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1.
Stream pollution by industrial wastes is posing a problem in Uttar Pradesh. In the present investigations an attempt has been made to study the ecological features of a section of the Kalinadi so as to find out the cumulative or detrimental effect of pollution on fish and fisheries by the effluent discharge of sugar factory and distillery wastes near Mansurpur (District Muzaffarnagar), U. P. This paper is part I of the project. The liquid wastes produced by the sugar factory vary from 66 × 106 to 88 × 106 litres/day excluding condenser water and contain variable quantities of cane fibres, cellulose, lime, waxes, fermented sugar juice, mollasses, and some quantities of sulphate, phosphate, and nitrogen, the oxygen being nil with high values of B. O. D. and C. O. D. The liquid waste from the distillery is called spent wash. The spent wash (62 × 104 litres/day) is highly coloured and acidic (pH 4.3 … 2.9). The B. O. D. and C. O. D. values were very high in the order of 28,526 mg/1 … 45,146 mg/1 and 52,516 mg/1 to 66,862 mg/1. Thus total waste of about 17.3 × 106 litres with no oxygen and high B. O. D. (9,600 mg/1 … 10,116 mg/1) is let off into the Kalinadi. Hydrometric observations on the Kalinadi show that the pollutional hazard is appreciable during the low flow period of the river. The wastes affect the river in a number of ways:
- - The deposition of cellulose fibres, organic and inorganic matter affects the substratum adversely. The blackish brown colour of the wastes affects the light penetration by limiting the growth of phytoplankton.
- - There appears to be no potential danger to the river from the electrolyte pollution as the specific conductivity lies below limiting values.
- - Changes in pH in river water due to the acidic nature of the wastes do not affect directly the fauna and flora, but the acidic condition becomes lethal in the presence of low oxygen and high temperature values.
- - The high load of organic matter present in the wastes draws heavily on the oxygen budget of the river and adversely changes the water and bottom quality of the river for a stretch of 10 km, which adversely affects the environmental condition of both fish and fish food.
- - The presence of sulphuric acid in distillery waste and hydrogen sulphide in river water is toxic to fish and fish food.
- - The decomposition of organic matter in an anaerobic condition and in another favourable environment, as with a low redox potential, the presence of sufficient organic matter and a constant supply of sulphur-reducing bacteria, produces more hydrogen sulphide which may be detrimental or sublethal in the presence of a low oxygen saturation and high temperature.
- - The oxygen level increases at each succeeding station through reaeration and dilution with the lowering of B. O. D. and C. O. D. The oxygen-sag curve is like a typical spoon with handle-shape.
2.
In laboratory experiments the adsorption of eleven different organic substances in water is individually tested in the range of concentration of 0.2… 5.0 mg/l on EP 60 and EP 61 (styrene-divinylbenzene, non-polar) and EP 62 and Y 59 (acrylic-acid-ester-divinylbenzene, polar). In batch experiments the elimination at 1… 2 g/l adsorber quantity was 35… 80%, strongly dissociated anionic substances as benzoic acid being adsorbed only to a low degree and weakly cationic and undissociated substances being adsorbed well. Within a homologous series adsorption increases with the molar mass until the pore diameter will become too small for the taking up of substances. Under dynamic conditions (filtration technology) an elimination of 90… 100% can be expected. As a whole, the adsorption on activated carbon was better in all cases than the adsorption on the polymers. The desorption for the regeneration of the polymers is the more difficult the better the substance contained is adsorbed. By repeated loading and regeneration only a slight influence on the adsorption and desorption of a substance was found. 相似文献
3.
A. Lawerenz 《洁净——土壤、空气、水》1983,11(3):259-268
The river with a catchment of 5,400 km2 is investigated over a length of 230 km at seven stations for the total concentration of six polycyclic aromatic hydrocarbons (PAH) and the total of three carcinogenic polycyclic substances (CPS) in the water by means of thin-layer chromatography. The maximum load occurs in the lower course downstream of large industrial wastewater introduction points with 5.1 μg/l polycyclic aromatic hydrocarbons, whereas in the upper course the maxima are at 2 … 3 μg/l polycyclic aromatic hydrocarbons for a mainly municipal pollution. The average daily load increases from 0.146 kg/d PAH and 0.048 kg/d CPS to 4.168 and 1.401 kg/d, respectively. In the flowing water there cannot be observed any self-purification concerning these substances, by an interconnected storage reservoir seston is reduced and thus also the PAC-concentrations are reduced by 50 … 60%. The PAH-concentration shows a significant positive correlation with the COD-Mn and the ammonium concentration. There is also a good agreement between the concentrations measured and the concentrations calculated from the wastewater load in the longitudinal section of the river. 相似文献
4.
