Bernhard Peucker-ehrenbrink - Academia.edu (original) (raw)
Papers by Bernhard Peucker-ehrenbrink
In this paper we compare multivariate methods using both traditional approaches, which ignore iss... more In this paper we compare multivariate methods using both traditional approaches, which ignore issues of closure and provide relatively simple methods to deal with censored or missing data, and log-ratio methods to determine the sources of trace constituents in the atmosphere. The data set examined was collected from April to July 2008 at a sampling site near Woods Hole, Massachusetts, along the northeastern United States Atlantic coastline. The data set consists of trace gas mixing ratios (O 3 , SO 2 , NO x , elemental mercury [Hg o ], and reactive gaseous mercury [RGM]), and concentrations of trace elements in fine (<2.5 µm) particulate matter (Al,
Geociências, Apr 6, 2019
Introdução Área de estudo Desenvolvimento Metodológico Resultados e Discussão Conclusões Agradeci... more Introdução Área de estudo Desenvolvimento Metodológico Resultados e Discussão Conclusões Agradecimentos Referências RESUMO-O rio Tapajós é um afluente de águas claras da margem direita do rio Amazonas, drenando uma área de 492.263 km 2 da região central do Brasil para a porção central do estado do Pará. O objetivo deste estudo é determinar as concentrações de carbono orgânico (COP e COD) transportados no rio Tapajós próximo à cidade de Itaituba/PA, avaliando a influência da vazão e as mudanças hidrológicas sazonais no transporte destes compostos. Amostras mensais de água da superfície do rio foram coletadas em 2016 e os parâmetros biogeoquímicos (pH, condutividade elétrica, oxigênio dissolvido e temperatura) foram medidos in situ. As concentrações de sedimento foram analisados através de testes estatísticos em relação aos dados hidrológicos (precipitação, cota e vazão) fornecidos pelo INMET e banco de dados HyBam. COP teve uma média anual de 14±10,0 mg L-1 , com média de 20,8 mg L-1 na fase de cheia e de 7,9 mg L-1 na fase de seca. O COD teve média anual de 3,8±2,2 mg L-1 , com média de 5,0 mg L-1 na cheia e de 2,3 mg L-1 na seca. Os resultados obtidos sugerem que as mudanças hidrológicas sazonais são a principal causa das variações na concentração de sedimentos transportados pelo rio Tapajós, com possíveis associações às atividades de mineração e outras ações antrópicas ao longo de seus afluentes. Palavras-Chave-Parâmetros biogeoquímicos, hidrologia e sedimentos.
Global Biogeochemical Cycles, Jun 1, 2021
Inland waters have been increasingly recognized as hotspots for global carbon cycling, moving awa... more Inland waters have been increasingly recognized as hotspots for global carbon cycling, moving away from being viewed as passive transporters and reservoirs, to being accepted as interwoven conveyers and reactors (
Atmospheric Environment, Nov 1, 2013
h i g h l i g h t s Contribution of natural and anthropogenic PM 2.5 sources is quantified. Back-... more h i g h l i g h t s Contribution of natural and anthropogenic PM 2.5 sources is quantified. Back-trajectories for marine and crustal sources each show input from offshore. Results for crustal source are explained by long-range transport of Saharan dust. Results for Hg species, SO 2 and NO x show influence of combustion-related plumes. Results for RGM show diurnal cycle of production characteristic of marine influence.
Earth and Planetary Science Letters, Jun 1, 2011
Abundant chromite grains with L-chondritic composition in the resurge deposits of the Lockne impa... more Abundant chromite grains with L-chondritic composition in the resurge deposits of the Lockne impact crater (458 Myr old; dia. ~10 km) in Sweden have been inferred to represent relict fragments of an impactor from the break-up of the L-chondrite parent body at 470 Ma. This view has been challenged based on Ir/Cr and platinum group element (PGE) patterns of the same resurge deposits, and a reinterpretation of the origin of the chromite grains. An impactor of the non-magmatic iron meteorite type was proposed instead. Here we show that single-grain oxygen and noble-gas isotope analyses of the chromite grains from the resurge deposits further support an origin from an L-chondritic asteroid. We also present PGE analyses and Ir/Cr ratios for fossil L-chondritic meteorites found in mid-Ordovician marine limestone in Sweden. The L-chondritic origin has been confirmed by several independent methods, including major element and oxygen isotopic analyses of chromite. Although the meteorites show the same order-of-magnitude PGE and Cr concentrations as recent L chondrites, the elements have been redistributed to the extent that it is problematic to establish the original meteorite type from these proxies. Different 2 PGE data processing approaches can lead to highly variable results, as also shown here for the Lockne resurge deposits. We conclude that the Lockne crater was formed by an Lchondritic impactor, and that considerable care must be taken when inferring projectile type from PGEs in sedimentary ejecta deposits.
