The use of salinity contrast for density difference compensation to improve the thermal recovery efficiency in high-temperature aquifer thermal energy storage systems     

Jan H. van Lopik  Niels Hartog  Willem Jan Zaadnoordijk 《Hydrogeology Journal》2016,24(5):1255-1271

The efficiency of heat recovery in high-temperature (>60 °C) aquifer thermal energy storage (HT-ATES) systems is limited due to the buoyancy of the injected hot water. This study investigates the potential to improve the efficiency through compensation of the density difference by increased salinity of the injected hot water for a single injection-recovery well scheme. The proposed method was tested through numerical modeling with SEAWATv4, considering seasonal HT-ATES with four consecutive injection-storage-recovery cycles. Recovery efficiencies for the consecutive cycles were investigated for six cases with three simulated scenarios: (a) regular HT-ATES, (b) HT-ATES with density difference compensation using saline water, and (c) theoretical regular HT-ATES without free thermal convection. For the reference case, in which 80 °C water was injected into a high-permeability aquifer, regular HT-ATES had an efficiency of 0.40 after four consecutive recovery cycles. The density difference compensation method resulted in an efficiency of 0.69, approximating the theoretical case (0.76). Sensitivity analysis showed that the net efficiency increase by using the density difference compensation method instead of regular HT-ATES is greater for higher aquifer hydraulic conductivity, larger temperature difference between injection water and ambient groundwater, smaller injection volume, and larger aquifer thickness. This means that density difference compensation allows the application of HT-ATES in thicker, more permeable aquifers and with larger temperatures than would be considered for regular HT-ATES systems.  相似文献   

The geography of urban greenhouse gas emissions in Asia: A regional analysis     

Peter J. Marcotullio  Andrea Sarzynski  Jochen Albrecht  Niels Schulz 《Global Environmental Change》2012,22(4):944-958

This paper aims to advance two objectives: (1) identify and explore greenhouse gas emissions from urban areas in Asia at the regional level; and (2) explore covariates of urban greenhouse gas emissions. We use the Emissions Database for Global Atmospheric Research estimates for carbon dioxide, methane, nitrous oxide, and sulfur hexafluoride from 14 source activities for the year 2000, which are allocated on a 1/10° global grid. We extract emissions for 3535 urban extents all with populations over 50,000, accounting for approximately 91% of the region's urban population. We use regression analysis to associate emissions with urban area and growth, economic, and biophysical characteristics. Our findings suggest that urban areas account for between 30 and 38% of total anthropogenic greenhouse gas emissions for the region and that emission per capita averages from urban areas are lower than those at the national level. Important covariates for total urban greenhouse gas emissions include population size, density and growth rate, income per capita, development status and elevation. This is a first and preliminary assessment of regional baseline trends using these data and this top-down analysis.  相似文献   

Environmental reconstructions of Eemian Stage interglacial marine records in the Lower Vistula area,southern Baltic Sea     

Karen Luise Knudsen  Hui Jiang  Philip L. Gibbard  Peter Kristensen  Marit‐Solveig Seidenkrantz  Zofia Janczyk‐Kopikowa  Leszek Marks 《Boreas: An International Journal of Quaternary Research》2012,41(2):209-234

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Mobility and potential bioavailability of traffic-derived trace metals in a ‘wet–dry’ tropical region,Northern Australia     

Niels C. Munksgaard  Bernd G. Lottermoser 《Environmental Earth Sciences》2010,60(7):1447-1458

The aqueous mobility and potential bioavailability of metals and metalloids in road runoff in a ‘wet–dry’ tropical location were assessed by analysing metal and metalloid concentrations in particulate, total dissolved and labile dissolved phases in runoff waters. Road-derived Al, Cu, Pb, Sb and Zn concentrations were substantially elevated in runoff when compared to receiving creek waters. Median dissolved concentrations in road runoff exceeded those in creek waters by up to an order of magnitude. Leaching experiments of road sediments confirmed that several metals and metalloids were released in high concentrations from road sediments. Labile Zn and Cu concentrations measured by diffusion gradients in thin films (DGT) showed that almost all dissolved Zn and up to half of dissolved Cu in runoff waters and in road sediment leachate were potentially bioavailable. Comparisons of dissolved metal concentrations in receiving waters affected by road runoff with ecosystem guideline levels, indicated a risk of reaching toxic levels of Cu and Zn in the receiving waters in the absence of adequate treatment or dilution. Low dilution rates of road runoff are likely to occur during late ‘dry’ season/early ‘wet’ season storms which have the potential to produce high metal concentrations derived from long periods of accumulation of road sediment at a time when creek flow rates are at their annual minimum.  相似文献   

南极中山站至Dome A剖面表面雪样氧同位素组成          下载免费PDF全文

阎明  李院生  谭德军  温家洪  汪大立  Claus U.Hammer  孙波  康建成  刘雷保 《极地研究》2001,13(3):159-164

运用质谱技术 ,测定了南极中山站至 Dome A剖面 1 998/1 999年度表面雪样氧同位素组成。结果表明 ,表面雪样氧同位素组成变化范围相当大 (- 2 2 .5 1‰ - - 5 0 .6 7‰ ) ,且具有随距中山站距离逐渐增大、海拔高度逐渐增加而逐渐减小的趋势。线性回归分析显示表面雪样氧同位素组成与距中山站距离、海拔高度和纬度存在着很好的相关性 ,这实际上反映出稳定同位素组成和温度之间的密切联系  相似文献   

