Chemical characterization of fine particulate matter during peak PM10 episodes in Apulia (South Italy)     

Martino Amodio  Paolo Bruno  Maurizio Caselli  Gianluigi de Gennaro  Paolo Rosario Dambruoso  Barbara Elisabetta Daresta  Pieirna Ielpo  Francesco Gungolo  Claudia Marcella Placentino  Vincenzo Paolillo  Maria Tutino 《Atmospheric Research》2008,90(2-4):313-ICNAA07

Some peak PM10 episodes, occurred during PM monitoring campaigns performed on October 2005 and February and June 2006 in Bari town, have been characterized. Moreover back trajectories of air masses and Principal Component Analyses were applied. Three of the peak PM10 episodes investigated were related to local emissions of primary pollutants during poor atmospheric dispersion conditions. The other two peak PM10 episodes considered are related with long range transport air masses toward Apulia region: in one case the chemical characterization and the back trajectories analysis indicate that high PM10 value detected is due to the Saharan dust advection in the Apulia region; in the other case air masses with different origin give rise to high PM10 value.Moreover PM10 daily mean concentrations, presented in this paper collected from January 2005 to August 2007 and obtained by automatic device in six stations of air quality monitoring networks in Bari territory, do not show a seasonal trend for PM10 concentrations, contrary to the PM10 trend shown in the towns of North Italy. This can be explained mostly considering that our region presents generally meteo-climatic conditions that favour pollutants dispersion.  相似文献   

Towards molecular-level understanding of geochemical processes in mineral exploration     

Joël Brugger  Allan Pring  Frank Reith  Barbara Etschmann  Weihua Liu 《Journal of Geochemical Exploration》2009

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A synchrotron X-ray absorption spectroscopic study of copper solubility and speciation in supercritical water     

Weihua Liu  Joël Brugger  Barbara Etschmann  Denis Testemale  Jean-Louis Hazemann 《Journal of Geochemical Exploration》2009

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A modified peak‐bagging technique for fitting low‐𝓁 solar p‐modes     

S.T. Fletcher  W.J. Chaplin  Y. Elsworth  R. New 《Astronomische Nachrichten》2008,329(5):447-452

We introduce a modified version of a standard power spectrum ‘peak‐bagging’ technique which is designed to gain some of the advantages that fitting the entire low‐degree p‐mode power spectrum simultaneously would bring, but without the problems involved in fitting a model incorporating many hundreds of parameters. Employing Monte‐Carlo simulations we show that by using this modified fitting code it is possible to determine the true background level in the vicinity of the p‐mode peaks. In addition to this we show how small biases in other mode parameters, which are related to inaccurate estimates of the true background, are also consequently removed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

The visibility of low‐frequency solar acoustic modes     

A. M. Broomhall  W. J. Chaplin  Y. Elsworth  S. T. Fletcher 《Astronomische Nachrichten》2008,329(5):461-469

We make predictions of the detectability of low‐frequency p modes. Estimates of the powers and damping times of these low‐frequency modes are found by extrapolating the observed powers and widths of higher‐frequency modes with large observed signal‐to‐noise ratios. The extrapolations predict that the low‐frequency modes will have small signal‐to‐noise ratios and narrow widths in a frequency‐power spectrum. Monte Carlo simulations were then performed where timeseries containing mode signals and normally distributed Gaussian noise were produced. The mode signals were simulated to have the powers and damping times predicted by the extrapolations. Various statistical tests were then performed on the frequency‐amplitude spectra formed from these timeseries to investigate the fraction of spectra in which the modes could be detected. The results of these simulations were then compared to the number of p‐modes candidates observed in real Sun‐as‐a‐star data at low frequencies. The fraction of simulated spectra in which modes were detected decreases rapidly as the frequency of modes decreases and so the fraction of simulations in which the low‐frequency modes were detected was very small. However, increasing the signal‐to‐noise (S/N) ratio of the low‐frequency modes by a factor of 2 above the extrapolated values led to significantly more detections. Therefore efforts should continue to further improve the quality of solar data that is currently available. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Warming the early earth—CO₂ reconsidered     

Philip von Paris  Heike Rauer  J. Lee Grenfell  Beate Patzer  Barbara Stracke  Franz Schreier 《Planetary and Space Science》2008,56(9):1244-1259

Despite a fainter Sun, the surface of the early Earth was mostly ice-free. Proposed solutions to this so-called “faint young Sun problem” have usually involved higher amounts of greenhouse gases than present in the modern-day atmosphere. However, geological evidence seemed to indicate that the atmospheric CO₂ concentrations during the Archaean and Proterozoic were far too low to keep the surface from freezing. With a radiative-convective model including new, updated thermal absorption coefficients, we found that the amount of CO₂ necessary to obtain 273 K at the surface is reduced up to an order of magnitude compared to previous studies. For the late Archaean and early Proterozoic period of the Earth, we calculate that CO₂ partial pressures of only about 2.9 mb are required to keep its surface from freezing which is compatible with the amount inferred from sediment studies. This conclusion was not significantly changed when we varied model parameters such as relative humidity or surface albedo, obtaining CO₂ partial pressures for the late Archaean between 1.5 and 5.5 mb. Thus, the contradiction between sediment data and model results disappears for the late Archaean and early proterozoic.  相似文献   

