pH < 3). To identify links between groundwater‐lake exchange rates and acid neutralization processes in the sediments, exchange rates were quantified and related to pore‐water pH, sulfate and iron concentrations as well as sulfate reduction rates within the sediment. Seepage rates measured with seepage meters (?2.5 to 5.8 L m^‐2 d^‐1) were in reasonable agreement with rates inverted from modeled chloride profiles (?1.8 to 8.1 L m^‐2 d^‐1). Large‐scale exchange patterns were defined by the (hydro)geologic setting but superimposed by smaller scale variations caused by variability in sediment texture. Sites characterized by groundwater upwelling (flow into the lake) and sites where flow alternated between upwelling and downwelling were identified. Observed chloride profiles at the alternating sites reflected the transient flow regime. Seepage direction, as well as seepage rate, were found to influence pH, sulfate and iron profiles and the associated sulfate reduction rates. Under alternating conditions proton‐consuming processes, for example, sulfate reduction, were slowed. In the uppermost layer of the sediment (max. 5 cm), sulfate reduction rates were significantly higher at upwelling (>330 nmol g^‐1 d^‐1) compared to alternating sites (<220 nmol g^‐1 d^‐1). Although differences in sulfate reduction rates could not be explained solely by different flux rates, they were clearly related to the prevailing groundwater‐lake exchange patterns and the associated pH conditions. Our findings strongly suggest that groundwater‐lake exchange has significant effects on the biogeochemical processes that are coupled to sulfate reduction such as acidity retention and precipitation of iron sulfides. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

P-T evolution and fluid inclusion characteristics of retrograded eclogites,Münchberg Gneiss Complex,Germany     

Reiner Klemd 《Contributions to Mineralogy and Petrology》1989,102(2):221-229

Kyanite eclogites occur as part of the Münchberger nappe pile in NE-Bavaria, West Germany. Eclogites are overprinted by subsequent amphibolite facies metamorphism. The preservation of primary eclogitic textures as well as symplectitic textures are indicative of rapid decompression. Eclogite formation is estimated to have occurred under conditions of high H₂O-activities at pressures between 20 and 26 kbar and temperatures ranging between 590 and 660° C, as is shown by the coexistence of omphacite (Jd 50), kyanite, zoisite and quartz. Minimum pressure estimates, independent of the water activity, range between 9 and 16 kbar at the relevant temperatures. Detailed studies of fluid inclusion reveal two predominant groups of aqueous-brine inclusions: high salinity (14–17 wt% NaCl equiv.) and low salinity (0–8 wt% NaCl equiv.) inclusions. Fluid compositions of both groups of inclusions yield isochores passing close to the estimated amphibolite facies PT-field. The compositions of these fluids are in good agreement with fluid compositions considered from mineral equilibria. None of the fluid inclusions has densities appropriate for eclogite facies metamorphism, but probably reflect later amphibolite facies metamorphism.  相似文献   

On the enhanced smoothing over topography in some mesometeorological models     

P. Alpert  J. Neumann 《Boundary-Layer Meteorology》1984,30(1-4):293-312

An equation is derived for the components of the horizontal (turbulent) frictional force in the -coordinate system with special attention to mesometeorological flow models. The starting point is the horizontal equation of motion in its flux-form in the -system in which we replace (following Reynolds' procedure) the velocity components u,v and % MathType!MTEF!2!1!+- % feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGafq4WdmNbai % aaaaa!37B8! \[ \dot \sigma \] aswell as other relevant quantities by terms of the form u = + u,..., = ± + % MathType!MTEF!2!1!+- % feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGafq4WdmNbai % Gbauaaaaa!37C3! \[ \dot \sigma ' \] , etc. ( = time average of u; u = fluctuating part of u.) Next, the equation is averaged with respect to time and terms which we believe are small in mesometeorological flows, are neglected. On expressing by an appropriate expression that involves w, the result shows the appearance of two new terms which, have not been considered previously in the published literature. While the expression earlier used in the literature involved the -derivative of % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa0aaaeaace% WG1bGbauaaceWG3bGbauaaaaaaaa!380B!\[\overline {u'w'} \] alone, the new terms add the -derivatives of % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa0aaaeaace% WG1bGbauaadaahaaWcbeqaaiaaikdaaaaaaaaa!37EC!\[\overline {u'^2 } \] and % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa0aaaeaace% WG1bGbauaaceWG2bGbauaaaaaaaa!380A!\[\overline {u'v'} \] for the x-component of the force, and the -derivatives of % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa0aaaeaace% WG2bGbauaadaahaaWcbeqaaiaaikdaaaaaaaaa!37ED!\[\overline {v'^2 } \]} and % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa0aaaeaace% WG1bGbauaaceWG2bGbauaaaaaaaa!380A!\[\overline {u'v'} \] for the y-component, where and are the slopes of the -surfaces in the x- and y-directions, respectively. Further, a few numerical simulations of the sea-breeze over topography are carried out with and without the correction terms. It is shown that when corrections terms are not included the effective smoothing is stronger above the sloping regions and may amount to as high as 50 percent of the convergence with slopes of ~.04. The ìnclusìon of the new terms does not lead to any special computational difficulties and for that reason there is no compelling reason to neglect them, all the more so because, as is shown, the addition of the new terms results in a consistent apportioning of the degree of horizontal diffusion.On leave from CIMMS, Norman, OK.Now visiting Dept. of Met., Helsinki, Finland.  相似文献   