Fish were kept in non-toxic water or at 0.5, 0.25 and 0.125 of the LC50,96h of the ten-side or insecticide for 24 h and fed with toxified and non-toxified feed. Toxified feed in normal water resulted in a maximum feed intake, while normal feed in toxified water resulted in a minimum one. In each case, the feed intake was lower compared with the control, and the feed intake was inversely proportional to the toxicant concentration. In a simple respirometer the oxygen consumption in mg · kg?1 · h?1 was tested for 1, 2, 4, 6, 8, 10, 12, 24, 36, 48, 60, 72, 84 and 96 h of exposure to 1.5, 1.0 and 0.5 of the LC50,96h of both substances. It was a flow device which was closed only for measurement for one hour. 1.5 LC50 Aldrin causes a continuous reduction of respiration until death. The same effect occurred with Cl. batrachus for 1.5 LC50 of the tenside, whereas with C. mrigala death was caused by a pronounced increase of respiration. In all other cases, after a phase of sensitization for 4 … 8 h respiration increased considerably to more than 300% of the control, which was followed after 12 … 24 h by acclimatization to normal respiration values. 相似文献
5.
There is determined the LC50 for 24 … 96 h of phenol, 2,4-dinitrophenol and pentachlorophenol as sodium salt by static assay at water temperatures of 16, 23 and 36°C. In addition, the combinations of the three substances were tested in the same way. With decreasing temperature, the toxicity of the individual substances decreased by 6.5 … 22%, that of the mixtures by 10 … 87%; with rising temperature, the toxicity increased by 38 … 747% and 75 … 744%, respectively. The safety limits at 23°C lie between 0.3 μg/l for a synergistically acting mixture and 0.9 mg/l for an antagonistically acting one; for the individual substances this range is 3.5 μg/l to 0.5 mg/l. 相似文献
6.
The role of the benthic ciliofauna of the Tsibulnik bay of the Kremenchug reservoir in the comsumption of the primary production of phytomicrobenthos and the destruction of organic Substances is shown. In July all over the buy ciliates had consumed 41 % of the benthic primary production. During the process, consumption rates had reached 1.34 kJ/m2 d on seperate sections of the bottom. Sufficiently high is the role of these protists in the destruction of organic substances. They had destroyed 1.4… 1.5% of the whole mineralised organic substances in summer and 10… 11% in autumn. The authors made a conclusion on the importance of the benthic ciliofauna in the transformation of organic substances in an eutrophic bay. 相似文献
7.
Hugh P. Taylor 《Earth and Planetary Science Letters》1978,38(1):177-210
The primary δD values of the biotites and hornblendes in granitic batholiths are remarkably constant at about ?50 to ?85, identical to the values in regional metamorphic rocks, marine sediments and greenstones, and most weathering products in temperate climates. Therefore the primary water in these igneous rocks is probably not “juvenile”, but is ultimately derived by dehydration and/or partial melting of the lower crust or subducted lithosphere. Most granitic rocks have δ18O = +7.0 to +10.0, probably indicating significant involvement of high-18O metasedimentary or altered volcanic rocks in the melting process; such an origin is demanded for many other granodiorites and tonalites that have δ18O = +10 to +13. Gigantic meteoric-hydrothermal convective circulation systems were established in the epizonal portions of all batholiths, locally producing very low δ18O values (particularly in feldspars) during subsolidus exchange. Some granitic plutons in such environments also were emplaced as low-18O magmas probably formed by melting or assimilation of hydrothermally altered roof rocks. However, the water/rock ratios were typically low enough that over wide areas the only evidence for meteoric water exchange in the batholiths is given by low D/H ratios (δD as low as ?180); for example, because of latitudinal isotopic variations in meteoric waters, as one moves north through the Cordilleran batholiths of western North America an increasingly higher proportion of the granitic rocks have δD values lower than ?120. The lowering of δD values commonly correlates with re-setting of K-Ar ages, and in the Idaho batholith two broad zones (10,000 km2) can be defined where δD biotite <?100 and K-Ar “ages” have all been re-set to values less than 60 m.y., suggesting that the Ar loss was caused by the meteoric-hydrothermal circulation systems. In certain Precambrian batholiths, a much different type of very low-temperature, regional alteration by surface-derived waters took place over an extended period long after emplacement, producing “brick-red” feldspars and markedly discordant Rb-Sr isochron “ages”. 相似文献
8.