Southern high latitude climate variability in the Late Cretaceous greenhouse world     

Stephen J. Gallagher  Barbara E. Wagstaff  Jennifer G. Baird  Malcolm W. Wallace  Chung Leong Li 《Global and Planetary Change》2008,60(3-4):351-364

A palynological study of oil exploration wells in the Gippsland Basin southeastern Australia has provided a record of southern high latitude climate variability for the last 12 million years of the Cretaceous greenhouse world. During this time, the vegetation was dominated by a cool to temperate flora of Podocarpaceae, Proteaceae and Nothofagidites spp. at a latitude of 60°S. Milankovitch forced cyclic alternations from drier to wetter climatic periods caused vegetation variability from 72 to 77 Ma. This climate change was probably related to the waxing and waning of ephemeral (100 ky) small ice sheets in Antarctica during times of insolation minima and maxima. Drying and cooling after 72 Ma culminated from 68 to 66 Ma, mirroring trends in global δ¹⁸O data. Quantitative palynofloral analyses have the potential to provide realistic proxies for small-scale climate variability in the predominantly ice-free Late Cretaceous.  相似文献   

Phase equilibrium modelling of the amphibolite to granulite facies transition in metabasic rocks (Ivrea Zone,NW Italy)     

Barbara E. Kunz  Richard W. White 《Journal of Metamorphic Geology》2019,37(7):935-950

The development of thermodynamic models for tonalitic melt and the updated clinopyroxene and amphibole models now allow the use of phase equilibrium modelling to estimate P–T conditions and melt production for anatectic mafic and intermediate rock types at high‐T conditions. The Permian mid‐lower crustal section of the Ivrea Zone preserves a metamorphic field gradient from mid amphibolite facies to granulite facies, and thus records the onset of partial melting in metabasic rocks. Interlayered metabasic and metapelitic rocks allows the direct comparison of P–T estimates and partial melting between both rock types with the same metamorphic evolution. Pseudosections for metabasic compositions calculated in the Na₂O–CaO–K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O–TiO₂–O (NCKFMASHTO) system are presented and compared with those of metapelitic rocks calculated with consistent end‐member data and a–x models. The results presented in this study show that P–T conditions obtained by phase equilibria modelling of both metabasic and metapelitic rocks give consistent results within uncertainties, allowing integration of results obtained for both rock types. In combination, the calculations for both metabasic and metapelitic rocks allows an updated and more precisely constrained metamorphic field gradient for Val Strona di Omegna to be defined. The new field gradient has a slightly lower dP/dT which is in better agreement with the onset of crustal thinning of the Adriatic margin during the Permian inferred in recent studies.  相似文献   

Quality and timing of crowd-based water level class observations     

Simon Etter  Barbara Strobl  Ilja van Meerveld  Jan Seibert 《水文研究》2020,34(22):4365-4378

Crowd-based hydrological observations can supplement existing monitoring networks and allow data collection in regions where otherwise no data would be available. In the citizen science project CrowdWater, repeated water level observations using a virtual staff gauge approach result in time series of water level classes (WL-classes). To investigate the quality of these observations, we compared the WL-class data with “real” (i.e., measured) water levels from the same stream at a nearby gauging station. We did this for nine locations where citizen scientists reported multiple observations using a smartphone app and at 12 locations where signposts were set up to ask citizens to record observations on a paper form that could be left in a letterbox. The results indicate that the quality of the data collected with the app was better than for the forms. A possible explanation is that for each app location, a single person submitted the vast majority of the observations, whereas at the locations of the forms almost every observation was made by a different person. On average, there were more contributions between May and September than during the other months. Observations were submitted for a range of flow conditions, with a higher fraction of high flow observations for the locations were data were collected with the app. Overall, the results are encouraging for citizen science approaches in hydrology and demonstrate that the smartphone application and the virtual staff gauge are a promising approach for crowd-based water level class observations.  相似文献   

What is Moss?     

Berger  T.E.  De Pontieu  B.  Fletcher  L.  Schrijver  C.J.  Tarbell  T.D.  Title  A.M. 《Solar physics》1999,190(1-2):409-418

TRACE observations of active regions show a peculiar extreme ultraviolet (EUV) emission over certain plage areas. Termed `moss' for its spongy, low-lying, appearance, observations and modeling imply that the phenomenon is caused by thermal conduction from 3–5 MKcoronal loops overlying the plage: moss is the upper transition region emission of hot coronal loops. The spongy appearance is due to the presence of chromospheric jets or `spicules' interspersed with the EUV emission elements. High cadence TRACE observations show that the moss EUV elements interact with the chromospheric jets on 10 s time scales. The location of EUV emission in the moss does not correlate well to the locations of underlying magnetic elements in the chromosphere and photosphere, implying a complex magnetic topology for coronal loop footpoint regions. We summarize here the key observations leading to these conclusions and discuss new implications for understanding the structuring of the outer solar atmosphere. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005286503963  相似文献