Characteristics of turnover of carbonyl sulfide in four different soils     

Susanne Lehmann  Ralf Conrad 《Journal of Atmospheric Chemistry》1996,23(2):193-207

Release and uptake of carbonyl sulfide (OCS) were measured at 25°C in samples of three forest soils (BL, BW, PBE) and one soil from a rape field (RA). The soil samples were flushed with a constant flow of either air (oxic conditions) or nitrogen (anoxic conditions) containing defined concentrations of OCS. A cryogenic trapping technique with liquid argon (-186 °C) was used to collect gas samples for analysis in a gas chromatograph equipped with a flame-photometric detector. The dependence of net OCS fluxes between soil and atmosphere could be described by a simple model of simultaneous OCS production and OCS uptake. By using this model, production rates (P), uptake rate constants (k) and compensation concentrations (m _c ) of OCS could be determined as function of the soil type and the incubation conditions. Under oxic conditions, OCS production (P) and uptake were observed in all soils tested. However, the compensation concentrations (<166 ng l^-1; 1 ng OCS l^-1=0.41 ppbv) that were calculated from the model were high relative to the ambient OCS concentration (ca. 0.5 ppbv). The production rates (0.16–1.9 ng h^-1 g^-1 dw) that were actually measured when flushing the soil samples with air containing zero OCS were smaller than those (17–114 ng h^-1 g^-1 dw) calculated from the model. This observation was explained by two different concepts: one assuming the existence of a threshold concentration (m _t ) below which OCS was no longer consumed in the soil; the other assuming the existence of two different OCS consumption processes, of which only the process active at elevated OCS concentrations was covered by the experiments. The latter concept allowed the estimation of OCS compensation concentrations that were partially low enough to allow the uptake of atmospheric OCS by soil. Both OCS production and uptake in PBE soil were dependent on soil temperature (optimum 20 °C) indicating a microbial process. However, both production and consumption of OCS were not consistently inhibited by sterilization of the soil, suggesting that they were not exclusively due to microbiological processes. Under anoxic conditions, OCS was also produced, but was not consumed except in one soil (RA). Production of OCS in the soils was stimulated after addition of thiocyanate, but not thiourea, thiosulfate, thioglycolate, tetrathionate, sulfate, elemental sulfur, cysteine and methionine.  相似文献   

Flux between soil and atmosphere, vertical concentration profiles in soil, and turnover of nitric oxide: 2. Experiments with naturally layered soil cores     

Jutta Rudolph  Ralf Conrad 《Journal of Atmospheric Chemistry》1996,23(3):275-300

Intact soils cores were taken with a stainless steel corer from a sandy podzol and a loamy luvisol, and used to measure the flux (J) of NO between soil and atmosphere and the vertical profile of the NO mixing ratios (m) in the soil atmosphere, both as function of the NO mixing ratio (m _a) in the atmosphere of the headspace. These measurements were repeated after stepwise excavation of the soil column from the top, e.g. by removing the upper 2 cm soil layer. The gaseous diffusion coefficients of NO in the soil cores were either computed from soil porosity or were determined from experiments using SF6. The NO fluxes (J) that were actually measured at the soil surface were compared to the fluxes which were calculated either from the vertical NO profiles (J _c ) or from the NO production and uptake rates (J _m ) determined in the excavated soil samples. In the podzol, the actually measured (J) and the calculated (J _m , J_m) NO fluxes agreed within a factor of 2. In the luvisol, the measured NO fluxes (J) and those calculated from the vertical NO profiles (J _c ) also agreed well, but in the upper 6 cm soil layer the NO fluxes (J _m ) calculated from NO production and uptake rates were up to 7 times higher than the measured NO fluxes. This poor agreement was probably due to the inhomogeneous distribution of NO production and consumption processes and the change of diffusivities within the top layers of the luvisol. Indeed, the luvisol showed a pronounced maximum of the NO mixing ratios at about 6 cm depth, whereas the podzol column exhibited a steady and exponential decrease of the NO mixing ratios with depth. The inhomogeneities in the luvisol were confirmed by incubation of the soil cores under anoxic conditions. This treatment resulted in production of NO at several depths indicating a zonation of increased potential activities within the luvisol profile which may have biased the modelling of the NO surface flux from turnover measurements in soil samples. Inhomogeneities could be achieved even in homogenized soil by fertilization with nitrate solution.  相似文献   

灰色动态预测方法及其在变形预测中的应用     

尹晖  丁窘  张琰  邓康伟 《武汉大学学报(信息科学版)》1996,(1)

在分析比较了ＧＭ（１，１）预测模型的不足之后，提出一种实时引入新信息的等维新息和等维灰数递补组合动态预测方法。首先同常规预测法作了比较，然后进行了三峡链子崖危岩体变形发展趋势预测及有效性验证。  相似文献   

The growth of Rayleigh–Taylor-type instabilities in the lithosphere for various rheological and density structures     

Clinton P. Conrad  Peter Molnar 《Geophysical Journal International》1997,129(1):95-112

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Geology of the Miami Terrace and its paleo-oceanographic implications     