Formation of Artefacts and its Suppression during the Determination of Volatile Halogenated Hydrocarbons in Water by Means of Headspace Gas Chromatography under the Standard Conditions of DIN 38407-F5. Part I: Formation of Dehydrohalogenation Products from Saturated Halogenated Hydrocarbons Under the conditions recommended by DIN 38407-F5 for the headspace gas-chromatographic determination of volatile halogenated organic substances in water (equilibration at 60…80°C for a least 60 min) several halocarbons are degraded by dehydrohalogenation resulting in the formation of unsaturated artefacts with one halogen atom less. Thus pentachloroethane and 1,1,2,2-tetrachloroethane are decomposed to form tetrachloroethylene and trichloroethylene, respectively. This leads to low results of the analytes and to false-positive detection of the reaction products. The unwanted degradation reactions can be reduced by decreasing the temperature and duration of equilibration, and they are completely suppressed by acidification of the samples. 相似文献
9.
The acute static bioassays with heavy metals at 13 ± 1.5 °C in hard water (total hardness = 240 ppm as CaCO3) were conducted in the laboratory with Daphnia magna. The 48 hr LC values and their 95 per dent confidence limits in ppm of metal were: 0.0038 (0.0027… 0.0053) for Hg; 0.015 (0.009… 0.026) for Ag; 0.1 (0.063… 0.16) for Cu; 0.69 (0.48… 1.0) for Zn; 1.52 (1.01… 2.28) for Co; 1.8 (1.16… 2.70) for Cr; 1.5 (1.07… 2.1) for Cd; 2,63 (1.7… 4.08) for Pb; 7.3 (5.49… 9.71) for Ni and 19.5 (13.45… 28.3) for Sn. At the close of 24 h of exposure Zn and Cd solutions showed milky white precipitation. The order of toxicity of heavy metals in this model was: Hg>Ag>Cu>Zn>Cd>Co>Cr>Pb>Ni>Sn. Comparison of D. magna and mouse LC50 data showed that Daphnia were sensitive at 1/2710, 1/83, 1/123 and 1/5.5, the LC50 values of Hg, Cu and Zn, respectively. Toxicity test with D. magna is simple, requiring less space, time, facilities, acclimatization time and equipment. Furthermore, Daphnia is more functional, reliable and gives reproducible results. Based on this data we believe the Daphnia magna model can be used as a model to study heavy metal toxicity. 相似文献
10.
Jan Kocum Filip Oulehle Bohumír Janský František Bůzek Jakub Hruška Lukáš Vlček 《水文科学杂志》2013,58(14):2579-2589
ABSTRACTA geochemical approach using stable oxygen isotopes was used to understand streamflow generation processes in the highly peaty catchment of the Rokytka Brook in the headwaters of the Vltava River, Czech Republic. The contribution of water from peat bog areas to the total surface runoff was assessed using a hydrological time series, as well as geochemical, hydrochemical and isotope-hydrological approaches for unit hydrogram separation by means of anion deficiency. Using data from the hydrological year 2008, the role of an existing peat bog in the runoff formation dynamics of the Rokytka Brook catchment was determined, and the hydrological cycle was described and assessed using stable 18O/16O isotopes. The research findings strongly support the fact that peatland areas within the studied catchment do not significantly communicate hydraulically with surface streams, and their hydrological function in this region is insignificant.
Editor M. C. Acreman; Associate editor not assigned 相似文献
11.