An Improved 20-Year Arctic Ocean Altimetric Sea Level Data Record     

Yongcun Cheng  Per Knudsen 《Marine Geodesy》2013,36(2):146-162

For ocean and climate research, it is essential to get long-term altimetric sea level data that is as accurate as possible. However, the accuracy of the altimetric data is frequently degraded in the interior of the Arctic Ocean due to the presence of seasonal or permanent sea ice. We have reprocessed ERS-1/2/Envisat satellite altimetry to develop an improved 20-year sea level dataset for the Arctic Ocean. We have developed both an along-track dataset and three-day gridded sea level anomaly (SLA) maps from September 1992 to April 2012. A major improvement in data coverage was gained by tailoring the standard altimetric editing criteria to Arctic conditions. The new reprocessed data has significant increased data coverage with between 4 and 10 times the amount of data in regions such as the Beaufort Gyre region compared with AVISO and RADS datasets. This allows for a more accurate estimation of sea level changes from satellite altimetry in the Arctic Ocean. The reprocessed dataset exhibit a mean sea level trend of 2.1 ± 1.3 mm/year (without Glacial Isostatic Adjustment correction) covering the Arctic Ocean between 66°N and 82°N with significant higher spatial coherency in the ice-covered regions than the RADS and DUACS datasets.  相似文献   

Erratum to: A Simple Model for the Vertical Transport of Reactive Species in the Convective Atmospheric Boundary Layer     

Leif Kristensen  Donald H. Lenschow  David Gurarie  Niels Otto Jensen 《Boundary-Layer Meteorology》2010,135(1):181-183

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Palaeomagnetism of the Proterozoic Zig-Zag Dal Basalt and the Midsommersø Dolerites, eastern North Greenland     

Christian Marcussen  Niels Abrahamsen 《Geophysical Journal International》1983,73(2):367-387

Summary. Palaeomagnetic investigations are reported from 24 sites in the Proterozoic Zig-Zag Dal Basalt Formation and 12 sites in the Midsominersø Dolerites of eastern North Greenland. The Zig-Zag Dal Basalt is a typical tholeiitic flood basalt sequence, and dolerite intrusions in the underlying sandstones are thought to be genetically related to the basalts.
After a detailed AF demagnetization programme 19 sites in the basalts and 10 sites in the dolerites reveal one stable component of magnetization, probably of TRM and/or CRM origin residing in small single domain titano-magnetite grains. The degree of anisotropy has not affected the direction of the remanent magnetization. The maximum axis of the anisotropy ellipsoid is parallel to the flow direction of the magma, whereas the minimum axis is perpendicular to the flow plane.
Only one polarity of the geomagnetic field was found. The mean palaeomagnetic pole positions for the two rock types are not significantly different (basalt: 12.2°S, 62.8°E with A ₉₅= 3.8°; dolerites: 6.9°S, 62.0°E with A ₉₅ = 5.1°). After correction for Phanerozoic drift of Greenland the two mean poles compare closely to a relevant North American APW-curve for 1250–1350 Ma, in good agreement with Rb-Sr isochron ages of 1250 Ma obtained for the intrusives. The palaeogeographical position of Greenland was near equator with the major geographical axis orientated E-W.  相似文献   

Controls on englacial sediment deposition during the November 1996 jökulhlaup,Skeiđarárjökull,Iceland     

Matthew J. Roberts  Andrew J. Russell  Fiona S. Tweed   skar Knudsen 《地球表面变化过程与地形》2001,26(9):935-952

This paper presents sedimentary evidence for rapid englacial debris entrainment during jökulhlaups. Previous studies of jökulhlaup sedimentology have focused predominantly on proglacial impact, rather than depositional processes within glaciers. However, observations of supraglacial floodwater outbursts suggest that englacial sediment emplacement is possible during jökulhlaups. The November 1996 jökulhlaup from Skei?arárjökull, Iceland presented one of the first opportunities to examine englacial flood deposits in relation to former supraglacial outlets. Using observations from Skei?arárjökull, this paper identifies and explains controls on the deposition of englacial flood sediments and presents a qualitative model for englacial jökulhlaup deposition. Englacial jökulhlaup deposits were contained within complex networks of upglacier‐dipping fractures. Simultaneous englacial deposition of fines and boulder‐sized sediment demonstrates that englacial fracture discharge had a high transport capacity. Fracture geometry was an important control on the architecture of englacial jökulhlaup deposits. The occurrence of pervasively frozen flood deposits within Skei?arárjökull is attributed to freeze‐on by glaciohydraulic supercooling. Floodwater, flowing subglacially or through upglacier‐dipping fractures, would have supercooled as it was raised to the surface faster than its pressure‐melting point could increase as glaciostatic pressure decreased. Evidence for floodwater contact with the glacier bed is supported by the ubiquitous occurrence of sheared diamict rip‐ups and intra‐clasts of basal ice within jökulhlaup fractures, deposited englacially some 200–350 m above the bed of Skei?arárjökull. Evidence for fluidal supercooled sediment accretion is apparent within stratified sands, deposited englacially at exceptionally high angles of rest in the absence of post‐depositional disturbance. Such primary sediment structures cannot be explained unless sediment is progressively accreted to opposing fracture walls. Ice retreat from areas of former supraglacial outbursts revealed distinct ridges characterized by localized upwellings of sediment‐rich floodwater. These deposits are an important addition to current models of englacial sedimentation and demonstrate the potential for post‐jökulhlaup landform development. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Simple models of the thermal structure of the Venusian ionosphere     

R.C. Whitten  W.C. Knudsen 《Icarus》1980,44(1):85-92

Simple models, analytical and numerical, of plasma temperatures in the Venusian ionosphere are developed. They are applied to thermal-structure data obtained by the Pioneer Venus Orbiter to estimate the magnitudes of important plasma thermal parameters.  相似文献