Domestic Combustion of Biomass Fuels in Developing Countries: A Major Source of Atmospheric Pollutants   总被引：3，自引：0，他引：3  

J. Ludwig  L. T. Marufu  B. Huber  M. O. Andreae  G. Helas 《Journal of Atmospheric Chemistry》2003,44(1):23-37

Biomass burning has important impacts on atmospheric chemistry and climate. Fires in tropical forests and savannas release large quantities of trace gases and particulate matter. Combustion of biofuels for cooking and heating constitutes a less spectacular but similarly widespread biomass burning activity. To provide the groundwork for a quantification of this source, we determined in rural Zimbabwe the emissions of CO₂, CO, and NO from more than 100 domestic fires fueled by wood, agricultural residues, and dung. The results indicate that, compared to open savanna fires, emissions from domestic fires are shifted towards products of incomplete combustion. A tentative global analysis shows that the source strength of domestic biomass burning is on the order of 1500 Tg CO₂–C yr^–1, 140 Tg CO–C yr^–1, and 2.5 Tg NO–N yr^–1. This represents contributions of about 7 to 20% to the global budget of these gases.  相似文献   

Diagenetic Alteration of Magnetic Signals by Anaerobic Oxidation of Methane Related to a Change in Sedimentation Rate   总被引：1，自引：0，他引：1  

Natascha Riedinger  Kerstin Pfeifer  Johanna Fredrika Lukina Garming  Christian Hensen 《Geochimica et cosmochimica acta》2005,69(16):4117-4126

Geochemical and rock magnetic investigations of sediments from three sites on the continental margin off Argentina and Uruguay were carried out to study diagenetic alteration of iron minerals driven by anaerobic oxidation of methane (AOM). The western Argentine Basin represents a suitable sedimentary environment to study nonsteady-state processes because it is characterized by highly dynamic depositional conditions. Mineralogic and bulk solid phase data document that the sediment mainly consists of terrigenous material with high contents of iron minerals. As a typical feature of these deposits, distinct minima in magnetic susceptibility (κ) are observed. Pore water data reveal that these minima in susceptibility coincide with the current depth of the sulfate/methane transition (SMT) where HS⁻ is generated by the process of AOM. The released HS⁻ reacts with the abundant iron (oxyhydr)oxides resulting in the precipitation of iron sulfides accompanied by a nearly complete loss of magnetic susceptibility. Modeling of geochemical data suggest that the magnetic record in this area is highly influenced by a drastic change in mean sedimentation rate (SR) which occurred during the Pleistocene/Holocene transition. We assume that the strong decrease in mean SR encountered during this glacial/interglacial transition induced a fixation of the SMT at a specific depth. The stagnation has obviously enhanced diagenetic dissolution of iron (oxyhydr)oxides within a distinct sediment interval. This assumption was further substantiated by numerical modeling in which the mean SR was decreased from 100 cm kyr⁻¹ during glacial times to 5 cm kyr⁻¹ in the Holocene and the methane flux from below was fixed to a constant value. To obtain the observed geochemical and magnetic patterns, the SMT must remain at a fixed position for ∼9000 yrs. This calculated value closely correlates to the timing of the Pleistocene/Holocene transition. The results of the model show additionally that a constant high mean SR would cause a concave-up profile of pore water sulfate under steady state conditions.  相似文献   

Characterization of synthetic hedenbergite (CaFeSi2O6)–petedunnite (CaZnSi2O6) solid solution series by X-ray single crystal diffraction     

Matthias Heuer  Alexandra L. Huber  Geoffrey D. Bromiley  Karl Thomas Fehr  Klaus Bente 《Physics and Chemistry of Minerals》2005,32(8-9):552-563

Clinopyroxenes of the solid solution series hedenbergite (CaFeSi₂O₆)–petedunnite (CaZnSi₂O₆) were synthesized at temperatures of 825–1200°C and pressures of 0.5–2.5 GPa. Compositions were determined by electron microprobe analysis. Selected crystals were investigated by means of single crystal diffraction and structure refinement and the structural distortion was studied depending on the substitution of iron by zinc on the octahedral M1 site. It is shown that the coordination of the M1 site has the most significant effect on M–O bond lengths, with changes on the other sites accommodating this distortion. The mean quadratic elongation and the octahedral angle variance as quantitative measures of the distortion of the coordination polyhedron were correlated with former results of ⁵⁷Fe Mössbauer spectroscopy at 298 K. The results presented now complete an earlier work on synthetic, crystalline powders of the same material and deliver exact structural data that were not possible to obtain by Rietveld refinements on powder data.  相似文献   

