Source attribution of urban smog episodes caused by coal combustion   总被引：1，自引：0，他引：1  

D. Mira-Salama  C. Grüning  N.R. Jensen  P. Cavalli  J.-P. Putaud  B.R. Larsen  F. Raes  H. Coe 《Atmospheric Research》2008,88(3-4):294-304

Stable weather conditions together with extensive use of coal combustion often lead to severe smog episodes in certain urban environments, especially in Eastern Europe. In order to identify the specific sources that cause the smog episodes in such environments, and to better understand the mixing state and atmospheric processing of aerosols, both single particle and bulk chemical characterization analysis of aerosols were performed in Krakow, Poland, during winter 2005.Real-time measurements of the bulk PM10 aerosol during a severe smog episode (PM10 mass > 400 µg m^− 3) showed a stable concentration of black carbon in the aerosol, and an increase in the sulphate and chlorine mass contributions towards the end of the episode. Chemical characterization of single particles further helped to identify residential coal burning as the main source that caused this severe smog episode, consisting of single particles with major signals for carbon with simultaneous absence of sulphate, chlorine and calcium. Particles from industrial coal combustion gained importance towards the end of that episode, after residential coal combustion was switched off, indicated by an increase of the percentage of sulphate and chlorine containing particles. Traffic was not a significant source during the severe smog episode. During a lighter smog episode, residential and industrial coal combustion was still predominant, with an increased contribution of traffic and processed/aged aerosols. On a clean day, particle classes containing nitrate were the most abundant. In addition, the aerosol was more internally mixed showing that there were more sources contributing to the total aerosol population.  相似文献   

Dust attenuation in hydrodynamic simulations of spiral galaxies     

Miguel Rocha  Patrik Jonsson  Joel R. Primack  T. J. Cox 《Monthly notices of the Royal Astronomical Society》2008,383(4):1281-1291

  相似文献   

Distribution and Sources of Carbon,Nitrogen and Their Isotopic Compositions in Tropical Estuarine Sediments of Mtoni,Tanzania     

Mihale  Matobola Joel  Tungaraza  Clavery  Baeyens  Willy  Brion  Natacha 《Ocean Science Journal》2021,56(3):241-255

Ocean Science Journal - Elemental (C, N) and isotopic (δ13C, δ15N) signatures were used as proxies to identify seasonal changes in proportions of sedimentary organic matter (OM) in the...  相似文献   

Late Pleistocene stratigraphy and sedimentary environments of the Severnaya Dvina‐Vychegda region in northwestern Russia     

Astrid Lyså  Eiliv Larsen  Jan‐Pieter Buylaert  Ola Fredin  Maria A. Jensen  Denis Kuznetsov  Andrew S. Murray  Dmitry A. Subetto  Aurelien van Welden 《Boreas: An International Journal of Quaternary Research》2014,43(4):759-779

The Late Pleistocene stratigraphy from the Severnaya Dvina‐Vychegda region of northwestern Russia is revised based on investigations of new localities, revisiting earlier localities, introduction of about 110 new OSL dates and burial depth corrections of earlier published OSL dates, in addition to six new radiocarbon dates. Most of the OSL samples studied here are from fluvial and subaquaeous sediments, which we found to be well bleached. Six chronostratigraphical units and their sedimentary environment are described, with the oldest unit consisting of pre‐Eemian glacial beds. For the first time, Early Weichselian sediments are documented from the region and a fluvial environment with some vegetation and permafrost conditions is suggested to have persisted from the end of the Eemian until at least about 92 ka ago. The period in which a Middle Weichselian White Sea Lake could have existed is constrained to 67?62 ka, but as the lake level never reached the thresholds of the drainage basin, the lake probably existed only for a short interval within this time‐span. Blocking and reversal of fluvial drainage started again around 21?20 ka ago when the Fennoscandian Ice Sheet advanced into the area, reaching its maximum 17?15 ka ago. At that time, an ice‐dammed lake reached its maximum water level, which was around 135 m above present sea level. Drainage of the lake started shortly after 15 ka ago, and the lake was emptied within 700 years. Severe periglacial conditions, with permafrost and aeolian activity, prevailed in the area until about 10.7 ka.  相似文献   

