${}^3\text{He}{}^4\text{He}$ ratio,noble gas abundance and K-Ar dating of diamonds—An attempt to search for the records of early terrestrial history     

M. Ozima  S. Zashu  O. Nitoh 《Geochimica et cosmochimica acta》1983,47(12):2217-2224

The ${}^3\text{He}{}^4\text{He}$ ratios measured in 27 Southern Africa diamond stones, four from Premier Mine and the rest of unidentified origin, range from 4.2 × 10^?8 to 3.2 × 10^?4, with three stones above 1 × 10^?4. We conclude that the initial helium isotopic ratio (${}^3\text{He}{}^4\text{He)}{}_0$ in the earth was significantly higher than that of the planetary helium-A (${}^3\text{He}{}^4\text{He = 1.42 × 10}{}^{\mathrm{?4}}$), but close to the solar helium (${}^3\text{He}{}^4\text{He ? 4 × 10}{}^{\mathrm{?4}}$).The apparent K-Ar ages for the twelve diamonds of unidentified origin show enormously old age, indicating excess argon-40. ${}^3\text{He}{}^4\text{He}$ evolution in diamonds suggests that the diamonds with the high ${}^3\text{He}{}^4\text{He}$ ratio (>2 × 10^?4) may be as old as the earth.Noble gas elemental abundance in the diamonds relative to the air noble gas abundance shows monotonie decrease with a decreasing mass number.This paper discusses the implications of these observations on the early solar system and the origin of diamonds.  相似文献   

Light hydrocarbons in Red Sea brines and sediments     

Roger A. Burke  James M. Brooks  William M. Sackett 《Geochimica et cosmochimica acta》1981,45(5):627-634

Light hydrocarbon (C₁-C₃) concentrations in the water from four Red Sea brine basins (Atlantis II, Suakin, Nereus and Valdivia Deeps) and in sediment pore waters from two of these areas (Atlantis II and Suakin Deeps) are reported. The hydrocarbon gases in the Suakin Deep brine (T = ~ 25°C, $\text{Cl}{}^{\mathrm{?}}\text{= ~ 85‰}$, $\text{CH}{}_4\text{=}\text{~ 71}\text{1}$) are apparently of biogenic origin as evidenced by $\text{C}{}_1\text{(C}{}_2\text{+ C}{}_3$) ratios of ~ 1000. Methane concentrations (6–8 μl/l) in Suakin Deep sediments are nearly equal to those in the brine, suggesting sedimentary interstitial waters may be the source of the brine and associated methane.The Atlantis II Deep has two brine layers with significantly different light hydrocarbon concentrations indicating separate sources. The upper brine (T = ~ 50°C, $\text{Cl}{}^{\mathrm{?}}\text{= ~ 73‰}$, CH₄ = ~ 155 μl/l) gas seems to be of biogenic origin [$\text{C}{}_1\text{(C}{}_2\text{+ C}{}_3\text{) = ~1100}$], whereas the lower brine (T = ~ 61°C, $\text{Cl}{}^{\mathrm{?}}\text{= ~ 155‰}$, CH₄ = ~ 120μl/l) gas is apparently of thermogenic origin [$\text{C}{}_1\text{(C}{}_2\text{+ C}{}_3\text{) = ~ 50}$]. The thermogenic gas resulting from thermal cracking of organic matter in the sedimentary column apparently migrates into the basin with the brine, whereas the biogenic gas is produced in situ or at the seawater-brine interface. Methane concentrations in Atlantis II interstitial waters underlying the lower brine are about one half brine concentrations; this difference possibly reflects the known temporal variations of hydrothermal activity in the basin.  相似文献   

Methane anomalies in seawater above the Loihi submarine summit area,Hawaii     

《Geochimica et cosmochimica acta》1987,51(10):2857-2864

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Intensive sampling of noble gases in fluids at Yellowstone: I. Early overview of the data; regional patterns     

B.M. Kennedy  M.A. Lynch  J.H. Reynolds  S.P. Smith 《Geochimica et cosmochimica acta》1985,49(5):1251-1261

