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The kinetics of conversion of iron(III) (hydr)oxides to ferrous iron mediated by fulvic acid have been investigated in order to improve the understanding of the redox cycling of iron at the oxic-anoxic boundary in natural waters. Under the conditions similar to natural waters, fulvic acid is able to reduce the iron(III) (hydr)oxide. The kinetics of the reaction depend on the reactivity of iron(III) (hydr)oxides and the reducing power of the fulvic acid. The rate of reaction is 60 nm/h obtained under following conditions: total concentration of Fe(III) 1.0 × 10–4 M, pH 7.5, fulvic acid 5 mg/L. The rate is considered as a net result of reduction and oxidation in the > FeIII-OH/Fe(II) wheel coupled with fulvic acid. In a real natural water system, reductants other than fulvic acid may be of importance. The results obtained in the laboratory, however, provide evidence that the Fe(OH)3(s)/Fe(II) redox couple is able to act as an electron-transfer mediator for the oxidation of natural organic substances, such as fulvic acid by molecular oxygen either in the absence of microorganisms or as a supplement to microbial activity. 相似文献
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Thermodynamic conditions (first of all, temperature) are the main dynamic factors in the transformation process of ferrous
to ferric iron (TFFI). TFFI usually takes place within a temperature range of 473–843 K (most active at temperatures above
673 K) and does not require presence of the oxidizing agents above 673 K. Analysis of the chemical composition of different
rocks and minerals indicates that only for some sedimentary rocks is the relative content of ferrous iron oxide less than
its value in magnetite, and this value is minimal for oceanic sediments. The relative content of ferrous iron oxide in oceanic
magmatic rocks exceeds this value in continental magmatic rocks and depends on the rate of rock cooling. An investigation
of the role of the titanium oxide content of different rocks on stability of ferrous iron oxide against its transformation
to ferric iron oxide shows that a significant correlation (r = 0.79) does exist between the relative content of ferrous iron oxide and ratio of TiO2/Fe2O3. Temperature within the solar nebula at location of the Earth was within the temperature range of the TFFI. During the Earth
accretion and its early evolution, ferric iron oxide was unstable and most likely did not exist. The first magnetic minerals
containing ferric iron could have appeared only after the Earth’s surface had cooled below ∼843 K. The formation of the first
Algoma-type banded iron formations could be used as a marker of the Earth’s surface cooling below ∼843 K. 相似文献
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The solubility of iron sulphides in synthetic and natural waters at ambient temperature 总被引：1，自引：1，他引：0
W. Davison 《Aquatic Sciences - Research Across Boundaries》1991,53(4):309-329
A critical evaluation of literature values for the solubility products, K
sp
NBS
= [Fe2+][HS–] Fe2+
HS– (H
NBS
+
)–1, of various iron sulphide phases results in consensus values for the pKs of 2.95 ± 0.1 for amorphous ferrous sulphide, 3.6 ± 0.2 for mackinawite, 4.4 ± 0.1 for greigite, 5.1 ± 0.1 for pyrrhotite, 5.25 ± 0.2 for troilite and 16.4 ± 1.2 for pyrite.Where the analogous ion activity products have been measured in anoxic freshwaters in which there is evidence for the presence of solid phase FeS, the values lie within the range of 2.6–3.22, indicating that amorphous iron sulphide is the controlling phase. The single value for a groundwater of 2.65 (2.98 considering carbonate complexation) agrees. In seawater four values range between 3.85 to 4.2, indicating that mackinawite or greigite may be the controlling phase. The single low value of 2.94 is in a situation where particularly high fluxes of Fe (II) and S (–II) may result in the preferential precipitation of amorphous iron sulphide. Formation of framboidal pyrite in these sulphidic environments may occur in micro-niches and does not appear to influence bulk concentrations. Calculations show that the formation of Fe2S2 species probably accounts for very little of the iron or sulphide in most natural waters. Previously reported stability constants for the formation of Fe (HS)2 and (Fe (HS)3)– are shown to be suspect, and these species are also thought to be negligible in natural waters. In completely anoxic pore waters polysulphides also have a negligible effect on speciation, but in tidal sediments they may reach appreciable concentrations and lead to the direct formation of pyrite. Concentrations of iron and sulphide in pore waters can be controlled by the more soluble iron sulphide phase. The change in the IAP with depth within the sediment may reflect ageing of the solid phase or a greater flux of Fe (II) and S (–II) nearer the sediment surface. This possible kinetic influence on the value of IAPs has implications for their use in geochemical studies involving phase formation. 相似文献
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Theodor Stocks 《Ocean Dynamics》1955,8(3):112-118
Zusammenfassung Der Steingrund, eine Bank in etwa 9 m Tiefe, 5–6 sm nordostwärts von Helgoland, wurde 1953 von Atair mit modernen Methoden vermessen, nachdem sich die Notwendigkeit herausgestellt hatte, die letzte vorhergehende Vermessung (1908) zu überholen. Die Form des Grundes wurde in fast der gleichen Gestalt bestätigt, und auch die geographische Lage wurde mit derjenigen von 1908 in Übereinstimmung befunden.
