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Dive into the research topics where Ulrich Berner is active.

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Featured researches published by Ulrich Berner.


Organic Geochemistry | 1996

Empirical carbon isotope/maturity relationships for gases from algal kerogens and terrigenous organic matter, based on dry, open-system pyrolysis

Ulrich Berner; Eckhard Faber

Abstract Pyrolyses experiments (dry, open-system) on algal kerogens and landplant material (Berner et al., 1995) have shown that carbon isotopic variations of methane, ethane and propane obtained from laboratory simulations mimic isotope variations of natural thermal gases. These isotope variations can be approximated through kinetic models (Berner et al., 1995). Also, maturity parameters like vitrinite reflectance and Rock-Eval Tmax are reliably calculated from kinetic models that are based on pyrolysis experiments. User-friendly versions of isotope/maturity models for methane, ethane and propane were obtained from application of statistical curve-fitting procedures to the results of instantaneous kinetic models of Berner et al. (1995). The resulting simple empirical functions relate carbon isotopic variations of light hydrocarbons directly to source rock maturity and can be applied where gases have accumulated instantaneously. They allow flexible calculations that account for carbon isotopic variability of precursor sites of the individual gases. Application of the model enables detection of mixing between bacterial and thermal gases, as well as mixing between thermal gases of different maturities. The application of the proposed models is demonstrated in two case studies (Green Tuff Basin, Japan; Cooper Basin, Australia) with data taken from the literature (Rigby and Smith, 1981; Sakata, 1991).


Nature | 1998

Stable phytoplankton community structure in the Arabian Sea over the past 200,000 years

C. J. Schubert; J. Villanueva; S. E. Calvert; Gregory L. Cowie; U. von Rad; Hartmut Schulz; Ulrich Berner; H. Erlenkeuser

Glacial to interglacial climate changes have been related to organic carbon cycling in oceanic surface waters, and this possible link has led to the development of sedimentary tracers of past marine biological production. For example, sediment records of organic carbon, opal and biogenic barium have been used to reconstruct past variations in production in different oceanic regimes, but these tracers cannot be used to discriminate between the relative contributions of different phytoplankton groups. Such a discrimination would provide greater insight into the operation of the biological ‘pump’ transporting material down out of surface waters, and into the possible influence of the structure of oceanic food chains on carbon fluxes. Several organic biomarker compounds have now been established for tracing the contribution of different planktonic groups to organic carbon in sediments. Here we show that four such biomarkers—dinosterol, alkenones, brassicasterol and chlorins, which represent dinoflagellates, prymnesiophytes, diatoms and chlorophyll-producers, respectively—have concordant concentration maxima that coincide with organic carbon maxima over the past 200,000 years in a sediment core from the northeastern Arabian Sea. Not only do these organic tracers track changes in ocean production in this region, but the similar distributions of dinosterol and brassicasterol indicate that the relative contributions of the dominant members of the phytoplankton community (diatoms and dinoflagellates) to production were roughly uniform on timescales greater than 3,000–4,000 years over the past 200,000 years.


Palaeogeography, Palaeoclimatology, Palaeoecology | 1999

Multiple monsoon-controlled breakdown of oxygen-minimum conditions during the past 30,000 years documented in laminated sediments off Pakistan

Ulrich von Rad; Hartmut Schulz; Volkher Riech; Maryke den Dulk; Ulrich Berner; Frank Sirocko

Abstract Late Holocene laminated sediments from a core transect centred in the oxygen minimum zone (OMZ) impinging at the continental slope off Pakistan indicate stable oxygen minimum conditions for the past 7000 calendar years. High SW-monsoon-controlled biological productivity and enhanced organic matter preservation during this period is reflected in high contents of total organic carbon (TOC) and redox-sensitive elements (Ni, V), as well as by a low-diversity, high-abundance benthic foraminiferal Buliminacea association and high abundance of the planktonic species Globigerina bulloides indicative of upwelling conditions. Surface-water productivity was strongest during SW monsoon maxima. Stable OMZ conditions (reflected by laminated sediments) were found also during warm interstadial events (Preboreal, Bolling–Allerod, and Dansgaard–Oeschger events), as well as during peak glacial times (17–22.5 ka, all ages in calendar years). Sediment mass accumulation rates were at a maximum during the Preboreal and Younger Dryas periods due to strong riverine input and mobilisation of fine-grained sediment coinciding with rapid deglacial sea-level rise, whereas eolian input generally decreased from glacial to interglacial times. In contrast, the occurrence of bioturbated intervals from 7 to 10.5 ka (early Holocene), in the Younger Dryas (11.7–13 ka), from 15 to 17 ka (Heinrich event 1) and from 22.5 to 25 ka (Heinrich event 2) suggests completely different conditions of oxygen-rich bottom waters, extremely low mass and organic carbon accumulation rates, a high-diversity benthic fauna, all indicating lowered surface-water productivity. During these intervals the OMZ was very poorly developed or absent and a sharp fall of the aragonite compensation depth favoured the preservation of pteropods. The abundance of lithogenic proxies suggests aridity and wind transport by northwesterly or northeasterly winds during these periods coinciding with the North Atlantic Heinrich events and dust peaks in the Tibetan Loess records. The correlation of the monsoon-driven OMZ variability in the Arabian Sea with the rapid climatic fluctuations in the high northern latitudes suggests a close coupling between the climates of the high and low latitudes at a global scale.


