The occurrence of distal Icelandic and Italian tephra in the Lateglacial of Lake Bled,Slovenia     

Christine S. Lane  Maja Andrič  Victoria L. Cullen  Simon P.E. Blockley 《Quaternary Science Reviews》2011,30(9-10):1013-1018

The discovery of sites preserving tephra layers from multiple volcanic centres is key to constructing a single European tephrostratigraphic framework for the Late Quaternary. Until now, the tephrostratigraphy of Europe has been divided into two halves: sites in the North Atlantic and northern Europe regions link the Icelandic, Eifel, and the Massif Central volcanic histories; whilst sites in southern Europe record the sequence of tephra layers produced by circum-Mediterranean volcanic provinces. The missing link, able to tie together these two halves, is found in the tephrostratigraphic record of Lake Bled, Slovenia.Lake Bled, in the Julian Alps, Slovenia, holds a high resolution multi-proxy palaeoenvironmental archive for the Lateglacial of south-central Europe. Cryptotephra investigations have revealed three tephra layers: two closely spaced within Younger Dryas stadial sediments and one shortly after the start of the Bølling-Allerød interstadial warming. Two of the tephra layers (Bld_T120 and Bld_T240) are of Campanian origin and are correlated to deposits of the Pomici Principali (PP) and Neapolitan Yellow Tuff (NYT) eruptions, respectively. The third layer (Bld_T122) correlates to the Icelandic Vedde Ash (VA), extending the known fallout of this widespread marker layer farther to the southeast.The Lake Bled record also allows the stratigraphic relationship and relative ages of the VA and the PP eruption to be discerned for the first time. Whilst existing numerical age estimates for these two deposits are indistinguishable within errors, their close occurrence in the same lacustrine sediment sequence shows that the VA was erupted shortly prior to the PP eruption.The tephrostratigraphy of Lake Bled developed here helps us to tie together regional volcanic stratigraphies into a broader, continental-scale lattice of sites, with the potential to allow the transfer of dates between remote sequences and the construction of relative chronologies, beneficial in particular for environmental and archaeological research.  相似文献   

Organic and inorganic matter in Louisiana coastal waters: Vermilion, Atchafalaya, Terrebonne, Barataria, and Mississippi regions     

Schaeffer BA  Conmy RN  Aukamp J  Craven G  Ferer EJ 《Marine pollution bulletin》2011,62(2):415-422

Chromophoric dissolved organic matter (CDOM) spectral absorption, dissolved organic carbon (DOC) concentration, and the particulate fraction of inorganic (PIM) and organic matter (POM) were measured in Louisiana coastal waters at Vermilion, Atchafalaya, Terrebonne, Barataria, and Mississippi River locations, in 2007-2008. The range of CDOM was 0.092 m⁻¹ at Barataria in June 2008 to 11.225 m⁻¹ at Mississippi in February 2008. An indicator of organic matter quality was predicted by the spectral slope of absorption coefficients from 350 to 412 nm which was between 0.0087 m⁻¹ at Mississippi in May 2008 and 0.0261 m⁻¹ at Barataria in June 2008. CDOM was the dominant component of light attenuation at Terrebonne and Barataria. Detritus and CDOM were the primary components of light attenuation at Vermilion, Atchafalaya, and Mississippi. DOC ranged between 65 and 1235 μM. PIM ranged between 1.1 and 426.3 mg L⁻¹ and POM was between 0.3 and 49.6 mg L⁻¹.  相似文献   

Archaeol as a methanogen biomarker in ombrotrophic bogs     

Richard D. Pancost  Erin L. McClymont  Elizabeth M. BinghamZoë Roberts  Dan J. CharmanEdward R.C. Hornibrook  Anthony BlundellFrank M. Chambers  Katie L.H. LimRichard P. Evershed 《Organic Geochemistry》2011,42(10):1279-1287

