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51.
Meng-Dawn Cheng 《Journal of Atmospheric Chemistry》2018,75(1):1-16
Although a large volume of monitoring and computer simulation data exist for global coverage of HF, study of HF in the troposphere is still limited to industry whose primary interest is the safety and risk assessment of HF release because it is a toxic gas. There is very limited information on atmospheric chemistry, emission sources, and the behavior of HF in the environment. We provide a comprehensive review on the atmospheric chemistry of HF, modeling the reactions and transport of HF in the atmosphere, the removal processes in the vertical layer immediately adjacent to the surface (up to approximately 500 m) and recommend research needed to improve our understanding of atmospheric chemistry of HF in the troposphere. The atmospheric chemistry, emissions, and surface boundary layer transport of hydrogen fluoride (HF) are summarized. Although HF is known to be chemically reactive and highly soluble, both factors affect transport and removal in the atmosphere, the chemistry can be ignored when the HF concentration is at a sufficiently low level (e.g., 10 ppmv). At a low concentration, the capability for HF to react in the atmosphere is diminished and therefore the species can be mathematically treated as inert during the transport. At a sufficiently high concentration of HF (e.g., kg/s release rate and thousands of ppm), however, HF can go through a series of rigorous chemical reactions including polymerization, depolymerization, and reaction with water to form molecular complex. As such, the HF species cannot be considered as inert because the reactions could intimately influence the plume’s thermodynamic properties affecting the changes in plume temperature and density. The atmospheric residence time of HF was found to be less than four (4) days, and deposition (i.e., atmosphere to surface transport) is the dominant mechanism that controls the removal of HF and its oligomers from the atmosphere. The literature data on HF dry deposition velocity was relatively high compared to many commonly found atmospheric species such as ozone, sulfur dioxide, nitrogen oxides, etc. The global average of wet deposition velocity of HF was found to be zero based on one literature source. Uptake of HF by rain drops is limited by the acidity of the rain drops, and atmospheric particulate matter contributes negligibly to HF uptake. Finally, given that the reactivity of HF at a high release rate and elevated mole concentration cannot be ignored, it is important to incorporate the reaction chemistry in the near-field dispersion close to the proximity of the release source, and to incorporate the deposition mechanism in the far-field dispersion away from the release source. In other words, a hybrid computational scheme may be needed to address transport and atmospheric chemistry of HF in a range of applications. The model uncertainty will be limited by the precision of boundary layer parameterization and ability to accurately model the atmospheric turbulence. 相似文献
52.
Thomas K. Flesch Lowry A. Harper Raymond L. Desjardins Zhiling Gao Brian P. Crenna 《Boundary-Layer Meteorology》2009,132(1):11-30
Inverse-dispersion calculations can be used to infer atmospheric emission rates through a combination of downwind gas concentrations
and dispersion model predictions. With multiple concentration sensors downwind of a compound source (whose component positions
are known) it is possible to calculate the component emissions. With this in mind, a field experiment was conducted to examine
the feasibility of such multi-source inferences, using four synthetic area sources and eight concentration sensors arranged
in different configurations. Multi-source problems tend to be mathematically ill-conditioned, as expressed by the condition
number κ. In our most successful configuration (average κ = 4.2) the total emissions from all sources were deduced to within 10% on average, while component emissions were deduced
to within 50%. In our least successful configuration (average κ = 91) the total emissions were calculated to within only 50%, and component calculations were highly inaccurate. Our study
indicates that the most accurate multi-source inferences will occur if each sensor is influenced by only a single source.
A “progressive” layout is the next best: one sensor is positioned to “see” only one source, the next sensor is placed to see
the first source and another, a third sensor is placed to see the previous two plus a third, and so on. When it is not possible
to isolate any sources κ is large and the accuracy of a multi-source inference is doubtful. 相似文献
53.
Shovan Lal Chattoraj Santanu Banerjee P. K. Saraswati 《Journal of the Geological Society of India》2009,73(4):567-574
Glauconitic minerals are considered as one of the valuable input parameters in sequence stratigraphic analysis of a basin.
In the present study glauconitic minerals are reported from subtidal green shale facies in the lower part of the Late Paleocene-Early
Eocene Naredi Formation of western Kutch. On the basis of the foraminiferal assemblage the glauconite bearing beds are interpreted
to have formed in a mid shelf depositional settings of an unstable marine conditions. XRD studies confirm the glauconite mineralogy
of the green pellets and provide an estimation of glauconite maturity. Textural attributes of the glauconites confirm their
derivation by different degrees of alteration of precursor feldspar grains. Because of the authigenic origin and autochthonous
nature, these glauconites hold promise for understanding sequence stratigraphy of the Palaeogene succession of the western
Kutch. 相似文献
54.
Lin-gun Liu C.-C. Lin Y. J. Yung T. P. Mernagh T. Irifune 《Physics and Chemistry of Minerals》2009,36(3):143-149
K-lingunite is a high-pressure modification of K-feldspar that possesses the tetragonal hollandite structure. Variations of
the Raman spectra of K-lingunite were studied up to ~31.5 GPa at room temperature, and in the range 79–823 K at atmospheric
pressure. The Raman frequencies of all bands were observed to increase with increasing pressure, and decrease with increasing
temperature for K-lingunite. This behavior is in line with those observed for most of other materials. New sharp Raman bands
appear at pressures greater than 13–15 GPa, suggesting a phase transition in K-lingunite with increasing pressure. The transition
is reversible when pressure was released. The appearance of these new Raman bands may correspond to the phase transition revealed
earlier at around 20 GPa by X-ray diffraction studies. Instead of transforming back to its stable minerals, such as orthoclase,
microcline or sanidine, K-lingunite became amorphous in the temperature range 803–823 K at atmospheric pressure. 相似文献
55.
