Industrialization affects heavy metal and carbon isotope concentrations in recent Baltic Sea sediments     

Helmut Erlenkeuser  Erwin Suess  Horst Willkomm 《Geochimica et cosmochimica acta》1974,38(6):823-842

Recent sediment cores of the western Baltic Sea were analyzed for heavy metal and carbon isotope contents. The sedimentation rate was determined from radiocarbon dates to be 1.4 mm/yr. The ‘recent age’ of the sediment was about 850 yr. Within the upper 20 cm of sediment, certain heavy metals became increasingly enriched towards the surface; Cd, Pb, Zn and Cu increased 7-, 4-, 3- and 2-fold, respectively, whereas Fe, Mn, Ni and Co remained unchanged. Simultaneously, the radiocarbon content decreased by about 14 per cent. The enrichment in heavy metals as well as the decrease in the ¹⁴C-concentration during the last 130 ± 30yr parallels industrial growth as reflected in European fossil fuel consumption within that same period of time. The near-surface sediments are affected by residues released from fossil fuels at the rate of about 30 g/m² yr for the past two decades. The residues have a pronounced effect on the heavy metal and carbon isotope composition of the most Recent sediments allowing estimates to be made for sedimentation, erosion and heavy metal pollution.  相似文献   

Aquifer Tuning for Optimum Performance of In Situ Remedies     

Suthan Suthersan  John Horst  Denice Nelson  Scott Potter 《Ground Water Monitoring & Remediation》2010,30(3):39-44

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Illite authigenesis in sandstones of the Guaritas Allogroup (Early Paleozoic): Implications for the depositional age,stratigraphy and evolution of the Camaquã Basin (Southern Brazil)     

Anderson José Maraschin  Ana Maria Mizusaki  Horst Zwingmann  André Weissheimer de Borba  Gesiane Fraga Sbrissa 《Journal of South American Earth Sciences》2010,29(2):400-411

Several analytical studies performed on alluvial-eolian sandstones of the Early Paleozoic Guaritas Allogroup (Camaquã Basin, southern Brazil) indicate illite to be abundant, showing different morphologies as authigenic grain rims and pore-bridging filaments. Authigenic illite separates of variable grain sizes from distinct stratigraphic intervals of the Guaritas Allogroup yielded ⁴⁰K–⁴⁰Ar ages from 521.7 ± 10.3 to 473.7 ± 9.4 Ma. These ages, interpreted to record the timing of illite authigenesis, are coincident with the age of emplacement of the Rodeio Velho andesites (470 ± 19 Ma). Moreover, field structures suggest interaction between hot, andesite lava flows and wet, poorly consolidated sediments of the Pedra Pintada Alloformation (lower strata of the Guaritas Allogroup). This set of data indicates that the Rodeio Velho volcanism could have been responsible for a widespread remobilization of interstitial fluids and consequent authigenic illite precipitation in the sandstones of the Guaritas Allogroup.  相似文献   

Activity of comets: Gas transport in the near-surface porous layers of a cometary nucleus     

Yuri V. Skorov  Rik van Lieshout  Horst U. Keller 《Icarus》2011,212(2):867-876

The gas transport through non-volatile random porous media is investigated numerically. We extend our previous research of the transport of molecules inside the uppermost layer of a cometary surface ( [Skorov and Rickman, 1995] and [Skorov et al., 2001]). We assess the validity of the simplified capillary model and its assumptions to simulate the gas flux trough the porous dust mantle as it has been applied in cometary physics. A microphysical computational model for molecular transport in random porous media formed by packed spheres is presented. The main transport characteristics such as the mean free path distribution and the permeability are calculated for a wide range of model parameters and compared with those obtained by more idealized models. The focus in this comparison is on limitations inherent in the capillary model. Finally a practical way is suggested to adjust the algebraic Clausing formula taking into consideration the nonlinear dependence of permeability on layer porosity. The retrieved dependence allows us to accurately calculate the permeability of layers whose thickness and porosity vary in the range of values expected for the near-surface regions of a cometary nucleus.  相似文献   

Geotechnical characteristics of deep-sea sediments from the North Atlantic and North Pacific oceans     

Horst G. Brandes 《Ocean Engineering》2011,38(7):835-848

Geotechnical properties from a series of deep-sea sites in the North Atlantic and North Pacific oceans are examined to evaluate overall trends and to compare with similar fine-grained soils found on land. The study areas encompass a range of sedimentary environments dominated by combinations of turbidite and pelagic deposits. Carbonate content in excess of 20% is seen to result in a decrease in liquid limit and compressibility. Vertical profiles of geotechnical properties in the North Pacific show broader changes in down-core geotechnical properties compared to the North Atlantic and reflect the effects of long-term climatic changes and seafloor spreading. Sediments in the North Atlantic indicate significant differences depending on location, which is attributed to variability in turbidite deposition, water depth, distance from sediment sources, and the effects of bottom currents. Compared to equivalent fine-grained soils on land, deep-sea sediments are generally softer, more compressible and have higher friction angles at comparable Atterberg limits. Deeper and older sediments in the North Pacific are characterized by unusually large plastic limits, which are attributed to the presence of volcanic fractions. Empirical relationships for compression index and friction angle are discussed for sediments from both oceans.  相似文献   