In order to develop new tools in the reconstruction of microbiological processes in ancient continental settings, we determined the concentration of archaeol and sn-2-hydroxyarchaeol in four Holocene ombrotrophic peatlands, spanning a range of European climate zones. Neither ether lipid was present in the aerobic acrotelm peat, consistent with an origin from anaerobic archaea, presumably methanogens. At the depth of the maximum seasonal water table, archaeol and sn-2-hydroxyarchaeol concentration markedly increased at all four sites, again consistent with an anaerobic source, but differed strongly among sites. The differences apparently reflect a combination of vegetation - ericaceous and graminoid plants as opposed to Sphagnum spp. and other mosses lacking root systems - and temperature influence on methanogenesis. In particular, low ether lipid concentrations in Finland probably reflect the lack of vascular vegetation possessing well-developed root systems, together with low mean annual temperature. Similarly low concentrations of archaeol and sn-2-hydroxyarchaeol in a German bog likely result from winter temperatures below 0 °C and a relatively shorter growing season. The occurrence of sn-2-hydroxyarchaeol is limited to a narrow and shallow depth range, indicating that it is poorly preserved, but archaeol persists throughout the cores. Decoupling the concentration of archaeol and the more labile sn-2-hydroxyarchaeol below ca. 50 cm suggests that the former records fossil biomass rather than living biomass. If so, then downcore variation in archaeol concentration likely reflects past changes in methane cycling, and archaeol, pending further developmental research, could serve as a new tool for reconstruction of past peatland biogeochemistry.  相似文献   

Pyrolysis GC-MS as a rapid screening tool for determination of peat-forming plant composition in cores from ombrotrophic peat     

Erin L. McClymont  Elizabeth M. BinghamChris J. Nott  Frank M. ChambersRichard D. Pancost  Richard P. Evershed 《Organic Geochemistry》2011,42(11):1420-1435

Peat cores provide decadal to centennial records of climatic and environmental change, including evidence for human/environment interaction. Existing palaeoenvironmental proxies (macrofossils, pollen, humification, testate amoebae, lipid composition) require multiple laboratory preparation steps and may be subject to differential preservation that can limit production of a continuous time series. The potential for pyrolysis gas-chromatography-mass-spectrometry (Py-GC-MS) to be applied to bulk peat samples is investigated here. The only preparatory step required was freeze drying. Analysis of a range of important peat-forming plants demonstrates that Sphagnum moss species are unique in containing the pyrolysis product of sphagnum acid, 4-isopropenylphenol. In contrast, non-Sphagnum species are rich in lignin pyrolysis products, which are absent from Sphagnum. The presence of these pyrolysis markers is reflected in bulk peat composition and tested here using archives from Bolton Fell Moss and Butterburn Flow (UK), Kontolanrahka (Finland) and Bissendorfer Moor (Germany). A ratio between 4-isopropenylphenol and two lignin pyrolysis products is proposed as a proxy for total Sphagnum input to peat archives and shows potential for use as a rapid screening tool for characterising bulk peat composition before more intensive analysis.  相似文献   

Systematic errors in weak lensing: application to SDSS galaxy–galaxy weak lensing     

Rachel Mandelbaum  Christopher M. Hirata  Uro&#; Seljak  Jacek Guzik  Nikhil Padmanabhan  Cullen Blake  Michael R. Blanton  Robert Lupton  Jonathan Brinkmann 《Monthly notices of the Royal Astronomical Society》2005,361(4):1287-1322

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Effects of iron limitation on intracellular cadmium of cultured phytoplankton: Implications for surface dissolved cadmium to phosphate ratios     

Erin S. Lane  David M. Semeniuk  Robert F. Strzepek  Jay T. Cullen  Maria T. Maldonado   《Marine Chemistry》2009,115(3-4):155-162

This study compares intracellular Cd content (Cd:C) of cultured marine phytoplankton grown under various Fe levels, with estimated particulate Cd:P ratios derived from regression slopes of Cd versus PO₄³⁻ relationships from a global dataset. A 66-fold difference in Cd:C ratios was observed among the seven species grown under identical Fe concentrations, with oceanic diatoms having the highest Cd quotas and prymesiophytes the lowest. Interestingly, all species significantly increased their Cd:C ratios under Fe-limitation (on average 2-fold). The global data set also showed that the mean estimated Cd:P ratio of surface water particulates in HNLC (high nutrient low chlorophyll) regions were approximately 2-fold higher than non-HNLC regions. A sequence of events are proposed to explain high Cd:P ratios in HNLC waters. First, the seasonal relief from Fe-limitation in HNLC regions leads to blooms of large chain forming diatoms with high intrinsic Cd:P ratios. These large blooms may, in theory, deplete surface water CO₂ and Zn concentrations, which ultimately, would result in increased Cd uptake. Eventually these blooms will run out of Fe, which has been shown to further increase intercellular Cd via growth biodilution and increased Cd uptake through non-specific Fe(II) transporters. Ultimately, Fe-limited diatoms with enhanced Cd quotas will sink out of surface waters leading to pronounced regional differences in Cd:P ratios between HNLC and non-HNLC waters in the global ocean.  相似文献   