Nicola Nocilla Aldo Evangelista Anna Scotto di Santolo 《Rock Mechanics and Rock Engineering》2009,42(5):815-833
In recent years, rock fall phenomena in Italy have received considerable attention for risk mitigation through in situ observations
and experimental data. This paper reports the study conducted at Camaldoli Hill, in the urban area of Naples, and at Monte
Pellegrino, Palermo, Italy. The rocks involved are volcanic Neapolitan yellow tuff (NYT) in the former area and dolomitic
limestone in the latter. Both rocks, even though with different strength characteristics, have shown a significant tendency
towards rock fragmentation during run out. This behavior was first investigated by comparing the volumes of removable blocks
on the cliff faces (V
0) and fallen blocks on the slopes (V
f). It was assumed that the ratio V
f/V
0 decreases with the distance (x
f) from the detachment area by an empirical law, which depends on a coefficient α, correlated with the geotechnical properties of the materials involved in the rock fall. Finally, this law was validated
by observation of well-documented natural rock falls (Palermo) and by in situ full-scale tests (Naples). From the engineering
perspective, consideration of fragmentation processes in rock fall modeling provides a means for designing low-cost mitigation
measures. 相似文献
56.
Pablo?SarricoleaEmail authorView authors OrcID profile Oliver?Meseguer-Ruiz Javier?Martín-Vide Luis?Outeiro 《Theoretical and Applied Climatology》2018,134(1-2):193-204
Atmospheric circulation patterns in southern Chile (42° 30′ S) were studied in order to determine and analyse the most characteristic synoptic types and their recent trends, as well as to gain an understanding of how they are associated with low-frequency variability patterns. According to the Jenkinson and Collison (J&C) classification method, a 16-point grid of sea-level pressure data was employed. The findings reveal that some synoptic types show statistically significant trends with a 95% confidence level, positively for anticyclonic westerly hybrids (AW) and advective types for third and fourth quadrant wind flows (W, NW, and N) and negatively for SW and cyclonic hybrids (CS and CSW). A model has been constructed of the linear regression of some weather types with teleconnections that most affect Chile: the undetermined types (U), AW were associated with El Niño or the warm phase of the Pacific Decadal Oscillation (PDO), whereas the cyclonic northerly and cyclonic northeasterly types (CN and CNE) were associated with La Niña or cool phase of the PDO. The weather types associated with Antarctic Oscillation (AAO) in its positive phase are anticyclonic northerly and northeasterly and northerly advection types, while in its negative phase are cyclonic southwesterly and advection types. 相似文献
57.
The climate–population relationship has long been conceived. Although the topic has been repeatedly investigated, most of
the related works are Eurocentric or qualitative. Consequently, the relationship between climate and population remains ambiguous.
In this study, fine-grained temperature reconstructions and historical population data sets have been employed to statistically
test a hypothesized relationship between temperature change and population growth (i.e., cooling associated with below average
population growth) in China over the past millennium. The important results were: (1) Long-term temperature change significantly
determined the population growth dynamics of China. However, spatial variation existed, whilst population growth in Central
China was shown to be responsive to both long- and short-term temperature changes; in marginal areas, population growth was
only sensitive to short-term temperature fluctuations. (2) Temporally, the temperature–population relationship was obscured
in some periods, which was attributable to the factors of drought and social buffers. In summary, a temperature–population
relationship was mediated by geographic factors, the aridity threshold, and social factors. Given the upcoming threat posed
by climate change to human societies, this study seeks to improve our knowledge and understanding of the climate–society relationship. 相似文献
58.
Kristie?L.?EbiEmail author Jessica?Hartman Nathan?Chan John?Mcconnell Michael?Schlesinger John?Weyant 《Climatic change》2005,73(3):375-393
Climate is one factor that determines the potential range of malaria. As such, climate change may work with or against efforts
to bring malaria under control. We developed a model of future climate suitability for stable Plasmodium falciparum malaria transmission in Zimbabwe. Current climate suitability for stable malaria transmission was based on the MARA/ARMA
model of climatic constraints on the survival and development of the Anopheles vector and the Plasmodium falciparum malaria parasite. We explored potential future geographic distributions of malaria using 16 projections of climate in 2100.
The results suggest that, assuming no future human-imposed constraints on malaria transmission, changes in temperature and
precipitation could alter the geographic distribution of malaria in Zimbabwe, with previously unsuitable areas of dense human
population becoming suitable for transmission. Among all scenarios, the highlands become more suitable for transmission, while
the lowveld and areas with low precipitation show varying degrees of change, depending on climate sensitivity and greenhouse
gas emission stabilization scenarios, and depending on the general circulation model used. The methods employed can be used
within or across other African countries. 相似文献
59.
Adequate high-quality data on three-dimensional velocities in the atmospheric surface layer (height \(\delta \)) were acquired in the field at the Qingtu Lake Observation Array. The measurement range occupies nearly the entire logarithmic layer from approximately \(0.006\delta \)–\(0.2\delta \). The turbulence intensity and eddy structures of the velocity fluctuations in the logarithmic region were primarily analyzed, and their variations in the z (wall-normal) direction were revealed. The primary finding was that the turbulent intensity of wall-normal velocity fluctuations exhibits a sharp upswing in the logarithmic region, which differs from classic scaling law and laboratory results. The upswing of the wall-normal turbulence intensity in the logarithmic region is deemed to be linear based on an ensemble of 20 sets of data. In addition, the wall-normal extent of the correlated structures and wall-normal spectra were compared to low Reynolds number results in the laboratory. 相似文献
60.