The thermodynamics and kinetics of the hydrogen sulfide system in natural waters     

Frank J Millero 《Marine Chemistry》1986,18(2-4)

The thermodynamics and kinetics of the H₂S system in natural waters have been critically reviewed. Equations have been derived for the solubility and ionization of H₂S in water and seawater as a function of salinity, temperature and pressure. Pitzer parameters for the interaction of the major cations (Na⁺, Mg²⁺ and Ca²⁺) with HS⁻ have been determined to allow one to calculate values of pK₁^* in various ionic media. The limited data available for the interaction of trace metals for HS⁻ are summarized and future work is suggested.The kinetics of oxidation of H₂S have also been examined as a function of pH, temperature, and salinity. The discrepancies in the available data are largely due to the different [O₂]/[HS−] ratios used in various studies. Over a limited pH range (6–8) the pseudo first order rate constant for the oxidation is shown to be directly proportional to the activity of HS⁻. Further studies are suggested to examine the effect of ionic media and temperature on the rate of oxidation.  相似文献   

Advancing Science with VGI: Reproducibility and Replicability of Recent Studies using VGI   总被引：4，自引：2，他引：2       下载免费PDF全文

Frank O. Ostermann  Carlos Granell 《Transactions in GIS》2017,21(2):224-237

In scientific research, reproducibility and replicability are requirements to ensure the advancement of our body of knowledge. This holds true also for VGI‐related research and studies. However, the characteristics of VGI suggest particular difficulties in ensuring reproducibility and replicability. In this article, we aim to examine the current situation in VGI‐related research, and identify strategies to ensure realization of its full potential. To do so, we first investigate the different aspects of reproducibility and replicability and their impact on VGI‐related research. These impacts are different depending on the objectives of the study. Therefore, we examine the study focus of VGI‐related research to assess the current body of research and structure our assessment. This work is based on a rigorous review of the elements of reproducibility and a systematic mapping and analysis of 58 papers on the use of VGI in the crisis management field. Results of our investigation show that reproducibility issues related to data are a serious concern, while reproducibility issues related to analysis methods and processes face fewer challenges. However, since most studies still focus on analyzing the source data, reproducibility and replicability are still an unsolved problem in VGI‐related research. Therefore, we show initiatives tackling the problem, and finally formulate strategies to improve the situation.  相似文献   

Observations of the Temperature and Humidity Structure Parameter Over Heterogeneous Terrain by Airborne Measurements During the LITFASS-2003 Campaign     

Andreas Platis  Arnold F. Moene  Daniel Martínez Villagrasa  Frank Beyrich  David Tupman  Jens Bange 《Boundary-Layer Meteorology》2017,163(3):447-467

We used numerical simulations to investigate the general relationship between urban morphology and the intensity of wind gusts in built-up areas at the pedestrian level. The simulated urban boundary layer developed over a 19.2 km (length) \(\times \) 4.8 km (width) \(\times \) 1.0 km (height) simulation domain, with 2-m resolution in all directions, to explicitly resolve the detailed shapes of buildings and the flow at the pedestrian level. This complex computation was accomplished using the lattice Boltzmann method and by implementing a large-eddy simulation model. To generalize the results, a new parameter that expresses the intensity of gusts (the gust index, \({\tilde{U}}_{ max})\) was defined as the local maximum wind speed divided by the freestream velocity. In addition, this parameter was decomposed into the mean wind-speed ratio, \({\tilde{U}} \) and turbulent gust ratio, \({\tilde{U}}^{{\prime }}\) to evaluate the qualities of gusts. These parameters were useful for quantitatively comparing the gust intensities within urban canopies at different locations or even among different experiments. In addition, the entire horizontal domain was subdivided into homogeneous square patches, in which both the simulated gust parameters and the morphological characteristics of building geometries were averaged. This procedure masked the detailed structure of individual buildings but retained the bulk characteristics of the urban morphology. At the pedestrian level, the gust index decreased with increasing building cover. Compared to \({\tilde{U}} \), the quantity \({\tilde{U}}^{{\prime }}\) notably contributed to the index throughout the range of plan area index \((\lambda _p)\) values. The dependences of all normalized wind-speed ratios transiently changed at \(\lambda _p =~0.28\). In cases where \(\lambda _p < 0.28, {\tilde{U}} \) decreased with increasing \(\lambda _p \), although \({\tilde{U}}^{{\prime }}\) was almost constant. In cases where \(\lambda _p > 0.28, {\tilde{U}}\) was almost constant and \({\tilde{U}}^{{\prime }}\) decreased with increasing \(\lambda _p \). This was explained by the change in flow regimes within the building canyon. At a higher elevation above the canopy layer, \(\lambda _p \) becomes less relevant to normalized wind-speed ratios, and instead the aerodynamic roughness length became important.  相似文献   