Henry T. Mullins  A.Conrad Neumann 《Marine Geology》1979,30(3-4):205-232

The Miami Terrace is a drowned early to middle Tertiary carbonate platform, the outer margin of which has been deeply incised by submarine erosion subsequent to deposition of the limestone terrace. This interpretation is based on the study of high-resolution seismic reflection profiles, rock dredge samples, observations from deep-diving submersibles, and correlation with drill-hole data. The karstic upper terrace (200–375 m) yields limestones and dolostones of early middle Miocene age that have shallow-shelf affinities. Truncated beds of an eastward-dipping deeper-water slope facies are exposed on the upper surface of the erosional lower terrace at 600–700 m. The upper and lower terraces are separated by a discontinuous ridge, probably a drowned Miocene, or post-Miocene bank margin complex. Both terraces and the ridge are capped by dense conglomeratic phosphorites and phosphatic limestones. Phosphorite nodules are more common on the lower terrace whereas the upper terrace yields large phosphorite slabs as well as shark's teeth and bones of marine mammals.

Petrographic study of dredged and submersible-sampled rocks shows that two or more episodes of phosphatization took place intermittent with erosion, grain rounding, reworking and redeposition. Early stages of phosphatization appear to be selective, replacing the more unstable carbonate minerals first, while later stages are nonselective. The origin of most of the phosphorites is the diagenetic replacement of calcium carbonate by francolite.

The karst surface of the upper terrace appears to have been produced by subaerial exposure in the middle to late Miocene as evidenced by shallow-water components in the rocks of the upper terrace plus considerations of local subsidence and eustatic sea-level curves. The erosional lower terrace, 200–300 m deeper than the upper terrace, would have been too deep to have been produced by subaerial or wave erosion. An erosional hiatus of middle Miocene age in JOIDES drill holes on the Blake Plateau indicates that bottom-current velocities in this area increased over this interval. The formation of the lower erosional terrace is related to increased flow of the Gulf Stream system (Florida Current) and bioerosion concurrent with the tectonic uplift and oceanographic closure of the western Caribbean in mid-Miocene time.

The bathymetry, petrology, structure and paleontology of the Miami Terrace, along with correlative data from adjacent areas, argue that a more active Gulf Stream system began as early as the middle Miocene (10.5–16 m.y.B.P.) rather than the early to middle Pliocene (3.5–4.0 m.y.B.P.) as previously suggested.  相似文献   

Potentielle Mineralbestände kalitrachybasaltisch-karbonatischer Syntektika und die Zukunft des Vesuvmagmas     

Prof. Dr. Conrad Burri 《International Journal of Earth Sciences》1968,57(3):744-765

Zusammenfassung Die Magmenentwicklung des Vesbischen Vulkans (Somma-Vesuv) ist nachRittmann durch eine zeitlich progressive Desilifizierung gekennzeichnet, welche ihre Ursache in der Assimilation von Karbonatgesteinen, vorwiegend Triasdolomiten, besitzt, gefolgt von einer Differentiation der so gebildeten Syntektika. Im Anschluß an diese Vorstellungen werden ganz allgemein die potentiellen Mineralbestände derartiger Schmelzen in verschiedenen heteromorphen Fazien untersucht. Dabei wird vom mittleren kalitrachybasaltischen Stammagma des Tyrrhenisgebietes ausgegangen und sowohl Kalk- wie Dolomitsyntexis in Betracht gezogen. Anschließend werden auf Grund der in benachbarten Gebieten (Mti. Volsini und Vulcano Laziale) herrschenden Verhältnisse sowie des Auftretens von niedrigst silifizierten Auswürflingen am Vesuv selbst (sog. Vesbite vonWashington), Mutmaßungen über die zukünftige Entwicklung des Vesuvmagmas geäußert.

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According toRittmann, the magmatic evolution of the Vesbian Volcano (Somma-Vesuvius) is characterized by progressive desilication due to the assimilation of carbonatic rocks, chiefly triassic dolomites, followed by differentiation of the sintectic melts so produced. In the present paper the potential normative mineral composition in various heteromorphic facies of melts arising from this conception is examined. Starting point for the calculations is a potassic trachybasaltic magma, corresponding to the average composition of the Tyrrhenian primary magma, and the incorporation of limestones as well as of dolomite is considered. Some speculative ideas concerning the future evolution of the Vesuvian magma, based on the nature of ejected blocks of low silification, the so-called Vesbites ofWashington, and on some peculiar features of the neighbouring volcanic regions of the Monti Volsini and of the Alban Hills, are also put forward.

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Résumé D'aprèsRittmann, l'évolution magmatique du Volcan (Somma-Vésuve) est caractérisée par une désilication progressive, ayant pour cause l'assimilation de roches carbonatiques, surtout de dolomies triassiques, et suivies par la différentiation des produits syntectiques ainsi formés. Par suite à ces idées, la compsition minéralogique potentielle de tels mélanges est calculée et examinée d'une manière générale et dans ses divers faciès hétéromorphiques. Comme point de départ des calculs, la composition moyenne du magma trachybasaltique primaire de la région tyrrhénienne est choisie, tout en tenant compte de l'incorporation de chaux comme de celle de dolomie. Enfin quelques idées spéculatives sur le développement futur du magma vésuvien sont énoncées, en se basant sur des renseignements fournis par les régions avoisinantes des Monts Vulsiniens et du Volcan Lazial, ainsi que sur la composition minéralogique et chimique de blocs projetés à silicification très basse, rejetés par le Vésuve-même (les soi-disants vésbites deWashington).