Geology, Mar 1, 2012
Knowledge of the 187 Os/ 188 Os ratio as well as the inventories of rhenium and platinum group el... more Knowledge of the 187 Os/ 188 Os ratio as well as the inventories of rhenium and platinum group elements (PGE) in oceanic crust allows quantification of the proportion of recycled oceanic crust in oceanic basalt sources. Our knowledge is limited by the availability of well-characterized sections of oceanic crust, specifically of the plutonic, lower portion that has not been drilled in situ to the Moho. Here we report new data for plutonic rocks that compose the bottom 4680 m of an ocean crust section from the Oman ophiolite. Major and trace element data as well as mineral analyses indicate that Oman gabbros are primitive cumulates from melts similar to typical mid-oceanic ridge basalt. The mean weighted composition of this section (Re: 427 pg/g; Os: 55 pg/g; Ir: 182 pg/g; Pd: 2846 pg/g; Pt: 4151 pg/g; initial 187 Os/ 188 Os: 0.142) indicates significantly higher Os and lower Re concentrations than previously analyzed partial sections of ocean crust that lack cumulate lower crust [Deep Sea Drilling Project–Ocean Drilling Program (DSDP-ODP) Hole 504B, ODP Hole 735B], emphasizing that the lower, cumulate oceanic crust dominates the Os budget of oceanic crust. Analyses of mineral grain size fractions indicate that rhenium, PGE, and lead are enriched in the sulfur-rich, fine fraction. This corroborates the notion that small accessory phases, and the melt migration processes affecting them, control these elements’ budgets, distributions, and susceptibilities to alteration. The Re-Os-PGE inventories of a hypothetical 6.5-km-thick composite section that consists of 1825 m of DSDP Hole 504B−like upper oceanic crust and 4680 m of Oman-like lower ocean crust (Re: 736 pg/g; Os: 45 pg/g; Ir: 133 pg/g; Pd: 2122 pg/g; Pt: 2072 pg/g; initial 187 Os/ 188 Os: 0.146) provide a new comprehensive assessment of oceanic crust composition. Upon recycling and mixing with reasonable proportions of mantle peridotite, this composite requires at least 2 G.y. to develop sufficiently radiogenic 187 Os/ 188 Os to generate high μ (HIMU: μ = 238 U/ 204 Pb) basalts.
Environmental Science & Technology, Jul 27, 2012
The extent to which humans are modifying Earth's surface chemistry can be quantified by comparing... more The extent to which humans are modifying Earth's surface chemistry can be quantified by comparing total anthropogenic element fluxes with their natural counterparts (Klee & Graedel, 2004). We quantify anthropogenic mass transfer of 77 elements from mining, fossil fuel burning, biomass burning, construction activities, and human apportionment of terrestrial net primary productivity, and compare it to natural mass transfer from terrestrial and marine net primary productivity, riverine dissolved and suspended matter fluxes to the ocean, soil erosion, eolian dust, sea-salt spray, cosmic dust, volcanic emissions and-for helium-hydrodynamic escape from the Earth's atmosphere. We introduce an approach to correct for losses during industrial processing of elements belonging to geochemically coherent groups, and explicitly incorporate uncertainties of element mass fluxes through Monte Carlo simulations. We find that at the Earth's surface anthropogenic fluxes of iridium, osmium, helium, gold, ruthenium, antimony, platinum, palladium, rhenium, rhodium and chromium currently exceed natural fluxes. For these elements mining is the major factor of anthropogenic influence, whereas petroleum burning strongly influences the surficial cycle of rhenium. Our assessment indicates that if anthropogenic contributions to soil erosion and eolian dust are considered, anthropogenic fluxes of up to 62 elements surpass their corresponding natural fluxes.
2016 AGU Fall Meeting, Dec 13, 2016
Climate has been proposed to control both the rate of terrestrial silicate weathering and the exp... more Climate has been proposed to control both the rate of terrestrial silicate weathering and the export rate of associated sediments and terrestrial organic carbon to river-dominated margins-and thus the rate of sequestration of atmospheric CO 2 in the coastal ocean-over glacial-interglacial timescales. Focused on the Ganges-Brahmaputra rivers, this study presents records of post-glacial changes in basinscale Indian summer monsoon intensity and vegetation composition based on stable hydrogen (δD) and carbon (δ 13 C) isotopic compositions of terrestrial plant wax compounds preserved in the channel-levee system of the Bengal Fan. It then explores the role of these changes in controlling the provenance and degree of chemical weathering of sediments exported by these rivers, and the potential climate feedbacks through organic-carbon burial in the Bengal Fan. An observed 40h shift in δD and a 3-4h shift in both bulk organic-carbon and plant-wax δ 13 C values between the late glacial and mid-Holocene, followed by a return to more intermediate values during the late Holocene, correlates well with regional post-glacial paleoclimate records. Sediment provenance proxies (Sr, Nd isotopic compositions) reveal that these changes likely coincided with a subtle focusing of erosion on the southern flank of the Himalayan range during periods of greater monsoon strength and enhanced sediment discharge. However, grain-size-normalized organic-carbon concentrations in the Bengal Fan remained constant through time, despite order-of-magnitude level changes in catchment-scale monsoon precipitation and enhanced chemical weathering (recorded as a gradual increase in K/Si * and detrital carbonate content, and decrease in H 2 O + /Si * , proxies) throughout the study period. These findings demonstrate a partial decoupling of climate change and silicate weathering during the Holocene and that marine organiccarbon sequestration rates primary reflect rates of physical erosion and sediment export as modulated by climatic changes. Together, these results reveal the magnitude of climate changes within the Ganges-Brahmaputra basin following deglaciation and a closer coupling of monsoon strength with OC burial than with silicate weathering on millennial timescales.