Mineralogy,microtexture, and composition of shock‐induced melt pockets in thi Los Angeles basaltic shergottite     

Erin L. WALTON  John G. SPRAY 《Meteoritics & planetary science》2003,38(12):1865-1875

Abstract— Analytical electron microscopy of shock features in the basaltic shergottite Los Angeles (stone 1) reveals: 1) shock recorded in the bulk sample; and 2) localized pressure and temperature excursions that have generated melt pockets up to 4 mm in diameter. Bulk shock effects include microfaulting (offsets 1–200 μm), mosaicism, deformed exsolution lamellae and planar fracturing in pyroxene, undulose extinction in whitlockite, mechanical twinning in titanomagnetite and ilmenite, and the transformation of plagioclase to maskelynite (≤4% remnant reduced birefringence). The pressure estimates for bulk shock are 35–40 GPa. Localized shock excursions have generated three types of discrete melt zones (0.07 times 1.3 mm to 3.0 times 3.5 mm apparent diameter) possessing glassy to microcrystalline groundmasses. These melt pockets are differentiated on the basis of size, clast volume, and degree of crystallization and vesiculation. Melt veins and melt dikelets emanate from the melt pockets up to 3 mm into the host rock but do not necessarily connect with other melt pockets. The melt pockets were generated by pressure‐temperature excursions of 60–80 GPa and 1600–2000°C, resulting in discrete melting of adjacent host rock minerals at grain boundary margins. Concentric zoning in the margins of clinopyroxenes coincides with a progressive reduction in birefringence as melt pockets are approached. This suggests that the shock excursions were focused as point sources in the wake of the shock front that induced bulk damage.  相似文献   

The hot, warm and cold gas in Arp 227 – an evolving poor group     

R. Rampazzo  P. Alexander  C. Carignan  M. S. Clemens  H. Cullen  O. Garrido  M. Marcelin  K. Sheth  G. Trinchieri 《Monthly notices of the Royal Astronomical Society》2006,368(2):851-863

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Estimated supply of RED credits 2011–2035     

Michael J. Coren  Erin Myers Madeira 《Climate Policy》2013,13(6):1272-1288

Previous attempts to estimate the supply of greenhouse gas emission reductions from reduced emissions from deforestation (RED) have generally failed to incorporate policy developments, country-specific abilities and political willingness to supply offsets for developed countries’ emissions. To address this, we estimate policy-appropriate projections of creditable emission reductions from RED. Two global forest carbon models are used to examine major assumptions affecting the generation of credits. The results show that the estimated feasible supply of RED credits is significantly below the biophysical mitigation potential from deforestation. A literature review identified an annual RED emission reduction potential between 1.6 and 4.3 Gt CO₂e. Feasible RED supply estimates applying the OSIRIS model were 1.74 Gt CO₂e annually between 2011 and 2020, with a cumulative supply of 17.4 Gt CO₂e under an ‘own-efforts’ scenario. Estimates from the Forest Carbon Index were very low at $5/t CO₂e with 8 million tonne CO₂e annually, rising to 1.8 Gt CO₂e at $20/t CO₂e. Cumulative abatement between 2011 and 2020 was 9 billion Gt CO₂e ($20/t CO₂e). These volumes were lower, sometimes dramatically, at prices of $5/t CO₂e suggesting a non-linear supply of credits in relation to price at a low payment level. For policy makers, the results suggest that inclusion of RED in a climate framework increases abatement potential, although significant constraints are imposed by political and technical issues.  相似文献   

Presence, infectivity, and stability of enteric viruses in seawater: relationship to marine water quality in the Florida Keys     

Wetz JJ  Lipp EK  Griffin DW  Lukasik J  Wait D  Sobsey MD  Scott TM  Rose JB 《Marine pollution bulletin》2004,48(7-8):698-704

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