Organic geochemistry and pore water chemistry of sediments from Mangrove Lake,Bermuda     

Patrick G. Hatcher  Bernd R.T. Simoneit  Fred T. Mackenzie  A.Conrad Neumann  Donald C. Thorstenson  Sol M. Gerchakov 《Organic Geochemistry》1982,4(2):93-112

Mangrove Lake, Bermuda, is a small coastal, brackish-water lake that has accumulated 14 m of banded, gelatinous, sapropelic sediments in less than 10⁴ yr. Stratigraphic evidence indicates that Mangrove Lake's sedimentary environment has undergone three major depositional changes (peat, freshwater gel, brackish-water gel) as a result of sea level changes. The deposits were examined geochemically in an effort to delineate sedimentological and diagenetic changes. Gas and pore water studies include measurements of sulfides, ammonia, methane, nitrogen gas, calcium, magnesium, chloride, alkalinity, and pH. Results indicate that sulfate reduction is complete, and some evidence is presented for bacterial denitrification and metal sulfide precipitation. The organic-rich sapropel is predominantly algal in origin, composed mostly of carbohydrates and insoluble macromolecular organic matter called humin with minor amounts of proteins, lipids, and humic acids. Carbohydrates and proteins undergo hydrolysis with depth in the marine sapropel but tend to be preserved in the freshwater sapropel. The humin, which has a predominantly aliphatic structure, increases linearly with depth and composes the greatest fraction of the organic matter. Humic acids are minor components and are more like polysaccharides than typical marine humic acids. Fatty acid distributions reveal that the lipids are of an algal and/or terrestrial plant source. Normal alkanes with a total concentration of 75 ppm exhibit two distribution maxima. One is centered about n-C₂₂ with no odd/even predominance, suggestive of a degraded algal source. The other is centered at n-C₃₁ with a distinct odd/even predominance indicative of a vascular plant origin. Stratigraphic changes in the sediment correlate to observed changes in the gas and pore water chemistry and the organic geochemistry.  相似文献   

Dissolution of secondary copper sulphides using complex-forming agents (EDTA,EDA). Part I: Covellite dissolution in EDTA and EDA     

J. Tomásek  L. Neumann 《International Journal of Mineral Processing》1982,9(1):23-40

Problems of dissolution of the so-called secondary copper sulphides are very important for dynamic as well as percolation leaching of ores. This paper deals with dissolution kinetics of sulphides in an alkaline medium, using complex-forming agents in connection with possibility to leach basic, partially oxidized ores. Natural minerals and their polydispersions were investigated and the so-called geometrical model was used for evaluation. Basic dependences of the dissolution rate on the reagent concentration and pH value of the leaching solution were found and an attempt at their mathematical expression and physical interpretation was made. The first part of this work refers to the systems of covellite-ethylene diamine tetra-acetic acid (EDTA) and covellite-ethylene diamine (EDA). The established dependences are not only of theoretical but also of practical importance.  相似文献   

Dissolution of secondary copper sulphides using complex-forming agents (EDTA,EDA). Part II: Chalcocite dissolution in EDTA and EDA     

J. Tomášek  L. Neumann 《International Journal of Mineral Processing》1982,9(1):41-57

This work is immediate continuation of Part I, using an identical method and evaluation for kinetic studies. The systems chalcocite-ethylene diamine tetra-acetic acid and chalcocite-ethylene diamine were studied. It was necessary to refine the geometrical model method for chalcocite in order to establish dissolution kinetics of polydispersions. This work confirms that chalcocite leaching proceeds through covellite even in the medium of complex-forming agents and kinetic equations for both leaching stages were evaluated with an attempt at physical interpretation.  相似文献   

The rare alkalies in hydrothermal alteration at Wairakei and Broadlands,geothermal fields,N.Z.     