AGUFM, Dec 1, 2005
Abstract Platinum Group Elements (PGE: Os, Ir, Rh, Ru, Pt, Pd) and osmium isotopes measured in ma... more Abstract Platinum Group Elements (PGE: Os, Ir, Rh, Ru, Pt, Pd) and osmium isotopes measured in marine and terrestrial sediment, snow and ice records are important paleo-tracers of riverine, hydrothermal, extraterrestrial, volcanic and anthropogenic inputs into the global surficial environment. For instance, the marine Os isotope record across the Cretaceous-Tertiary Boundary (KTB) indicates that the onset of the main phase of Deccan volcanism and the transient late Maastrichtian warming preceded the large extraterrestrial ...
Environmental Science & Technology, Aug 27, 2013
Platinum group elements (PGE) of anthropogenic origin have been reported in rainwater, snow, road... more Platinum group elements (PGE) of anthropogenic origin have been reported in rainwater, snow, roadside soil and vegetation, industrial waste, and urban airborne particles around the world. As recent studies have shown that PGE are bioavailable in the environment and pose health risks at chronic levels, the extent of PGE pollution is of global concern. In this study, we report PGE concentrations and osmium isotope ((187)Os/(188)Os) ratios of airborne particles (particulate matter, PM10) collected in Woods Hole, a small coastal village on Cape Cod, Massachusetts, U.S.A. The sampling site is more than 100 km away from the nearest urban centers (Boston, Providence) and has no large industrial emission center within a 30 km radius. The study reveals that, although PGE concentrations in rural airborne particulate matter are orders of magnitude lower than in urban aerosols, 69% of the total osmium is of anthropogenic origin. Anthropogenic PGE signatures in airborne particles are thus not restricted to large cities with high traffic flows and substantial industries; they can also be found in rural environments. We further conclude that the combination of Pt/Rh concentration ratios and (187)Os/(188)Os composition can be used to trace PGE sources. The Pt/Rh and (187)Os/(188)Os composition of Woods Hole aerosols indicate that the anthropogenic PGE fraction is primarily sourced from ore smelting processes, with possible minor contributions from fossil fuel burning and automobile catalyst-derived materials. Our results further substantiate the use of (187)Os/(188)Os in source apportionment studies on continental scales.
Journal of Radioanalytical and Nuclear Chemistry, Sep 1, 1991
The concentrations of 35 trace elements in the UNS-SpS glass sand reference material have been de... more The concentrations of 35 trace elements in the UNS-SpS glass sand reference material have been determined by instrumental neutron activation analysis involving short- and long-term irradiations. For analysis, the so-called “absolute monostandard method” was used, i.e. the concentrations were calculated from the measured gamma-activity and not by comparison with a reference sample of known composition. The results of up to 25 independent determinations are compared with the values given by UNS and other investigators. Most element contents agree well with the published values expecting K, Ga, and La, which will be discussed. Trace element contents for Cl, As, Br, Dy, and Au are reported for the first time.
Geochemistry Geophysics Geosystems, 2004
We quantitatively analyze the area-age distribution of sedimentary, igneous and metamorphic bedro... more We quantitatively analyze the area-age distribution of sedimentary, igneous and metamorphic bedrock based on data from the most recent digital geologic maps of East and Southeast Asia (Coordinating Committee for Coastal and Offshore Geosciences Programmes in East and Southeast Asia (CCOP) and the Geologic Survey of Japan, 1997; 1:2,000,000), published as Digital Geoscience Map G-2 by the Geological Survey of Japan. Sedimentary rocks, volcanic rocks, plutonic rocks, ultramafic rocks and metamorphic rocks cover 73.3%, 8.5%, 8.8%, 0.9%, and 8.6% of the surface area, respectively. The average ages of major lithologic units, weighted according to bedrock area, are as follows: sedimentary rocks (average stratigraphic age of 123 Myr/median age of 26 Myr), volcanic rocks (84 Myr/20 Myr), intrusive rocks (278 Myr/195 Myr), ultramafic rocks (unknown) and metamorphic rocks (1465 Myr/1118 Myr). The variability in lithologic composition and age structure of individual countries reflects the complex tectonic makeup of this region that ranges from Precambrian cratons (e.g., northeast China and North Korea) to Mesozoic-Cenozoic active margins (e.g., Japan, the Philippines, Indonesia and New Guinea). The spatial resolution of the data varies from 44 km 2 per polygon (Japan) to 1659 km 2 per polygon (Taiwan) and is, on average (490 km 2 /polygon), similar to our previous analyses of the United States of America and Canada. The temporal and spatial resolution is sufficiently high to perform age-area analyses of individual river basins larger than $10,000 km 2 and to quantitatively evaluate the relationship between bedrock geology and river chemistry. As many rivers draining tropical, mountainous islands of East and Southeast Asia have a disproportionate effect on the dissolved and particulate load delivered to the world oceans, bedrock geology in such river drainage basins disproportionately affect ocean chemistry.