The Steingrund near the Island of Heligoland
Summary The Steingrund, a bank at a depth of about 9 m, located at a distance of about 5–6 sm northeast from the Island of Heligoland was surveyed for the first time in 1908. As a verification proved to be necessary, another survey was undertaken with modern methods on board the surveying cutter Atair in 1953. According to this survey the form of the Steingrund as well as its geographical position were found to correspond almost completely with the 1908 records.
Le Steingrund au voisinage de l'île d'Heligoland
Résumé Le Steingrund, un banc en 9 mètres de profondeur, situé à une distance de 5–6 milles marins environ au nord-est de l'île d'Heligoland fut relevé dernièrement en 1908. Comme il se montra nécessaire d'en vérifier les résultats, on effectua un autre relèvement avec des méthodes modernes à bord de la chaloupe hydrographique Atair en 1953. On trouva que la forme actuelle du Steingrund se confond prèsque complètement avec celle que l'on avait constatée en 1908 et que sa position géographique correspond également avec celle déterminée en 1908.相似文献
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The contribution of organic bases to the alkalinity of the anoxic hypolimnetic water of a small lake has been studied. By means of potentiometric titrations the presence of a protolyte, best described as a one-protonic acid (HL) could be shown. The pka of HL was found to be 4.24±0.08 (3σ) and it reached a concentration of 0.4 mM close to the sediment surface. Because of precipitation reactions titration experiments could not be performed above pH≈6.8, but indications of additional bases having a pka >8were found. The results indicate the presence of low molecular weight carboxylic acids and free amino acids originating from bacterial decomposition of organic material. Polarographically measured Fe2+ concentrations, in situ pH measurements and various model ligands were used to assess the metal speciation in the hypolimnion. Although strong metal complexing agents such as citrate and glutamine may be present, the total concentrations of both Fe2+ (up to 0.6 mM) and ligands are too low to bind more than at maximum 20% of the ferrous iron. 相似文献
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Jaroslava Plomerová Vladislav Babuška Libuše Ruprechtová Reviewer A. Zátorek 《Studia Geophysica et Geodaetica》1981,25(4):356-365
mau x¶rt; u a¶rt;u 8 ¶rt;nu mau ¶rt; uu mu u -ana¶rt; auu naa num mam u u na n, g, Sn u Sg mum ma¶rt;am¶rt;a ¶rt; uu mu. a¶rt;u lam mu aua u umau u mm u a amuu ¶rt; En. 相似文献
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Summary Using the optimal shape design method, which is generally described, and von Herzen's et al. measurements of the heat flow, the shape of the lithosphere and its thermal field is computed in the vertical plane parallel to the hot spot source versus the plate velocity at a distance of about 250 km from the axis of the Hawaiian Island chain. The results are compared with the computations based on Crough's idea of thermal rejuvenation of the oceanic lithosphere above a hot spot source. If we assume that the lateral cross-section of the lithospheric bottom is described by the Gaussian curve h=h0
exp (–y2/22), we obtain h035 km and 130 km, where h is the value of lithospheric thinning and y the lateral coordinate. We thus obtain the lower limit of the lateral dimension of the Hawaiian anomaly.