《Continental Shelf Research》2007,27(3-4):338-358
Thirty-three surface sediment samples from cross-shelf transects on the northern Adriatic shelf were collected in December 2000, soon after a 100-yr flood of the Po River, in order to determine the distribution of organic carbon (OC) along the main sediment dispersal system. To evaluate the temporal variability, stations were re-occupied eight times at seasonal intervals until June 2003. Downcore sediment profiles from two sites characterized by high flood deposit thicknesses were also examined to assess the OC variability within the flood layer. In December 2000, the highest contents of OC (up to 1.24 wt%) were measured in front of the main distributary mouths (Pila, Tolle and Gnocca-Goro) where the greatest thicknesses of the flood deposit were recorded. However, the influence of the Po di Gnocca-Goro sediment supply on the OC surface distribution declined after ∼1.5 years from the fall-2000 river flood, probably because these mouths are less active when the water discharge is lower. The δ13C of organic matter was used to trace the dispersal of fluvial OC on the continental shelf. The δ13C values ranged from −25.9‰ to −23.1‰. The fraction of fluvially derived organic particles decreased with increasing water depth according to a radial dispersal pattern around the Po River delta. This pattern persisted in all cruises. δ13C values increased progressively until April 2002, suggesting an increasing marine contribution to the OC content but decreased again following a second minor flood event in November 2002. The molar C/N ratio was on average 10.0±1.6, with slightly lower values in southern and central areas.Assuming contributions from three OC end-members (terrestrial, riverine and marine), a mixing model based on δ13C and the ratio of N to C (statistically more robust than C/N; Goñi, M.A., Teixeir, M.J., Perkley, D.W., 2003. Sources and distribution of organic matter in a river-dominated estuary (Winyah Bay, SC, USA). Estuarine, Coastal and Shelf Science 57, 1023–1048) was applied in order to quantitatively assess the OC sources for Po shelf sediments. δ13C is significantly and positively correlated with the marine OC fraction. The terrestrial fraction is inversely correlated with N/C, while the riverine fraction is positively correlated with N/C. The terrestrial OC source was the most abundant end-member (>70%) showing only little temporal variability regardless of the Po River water discharge. Temporal and spatial changes in OC composition suggest that: (a) the Po River prodelta is always dominated from terrestrial OC input; (b) the Po della Pila supplies most terrestrial OC, whilst other tributaries (e.g., Po di Gnocca-Goro) are secondary sources. However, these mouths are as important as the Po della Pila in affecting the riverine OC signature; (c) offshore, biological primary production raises the marine OC contribution.At two sites on the Po River prodelta, the 2000-flood deposit shows slight but consistent compositional changes of organic matter (N/C and δ13C) which can help to recognize other flood events in the sedimentary record. The OC budget for the 2000-flood deposit accounts for a terrestrial+riverine OC supply of 68–162 Gg (109 g) against an OC deposition of 106–162 Gg (excluding the marine fraction), which implies a rapid and efficient sedimentation of the flood material, and scarce or negligible export out the study area. Flood events may thus enhance terrestrial carbon burial, whereas marine carbon arrives more slowly and may be largely mineralized at the sediment–water interface. 相似文献
12.
Increasing groundwater salinity and depletion of the aquifers are major concerns in the UAE. Isotopes of oxygen, hydrogen, and carbon concentrations in groundwater were used to estimate evaporation loss using the isotopes of oxygen and hydrogen, and using a carbon isotope to trace inorganic carbon cycling in two main aquifers in the eastern part of the United Arab Emirates. The δD‐δ18O of groundwater samples plotted on a line given by: δD = 4 δ18O + 4 ·4 (r2 = 0·4). In comparison, the local meteoric water line (LMWL) has been defined by the line: δD = 8 δ18O + 15. In order to better understand the system investigated, samples were separated into two groups based on the δD‐δ18O relationship. These are (1) samples that plot above the LMWL (δD = 6·1 δ18O + 12·4, r2 = 0·8) and which are located predominantly in the north of the study area, and (2) samples that plot below the LMWL (δD = 5·6 δ18O + 6·2, r2 = 0·8) and which are mostly distributed in the south. Slopes for both the groups are similar and lower than that for LMWL indicating potential evaporation of recharging water. However, the y‐intercept, which differs between the two groups, suggests evaporation of return flow and evapotranspiration in the unsaturated zone to be more significant in the south. This is attributed to intense agricultural activities in the region. Samples from the eastern Gravel Plain aquifer have δ13C and dissolved inorganic carbon (DIC) values in the range from ? 10 to 17‰, and 12–100 mg C/l, respectively, while the range for those from the Ophiolite aquifer is from ? 11 to ? 16.4‰, and 16–114 mg C/l respectively. This suggests the control of C‐3 and C‐4 plants on DIC formation, an observation supported by the range δ13C of soil organic matter (from ? 18·5 to ? 22·1‰.) Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
13.