Analytical Chemistry, Mar 6, 2014
The (187)Os/(188)Os ratio that is based on the β(-)-decay of (187)Re to (187)Os (t1/2 = 41.6 bill... more The (187)Os/(188)Os ratio that is based on the β(-)-decay of (187)Re to (187)Os (t1/2 = 41.6 billion years) is widely used to investigate petroleum system processes. Despite its broad applicability to studies of hydrocarbon deposits worldwide, a suitable matrix-matched reference material for Os analysis does not exist. In this study, a method that enables Os isotope measurement of crude oil with in-line Os separation and purification from the sample matrix is proposed. The method to analyze Os concentration and (187)Os/(187)Os involves sample digestion under high pressure and high temperature using a high pressure asher (HPA-S, Anton Paar), sparging of volatile osmium tetroxide from the sample solution, and measurements using multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). This methods significantly reduced the total procedural time compared to conventional Carius tube digestion followed by Os separation and purification using solvent extraction, microdistillation and N-TIMS analysis. The method yields Os concentration (28 ± 4 pg g(-1)) and (187)Os/(188)Os (1.62 ± 0.15) of commercially available crude oil reference material NIST 8505 (1 S.D., n = 6). The reference material NIST 8505 is homogeneous with respect to Os concentration at a test portion size of 0.2 g. Therefore, (187)Os/(188)Os composition and Os concentration of NIST 8505 can serve as a matrix-matched reference material for Os analysis. Data quality was assessed by repeated measurements of the USGS shale reference material SCo-1 (sample matrix similar to petroleum source rock) and the widely used Liquid Os Standard solution (LOsSt). The within-laboratory reproducibility of (187)Os/(188)Os for a 5 pg of LOsSt solution, analyzed with this method over a period of 12 months was ∼1.4% (1 S.D., n = 26), respectively.
Geochimica et Cosmochimica Acta, Oct 1, 1998
The effects of weathering of freshly exposed Precambrian rocks on the mobility of osmium were stu... more The effects of weathering of freshly exposed Precambrian rocks on the mobility of osmium were studied on soils developed on a chronosequence of glacial moraines from the western Wind River Range in Wyoming. The Os budget of the Precambrian granitoid source rocks is dominated by Os-rich trace phases, such as magnetite. Amongst the major silicates, biotite, or a trace phase in biotite, carries most of the Os and Re and is also the most radiogenic mineral with 187 Os/ 186 Os of ϳ113 and 187 Re/ 186 Os of ϳ2,000. Re-Os isotope systematics of source rocks and soils indicate that rapid oxidation of magnetite mobilizes Os with an isotopic composition similar to the isotopic composition of the bulk soils. A very radiogenic fraction of Os is mobilized through preferential weathering of biotite. Radiogenic runoff from Precambrian shields, inferred from osmium isotope analyses of freshwater Fe-Mn-nodules suggests that high-latitude Precambrian shields are important source areas of radiogenic Os in seawater. We propose that glacial scouring and weathering of glacial tills exposed after deglaciation of Precambrian shields surrounding the North Atlantic provides a mechanism for the slightly more radiogenic nature of North Atlantic seawater compared to other seawater masses. Glacial-interglacial variations in the osmium isotopic composition of seawater seem plausible and may be triggered by changes in weathering regimes on glacial-interglacial time scales in high-latitude shield areas surrounding the North Atlantic.
Large rivers integrate processes occurring throughout their watersheds, and are therefore sentine... more Large rivers integrate processes occurring throughout their watersheds, and are therefore sentinels of change across broad spatial scales. Riverine chemistry also regulates ecosystem function across Earth’s land-ocean continuum, exerting control from the micro- (e.g., food web) to the macro- (e.g., carbon cycle) scale. In the rapidly warming Arctic, a wide range of processes have been hypothesized to alter river water chemistry. However, it is unknown how the land-ocean flux of waterborne constituents is changing at the pan-Arctic scale. Here, we show profound shifts in the concentration and transport of biogeochemical constituents in the six largest Arctic rivers (the Ob’, Yenisey, Lena, Kolyma, Yukon, and Mackenzie) since 2003, near river mouths capturing two-thirds of the pan-Arctic watershed. While some constituent fluxes increase substantially at the pan-Arctic scale (alkalinity and associated ions), others decline (nitrate and associated inorganic nutrients) or are overall unc...
AGU Fall Meeting Abstracts, Dec 1, 2017
Geochemistry, Geophysics, Geosystems, 2017
The sources of terrestrial material delivered to the California margin over the past 7 Myr were a... more The sources of terrestrial material delivered to the California margin over the past 7 Myr were assessed using 187Os/188Os, Nd, and Pb isotopes in hydrogenetic ferromanganese crusts from three seamounts along the central and southern California margin. From 6.8 to 4.5 (±0.5) Ma, all three isotope systems show more radiogenic values at Davidson Seamount, located near the base of the Monterey Canyon System, than in Fe‐Mn crusts from the more remote Taney and Hoss Seamounts. At the Taney Seamounts, approximately 225 km farther offshore from Davidson Seamount, 187Os/188Os values, but not Pb and Nd isotope ratios, also deviate from the Cenozoic seawater curve toward more radiogenic values from 6.8 to 4.5 (±0.5) Ma. However, none of the isotope systems in Fe‐Mn crusts deviate from seawater at Hoss Seamount located approximately 450 km to the south. The regional gradients in isotope ratios indicate that substantial input of dissolved and particulate terrestrial material into the Monterey C...