Desert isotope hydrology: Water sources of the Sinai Desert     

Joel R Gat  Arie Issar 《Geochimica et cosmochimica acta》1974,38(7):1117-1131

The isotopic composition of groundwater sources of the Sinai Desert was surveyed. The results are characterized by a large spread in the oxygen-18 and deuterium abundances, compared to equivalent systems from less arid climates. The variability reflects differences in the altitude at which precipitation occurred, the evaporation from stagnant surface waters prior to their infiltration into the ground and admixtures of waters which are not of meteoric or recent origin. It is difficult to distinguish between water sources recharged by direct infiltration and others recharged through the intermediary of flood waters, on the basis of their isotope composition. The isotopio composition enables a clearcut distinction, however, between paleowaters and more recently recharged groundwaters. Among the conclusions: paleowaters play a central role in the deep aquifers of desert areas; direct rain recharge to aquifers is widespread; surface waters which have undergone extensive evaporation contribute their water to local perched aquifers which are found along their route.  相似文献   

Simplification and Validation of a Spectral-Tensor Model for Turbulence Including Atmospheric Stability   总被引：1，自引：1，他引：0  

Abhijit Chougule  Jakob Mann  Mark Kelly  Gunner C. Larsen 《Boundary-Layer Meteorology》2018,167(3):371-397

A spectral-tensor model of non-neutral, atmospheric-boundary-layer turbulence is evaluated using Eulerian statistics from single-point measurements of the wind speed and temperature at heights up to 100 m, assuming constant vertical gradients of mean wind speed and temperature. The model has been previously described in terms of the dissipation rate \(\epsilon \), the length scale of energy-containing eddies \(\mathcal {L}\), a turbulence anisotropy parameter \(\varGamma \), the Richardson number Ri, and the normalized rate of destruction of temperature variance \(\eta _\theta \equiv \epsilon _\theta /\epsilon \). Here, the latter two parameters are collapsed into a single atmospheric stability parameter z / L using Monin–Obukhov similarity theory, where z is the height above the Earth’s surface, and L is the Obukhov length corresponding to \(\{Ri,\eta _\theta \}\). Model outputs of the one-dimensional velocity spectra, as well as cospectra of the streamwise and/or vertical velocity components, and/or temperature, and cross-spectra for the spatial separation of all three velocity components and temperature, are compared with measurements. As a function of the four model parameters, spectra and cospectra are reproduced quite well, but horizontal temperature fluxes are slightly underestimated in stable conditions. In moderately unstable stratification, our model reproduces spectra only up to a scale \(\sim \) 1 km. The model also overestimates coherences for vertical separations, but is less severe in unstable than in stable cases.  相似文献   

Evaluation of spatial and temporal characteristics of GNSS-derived ZTD estimates in Nigeria     

Isioye  Olalekan Adekunle  Combrinck  Ludwig  Botai  Joel 《Theoretical and Applied Climatology》2018,132(3-4):1099-1116

Theoretical and Applied Climatology - This study presents an in-depth analysis to comprehend the spatial and temporal variability of zenith tropospheric delay (ZTD) over Nigeria during the period...  相似文献   

Performance of the WRF model to simulate the seasonal and interannual variability of hydrometeorological variables in East Africa: a case study for the Tana River basin in Kenya     

Kerandi  Noah Misati  Laux  Patrick  Arnault  Joel  Kunstmann  Harald 《Theoretical and Applied Climatology》2017,130(1-2):401-418