In the present work the kinetics and the feasibility of batch anaerobic filter operations for the treatment of beet molasses distillery slops have been investigated. Up to 50% of the influent COD up to 25 g/l are removed after 5… 10 h and up to 80% after 24… 40 h treating time. Highest removal rates were obtained for 50% removal and influent COD concentration ≧13 kg. m?3. The highest methane productivity was observed in the same range of COD influent concentration during the first 10 hours (initial velocity) of the treatment. The benefits of the anaerobic treatment of waste water applying systems with biomass retention are discussed. 相似文献
14.
Rain and surface water samples from Southern Germany were investigated from 1991 to 1995 for terbuthylazine and one of its major metabolites, deethylterbuthylazine. The concentrations observed were compared to the concentrations found for atrazine and deethylatrazine in the same water samples. Concentrations ranged from < 0.02 μg/L to 0.7 μg/L for terbuthylazine and from < 0.02 μg/L to 0.6 μg/L for deethylterbuthylazine, compared to concentrations of < 0.02 μg/L to 3 μg/L and < 0.02 μg/L to 0.5 μg/L for atrazine and deethylatrazine, respectively. The ratios of metabolite concentrations to parent compound concentrations were calculated for deethylterbuthylazine to terbuthylazine (DTR) and deethylatrazine to atrazine (DAR). In rain water, DTR of 0.8…3.0 and DAR of 0.3… 1.9 were determined with mean values of 0.9… 1.7 for DTR and 0.6…0.9 for DAR in the different years. The ratios increased during summer periods. The highest ratios were observed in samples from forest stands, showing that degradation of the herbicide has occurred during transport between the source and the sampling site. The DTR in rain water were about 50… 100% higher than the DAR. This indicates a higher degradation rate of terbuthylazine during atmospheric transport. In surface water, DTR of 0.3… 1.2 with mean values of 0.5…0.8 and DAR of 0.2…2.2 with mean values of 0.2… 1.3 were observed. The ratios increased from June to September. 相似文献
15.
Wofatit Y 77 is presented as a novel non-ionogenic hydrophilic adsorbing polymer having a large specific BET surface (800 … 1500 m2/g) and a narrow pore size distribution. By the example of selected aromatic compounds with different molar masses it is shown on the basis of the adsorption of individual substances that the adsorption capacity primarily depends on the molecular size and not on the specific inner surface of the adsorber polymer. Favourable possibilities are derived from that for. 相似文献
16.
The method is based on the determination of the number of the nonmotile sperms and/or the lethally damaged sperms with the aid of the fluorescent dye primuline. Incubation takes place at a suspension density of 10.000/mm3… 38.000/mm3, at 40°C or 46 °C for 15… 60 min. During the test with sublimate the loss of motility amounts to 55% at 4 mg/l Hg2+, the LC50 is 7.3 mg/l Hg2+. Phenyl-mercuric acetate causes the total loss of motility with 20 mg/l, the LC50 is above 168 mg/l (equivalent to 100 mg/l Hg2+). The LC50 of sodiumpentadecylmonosulphonate and dodecylpyridinchloride are 11.6 and 15.8 mg/l, resp. Filtrates of blooming of cyanophyceae on Baltic, having been digested by repeated freezing and thawing, with 1.5… 6.4 g/l dry matter showed motility losses of 30… 100 % for Nodularia spumigena, whereas no significant effect was produced by a filtrate of Microcystis aeruginosa with 28.2 g/l dry matter as well as water-blooming of Nodularia spumigena from the Small Jasmund Bodden. 相似文献
17.
The long term systematic investigations of ion composition components (bicarbonates, chlorides, sulphates, magnesium, calcium, sodium, potassium) and trophic status components (suspension, chlorophyll-a, mineral and organic forms phosphorus and nitrogen, carbon, silica) of water from the lake proper, its tributaries and atmospheric precipitation, which make up the main share of substance supply in to the lake, as well as the Angara river, being the source of substance discharge allowed the lake recent state to be evaluated in terms of both chemical pollution and possible eutrophication of its water. The similar (in terms of river runojf) periods of 50-ies and 80-ies have been compared. It was revealed that as a result of industrial activity 409 thousand tons of mineral substances (27.2 thousand tons of chlorides, 162 thousand tons of sulphates and over 200 thousand tons of organic substances) are supplied in the lake annually. The supply of substances of the anthropogenic origin is higher for the South Baikal than that for the North and Middle Baikal (the sum of mineral substances in 3.6 times; sulphates in 5 times, organic substances, including hydrocarbons in 7 times).The absence of abundant phytoplankton in the period studied when the ratio of silica to phosphorus is optimum (over 100), as well as a revers correlation between winter nitrogen content and spring of chlorophyll-a concentration in the Baikal water and revers dependence between the suspension and chlorophyll-a along the Selenga river valley lead to the conclusion that Baikal water contains toxicants. It is verified by the presence of polychlorbiphenyls (PCB), poly-chlordibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) for the whole food web with the maximum PCDD/PCDF (TEQ to 175 P g · g-1) concentration in the seal blubber. The levels are comparable with those reported for ringed seal (phoca hispida), living in the Baltic sea and Bar-row Strait Inlet in the Canadian Arctic. 相似文献
18.