Marine Geology | 1996

Authigenic carbonates derived from oxidized methane vented from the Makran accretionary prism off Pakistan

Ulrich von Rad; Heinrich Rösch; Ulrich Berner; Mebus Geyh; Vesna Marchig; Hartmut Schulz

We report the first discovery and sampling of a methane-hydrogen sulfide rich “cold seep” from the Makran accretionary prism off Pakistan (Arabian Sea). A variety of cm- to m-scale pockmarks and gas seepage structures were identified from underwater TV-photo sled profiles crossing the oxygen minimum zone (OMZ), related to highresolution seismic (PARASOUND) records. From the seeps isotopically light, bacterially formed methane is emanating that is partly oxidized to HCO3− in the bacterial sulfate reduction zone. This results in the precipitation of irregular dark-gray to black crusts of indurated authigenic carbonates, mainly cryptocrystalline magnesian calcite and Ca-rich dolomite, near the sediment/seawater interface within the OMZ. Downcore, the crusts grade into hemipelagic carbonate-poor silty clays with transitional lithologies in between. Similar to the pockmark carbonates from the Oregon margin and in the North Sea, the authigenic carbonates are extremely depleted in 13C (δ13Ccarbonate < − 40%.). This suggests that they were derived from bacterial methane (δ13Cmethane: − 77.8%.) that was oxidized under anaerobic conditions. The authigenic carbonates are associated with white fluffy mats of chemoautotrophic H2S-oxidizing bacteria. Small pockmarks appear to be concentrated at small-scale escarpments, suggesting focussed fault-controlled pore fluid expulsion due to the tectonic dewatering and degassing of the accretionary prism, whereas diffuse discharge of pore fluids is inferred from the widespread occurrence of tiny gas bubble tubes.


Chemical Geology | 1995

Primary cracking of algal and landplant kerogens: Kinetic models of isotope variations in methane, ethane and propane

Ulrich Berner; Eckhard Faber; Georg Scheeder; Dieter Panten

Abstract Samples of an algae-rich kerogen and a xylite were subjected to an open-system pyrolysis that allows a simulation of primary cracking (temperatures: 20 to 810°C, heating rate: 5°C/min, helium flow: 21 ml/min) within the (measured) maturity range 0.3 to 5.4% vitrinite reflectance. Gases collected during pyrolysis were analyzed for their molecular composition and the carbon isotope ratios of methane, ethane and propane. With increasing maturity of the algae-rich kerogen, we observe an increase of the carbon isotope ratios of produced light hydrocarbons. Carbon isotope values of methane derived from xylite, however, show significant inversions with increasing maturity, that indicate an isotopic inhomogeneity of the precursors from which methane is generated. Hydrogen isotope values of methane from Kukersite vary between −211 and −84‰, whereas, hydrogen isotope ratios of methane from xylite increase from −314 to −164‰. The data of the pyrolysis experiments have been used to develop kinetic models of hydrocarbon generation that are combined with Rayleigh-distillation models to describe the isotope fractionation between organic matter and light hydrocarbons. Carbon isotope fractionation factors between kerogens and individual gas components are high for Kukersite (αCH4-Kuk = 1.017, αC2-Kuk = 1.009, αC3-Kuk = 1.005) and low for xylite (αCH4-Xyl = 1.0042, αC2-Xyl = 1.003, αC3-Xyl = 1.001). Hydrogen isotope fractionation factors are lower for Kukersite and higher for xylite (αCH4-Kuk = 1.1, αCH4-Xyl = 1.2). Gas generation and isotope models are combined with kinetic models of thermal kerogen alteration. The results of the calculations are compared to measured data of natural samples from the Delaware and Val Verde basins (U.S.A.).


Organic Geochemistry | 1988

Maturity related mixing model for methane, ethane and propane, based on carbon isotopes

Ulrich Berner; Eckhard Faber

Abstract Thermal hydrocarbons found in natural oil and gas deposits frequently represent gas mixtures, the differentiation of which can be difficult or impossible. A mathematical model has been developed to predict gas-mixtures from two known end-members. The basis for the model are the relationships between carbon isotope ratios of methane through propane, the molecular gas composition and the maturity of the organic precursor materials (sapropelic kerogen). Applying the model, it is possible to estimate the isotopic composition of mixed hydrocarbon gases from the maturities of the related source rocks.