Modelling of Seepage Water Composition from Experiments with an Acid Soil and a Calcareous Sediment     

Kerstin Michel  Bernard Ludwig 《洁净——土壤、空气、水》2005,33(6):595-604

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Siderophile geochemistry of ureilites: A record of early stages of planetesimal core formation     

Paul H. Warren  Finn Ulff-Møller  Heinz Huber  Gregory W. Kallemeyn 《Geochimica et cosmochimica acta》2006,70(8):2104-2126

New bulk-compositional data, including trace siderophile elements such as Ir, Os, Au, and Ni, are presented for 25 ureilites. Without exception, ureilites have siderophile abundances too high to plausibly have formed as cumulates. Ureilites undoubtedly underwent a variety of “smelting,” by which C was oxidized to CO gas while olivine FeO was reduced to Fe-metal. However, pressure-buffered equilibrium smelting is not a plausible model for engendering the wide range (75-96 mol%) of mafic-silicate core mg among ureilites. The smelting reaction produces too much CO gas. Even supposing a disequilibrium process with the smelt-gas leaking out of the mantle, none of the ureilites, least of all the ureilite with the most “reduced” (highest) olivine-core mg (ALH84136), has the high Fe-metal abundance predicted by the smelted-cores model. In principle, the Fe-metal generated by smelting could have been subsequently lost, but siderophile data show that ureilites never underwent efficient depletion of Fe-metal. Ureilites display strong correlations among siderophile ratios such as Au/Ir, Ni/Ir, Co/Ir, As/Ir, Se/Ir, and Sb/Ir. Ureilite siderophile depletion patterns loosely resemble siderophile fractionations, presumably nebular in origin, among carbonaceous chondrites. However, Zn, for an element of moderate volatility, is anomalously high in ureilites. A tight correlation between Au and Ni extrapolates to the low-Ni/Au side of the compositional range of carbonaceous chondrites. From this mismatch, mild but nonetheless significant depletions of refractory siderophile elements such as Ir and Os, and moderate depletions of strongly siderophile, weakly chalcophile elements such as Ni and Au, we infer that the ureilite siderophile fractionations are largely the result of a non-nebular process, i.e., removal of S-rich metallic melt, possibly with minor entrainment of Fe-metal. Several lines of trace-element evidence indicate that melt porosity during ureilite anatexis was at least moderate. The ureilite pattern of very mild depletions of extremely siderophile elements, but much deeper depletions of moderately siderophile, chalcophile elements, suggests that asteroidal core formation probably occurs in two discrete stages. In general, separation of a considerable proportion (several wt%) of S-rich metallic melt probably occurs long before, and at a far lower temperature than, separation of the remaining S-poor Fe-metal. Apart from the Fe-metal itself, only extremely siderophile elements wait until the second stage to sequester mainly into the core.  相似文献   

Phosphatase activities in the waters of a shallow estuary,Western Australia     

A.L. Huber  J.O. Gabrielson  D.K. Kidby 《Estuarine, Coastal and Shelf Science》1985,21(4):567-576

Phosphatase activities in a large, shallow estuary in south western Western Australia have been assessed. Differences were found in enzyme activities in the two sections of the estuary. There were seasonal and diurnal variations as well. Phosphatase activities were most closely correlated with chlorophyll and organic nitrogen concentrations. In diurnal studies, the rates of change of phosphatase activity corresponded with the rates of change in orthophosphate. The role of phosphatase activity in regeneration of esterified phosphorus in the estuary is discussed.  相似文献   

A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa     

Linnemann  Ulf  Pidal  Agustín Pieren  Hofmann  Mandy  Drost  Kerstin  Quesada  Cecilio  Gerdes  Axel  Marko  Linda  Gärtner  Andreas  Zieger  Johannes  Ulrich  Jens  Krause  Rita  Vickers-Rich  Patricia  Horak  Jana 《International Journal of Earth Sciences》2018,107(3):885-911

International Journal of Earth Sciences - In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such...  相似文献   

Effects of Hypoxia on Fish Survival and Oyster Growth in a Highly Eutrophic Estuary     