The Roving Automated Rare Gas Analysis (RARGA) lab of Berkeley's Physics Department was deployed in Yellowstone National Park for a 19 week period commencing in June, 1983. During this time 66 gas and water samples representing 19 different regions of hydrothermal activity within and around the Yellowstone caldera were analyzed on site. Routinely, the abundances of five stable noble gases and the isotopic compositions of He, Ne, and Ar were determined for each sample. In a few cases the isotopes of Kr and Xe were also determined and found to be of normal atmospheric constitution.Correlated variations in the isotopic compositions of He and Ar can be explained within the precision of the measurements by mixing of only three distinct components. The first component is of magmatic origin and is enriched in the primordial isotope ³He with ${}^3\text{He}{}^4\text{He}\text{≥ 16}$ times the air value. This component also contains radiogenic ⁴⁰Ar and possible ³⁶Ar with ${}^{40}\text{Ar}{}^{36}\text{Ar}\text{≥ 500}$, resulting in a ${}^3\text{He}{}^{36}\text{Ar}$ ratio ≥ 41,000 times the air value. The second component is assumed to be purely radiogenic ⁴He and ⁴⁰Ar (${}^{41}\text{He}{}^{401}\text{Ar}\text{= 4.08 ± .33}$). This component is the probable carrier of observed excesses of ²¹¹Ne, attributed to the α,n reaction on ¹⁸O. Its radiogenic character implies a crustal origin in U. Th, and Krich aquifer rocks. The third component, except for possible mass fractionation, is isotopically indistinguishable from the noble gases in the atmosphere. This component originates largely from infiltrating run-off water saturated with atmospheric gases.In addition to exhibiting nucleogenic ²¹¹Ne, Ne data show anomalies in the ratio ${}^{20}\text{Ne}{}^{20}\text{Ne}$, which correlate roughly with the ${}^{21}\text{Ne}{}^{22}\text{Ne}$ anomalies for the most part, but not as would occur from simple mass fractionation. Some exaggerated instances of the ${}^{20}\text{Ne}{}^{22}\text{Ne}$ anomaly occur which could be explained by combined mass fractionation of Ne and Ar isotopes to a severe degree coupled with remixing with normally isotopic gases. Otherwise exotic processes have to be invoked to explain the ²⁰Ne data.Relative abundances of the non-radiogenic and non-nucleogenic noble gases (²²Ne, ³⁶Ar, ⁸⁴Kr, and ¹³²Xe) are highly variable but strongly correlated. High Xe/Ar ratios are always accompanied by low Ne/ Ar ratios and vice versa. Except for water from the few cold (T < 20°C) springs analyzed, none of the samples have relative abundances consistent with air saturated water and the observed variations are not readily explained by the distillation of air saturated water.In characterizing each area of hydrothermal activity by the highest ${}^3\text{He}{}^4\text{He}$ ratio found for that area, we find that within the caldera this parameter is somewhat uniform at ~7 ± 1 times the air value. There are exceptions, most notably at Mud Volcano, an area located along a crest of recent and rapid uplift. Here the maximum ${}^3\text{He}{}^4\text{He}$ ratio is ~ 16 times the air value. Also noteworthy is Gibbon Basin which is in the vicinity of the most recent rhyolitic volcanism and exhibits a ${}^3\text{He}{}^4\text{He}$ ratio ~ 13 times the air value. Immediately outside the caldera the maximum $\text{sol}{}^3\text{He}{}^4\text{He}$ ratio decreases rapidly to values < ~3 times the air value.  相似文献   

Methane-producing bacteria: natural fractionations of the stable carbon isotopes   总被引：1，自引：0，他引：1  

Larry M. Games  J.M. HayesRobert  P. Gunsalus 《Geochimica et cosmochimica acta》1978,42(8):1295-1297

The ${}^{13}\text{C}{}^{12}\text{C}$ fractionation factors ($\text{CO}{}_2\text{CH}{}_4$) for the reduction of CO₂ to CH₄ by pure cultures of methane-producing bacteria are, for Methanosarcina barkeri at 40°C, 1.045 ± 0.002; for Methanobacterium strain M.o.H. at 40°C, 1.061 ± 0.002; and, for Methanobacterium thermoautotrophicum at 65°C, 1.025 ± 0.002. These observations suggest that the acetic acid used by acetate dissimilating bacteria, if they play an important role in natural methane production, must have an intramolecular isotopic fractionation ($\text{CO}{}_2\text{H}\text{CH}{}_3$) approximating the observed $\text{CO}{}_2\text{CH}{}_4$ fractionation.  相似文献   