This study investigates the ability of the regional climate model Weather Research and Forecasting (WRF) in simulating the seasonal and interannual variability of hydrometeorological variables in the Tana River basin (TRB) in Kenya, East Africa. The impact of two different land use classifications, i.e., the Moderate Resolution Imaging Spectroradiometer (MODIS) and the US Geological Survey (USGS) at two horizontal resolutions (50 and 25 km) is investigated. Simulated precipitation and temperature for the period 2011–2014 are compared with Tropical Rainfall Measuring Mission (TRMM), Climate Research Unit (CRU), and station data. The ability of Tropical Rainfall Measuring Mission (TRMM) and Climate Research Unit (CRU) data in reproducing in situ observation in the TRB is analyzed. All considered WRF simulations capture well the annual as well as the interannual and spatial distribution of precipitation in the TRB according to station data and the TRMM estimates. Our results demonstrate that the increase of horizontal resolution from 50 to 25 km, together with the use of the MODIS land use classification, significantly improves the precipitation results. In the case of temperature, spatial patterns and seasonal cycle are well reproduced, although there is a systematic cold bias with respect to both station and CRU data. Our results contribute to the identification of suitable and regionally adapted regional climate models (RCMs) for East Africa.

  相似文献   

Taming a “chaotic concept”: gentrification and segmented consumption in Brooklyn, 2002–2012     

Mike Owen Benediktsson  Brian Lamberta  Erika Larsen 《Urban geography》2016,37(4):590-610

Public debate and prior scholarship tend to emphasize the link between gentrification and high-end chain retail, underscoring the importance of taste cultures tied to social class in making sense of gentrification’s impact on neighborhood identity. In this study, we present evidence from 10 years of change in the businesses of Brooklyn, New York City, a period of extensive gentrification across a wide variety of neighborhood and census-tract level contexts. Adopting census tracts clustered in neighborhoods as the units of analysis, we model the effects of institutional and demographic change on two separate outcomes: chain retail density and homogeneity in the types of goods and services available. We argue that changes in consumer culture embedded in broader processes of gentrification are neither “chaotic” nor “unitary” but are “segmented” according to local spatial and demographic context, taking two discrete forms: institutionally facilitated corporatization; lifestyle-driven homogenization.  相似文献   

Relative contributions of sulfate- and iron(III) reduction to organic matter mineralization and process controls in contrasting habitats of the Georgia saltmarsh     

Jung-Ho Hyun  April C. Smith  Joel E. Kostka   《Applied Geochemistry》2007,22(12):2637

The objectives of this study were to partition out the predominant anaerobic respiration pathways coupled to C oxidation and to further elucidate the controls of anaerobic C respiration in three major saltmarsh habitats at Skidaway Island, GA; the short form of Spartina alterniflora (SS), the tall form of S. alterniflora (TS), and unvegetated, bioturbated creekbank (CB). Geochemical analysis of pore water and solid phase constituents revealed that the SS site experienced highly reducing conditions with two orders of magnitude higher pore water sulfide inventories (1.884 mmol m⁻²) than TS (0.003 mmol m⁻²) and CB (0.005 mmol m⁻²), respectively. Conversely, reactive Fe(III) inventories at TS (2208 mmol m⁻²) and CB (2881 mmol m⁻²) were up to 7–9 times higher than at SS (338 mmol m⁻²). Incubations and intact core experiments indicated that reduction accounted for 95% (SS), 37% (TS) and 66% (CB) of total anaerobic respiration. There was no detectable Fe(III) reduction at SS, while Fe(III) reduction accounted for up to 70% of C oxidation in the 3–6 cm depth interval at TS and 0–3 cm depth of CB, and on average, approximately 55% of C oxidation over two-thirds of marsh surface area. Laboratory manipulations provided further evidence for the importance of Fe(III) reduction as the accumulation rates of fermentation products were high when Fe(III) reduction was inhibited by removing the Fe(III) minerals from highly bioturbated CB sediments with higher Fe(III) mineral contents. Anaerobic C oxidation, - and Fe(III)-reduction rates appeared to be highest at the TS site during active plant growth in summer. Overall results suggest that bioturbation by macrofauna is the overriding factor in modulating the pathway of C mineralization in the saltmarsh, whereas availability of organic substrates from plants is a key factor in controlling the C oxidation rate.  相似文献