By diluting a boggy water there is produced water with a COD-Mn of 3.4 … 10.6 mg/l O2 which is due only to humic substances. The water is mixed with 2.5 … 12.9 mg/l Cl2 at pH-values of 5.2 … 8.5 and incubated for 24 h at 20°C. CHCl3 concentrations of 38 … 480 μg/l were found by the subsequent gas-chromatographic determination. The production of chloroform can be calculated by means of a quadratic polynomial in dependence on COD-Mn, chlorine concentration and pH-value. 相似文献
19.
From precipitation to runoff: stable isotopic fractionation effect of glacier melting on a catchment scale 
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下载免费PDF全文 Stable isotope variability and fractionation associated with transformation of precipitation/accumulation to firn to glacial river water is critical in a variety of climatic, hydrological and paleoenvironmental studies. This paper documents the modification of stable isotopes in water from precipitation to glacier runoff in an alpine catchment located in the central Tibetan Plateau. Isotopic changes are observed by sampling firnpack profiles, glacier surface snow/ice, meltwater on the glacier surface and catchment river water at different times during a melt season. Results show the isotopic fractionation effects associated with glacier melt processes. The slope of the δD‐δ18O regression line and the deuterium excess values decreased from the initial precipitation to the melt‐impacted firnpack (slope from 9.3 to 8.5 and average d‐excess from 13.4‰ to 7.4‰). The slope of the δD‐δ18O line further decreased to 7.6 for the glacier runoff water. The glacier surface snow/ice from different locations, which produces the main runoff, had the same δD‐δ18O line slope but lower deuterium excess (by 3.9‰) compared to values observed in the firnpack profile during the melt season. The δD‐δ18O regression line for the river water exhibited a lower slope compared to the surface snow/ice samples, although they were closely located on the δD‐δ18O plot. Isotope values for the river and glacier surface meltwater showed little scatter around the δD‐δ18O regression line, although the samples were from different glaciers and were collected on different days. Results indicate a high consistency of isotopic fractionation in the δD‐δ18O relationships, as well as a general consistency and temporal covariation of meltwater isotope values at the catchment scale. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
20.
Secondary calcite residing in open cavities in the unsaturated zone of Yucca Mountain has long been interpreted as the result of downward infiltration of meteoric water through open fractures. In order to obtain information on the isotopic composition (δD and δ18O) of the mineral-forming water we studied fluid inclusions from this calcite. Water was extracted from inclusions by heated crushing and the δD values were measured using a continuous-flow isotope-ratio mass spectrometry method. The δ18O values were calculated from the δ18O values of the host calcite assuming isotopic equilibrium at the temperature of formation determined by fluid-inclusion microthermometry.The δD values measured in all samples range between ? 110 and ? 90‰, similar to Holocene meteoric water. Coupled δ18O–δD values plot significantly, 2 to 8‰, to the right of the meteoric water line. Among the various processes operating at the topographic surface and/or in the unsaturated zone only two processes, evaporation and water–rock exchange, could alter the isotope composition of percolating water. Our analysis indicates, however, that none of these processes could produce the observed large positive δ18O-shifts. The latter require isotopic interaction between mineral-forming fluid and host rock at elevated temperature (>100 °C), which is only possible in the deep-seated hydrothermal environment. The stable isotope data are difficult to reconcile with a meteoric origin of the water from which the secondary minerals at Yucca Mountain precipitated; instead they point to the deep-seated provenance of the mineral-forming waters and their introduction into the unsaturated zone from below, i.e. a hypogene origin. 相似文献