The geochemical evolution of the Pleistocene Lake Lisan-Dead Sea system     

Amitai Katz  Yehoshua Kolodny  Arie Nissenbaum 《Geochimica et cosmochimica acta》1977,41(11):1609-1626

The geochemical history of Lake Lisan, the Pleistocene precursor of the Dead Sea, has been studied by geological, chemical and isotopic methods.Aragonite laminae from the Lisan Formation yielded (equivalent) Sr/Ca ratios in the range 0.5 × 10^?2?1 × 10^?2, Na/Ca ratios from 3.6 × 10^?3 to 9.2 × 10^?3, $\text{δ}{}^{18}\text{O}{}_{\mathrm{PDB}}$ values between 1.5 and 7%. and $\text{δ}{}^{13}\text{C}{}_{\mathrm{PDB}}$ from ?7.7 to 3.4%..The distribution coefficient of Na⁺ between aragonite and aqueous solutions, $\text{λ}{}^{\mathrm{A}}{}_{\mathrm{Na}}$, is experimentally shown to be very sensitive to salinity and nearly temperature independent. Thus, Na/Ca in aragonite serves as a paleosalinity indicator.Sr/Ca ratios and $\text{δ}{}^{18}\text{O}$ values in aragonite provide good long-term monitors of a lake's evolution. They show Lake Lisan to be well mixed, highly evaporated and saline. Except for a diluted surface layer, the salinity of the lake was half that of the present Dead Sea (15 vs 31%).Lake Lisan evolved from a small, yet deep, hypersaline Dead Sea-like, water body. This initial lake was rapidly filled-up to its highest stand by fresh waters and existed for about 40,000 yr before shrinking back to the present Dead Sea. The chemistry of Lake Lisan at its stable stand represented a material balance between a Jordan-like input, an original large mass of salts and a chemical removal of aragonite. The weighted average depth of Lake Lisan is calculated, on a geochemical basis, to have been at least 400, preferably 600 m.The oxygen isotopic composition of Lake Lisan water, which was higher by at least 3%. than that of the Dead Sea, was probably dictated by a higher rate of evaporation.Na/Ca ratios in aragonite, which correlate well with $\text{δ}{}^{13}\text{C}$ values, but change frequently in time, reflect the existence of a short lived upper water layer of varying salinity in Lake Lisan.  相似文献   

Variability of the He³ and Ne²¹ production rates in ordinary chondrites     

G.F Herzog 《Geochimica et cosmochimica acta》1973,37(9):2125-2133

Al²⁶ and noble gas contents of 6 ordinary chondrites with $\text{He}{}^3\text{Ne}{}^{21}$ ratios above 6.0 or below 4.0 are used to infer the variability of the production rates of He³ and Ne²¹ (P_He³ and P_Ne²¹). The ratio of the observed Al²⁶ content to a calculated, normal value is taken as a measure of the change of P_Ne²¹ from its normal value. The corresponding change in P_He³ is then computed from the observed $\text{He}{}^3\text{Ne}{}^{21}$ ratio and an average value of P_He³.According to these calculations which exclude orbital effects, P_He³ will be near the average value in meteorites with high $\text{He}{}^3\text{Ne}{}^{21}$ ratios, while P_Ne²¹ will be about 30 per cent below normal. In meteorites with low $\text{He}{}^3\text{Ne}{}^{21}$ ratios, P_He³ may be depressed by as much as 25 per cent from normal while P_Ne²¹ may be 15–20 per cent above the average.  相似文献   

Inert gases in a terra sample: measurements in six grain-size fractions and two single particles from Luna 20     

D Heymann  S Lakatos  J.R Walton 《Geochimica et cosmochimica acta》1973,37(4):875-885