u m¶rt; nmua nua amu, m u ma nuam, u ¶rt;a mn nm, ua a um u mn n mua nmu, naa mu um mum umua mu u ¶rt;a nuuum 250 m uuuaa aunaa. mam a uuu, au a u¶rt;u aa (Crough), aauu mn mu au um a¶rt; umu mu. u n¶rt;num, m ama nn u umu ¶rt;a nuam u aa h=h0 exp (–y2/22), m num h0 35 u 130 ,¶rt; h—umu mu u —amaa ¶rt;uama. ¶rt;am, =130 m u n¶rt; ama aaaa aauu.相似文献
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Summary Methods of checking the measured Earth's tides data by computer drawing are outlined.
3. 3. (, 1975) 相似文献
3. 3. (, 1975) 相似文献
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Summary The regular astronomical determinations of the geographic latitude and UT from Ondejov PZT observations were used to estimate the fluctuations with a frequency of 1.00217 of the sidereal day, corresponding to the theoretical value of the frequency of the nearly diurnal free wobble of the pole. The combined polar wobble and nutation as reflected in astronomical observations was analysed, and a method of estimating the amplitudes of the periodic components, based on observing changes of latitude and time during the separate observation nights, is proposed. The numerical solution indicates that fluctuations which can be considered a manifestation of retrograde free nutation with an amplitude of approximately 0.02, are present in the PZT observations.
uuau um u u u ¶rt; una ¶rt; u au amm 1,002 17 ¶rt; m, mmm ¶rt; um ¶rt;uu na, ¶rt;am aau uu ¶rt;u mauu u ¶rt;uu na amuu a¶rt;u. ¶rt;aam m¶rt; ¶rt; u nu¶rt;uu ua, u¶rt;u u uu um u u m¶rt; a¶rt;u. u mam u¶rt;um a ¶rt; um mauu anau nmu ¶rt;uu a mu anum¶rt; 0,02.相似文献
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The gravitational field of topographic-isostatic masses and the hypothesis of mass condensation 总被引：2，自引：0，他引：2
The topographic masses (TM) load the interfaces within the earth; namely TMs are compensated by an isostatic adjustment which might depend on time. Here we focus on the loading gravitational potential to which we refer as the topographic potential. We aim at a rigorous integral representation for the topographic potential of gravity which results in corollary one and two.In addition, a rigorous computation of the gravitational potential of a massive non-spherical shell is achieved which is limited by shape functions which represent the earth's topography (heights) and the negative topography (depths) which substitutes the internal surface of isostatic compensation. Finally by the third corollary the single layer potential is given of those masses which are condensed onto a reference sphere, the basis for the standard loading potential. The hypothesis of mass condensation is confronted with the exact representation, namely in the external distant zone, the near zone and the internal distant zone. 相似文献
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František Jiříček Pavel Tříska V. E. Jurov E. E. Titova Reviewer S. Fischer 《Studia Geophysica et Geodaetica》1981,25(1):81-86
auuau uu muna a f>1,5 , aumua ¶rt; a nmua uu m u a ¶rt; a mau. mu a aum nm uu, umu a mauu aa (L=2,1) n¶rt; nm uu (L=5). m mmmum mu umua uu, umu a mu mau. au uu a nm m, m a um nmam a 2000–3000 u anu u a L=2,2–5,9. au mmmu nma aamumu a u nmu uu a¶rt;am u amu aua uu a L 3,5. aa, m a mauu aa u ¶rt;a a¶rt; nuu uu a , umum uuu n¶rt; a¶rt;a a nmu. au a n¶rt;num, m am a L 3,5,¶rt; aam au uu u au mmu nma aamumu a u nmu uu, aa ¶rt;amua anau a nana. m u m amu mm au anum u ¶rt; ¶rt;a ua n¶rt;u anmau u ¶rt; — ua. 相似文献
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Pavla Kočíková Věnceslava Pretlová Reviewer O. Zikmunda 《Studia Geophysica et Geodaetica》1985,29(1):75-99
Summary The inclusion of cloudiness characteristics, obtained by computer analysis of multispectral satellite photographs, in the objective analysis of the dew-point temperature deficit is suggested for the mesomodel. The basic principle of the method is the correction of mathematically packed data using processed satellite cloudiness observations. Special fast algorithms for constructing bicubic splines are used to effect the basic mathematical packing.