Deep-sea Research Part Ii-topical Studies in Oceanography | 2003

Methane in ocean waters of the Bay of Bengal : its sources and exchange with the atmosphere

Ulrich Berner; Jürgen Poggenburg; Eckhard Faber; Detlef Quadfasel; Andrea Frische

Three legs of cruise SO93 of the German research vessel R/V SONNE provided information on the methane distribution along different profiles of the Bay of Bengal during the NE monsoon in January 1994. A 650-km-long profile from the Sri Lankan coast to the Equator revealed maximum methane concentrations clearly associated with different water masses. Peak concentrations of 105 nl/l occur below 45 m water depth. A 2600-km-long profile from the Equator to the shelf of Bangladesh showed elevated concentrations in the surface waters (up to 800 nl/l on the shelf close to the Ganges/Brahmaputra mouth). Waters at 700 and 2100 m off Bangladesh are enriched in methane. Seismic profiles of the Parasound system point to the existence of a mud diapir at 2100 m, and a seismic wipe out at 700 m points to gas-charged sediments. Sediment gases are assumed to be the source of the methane in the deep water of this area. However, no exchange with the surface waters was observed. Methane contents of the surface waters are related to bacterial processes as shown by isotope data of methane. This newly generated methane only partly contributes to the atmospheric methane concentrations, especially on the shelf of Bangladesh close to the Ganges/Brahmaputra mouth with flux rates of 145 kg km � 2 year � 1 . Large sections of the profiles, however, showed near-equilibrium conditions and even undersaturation of methane with respect to the atmosphere. r 2003 Elsevier Science Ltd. All rights reserved.


Environmental Monitoring and Assessment | 1994

Methane in Ocean Waters: Concentration and Carbon Isotope Variability at East Pacific Rise and in the Arabian Sea

Eckhard Faber; Peter Gerling; Ulrich Berner; E. Sohns

Methane concentrations and stable carbon isotope ratios of water samples from the East Pacific Rise (EPR) at 21°S and the Arabian Sea (24°N, 65°E) have been determined. EPR surface water is in equilibrium (ca. 50 nl/L and −50‰<δ13CH4<−46‰) with atmospheric methane. Deep “background” water has the signature of the remaining fraction of atmospheric methane partially oxidized in the water column by bacteria. Bottom near, hydrothermally influenced vent methane (>100nl/L and −30‰<δ13CH4<−22‰) is detectable only close to the seep site. There is no input of hydrothermal methane into the atmosphere. EPR water is considered to be rather a sink than a source of atmospheric methane. Surface waters of the Arabian Sea are enriched in methane relative to the atmosphere (source for atmospheric methane). Carbon isotope ratios point to a bacterial origin of methane (δ13CH4<−55‰) that is generated in the surface waters. Concentration changes and variations of carbon isotope ratios also suggest that methane seeping from the sea floor sediments of the Arabian Sea is oxidized by bacterial activity and does not reach the atmosphere.


Energy Conversion and Management | 1996

Isotopic tracing of methane in water and exchange with the atmosphere

Eckhard Faber; Ulrich Berner; Peter Gerling; A. Hollerbach; Wolfgang Stahl; H.G. Schröder

Sediments of Lake Constance are rich in bacterial methane (yield CH 4 -85‰). However, methane flux from the sediment into the water was not detected. Deep water (below ca. 50 m) has background signature (yield < 50 nL/L ; -40< δ 13 CH 4 < -30‰). Surface water is enriched in methane relative to atmospheric equilibrium, most probably the methane is produced by methanogens in the surface layers. The surface water is a source for atmospheric methane ; calculated flux rates exceed high values reported for ocean water. Deep water of the Bay of Bengal is generally low in methane (background signature). At two locations at the continental slope, bacterial methane (δ 13 CH 4 < -50‰) seeps from the sediments into the water. Methane concentration in the surface water is close to atmospheric equilibrium in the equatorial area but higher in the Ganges/Bramaputra mouth, where methane flux to the atmosphere reaches up to 30 kg km -2 yr -1 .


Global Biogeochemical Cycles | 2001

Calculation of global carbon dioxide emissions: Review of emission factors and a new approach taking fuel quality into consideration

M. Hiete; Ulrich Berner; Otto Richter

Anthropogenic carbon dioxide emissions resulting from fossil fuel consumption play a major role in the current debate on climate change. Carbon dioxide emissions are calculated on the basis of a carbon dioxide emission factor (CEF) for each type of fuel. Published CEFs are reviewed in this paper. It was found that for nearly all CEFs, fuel quality is not adequately taken into account. This is especially true in the case of the CEFs for coal. Published CEFs are often based on generalized assumptions and inexact conversions. In particular, conversions from gross calorific value to net calorific value were examined. A new method for determining CEFs as a function of calorific value (for coal, peat, and natural gas) and specific gravity (for crude oil) is presented that permits CEFs to be calculated for specific fuel qualities. A review of proportions of fossil fuels that remain unoxidized owing to incomplete combustion or inclusion in petrochemical products, etc., (stored carbon) shows that these figures need to be updated and checked for their applicability on a global scale, since they are mostly based on U.S. data.

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Guido Meinhold

University of Göttingen

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M. Hiete

University of Kassel

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Oliver Lehnert

Tallinn University of Technology

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