The inert gases have been measured in six size fractions covering the range below 500 μm, in a single feldspathic fragment weighing 523 μg, and in an agglutinate particle weighing 465 μg. The two size fractions between 125 and 250 μm as well as 250 and 500 μm were separated into magnetic and non-magnetic portions, which were measured separately. Like the Apollo and Luna 16 fines, the terra fines represented by Luna 20 are very rich in trapped solar-wind gases, but they contain relatively less He⁴ and Ne²⁰, which is revealed by their average $\text{He}{}^4\text{Ne}{}^{20}$ ratio of 35 and $\text{Ne}{}^{20}\text{Ar}{}^{36}$ ratio of 2.9. Obviously the terra materials are less retentive for solar-wind He and Ne than typical mare fines such as 10084. Whether this is due to the relatively small TiO₂ or the relatively large plagioclase content of the former is not resolved. ($\text{Ar}{}^{36}\text{Kr}{}^{84}\text{)}{}_{\mathrm{trapped}}$ and ($\text{Ar}{}^{36}\text{Xe}{}^{132}\text{)}{}_{\mathrm{trapped}}$ ratios are relatively large; the average values are 2800 and 14400, respectively. The apparent Ne²¹ radiation ages of all the size fractions are in the range 209–286 × 10⁶ yr; the average is 260 × 10⁶ yr. This is in the range of values known for the Apollo and Luna 16 fines. The feldspathic fragment has a much greater apparent Ne_c²¹ age of 780 × 10⁶ yr. The Ar⁴⁰-Ar³⁶ systematic reveals the presence of two Ar⁴⁰ components, because Ar⁴⁰ = (1.41 ± 0.076)Ar³⁶ + (0.490 ± 0.130) × 10^?4 (cm³ STP/g). The $\text{Ar}{}^{40}\text{Ar}{}^{36}$ slope of 1.41 is not inconsistent with an origin of the sample from a relatively old terra region.  相似文献   

Rare gases and ³⁶Cl in stony-iron meteorites: cosmogenic elemental production rates,exposure ages,diffusion losses and thermal histories     

F Begemann  H.W Weber  E Vilcsek  H Hintenberger 《Geochimica et cosmochimica acta》1976,40(3):353-368

Metal and silicate portions from 13 mesosiderites, one pallasite, Bencubbin (“unique”) and Udei Station (‘iron with silicate inclusions’) have been analysed for their content of He, Ne and Ar; in most cases ³⁶Cl could be determined as well. ³⁶Cl-³⁶Ar cosmic ray exposure ages fall between 10 and 160 Myr. Half of the metal samples show a deficit of spallogenic ³He (up to 30%) which we ascribe to a loss of tritium. The observed depletion of ³He in the silicates is correlated with their mineralogical composition: feldspar has lost its ³He in all cases, pyroxene definitely in one and possibly in five others, while olivine has been affected in only two meteorites. The thermal histories during their exposure to the cosmic radiation have been different for different meteoroids. Nevertheless, with the exception of Veramin, the data are compatible with the assumption of a continuous diffusion loss during a considerable fraction of the exposure era. For Veramin, however, an episodic event late in the exposure history is required. The exceptionally high ${}^{39}\text{Ar}{}^{36}\text{Cl}$ ratio in the metal, which is due to a high ³⁹Ar activity, indicates that the event occurred during the last 500,000 years or so and resulted in an extremely excentric orbit (large aphelion).Production rates of ^38,39Ar from Ca and ^21,22Ne from Mg are given. The ratio $\text{P}{}^{38}{}_{\mathrm{Ca}}\text{P}{}^{21}{}_{\mathrm{Mg}}$ is close to unity. The ratios $\text{P}{}^{38}{}_{\mathrm{Ca}}\text{P}{}^{38}{}_{\mathrm{Fe}}$ vary between 20 and 50, and are not correlated with the absolute production rate of ³⁸Ar from metal. The ${}^{22}\text{Ne}{}^{21}\text{Ne}$ production ratio from Mg is found to be close to but below unity.Of the mesosiderites only Veramin shows unambiguous evidence for primordial rare gases with larger amounts and a higher ${}^{20}\text{Ne}{}^{36}\text{Ar}$ ratio in the olivine, suggesting in situ fractionation to have at least been partly responsible for the abundance pattern found. Bencubbin contains large amounts of strongly fractionated primordial gases, but again part of the fractionation may have occurred in situ. Udei Station shows an excess of (3.5 ± 0.6) × 10^?10 cm³ STP ¹²⁹Xe/g in the non-magnetic portion.  相似文献   

Complexing of silica by iron(III) in natural waters     

E.J. Reardon 《Chemical Geology》1979,25(4):339-345

Determination of amorphous silica solubility in acidified ferric nitrate solutions confirms the presence of ferric silicate complexing. A dissociation constant for the reaction: of 10^?9.8 ± 0.3 pK units at room temperature (22 ± 3°C) is obtained, in close agreement with reported values at 25°C corrected to zero ionic strength of 10^?9.9 by Weber and Stumm and 10^?9.5 by Olson and O'Melia. Iron-silicate complexing may be of significance to the mobilization of silica in acid waters associated with oxidizing sulphide deposits and coal strip mining and the precipitation of secondary silicate mineral phases.  相似文献   