An Evaluation of Information Meetings as a Tool for Addressing Fear of Large Carnivores     

Maria Johansson  Jens Frank  Ole-Gunnar Støen  Anders Flykt 《社会与自然资源》2017,30(3):281-298

Managing authorities in Scandinavia arrange public information meetings when members of the public express fear because wolves or brown bears approach human settlements. This study aimed to increase the understanding of the potential effect of information meetings on self-reported fear of wolves and brown bears. In total, 198 participants completed questionnaires before and after the information meetings. Nine follow-up interviews were held 1 year later. The quantitative analyses revealed that participants who found the information credible reported a significant increase in social trust and a decrease in vulnerability and fear. The qualitative analyses pointed to the importance of information content and meta-communication, for example, nonverbal cues. It is proposed that, among participants who find the information credible, information meetings may change the appraisal of wolves and brown bears, and therefore they might prove useful as an intervention to address fear of these animals.  相似文献   

Paleolimnological features of a mega-lake phase in the Makgadikgadi Basin (Kalahari,Botswana) during Marine Isotope Stage 5 inferred from diatoms     

Mareike Schmidt  Markus Fuchs  Andrew C. G. Henderson  Annette Kossler  Melanie J. Leng  Anson W. Mackay  Elisha Shemang  Frank Riedel 《Journal of Paleolimnology》2017,58(3):373-390

The Makgadikgadi–Okavango–Zambezi basin (MOZB) is a structural depression in the south-western branch of the East African Rift System of the northern and middle Kalahari, central southern Africa. In the present day, the mainly dry subbasins of the MOZB are part of a long-lived lacustrine system that has likely existed since Early Pleistocene and from which an extant freshwater fish radiation emerged seeding all major river systems of southern Africa. During hydrologically favourable periods the subbasins were connected as a single mega-lake termed Lake Palaeo-Makgadikgadi. Previous geomorphological studies and OSL dates have provided evidence for repeated mega-lake periods since approximately 300 ka. The environmental and climatic implications of such large scale late Quaternary lake-level fluctuations are controversial, with the duration of mega-lake phases poorly constrained. Here, we present the first evidence for a Marine Isotope Stage (MIS) 5 mega-lake period (about 935–940 m a.s.l.) reconstructed from a diatom-rich, 30-cm-thick lacustrine sediment section, exposed close to a palaeo-shoreline of the Makgadikgadi Basin. Based upon the environmental setting and in comparison with sedimentation rates of other similar lake environments, we tentatively estimated that the highstand lasted approximately 1 ka during MIS 5d–b. The 30-cm section was sampled in 0.5-cm steps. Diatom species diversity ranges from 19 to 30 through the section. The dominant species are Pseudostaurosira brevistriata, Rhopalodia gibberula, Cyclotella meneghiniana and Epithemia sorex. The total of 60 sediment samples provide us with a record at decadal to bi-decadal resolution. Based on diatom assemblages and their oxygen isotope composition (δ¹⁸O) we infer an alkaline and mostly oligohaline lake with shallow water conditions prevailing in MIS 5, and is potentially analogous to a Heinrich event. The climate over southern Africa during MIS 5 has been considered very arid but the hydromorphological context of our sediment section indicates that we captured a mega-lake period providing evidence that short-term excursions to significantly higher humidity existed. A hydrologically more favourable environment during MIS 5 than formerly presumed is in line with the early human occupation of the Kalahari.  相似文献   

AMS radiocarbon dating of organic fractions from varved lake sediments: an empirical test of reliability     

Frank Oldfield  Peter R. J. Crooks  Douglas D. Harkness  Gunilla Petterson 《Journal of Paleolimnology》1997,18(1):87-91

Replicate cores of annually laminated (varved) sediments have been used to test the accuracy and precision of chronologies of lake sediment accumulation over the last 1000 years, based on AMS 14C measurements. The internally consistent results show that in the case of the soft-water lake sediments studied (Kassjön, northern Sweden), all the organic fractions that include aquatic components give significantly older dates than expected. Only the single terrestrial macrofossil and the fine, unidentified residual particulate fraction provide dates close to the true age of the sediments. The results also show that age discrepancies for some fractions are not constant over time. The age discrepancies may arise from some carbon reservoir effect within the aquatic ecosystem, from resuspension and focusing of older marginal organic material into the deepest part of the lake or from some combination of these processes. More work is needed on the 14C age of organic fractions in varve-dated sediments from a range of lake types.  相似文献   

Trace metal and magnetic studies of sediments in greek estuaries and enclosed gulfs     

Michael J. Scoullos  Frank Oldfield 《Marine Chemistry》1986,18(2-4)