In this paper we compare multivariate methods using both traditional approaches, which ignore iss... more In this paper we compare multivariate methods using both traditional approaches, which ignore issues of closure and provide relatively simple methods to deal with censored or missing data, and log-ratio methods to determine the sources of trace constituents in the atmosphere. The data set examined was collected from April to July 2008 at a sampling site near Woods Hole, Massachusetts, along the northeastern United States Atlantic coastline. The data set consists of trace gas mixing ratios (O 3 , SO 2 , NO x , elemental mercury [Hg o ], and reactive gaseous mercury [RGM]), and concentrations of trace elements in fine (<2.5 µm) particulate matter (Al,
Geociências, Apr 6, 2019
Introdução Área de estudo Desenvolvimento Metodológico Resultados e Discussão Conclusões Agradeci... more Introdução Área de estudo Desenvolvimento Metodológico Resultados e Discussão Conclusões Agradecimentos Referências RESUMO-O rio Tapajós é um afluente de águas claras da margem direita do rio Amazonas, drenando uma área de 492.263 km 2 da região central do Brasil para a porção central do estado do Pará. O objetivo deste estudo é determinar as concentrações de carbono orgânico (COP e COD) transportados no rio Tapajós próximo à cidade de Itaituba/PA, avaliando a influência da vazão e as mudanças hidrológicas sazonais no transporte destes compostos. Amostras mensais de água da superfície do rio foram coletadas em 2016 e os parâmetros biogeoquímicos (pH, condutividade elétrica, oxigênio dissolvido e temperatura) foram medidos in situ. As concentrações de sedimento foram analisados através de testes estatísticos em relação aos dados hidrológicos (precipitação, cota e vazão) fornecidos pelo INMET e banco de dados HyBam. COP teve uma média anual de 14±10,0 mg L-1 , com média de 20,8 mg L-1 na fase de cheia e de 7,9 mg L-1 na fase de seca. O COD teve média anual de 3,8±2,2 mg L-1 , com média de 5,0 mg L-1 na cheia e de 2,3 mg L-1 na seca. Os resultados obtidos sugerem que as mudanças hidrológicas sazonais são a principal causa das variações na concentração de sedimentos transportados pelo rio Tapajós, com possíveis associações às atividades de mineração e outras ações antrópicas ao longo de seus afluentes. Palavras-Chave-Parâmetros biogeoquímicos, hidrologia e sedimentos.
Global Biogeochemical Cycles, Jun 1, 2021
Inland waters have been increasingly recognized as hotspots for global carbon cycling, moving awa... more Inland waters have been increasingly recognized as hotspots for global carbon cycling, moving away from being viewed as passive transporters and reservoirs, to being accepted as interwoven conveyers and reactors (
Atmospheric Environment, Nov 1, 2013
h i g h l i g h t s Contribution of natural and anthropogenic PM 2.5 sources is quantified. Back-... more h i g h l i g h t s Contribution of natural and anthropogenic PM 2.5 sources is quantified. Back-trajectories for marine and crustal sources each show input from offshore. Results for crustal source are explained by long-range transport of Saharan dust. Results for Hg species, SO 2 and NO x show influence of combustion-related plumes. Results for RGM show diurnal cycle of production characteristic of marine influence.
Earth and Planetary Science Letters, Jun 1, 2011
Abundant chromite grains with L-chondritic composition in the resurge deposits of the Lockne impa... more Abundant chromite grains with L-chondritic composition in the resurge deposits of the Lockne impact crater (458 Myr old; dia. ~10 km) in Sweden have been inferred to represent relict fragments of an impactor from the break-up of the L-chondrite parent body at 470 Ma. This view has been challenged based on Ir/Cr and platinum group element (PGE) patterns of the same resurge deposits, and a reinterpretation of the origin of the chromite grains. An impactor of the non-magmatic iron meteorite type was proposed instead. Here we show that single-grain oxygen and noble-gas isotope analyses of the chromite grains from the resurge deposits further support an origin from an L-chondritic asteroid. We also present PGE analyses and Ir/Cr ratios for fossil L-chondritic meteorites found in mid-Ordovician marine limestone in Sweden. The L-chondritic origin has been confirmed by several independent methods, including major element and oxygen isotopic analyses of chromite. Although the meteorites show the same order-of-magnitude PGE and Cr concentrations as recent L chondrites, the elements have been redistributed to the extent that it is problematic to establish the original meteorite type from these proxies. Different 2 PGE data processing approaches can lead to highly variable results, as also shown here for the Lockne resurge deposits. We conclude that the Lockne crater was formed by an Lchondritic impactor, and that considerable care must be taken when inferring projectile type from PGEs in sedimentary ejecta deposits.