Variability of the Al²⁶ production rate in ordinary chondrites     

Gregory F Herzog  Philip J Cressy 《Geochimica et cosmochimica acta》1974,38(12):1827-1841

15 ordinary chondrites for which unusually high spallogenic $\text{Ne}{}^{22}\text{Ne}{}^{21}$ or $\text{He}{}^3\text{Ne}{}^{21}$ ratios had been reported and one meteorite with marked shock characteristics were selected in order to investigate the relations between $\text{Ne}{}^{22}\text{Ne}{}^{21}$ ratios, Al²⁶ contents and depth. We report Al²⁶ and K contents of 13 samples from 11 of these and-noble gas contents of 30 samples from all of these stones.A decrease in the Al²⁶ production rate accompanies the increase of $\text{Ne}{}^{22}\text{Ne}{}^{21}$ towards the pre-atmospheric surface: $\text{Al}{}_{\mathrm{obs}}{}^{26}\text{Al}{}_{\mathrm{calc}}{}^{26}\text{= 3.2?2.0}\text{Ne}{}^{22}\text{Ne}{}^{21}$ for $\text{1.08 ≤}\text{Ne}{}^{22}\text{Ne}{}^{21}\text{≤ 1.2}$. Large deviations from this relationship may indicate that a meteorite experienced an abnormal flux of cosmic rays.For $\text{Ne}{}^2\text{Ne}{}^{21}\text{> 1.2}$ this trend continues but the data scatter more, probably because of the steadily increasing influence of pre-atmospheric size. $\text{Ne}{}^{22}\text{Ne}{}^{21}$ ratios increase most rapidly in the outermost few centimeters according both to a plot of $\text{Ne}{}^{22}\text{Ne}{}^{21}$ vs (recovered mass)^{$\text{1}\text{3}$} and to track studies. The increase seems to derive from the enhanced importance of nuclear reactions on Si.$\text{Ne}{}^{22}\text{Ne}{}^{21}\text{< 1.08}$ defines a region where the Al²⁶ production rates are less sensitive to depth and vanish in the limit of large shielding; the weak correlation between $\text{Ne}{}^{22}\text{Ne}{}^{21}$ and Al²⁶ in this region rules out the use of the $\text{Ne}{}^{22}\text{Ne}{}^{21}$ ratio as a basis for a shielding correction to Al²⁶.  相似文献   

Partial molal volume calculations for the dissolution of aged amorphous silica in salt water and seawater at 0–2°C     

Joan D. Willey 《Geochimica et cosmochimica acta》1982,46(7):1307-1310

Measurement of solubility as a function of pressure allows calculation of $\text{3}\text{V}\text{?}{}_1$. Using this experimental approach, the best estimate of $\text{3}\text{V}\text{?}{}_1$ for the dissolution of aged amorphous silica in salt water or seawater at 0–2°C is ?9.9 cm³ mol^?1 (standard error = 0.4 cm³ mol^?1). This gives , which compares well with other published values of .  相似文献   

Isotopic anomalies of noble gases in meteorites and their origins—VI. Presolar components in the Murchison C2 chondrite     

Leo Alaerts  Roy S. Lewis  Jun-ichi Matsuda  Edward Anders 《Geochimica et cosmochimica acta》1980,44(2):189-209

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Helium accumulation in groundwater,I: An evaluation of sources and the continental flux of crustal ⁴He in the Great Artesian Basin,Australia     

T. Torgersen  W.B. Clarke 《Geochimica et cosmochimica acta》1985,49(5):1211-1218

The rate of accumulation of ⁴He in the groundwaters of the J-aquifer of the Great Artesian Basin, Australia has been determined using ¹⁴C and hydrologic ages. For groundwaters less than 50 Kyr in age, the ⁴He accumulation rate is 4.6 × 10^?12 HeAU (where ) in close agreement with in-situ production rate of ⁴He (3.95 × 10^?12 HeAU) based on U and Th concentrations of 1.7 and 6.1, respectively, of the sandstone. For groundwaters older than 100 Kyr, the rate of ⁴He accumulation is 2.91 × 10^?10 HeAU based on hydrologic ages; or 74 × the rate of in-situ production. The rate of ⁴He “production” due to weathering of the aquifer rock is calculated to be ~10^?16 HeAU, indicating that the weathering input of ⁴He is insignificant. If the groundwater of the GAB can be considered as a trap for the total crustal production of ⁴He, the rate of ⁴He accumulation under a steady-state flux is calculated to be 3.02 × 10^?10 HeAU, in agreement with the measured accumulation rate. It is concluded that over long times the ⁴He accumulation rate in groundwater aquifers may be controlled by the whole crust flux of ⁴He.  相似文献   