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Herrn Professor Dr. A.Rittmann zum 75. Geburtstag gewidmet  相似文献   

Selective extraction of organically bound gold in soils, lake sediments and stream sediments     

D.Conrad Gregoire 《Journal of Geochemical Exploration》1985,23(3):299-313

The extraction of organically bound gold from surficial materials is accomplished by using a solution of 5% sodium hypochlorite. A 10-g sample is digested at least twice with 50 mL of hypochlorite solution. The recovery of gold from the organic phase is nearly quantitative for lake sediments and stream sediments high in organic content. For stream sediments and soils low in organics, the recovery of gold is complicated by the sorption of released gold onto inorganic sample components. For these materials, recoveries as low as 70% of the organically bound gold are possible. For a stream sediment sample containing 53.4 ppb gold, the precision of the method is approximately 6% for a 10-g sample and 14% when a 5-g sample of stream sediment is used. The results obtained for all materials tested indicate that a substantial fraction of the gold found in sediments and soils exists as organically bound gold.  相似文献   

Les formations volcaniques récentes du Sud de l’Iran (Kouh-e-Shahsavaran): données pétrologiques préliminaires; implications structurales     

M. Girod  G. Conrad 《Bulletin of Volcanology》1975,39(4):495-511

Kouth-e-Shasavaran massif in South Iran (Baloutchistan) consists of Pliocene and Quaternary cale-alkaline lavas. Fourty one new chemical analysis have been carried out to identify the volcanic rock series. Andesites are more abundant than basic thigh alumina basalts) and acid lavas (dacites and rhyodacites). This volcanic area is probably connected with a subduction zone located on the North of Oman Gulf, between the arabic, indian and eurasian plates. In this respect, Makran range may be inerpreted as an emerged trench.  相似文献   

Quantifying the effect of humic matter on the emission of mercury from artificial soil surfaces     

Conrad Mauclair  Julie Layshock  Anthony Carpi 《Applied Geochemistry》2008

A set of surface samples was created using purified laboratory grade sand treated with 0.05 μg/g Hg as the HgCl₂ salt and various concentrations of purified humic and fulvic acids. Emissions of elemental Hg from these substrates to the atmosphere were inversely correlated with the organic content of the samples (99% confidence level). The greatest differences in Hg emissions were found between samples containing the lowest concentrations of humic matter (0% versus 0.01% humic, and 0.01% versus 0.1% humic), only small differences in Hg flux were found to exist for samples with higher concentrations of humic acid (1%, 5%, and 100%). This effect was independent of the type of humic substance used, with both humic and fulvic acids showing an inhibitory effect on surface Hg emissions.  相似文献   

Derived gravity field of the seismogenic upper crust of SE Germany and West Bohemia and its comparison with seismicity   总被引：2，自引：2，他引：0  

J. Švancara  J. Havíř  W. Conrad 《Studia Geophysica et Geodaetica》2008,52(4):567-588

The gravity field of the seismogenic upper crust was derived from the Bouguer gravity map by applying the Butterworth high-pass filter in the wave-number domain. The cutoff wavelength of the filter was 110 km, to pass the gravity signals of structures within the 18 km thick seismogenic layer. The derived residual gravity map reveals potential stress concentrating structures, which may cause seismicity provided they lie within the existing zones of weakness. Furthermore we derived a shaded relief map of the horizontal gravity gradient, which highlighted the tectonic lines accompanied by density contrast. The directional analysis of this map shows three dominant strike directions. The most prominent one is “the Hercynian” NW-SE strike direction represented by the Franconian Line, the Gera-Jáchymov Fault Zone and the Elbe Zone. The second dominant strike is the Rhenisch NNE-SSW trending represented by the Upper Rhine Graben Zone, Rheinsberg-Heldburg Line and several Proterozoic volcanic belts in the Teplá-Barrandien Unit. The third pronounced trending of the ENE-WSW direction is represented by the Erzgebirge and Eger Graben gravity low. The N-S trending Rostock-Leipzig-Regensburg Zone (Pritzwalk-Naab Lineament) is not distinctly reflected in the derived gravity maps, although many fault segments have a meridian direction. The relative reactivation potential of some pre-existing fault systems identified in the gravity map was studied with respect to the wide range of the recent stress configuration determined in the West Bohemia/Vogtland region. The resulting diagrams show that the steep NNW-SSE to N-S faults (represented by some segments of the Mariánské Lázně Fault Zone) are oriented favourably for reactivation. On the contrary, the orientation of the ENE-WSW faults limiting the Eger Graben (Litoměřice Fault, etc.) is unfavourable for reactivation for all dip values.  相似文献