Reiner Goguel 《Geochimica et cosmochimica acta》1983,47(3):429-437

Drillcores and waters from Wairakei and Broadlands geothermal areas New Zealand have been analyzed for Li, Rb, Cs, Na, K, Mg, Ca, Al, Ti, Mn, and Be. The drillcores were altered to various degrees at temperatures below 300°C in slightly alkaline chloride water, probably derived from rock-water interaction in untapped horizons at higher temperature. It changes its composition as it leaches Ca and Na from the rock and adds K, Rb, Cs and Li. Evaluation of these changes in relation to the dimensions of the altered zone under observation suggests that a high mass ratio of water to rock (e.g., 100) and a period of up to 1 million years are responsible for the present stage of alteration.Increase of K and Rb in the altered rocks is a result of the formation of abundant adularia in addition to illite. The $\text{K}\text{Rb}$ ratio of the rock decreases during alteration but remains higher than that of the fluid. Only clay materials and zeolites that preferentially absorb Rb give slightly lower $\text{K}\text{Rb}$ ratios than the fluid.The mineral phases responsible for the uptake of lithium during alteration are chlorite (300 ppm Li) and quartz (up to 430 ppm Li). Li uptake in quartz is considered to be the mechanism by which Al-rich quartz crystallises from alumino-silicates. $\text{Li}\text{Al}$ atomic ratios of 0.3–0.57 and Al concentrations up to 3000 ppm have been observed.Relatively small concentrations of Cs are found in potassic minerals (e.g. 10 ppm Cs in adularia, 44 ppm Cs in illite). However, 240 ppm Cs are found in wairakite from Wairakei equilibrated at 235°C. Lower equilibration temperatures may lead to higher cesium concentrations. This effect, in conjunction with a more concentrated hydrothermal fluid, could explain a content of 4500 ppm Cs in wairakite extracted from a drillcore taken in the El-Tatio geothermal field in Chile.  相似文献   

The Skien lavas, Oslo Rift: petrological disequilibrium and geochemical evolution     

E. Dunworth  E.-R. Neumann  J. Rosenbaum 《Contributions to Mineralogy and Petrology》2001,140(6):701-719

The Skien lavas, which form the earliest phase of basaltic magmatism within the Permo-Carboniferous Oslo Rift, contain multiple generations of clinopyroxene which exhibit strong petrological and geochemical disequilibrium. Three principal core compositions have been identified: (1) low-jadeite, high-Mg, Cr-diopside cores (CrMgDi) with strongly depleted trace-element signatures, which are believed to be xenocrystic in origin; (2) Mg-rich, Cr-poor diopside cores (MgDi) with moderately depleted trace-element signatures which probably represent early cognate growth; and (3) more dominant, low-Mg, phenocrystic diopside cores (PhenDi). Several samples contain CrMgDi or MgDi cores which have been subjected to resorption and partial re-equilibration with their host melts, indicative of extensive disequilibrium and magma mixing. These three core types are overgrown by trace-element-enriched Ti-augite, which also forms megacrysts and late-stage lava groundmass. Calculated Ti-augite/melt partition coefficients show clinopyroxene compatibility of the M-HREE, Zr, Hf and Y. The LILE, Sr, and Nb remain incompatible. )Sr₃₀₀ and )Nd₃₀₀ of Ti-augite overgrowths, phenocrystic diopside, and MgDi diopside cores show that intrasample isotopic disequilibrium existed when the host basalts were erupted. All epsilon values lie within the range of data previously published for the Skien lavas. Detailed examination of the chemical, isotopic and textural disequilibrium features seen in these lavas has enabled us to place constraints upon the magmatic evolution of this basalt suite, ranging from xenocryst incorporation to cognate multistage pyroxene growth, as well as identifying clear evidence of magma mixing and possible crustal contamination.  相似文献   

The mesoscale variability of nutrients and plankton as seen in a coupled model     

Wolfgang Fennel  Thomas Neumann 《Ocean Dynamics》1996,48(1):49-71

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Data for high wave conditions observed by the OWS “Weather Reporter” in December 1959     

C. L. Bretschneider  H. L. Crutcher  J. Darbyshire  G. Neumann  W. J. Pierson  H. Walden  B. W. Wilson 《Ocean Dynamics》1962,15(6):243-255

  相似文献