Distribution,abundance and carbon isotopic composition of gaseous hydrocarbons in Big Soda Lake,Nevada: An alkaline,meromictic lake     

Ronald S. Oremland  David J. Des Marais 《Geochimica et cosmochimica acta》1983,47(12):2107-2114

Distribution and isotopic composition (δ¹³C) of low molecular weight hydrocarbon gases were studied in Big Soda Lake (depth = 64 m), an alkaline, meromictic lake with permanently anoxic bottom waters. Methane increased with depth in the anoxic mixolimnion (depth = 20–35 m), reached uniform concentrations (55 μM/l) in the monimolimnion (35–64 m) and again increased with depth in monimolimnion bottom sediments (>400 μM/kg below 1 m sub-bottom depth). The μ¹³C[CH₄] values in bottom sediment below 1 m sub-bottom depth (<?70 per mil) increased with vertical distance up the core (δ¹³C[CH₄] = ?55 per mil at sediment surface). Monimolimnion δ¹³C[CH₄] values (?55 to ?61 per mil) were greater than most δ¹³C[CH₄] values found in the anoxic mixolimnion (92% of samples had δ¹³C[CH₄] values between ?20 and ?48 per mil). No significant concentrations of ethylene or propylene were found in the lake. However ethane, propane, isobutane and n-butane concentrations all increased with water column depth, with respective maximum concentrations of 260, 80, 23 and 22 nM/l encountered between 50–60 m depth. Concentrations of ethane, propane and butanes decreased with depth in the bottom sediments. Ratios of $\text{CH}{}_4\text{[C}{}_2\text{H}{}_6\text{+ C}{}_3\text{H}{}_8\text{]}$ were high (250–620) in the anoxic mixolimnion, decreased to ~161 in the monimolimnion and increased with depth in the sediment to values as high as 1736. We concluded that methane has a biogenic origin in both the sediments and the anoxic water column and that C₂-C₄ alkanes have biogenic origins in the monimolimnion water and shallow sediments. The changes observed in δ¹³C[CH₄] and $\text{CH}{}_4\text{(C}{}_2\text{H}{}_6\text{+ C}{}_3\text{H}{}_8\text{)}$ with depth in the water column and sediments are probably caused by bacteria] processes. These might include anaerobic methane oxidation and different rates of methanogenesis and C₂ to C₄ alkane production by microorganisms.  相似文献   

Use of Pitzer's equations to determine the media effect on the formation of lead chloro complexes     

Frank.J. Millero  Robert H. Byrne 《Geochimica et cosmochimica acta》1984,48(5):1145-1150

The spectrophotometric measurements of chloro complexes of lead in aqueous HCl, NaCl, MgCl₂ and CaCl₂ solutions at 25°C have been analyzed using Pitzer's specific interaction equations. Parameters for activity coefficients of the complexes PbCl⁺, PbCl₂⁰ and PbCl₃^? have been determined for the various media. Values of $\text{K}{}_1\text{= 30.0 ± 0.6}$, $\text{K}{}_2\text{= 106.7 ± 2.1}$ and $\text{K}{}_3\text{= 73.0 ± 1.5}$ were obtained for the cumulative formation constants. [$\text{Pb}{}^{\mathrm{2+}}\text{+ nCl}{}^{\mathrm{?}}\text{→ PbCl}{}_{\mathrm{n}}{}^{\mathrm{2?n}}\text{)}$]. These values are in reasonable agreement with literature data. The Pitzer parameters for the PbCl ion pairs in various media were used to calculate the speciation of Pb²⁺ in an artificial seawater solution.  相似文献   

Theoretical prediction of phase relations among aqueous solutions and minerals: Salton Sea geothermal system     

Dennis K. Bird  Denis L. Norton 《Geochimica et cosmochimica acta》1981,45(9):1479-1494