Minicores of seabottom sediments from typical coastal and estuarine areas of Greece (the Gulf of Elefsis and the estuaries of the Acheloos and Louros rivers), influenced in a widely varying degree by anthropogenic inputs, were analysed for trace metal content and measured for a series of magnetic properties (i.e., total magnetic susceptibility, frequency dependent susceptibility, isothermal remanent magnetization and demagnetization).Apparent linkages between trace metal content (total or in chemically leached fractions) and magnetic properties were found in cores from all areas. Variations in the relative importance of the non-leachable fraction of metals in the Elefsis Gulf sediments closely parallel changes in the percentage frequency dependent susceptibility, which can be considered as indicator of soil derived material.By combining chemical and magnetic data, very useful information was obtained on: (a) the origin (industrial) of the rapidly deposited sediments in the Gulf of Elefsis; (b) the deposition rate, which was estimated as 0.5 cm per annum; (c) the range and nature of the major natural particle assemblages present in the Acheloos and Louros estuaries; (d) the distinction between the assemblages deriving from the erosion of surface soils and from unweathered parent material; (e) the identification of particles acting as major trace metal carriers (viz. anthropogenic particulates and soil-derived clays).In general the results confirm that integrated trace metal—magnetic studies can provide valuable data on the origin, transport and sedimentation mechanisms of trace metals associated in various ways with particles in coastal and estuarine systems. New perspectives are briefly discussed.  相似文献   

TRADING AREA VARIATIONS FOR DIFFERENT GOODS SOLD IN THE SAME STORE     

Frank J. Sparicio 《The Professional geographer》1966,18(1):5-8

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Der impulsoptische Wolkenhöhenmesser     

Frank Frügel 《Theoretical and Applied Climatology》1960,10(2):243-251

Zusammenfassung Das Prinzip der trigonometrischen Messung von Wolkenhöhen wurde mittels Impulslicht sehr hoher Spitzenleuchtdichte (Edelgasfunkenstrecken) zu einer vollautomatischen Registrier-Anlage ausgebaut, die sich durch Tageslichtunabhängigkeit, große Meßhöhen von 1000 bzw. 3000 m und einfache Konstruktionselemente auszeichnet. Es wird sowohl die Wolken-untergrenze wie der Wolkencharakter aufgezeichnet.

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Summary The principle of trigonometric measurements of cloud heights was developed, by means of pulse light of very high maximum brightness (rare gas spark gap), to a full-automatic recording apparatus characterized by independence on day light, the possibility of measuring great heights from 1000 to 3000 m, and simple elements of construction. The lower limit as well as the kind of clouds are recorded.

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Résumé Mise au point d'une installation entièrement automatique pour la mesure de la hauteur des nuages par voie trigonométrique à l'aide d'impulsions lumineuses de très grande intensité. Le procédé est applicable de jour et de nuit, permet des mesures de 1000 à 3000 m. et utilise un apparaillage simple; il enregistre l'altitude de la base des nuages et le caractère de ceux-ci.

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Mit 4 Textabbildungen  相似文献   

Late Triassic initial subduction of the Bangong‐Nujiang Ocean beneath Qiangtang revealed: stratigraphic and geochronological evidence from Gaize,Tibet          下载免费PDF全文

Min Zeng  Xiang Zhang  Hui Cao  Frank R. Ettensohn  Wenbin Cheng  Xinghai Lang 《Basin Research》2016,28(1):147-157

Sedimentological and geochronological studies along a north–south traverse across the Bangong‐Nujiang suture zone (BNSZ) in Gaize, Tibet provide evidence for a Late Triassic–Jurassic accretionary wedge accreted to the south margin of Qiangtang. This wedge, preserved as the Mugagangri Group (MG), records evidence for the northward subduction of the Bangong‐Nujiang Ocean (BNO) beneath Qiangtang. The MG strata comprise two coarser intervals (lower olistostromes and upper conglomerates) intercalated within sandy turbidites, which are consistent with timing and forearc stratigraphy during subduction initiation predicted by geodynamic modelling. Following the model, the northward subduction of the BNO beneath Qiangtang and subsequent arc‐magmatism are inferred to have begun, respectively, at ca. 220 Ma and ca. 210 Ma, with respect to depositional ages constrained by youngest detrital‐zircon ages. The initiation of arc‐magmatism is also supported by provenance transition reflected by sandstone detrital modes and age patterns of detrital zircons. Previously, evidence for an incipient arc was lacking, but the timing of Late Triassic BNO subduction and related arc‐magmatism is coincident with an important Late Triassic magmatic event in central Qiangtang that probably represents the ‘missing’ arc. Other Qiangtang events, such as exhumation of the Qiangtang metamorphic belt as a source area, and development of the Late Triassic Nadigangri deposits and bimodal volcanism, are more easily explained in the tectonic context of early northward subduction of the BNO beneath Qiangtang, beginning at about 220 Ma.  相似文献