Rikke Jeppesen  Miguel Rodriguez  Jenna Rinde  John Haskins  Brent Hughes  Laura Mehner  Kerstin Wasson 《Estuaries and Coasts》2018,41(1):89-98

Human land use activities around estuaries can result in high levels of eutrophication. At Elkhorn Slough estuary, a highly eutrophic California estuary, we investigated the effects of impaired water quality on two stress-tolerant estuarine species, a common fish, the staghorn sculpin, Leptocottus armatus and a foundational invertebrate, the Olympia oyster, Ostrea lurida. We caged the two indicator species at six wetlands with different levels of water quality impairment, four of which had restricted tidal flow. We also recorded water quality parameters simultaneously at all sites using YSI sondes, and sampled nutrients and chlorophyll-a monthly, building on the National Estuarine Research Reserve System-wide Monitoring Program. We found that the monitored environmental variables predicted ecological responses by the indicator species. In particular, we found that the duration and severity of hypoxia were negatively correlated with fish survival and oyster growth. Further, our results corroborate previous studies that artificial tidal restriction leads to increased hypoxia stress. We conclude that large diurnal fluctuations in dissolved oxygen and extended nighttime hypoxia can have lethal and sub-lethal effects even on stress-tolerant organisms in the estuary. While laboratory experiments have often shown such effects, it is relatively rare to demonstrate negative effects of oxygen variation with in situ experiments, which provide stakeholders with concrete evidence for impaired water quality at local wetlands. Tidally restricted sites, which experience the largest fluctuations in dissolved oxygen and longest periods of hypoxia, harbor conditions harmful to vertebrates and invertebrates in the estuary. Reversing the anthropogenically induced low oxygen levels, by restoring more natural tidal exchange and by decreasing agricultural runoff, could improve the survival and growth of important estuarine organisms.  相似文献   

Risk-based characterisation of an urban building site     

Maximilian Huber  Fabrizio Marconi  Massimiliano Moscatelli 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2015,9(1):49-56

The evaluation of the underground soil stratigraphy is a key aspect in geotechnical site characterisation. However, these means of site exploration are only pinholing subsoil conditions and expert knowledge is needed to understand subsoil conditions in order to build a reliable geological-geotechnical model. This contribution employs a geostatistical simulation methodology for the simulation of random fields representing geological uncertainty. This combines borehole data and expert knowledge via a mathematical framework. Moreover a risk-based site characterisation scheme is developed for urban site characterisation. This novel characterisation scheme offers additional insight into the effects of large-scale, geological spatial variability by using fragility curves to quantify these effects.  相似文献   

The compensating effect of glaciers: Characterizing the relation between interannual streamflow variability and glacier cover     

Marit van Tiel  Irene Kohn  Anne F. Van Loon  Kerstin Stahl 《水文研究》2020,34(3):553-568

Meltwater from glaciers is not only a stable source of water but also affects downstream streamflow dynamics. One of these dynamics is the interannual variability of streamflow. Glaciers can moderate streamflow variability because the runoff in the glacierized part, driven by temperature, correlates negatively with the runoff in the non-glacierized part of a catchment, driven by precipitation, thereby counterbalancing each other. This is also called the glacier compensation effect (GCE), and the effect is assumed to depend on relative glacier cover. Previous studies found a convex relationship between streamflow variability and glacier cover of different glacierized catchments, with lowest streamflow variability at a certain optimum glacier cover. In this study, we aim to revisit these previously found curves to find out if a universal relationship between interannual streamflow variability and glacier cover exists, which could potentially be used in a space-for-time substitution analysis. Moreover, we test the hypothesis that the dominant climate drivers (here precipitation and temperature) switch around the suggested optimum of the curve. First, a set of virtual nested catchments, with the same absolute glacier area but varying non-glacierized area, were modelled to isolate the effect of glacier cover on streamflow variability. The modelled relationship was then compared with a multicatchment data set of gauged glacierized catchments in the European Alps. In the third step, changes of the GCE curve over time were analysed. Model results showed a convex relationship and the optimum in the simulated curve aligned with a switch in the dominant climate driver. However, the multicatchment data and the time change analyses did not suggest the existence of a universal convex relationship. Overall, we conclude that GCE is complex due to entangled controls and changes over time in glacierized catchments. Therefore, care should be taken to use a GCE curve for estimating and/or predicting interannual streamflow variability in glacierized catchments.  相似文献