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The ionization of acids in estuarine waters     

Frank J Millero 《Geochimica et cosmochimica acta》1981,45(11):2085-2089

The stoichiometric, $\text{K}{}_{\mathrm{HA}}{}^1$, and apparent, K'_HA, constants for the ionization of a number of weak acids (NH₄⁺, HSO₄^?, HF, H₂O, B(OH)₃, H₂CO₃, HCO₃^?, H₃PO₄, H₂PO₄^?, HPO₄², H₃AsO₄ H₂AsO₄^? and HAsO₄^2?) in seawater at 25°C diluted with water have been fitted to equations of the form (Millero, 1979). In $\text{K}{}_{\mathrm{HA}}{}^1\text{= In K}{}_{\mathrm{HA}}\text{+ AS}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{+ BS}$ where In K_HA is the thermodynamic constant in water, S is the salinity, A and B are adjustable parameters. The validity of this equation in estuarine waters has been examined by using an ion pairing model (Millero and Schreiber, 1981). The calculated values of $\text{K}{}_{\mathrm{HA}}{}^1$ and K'_HA at S = 35%. are in good agreement with the measured values for all the systems examined. The equation used to extrapolate the measured values to pure water K_HA predicted values that agreed with those determined by using the ion pairing model. The exception was the ionization of HPO₄^2? due to the strong interactions of Ca²⁺ and Mg²⁺ with PO₄^3?. The differences in the predicted values of $\text{K}{}_{\mathrm{HA}}{}^1$ in seawater diluted with pure water and average river water were very small for all the acids except HPO₄^2? (the maximum ΔpK = 0.96 in average river water). The larger difference in the $\text{K}{}_{\mathrm{HA}}{}^1$ for HPO₄^2? in river waters is due to the strong interactions of Ca²⁺ and PO₄^3?.  相似文献   

²⁶Al and rare gases in Allende,Bereba and Juvinas: implications for production rates     

W. Hampel  H. Wänke  H. Hofmeister  B. Spettel  G.F. Herzog 《Geochimica et cosmochimica acta》1980,44(3):539-547

The ²⁶Al, light rare gas and major and minor element contents of Al-rich and poor samples separated from Allende. Bereba and Junivas have been measured. The production rate of ²¹Ne from Al (²¹P_Al) is $\text{(1.9 ± 0.6) ×}{}^{21}\text{P}{}_{\mathrm{Si}}$ and ${}^{\mathrm{<mtext>22</mtext><mtext>21</mtext>}}\text{P}{}_{\mathrm{Al}}\text{= 1.4 ± 0.4.}$ The ³He, ²¹Ne and ³⁸Ar exposure ages of the eucritic pyroxenes agree suggesting complete cosmogenic gas retention. The eucritic feldspars have lost virtually all ³He and most radiogenic ⁴He. The equation ²⁶Al = 0.42 ± 0.41 Mg + 2.74 ± 0.21 Si + 4.92 ± 0.51 Al + 1.33 S + 0.24 Ca + 0.03 Fe reproduces within 15% our ²⁶Al measurements and the average values measured in ordinary chondrites without recourse to unusual cosmic-ray effects.  相似文献   

Speciation of boron with Cu2+, Zn2+, Cd2+ and Pb2+ in 0.7 M KNO3 and in sea-water     

Constant M.G. van den Berg 《Geochimica et cosmochimica acta》1984,48(12):2613-2617

The stability constants, $\text{K}{}^1{}_{\mathrm{MB}}$, for borate complexes with the ions of Cu, Pb, Cd and Zn are determined in this work by DPASV in 0.7 M KNO₃ at metal concentrations of 10^?7 M. The acidity constants of the Cu²⁺ ion are determined by DPASV in the same conditions. The following values for log $\text{K}{}^1{}_{\mathrm{MB}}$ () have been obtained: CuB: 3.48, CuB₂: 6.13, PbB: 2.20, PbB₂: 4.41, ZnB: 0.9, ZnB₂: 3.32, CdB: 1.42, and CdB₂: 2.7, while the values for the acidity constants of Cu are $\text{pK}{}^1{}_{\mathrm{CuOH}}\text{= 7.66}$ and . At the low concentration of boron in 35%. S sea-water complexes with borate represent only about 0.2% Cu, 0.03% Pb, 0.02% Zn and 0.003% Cd.  相似文献