Geology, Mar 1, 2012
Knowledge of the 187 Os/ 188 Os ratio as well as the inventories of rhenium and platinum group el... more Knowledge of the 187 Os/ 188 Os ratio as well as the inventories of rhenium and platinum group elements (PGE) in oceanic crust allows quantification of the proportion of recycled oceanic crust in oceanic basalt sources. Our knowledge is limited by the availability of well-characterized sections of oceanic crust, specifically of the plutonic, lower portion that has not been drilled in situ to the Moho. Here we report new data for plutonic rocks that compose the bottom 4680 m of an ocean crust section from the Oman ophiolite. Major and trace element data as well as mineral analyses indicate that Oman gabbros are primitive cumulates from melts similar to typical mid-oceanic ridge basalt. The mean weighted composition of this section (Re: 427 pg/g; Os: 55 pg/g; Ir: 182 pg/g; Pd: 2846 pg/g; Pt: 4151 pg/g; initial 187 Os/ 188 Os: 0.142) indicates significantly higher Os and lower Re concentrations than previously analyzed partial sections of ocean crust that lack cumulate lower crust [Deep Sea Drilling Project–Ocean Drilling Program (DSDP-ODP) Hole 504B, ODP Hole 735B], emphasizing that the lower, cumulate oceanic crust dominates the Os budget of oceanic crust. Analyses of mineral grain size fractions indicate that rhenium, PGE, and lead are enriched in the sulfur-rich, fine fraction. This corroborates the notion that small accessory phases, and the melt migration processes affecting them, control these elements’ budgets, distributions, and susceptibilities to alteration. The Re-Os-PGE inventories of a hypothetical 6.5-km-thick composite section that consists of 1825 m of DSDP Hole 504B−like upper oceanic crust and 4680 m of Oman-like lower ocean crust (Re: 736 pg/g; Os: 45 pg/g; Ir: 133 pg/g; Pd: 2122 pg/g; Pt: 2072 pg/g; initial 187 Os/ 188 Os: 0.146) provide a new comprehensive assessment of oceanic crust composition. Upon recycling and mixing with reasonable proportions of mantle peridotite, this composite requires at least 2 G.y. to develop sufficiently radiogenic 187 Os/ 188 Os to generate high μ (HIMU: μ = 238 U/ 204 Pb) basalts.
Environmental Science & Technology, Jul 27, 2012
The extent to which humans are modifying Earth's surface chemistry can be quantified by comparing... more The extent to which humans are modifying Earth's surface chemistry can be quantified by comparing total anthropogenic element fluxes with their natural counterparts (Klee & Graedel, 2004). We quantify anthropogenic mass transfer of 77 elements from mining, fossil fuel burning, biomass burning, construction activities, and human apportionment of terrestrial net primary productivity, and compare it to natural mass transfer from terrestrial and marine net primary productivity, riverine dissolved and suspended matter fluxes to the ocean, soil erosion, eolian dust, sea-salt spray, cosmic dust, volcanic emissions and-for helium-hydrodynamic escape from the Earth's atmosphere. We introduce an approach to correct for losses during industrial processing of elements belonging to geochemically coherent groups, and explicitly incorporate uncertainties of element mass fluxes through Monte Carlo simulations. We find that at the Earth's surface anthropogenic fluxes of iridium, osmium, helium, gold, ruthenium, antimony, platinum, palladium, rhenium, rhodium and chromium currently exceed natural fluxes. For these elements mining is the major factor of anthropogenic influence, whereas petroleum burning strongly influences the surficial cycle of rhenium. Our assessment indicates that if anthropogenic contributions to soil erosion and eolian dust are considered, anthropogenic fluxes of up to 62 elements surpass their corresponding natural fluxes.
2016 AGU Fall Meeting, Dec 13, 2016
Climate has been proposed to control both the rate of terrestrial silicate weathering and the exp... more Climate has been proposed to control both the rate of terrestrial silicate weathering and the export rate of associated sediments and terrestrial organic carbon to river-dominated margins-and thus the rate of sequestration of atmospheric CO 2 in the coastal ocean-over glacial-interglacial timescales. Focused on the Ganges-Brahmaputra rivers, this study presents records of post-glacial changes in basinscale Indian summer monsoon intensity and vegetation composition based on stable hydrogen (δD) and carbon (δ 13 C) isotopic compositions of terrestrial plant wax compounds preserved in the channel-levee system of the Bengal Fan. It then explores the role of these changes in controlling the provenance and degree of chemical weathering of sediments exported by these rivers, and the potential climate feedbacks through organic-carbon burial in the Bengal Fan. An observed 40h shift in δD and a 3-4h shift in both bulk organic-carbon and plant-wax δ 13 C values between the late glacial and mid-Holocene, followed by a return to more intermediate values during the late Holocene, correlates well with regional post-glacial paleoclimate records. Sediment provenance proxies (Sr, Nd isotopic compositions) reveal that these changes likely coincided with a subtle focusing of erosion on the southern flank of the Himalayan range during periods of greater monsoon strength and enhanced sediment discharge. However, grain-size-normalized organic-carbon concentrations in the Bengal Fan remained constant through time, despite order-of-magnitude level changes in catchment-scale monsoon precipitation and enhanced chemical weathering (recorded as a gradual increase in K/Si * and detrital carbonate content, and decrease in H 2 O + /Si * , proxies) throughout the study period. These findings demonstrate a partial decoupling of climate change and silicate weathering during the Holocene and that marine organiccarbon sequestration rates primary reflect rates of physical erosion and sediment export as modulated by climatic changes. Together, these results reveal the magnitude of climate changes within the Ganges-Brahmaputra basin following deglaciation and a closer coupling of monsoon strength with OC burial than with silicate weathering on millennial timescales.