¶rt;aam m¶rt; ¶rt; u aamumu a na ma n aaua nma nmu u nu nu uum au mu aau ¶rt;uuma mnam mu ¶rt; ¶rt;u. m¶rt;a m u amamuu nm ¶rt;a nu nu nmu u. aau ¶rt;a unm nua m aum ¶rt; muu uuu na.相似文献
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Daniela Řezáčová Sněžana Todorova Рецензенm J Bednář 《Studia Geophysica et Geodaetica》1987,31(4):397-403
nuam aau ¶rt; amu a um ¶rt; ¶rt;a uauu. ¶rt; ¶rt;a, ¶rt;mu auumu m mnam u nu mum ¶rt;a, umam m ¶rt;u z aa n¶rt; uuu, a aau. u¶rt; auum ¶rt;au z naa m mauu ¶rt; amu, naam, m ¶rt;au ¶rt;z naa zauuam u amu ¶rt;.
Summary A formation of ice particles on artificial deposition INis described. INacting in dependence on the temperature and supersaturation over the ice are considered in the 1 D SSconvection cloud model with detailed microphysics including freezing. The limiting influence of the water vapour pressure upon the concentration of active INis shown resulting from the dependence of water vapour pressure on the ice particle concentration.相似文献
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The materials presented in this paper were collected in the course of studies of phytoplankton and photosynthetic pigments in the Upper Volga reservoirs within the territory of Yaroslavl province. In 1995–2000, the phytoplankton in these water bodies was found to be represented mainly by diatom, blue-green, green, and in some cases, cryptophyte algae. It was found that in the channel parts of the reservoirs, the population of planktonic algae varied from 25 to 96180 thousand cell/l, their biomass, from 0.009 to 5.54 mg/l, and the chlorophyll content, from 0.4 to 22.4 g/l. The values of saprobity index in terms of phytoplankton were found to characterize waters of all the three reservoirs as -mesosaprobic, and the extent of blue-green algae development in the overwhelming majority of cases was classed as environmentally safe, although their abundance in the coastal zone sometimes is an indication of a substantial deterioration in water quality. 相似文献
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Jan Pretel Lilian Kiršnerová Reviewer K. Vaníček 《Studia Geophysica et Geodaetica》1987,31(4):390-396
Summary To be able to parameterize vertical heat and water vapour fluxes in the boundary layer of the atmosphere, it is necessary to determined, among other factors, the amount of incident total radiation under a generally arbitrary condition of the atmosphere at any instant of time. This paper deals with a simple model for computing the total radiation based on known solar elevation, total cloud cover and the atmospheric turbidity parameter. This variant of the model was formulated on the basis of a two-year series of total radiation observations made in the radiation network of the Czech Hydrometeorological Institute, and on the measurements and observations made at the observatory of the Institute of the Physics of the Atmosphere in Kopisty. An example of comparing the observed and theoretical values of total radiation will also be given.
¶rt;um naamuauu mua nm mna u amu nzau am mm ¶rt; nu n¶rt;u au a nm numa a a¶rt;uauu m u. mam auam n naamuauu a a¶rt;uauu n ¶rt;a m a, ammu am u mnu az na. ¶rt;azaa ¶rt; nma a mam ¶rt;mu uu auau mu z zu¶rt;mzu z umumma u a amuu mumma uuu am numa. mam ma nu¶rt; nu au u u n n¶rt; ¶rt;u u au a a¶rt;uauu.相似文献
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Summary On the basis of the 1966–73 data, the effect of the difference between pro- and anti-sectors of the IMF is found to be negligible in the winter midlatitude (Central Europe) ionosphere contrary to the dominant effect of this difference in the high-latitude ionosphere found earlier.
a ¶rt;a a 1966–73. u¶rt;m u m amu ¶rt; pro- u anti- mau . na a u ¶rt;um (¶rt; na) u, , a naa a, naum um u.相似文献