Thermophysical Modelling of Comet P/Borrelly Effects of Volume Energy Absorption and Volume Sublimation     

Skorov  Yuri V.  Keller  Horst U.  Jorda  Laurent  Davidsson  Bjørn J. R. 《Earth, Moon, and Planets》2002,90(1-4):293-303

In this work, we continue revising the theoretical basis ofnumerical models describing the transport of matter andenergy inside a porous dust-ice mixture at low temperature. Amodel of a light-absorbing near-surface layer of a comet nucleus isinvestigated. Gas transport is considered simultaneously with thesolution of the general heat transfer equation. Thequasi-stationary temperature distribution and the H₂O massflux and sublimation rate are computed for a nucleus model ofcomet 19P/Borrelly at the Deep Space 1 (DS1) encounter. Theenergy is deposited in a layer of about 20 particle radii: Thiscorresponds to a solid-state greenhouse effect. The surfacetemperature of the layer-absorbing model as well as the gasproduction rate are significantly smaller than the ones in thesurface-absorbing model. An active fraction of 40–50% would berequired to explain the observed water production rate ofP/Borrelly with our layer-absorption model at the time of the DS1encounter.  相似文献   

Reply to the Reply: New needs for latitudinal asymmetries     

Scherer  Horst  Fahr  Hans J. 《Solar physics》1997,170(2):371-372

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How societal expectations,new digital tools,and the COVID crisis are driving a step-change in human centric remediation     

John Horst  Carly Foster  Steven Perry  Ajani Stewart  Megan Klar  Beto Altamirano  Prasoon Sinha 《Ground Water Monitoring & Remediation》2021,41(3):13-21

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Attenuation of Scalar Fluxes Measured with Spatially-displaced Sensors   总被引：1，自引：0，他引：1  

T. W. Horst  D. H. Lenschow 《Boundary-Layer Meteorology》2009,130(2):275-300

Observations from the Horizontal Array Turbulence Study (HATS) field program are used to examine the attenuation of measured scalar fluxes caused by spatial separation between the vertical velocity and scalar sensors. The HATS data show that flux attenuation for streamwise, crosswind, and vertical sensor displacements are each a function of a dimensionless, stability-dependent parameter n _m multiplied by the ratio of sensor displacement to measurement height. The scalar flux decays more rapidly with crosswind displacements than for streamwise displacements and decays more rapidly for stable stratification than for unstable stratification. The cospectral flux attenuation model of Kristensen et al. agrees well with the HATS data for streamwise sensor displacements, although it is necessary to include a neglected quadrature spectrum term to explain the observation that flux attenuation is often less with the scalar sensor downwind of the anemometer than for the opposite configuration. A simpler exponential decay model provides good estimates for crosswind sensor displacements, as well as for streamwise sensor displacements with stable stratification. A model similar to that of Lee and Black correctly predicts flux attenuation for a combination of streamwise and crosswind displacements, i.e. as a function of wind direction relative to the sensor displacement. The HATS data for vertical sensor displacements extend the near-neutral results of Kristensen et al. to diabatic stratification and confirm their finding that flux attenuation is less with the scalar sensor located below the anemometer than if the scalar sensor is displaced an equal distance either horizontally or above the anemometer.  相似文献   

Attacks on oil transport pipelines in Nigeria: A quantitative exploration and possible explanation of observed patterns     

Babatunde Anifowose  Damian M. Lawler Dan van der Horst  Lee Chapman 《Applied geography (Sevenoaks, England)》2012,32(2):636-651

In countries with insufficient investments in infrastructure and weak environmental governance, oil leakage from pipelines often occurs as a result of poor management and maintenance. Nigeria has its share of such incidents, but also, it suffers a large number of deliberate attacks (‘interdictions’) on oil pipelines. Often these attacks are accompanied by oil theft, carried out by well-equipped professionals and/or at a smaller scale by opportunistic local residents. The causes of these attacks, and the extent of subsequent damage to local communities and the environment, are obscured by a complex web of stakeholders, claims and actions. Any efforts to mitigate the negative impacts of interdiction on the environment and people require a better understanding of its spatiotemporal pattern of occurrence. This article presents a first quantitative and regional exploration of the problem of oil pipeline interdiction in Nigeria. It illustrates geographic patterns through choroplethic and bivariate GIS (Geographical Information Systems) map overlays. We examine interdiction statistics, identify spatiotemporal patterns and discuss correlations with socioeconomic factors. Findings include: (a) strong negative correlation between pipeline interdiction and poverty; and (b) statistically and non-statistically significant mean differences in the pattern of interdiction occurrence amongst the five geographic regions. Finally, we highlight the need for much better data collection and reporting for the mitigation of the negative socio-environmental impacts of interdiction incidences.  相似文献