AGUFM, Dec 1, 2005
Abstract Platinum Group Elements (PGE: Os, Ir, Rh, Ru, Pt, Pd) and osmium isotopes measured in ma... more Abstract Platinum Group Elements (PGE: Os, Ir, Rh, Ru, Pt, Pd) and osmium isotopes measured in marine and terrestrial sediment, snow and ice records are important paleo-tracers of riverine, hydrothermal, extraterrestrial, volcanic and anthropogenic inputs into the global surficial environment. For instance, the marine Os isotope record across the Cretaceous-Tertiary Boundary (KTB) indicates that the onset of the main phase of Deccan volcanism and the transient late Maastrichtian warming preceded the large extraterrestrial ...
Environmental Science & Technology, Aug 27, 2013
Platinum group elements (PGE) of anthropogenic origin have been reported in rainwater, snow, road... more Platinum group elements (PGE) of anthropogenic origin have been reported in rainwater, snow, roadside soil and vegetation, industrial waste, and urban airborne particles around the world. As recent studies have shown that PGE are bioavailable in the environment and pose health risks at chronic levels, the extent of PGE pollution is of global concern. In this study, we report PGE concentrations and osmium isotope ((187)Os/(188)Os) ratios of airborne particles (particulate matter, PM10) collected in Woods Hole, a small coastal village on Cape Cod, Massachusetts, U.S.A. The sampling site is more than 100 km away from the nearest urban centers (Boston, Providence) and has no large industrial emission center within a 30 km radius. The study reveals that, although PGE concentrations in rural airborne particulate matter are orders of magnitude lower than in urban aerosols, 69% of the total osmium is of anthropogenic origin. Anthropogenic PGE signatures in airborne particles are thus not restricted to large cities with high traffic flows and substantial industries; they can also be found in rural environments. We further conclude that the combination of Pt/Rh concentration ratios and (187)Os/(188)Os composition can be used to trace PGE sources. The Pt/Rh and (187)Os/(188)Os composition of Woods Hole aerosols indicate that the anthropogenic PGE fraction is primarily sourced from ore smelting processes, with possible minor contributions from fossil fuel burning and automobile catalyst-derived materials. Our results further substantiate the use of (187)Os/(188)Os in source apportionment studies on continental scales.
Journal of Radioanalytical and Nuclear Chemistry, Sep 1, 1991
The concentrations of 35 trace elements in the UNS-SpS glass sand reference material have been de... more The concentrations of 35 trace elements in the UNS-SpS glass sand reference material have been determined by instrumental neutron activation analysis involving short- and long-term irradiations. For analysis, the so-called “absolute monostandard method” was used, i.e. the concentrations were calculated from the measured gamma-activity and not by comparison with a reference sample of known composition. The results of up to 25 independent determinations are compared with the values given by UNS and other investigators. Most element contents agree well with the published values expecting K, Ga, and La, which will be discussed. Trace element contents for Cl, As, Br, Dy, and Au are reported for the first time.
Geochemistry Geophysics Geosystems, 2004
We quantitatively analyze the area-age distribution of sedimentary, igneous and metamorphic bedro... more We quantitatively analyze the area-age distribution of sedimentary, igneous and metamorphic bedrock based on data from the most recent digital geologic maps of East and Southeast Asia (Coordinating Committee for Coastal and Offshore Geosciences Programmes in East and Southeast Asia (CCOP) and the Geologic Survey of Japan, 1997; 1:2,000,000), published as Digital Geoscience Map G-2 by the Geological Survey of Japan. Sedimentary rocks, volcanic rocks, plutonic rocks, ultramafic rocks and metamorphic rocks cover 73.3%, 8.5%, 8.8%, 0.9%, and 8.6% of the surface area, respectively. The average ages of major lithologic units, weighted according to bedrock area, are as follows: sedimentary rocks (average stratigraphic age of 123 Myr/median age of 26 Myr), volcanic rocks (84 Myr/20 Myr), intrusive rocks (278 Myr/195 Myr), ultramafic rocks (unknown) and metamorphic rocks (1465 Myr/1118 Myr). The variability in lithologic composition and age structure of individual countries reflects the complex tectonic makeup of this region that ranges from Precambrian cratons (e.g., northeast China and North Korea) to Mesozoic-Cenozoic active margins (e.g., Japan, the Philippines, Indonesia and New Guinea). The spatial resolution of the data varies from 44 km 2 per polygon (Japan) to 1659 km 2 per polygon (Taiwan) and is, on average (490 km 2 /polygon), similar to our previous analyses of the United States of America and Canada. The temporal and spatial resolution is sufficiently high to perform age-area analyses of individual river basins larger than $10,000 km 2 and to quantitatively evaluate the relationship between bedrock geology and river chemistry. As many rivers draining tropical, mountainous islands of East and Southeast Asia have a disproportionate effect on the dissolved and particulate load delivered to the world oceans, bedrock geology in such river drainage basins disproportionately affect ocean chemistry.
Analytical Chemistry, Mar 6, 2014
The (187)Os/(188)Os ratio that is based on the β(-)-decay of (187)Re to (187)Os (t1/2 = 41.6 bill... more The (187)Os/(188)Os ratio that is based on the β(-)-decay of (187)Re to (187)Os (t1/2 = 41.6 billion years) is widely used to investigate petroleum system processes. Despite its broad applicability to studies of hydrocarbon deposits worldwide, a suitable matrix-matched reference material for Os analysis does not exist. In this study, a method that enables Os isotope measurement of crude oil with in-line Os separation and purification from the sample matrix is proposed. The method to analyze Os concentration and (187)Os/(187)Os involves sample digestion under high pressure and high temperature using a high pressure asher (HPA-S, Anton Paar), sparging of volatile osmium tetroxide from the sample solution, and measurements using multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). This methods significantly reduced the total procedural time compared to conventional Carius tube digestion followed by Os separation and purification using solvent extraction, microdistillation and N-TIMS analysis. The method yields Os concentration (28 ± 4 pg g(-1)) and (187)Os/(188)Os (1.62 ± 0.15) of commercially available crude oil reference material NIST 8505 (1 S.D., n = 6). The reference material NIST 8505 is homogeneous with respect to Os concentration at a test portion size of 0.2 g. Therefore, (187)Os/(188)Os composition and Os concentration of NIST 8505 can serve as a matrix-matched reference material for Os analysis. Data quality was assessed by repeated measurements of the USGS shale reference material SCo-1 (sample matrix similar to petroleum source rock) and the widely used Liquid Os Standard solution (LOsSt). The within-laboratory reproducibility of (187)Os/(188)Os for a 5 pg of LOsSt solution, analyzed with this method over a period of 12 months was ∼1.4% (1 S.D., n = 26), respectively.
Geochimica et Cosmochimica Acta, Oct 1, 1998
The effects of weathering of freshly exposed Precambrian rocks on the mobility of osmium were stu... more The effects of weathering of freshly exposed Precambrian rocks on the mobility of osmium were studied on soils developed on a chronosequence of glacial moraines from the western Wind River Range in Wyoming. The Os budget of the Precambrian granitoid source rocks is dominated by Os-rich trace phases, such as magnetite. Amongst the major silicates, biotite, or a trace phase in biotite, carries most of the Os and Re and is also the most radiogenic mineral with 187 Os/ 186 Os of ϳ113 and 187 Re/ 186 Os of ϳ2,000. Re-Os isotope systematics of source rocks and soils indicate that rapid oxidation of magnetite mobilizes Os with an isotopic composition similar to the isotopic composition of the bulk soils. A very radiogenic fraction of Os is mobilized through preferential weathering of biotite. Radiogenic runoff from Precambrian shields, inferred from osmium isotope analyses of freshwater Fe-Mn-nodules suggests that high-latitude Precambrian shields are important source areas of radiogenic Os in seawater. We propose that glacial scouring and weathering of glacial tills exposed after deglaciation of Precambrian shields surrounding the North Atlantic provides a mechanism for the slightly more radiogenic nature of North Atlantic seawater compared to other seawater masses. Glacial-interglacial variations in the osmium isotopic composition of seawater seem plausible and may be triggered by changes in weathering regimes on glacial-interglacial time scales in high-latitude shield areas surrounding the North Atlantic.
Large rivers integrate processes occurring throughout their watersheds, and are therefore sentine... more Large rivers integrate processes occurring throughout their watersheds, and are therefore sentinels of change across broad spatial scales. Riverine chemistry also regulates ecosystem function across Earth’s land-ocean continuum, exerting control from the micro- (e.g., food web) to the macro- (e.g., carbon cycle) scale. In the rapidly warming Arctic, a wide range of processes have been hypothesized to alter river water chemistry. However, it is unknown how the land-ocean flux of waterborne constituents is changing at the pan-Arctic scale. Here, we show profound shifts in the concentration and transport of biogeochemical constituents in the six largest Arctic rivers (the Ob’, Yenisey, Lena, Kolyma, Yukon, and Mackenzie) since 2003, near river mouths capturing two-thirds of the pan-Arctic watershed. While some constituent fluxes increase substantially at the pan-Arctic scale (alkalinity and associated ions), others decline (nitrate and associated inorganic nutrients) or are overall unc...
AGU Fall Meeting Abstracts, Dec 1, 2017
Geochemistry, Geophysics, Geosystems, 2017
The sources of terrestrial material delivered to the California margin over the past 7 Myr were a... more The sources of terrestrial material delivered to the California margin over the past 7 Myr were assessed using 187Os/188Os, Nd, and Pb isotopes in hydrogenetic ferromanganese crusts from three seamounts along the central and southern California margin. From 6.8 to 4.5 (±0.5) Ma, all three isotope systems show more radiogenic values at Davidson Seamount, located near the base of the Monterey Canyon System, than in Fe‐Mn crusts from the more remote Taney and Hoss Seamounts. At the Taney Seamounts, approximately 225 km farther offshore from Davidson Seamount, 187Os/188Os values, but not Pb and Nd isotope ratios, also deviate from the Cenozoic seawater curve toward more radiogenic values from 6.8 to 4.5 (±0.5) Ma. However, none of the isotope systems in Fe‐Mn crusts deviate from seawater at Hoss Seamount located approximately 450 km to the south. The regional gradients in isotope ratios indicate that substantial input of dissolved and particulate terrestrial material into the Monterey C...