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101.
Nobuhisa Kashiwagi 《Environmetrics》2004,15(8):777-796
A chemical mass balance method is proposed for the case where the existence of an unknown source is suspected. In general, when the existence of an unknown source is assumed in statistical receptor modeling, unknown quantities such as the composition of an unknown source and the contributions of assumed sources become unidentifiable. To estimate these unknown quantities avoiding the identification problem, a Bayes model for chemical mass balance is constructed in the form of composition without using prior knowledge on the unknown quantities except for natural constraints. The covariance of ambient observations given in the form of composition is defined in several ways. Markov chain Monte Carlo is used for evaluating the posterior means and variances of the unknown quantities as well as the likelihood for the proposed model. The likelihood is used for selecting the best fit covariance model. A simulation study is carried out to check the performance of the proposed method. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
102.
When CO2 is injected into aquifers in a hydrocarbon basin, either for CO2 geological storage or enhanced oil recovery (EOR), these aquifers are most likely saturated with CH4. Dissolving CO2 into the aqueous phase will cause CH4 to come out of the aqueous phase and partitioning into the CO2‐rich non‐aqueous phase under static conditions. It is not well understood how this process develops under flow conditions, which is the subject of this paper. Although CH4 solubility in brine is low under the subsurface conditions, the effects of CH4 dissolved in saline aquifers cannot be ignored for CO2 sequestration projects. This is due to the changes of the phase behavior, capillary pressure, and relative permeability which has already been recognized by previous studies. This work couples a recently developed thermodynamic model of CO2‐CH4‐brine system with an industrial reservoir simulator and applies it in the simulation of CO2 injection into a CH4 saturated aquifer. Simulation results are compared to field observations from U‐tube sampling and used to provide reasonable explanations. From the simulations, the compositions in U‐tube samples are influenced by U‐tube inlet position, perforation and the reservoir (geological) properties. With the explanations, the U‐tube observations of gas samples can be well matched by numerical simulation results.© 2014 Society of Chemical Industry and John Wiley & Sons, Ltd 相似文献
103.
Marie Chavent Herv Gugan Vanessa Kuentz Brigitte Patouille Jrme Saracco 《Environmetrics》2009,20(8):928-942
Air pollution is a wide concern for human health and requires the development of air quality control strategies. In order to achieve this goal pollution sources have to be accurately identified and quantified. The case study presented in this paper is part of a scientific project initiated by the French Ministry of Ecology and Sustainable Development. For the following study measurements of chemical composition data for particles have been conducted on a French urban site. The first step of the study consists in the identification of the sources profiles which is achieved through principal component analysis (PCA) completed by a rotation technique. Then the apportionment of the sources is evaluated with a receptor modeling using positive matrix factorization (PMF) as estimation method. Finally the joint use of these two statistical methods enables to characterize and apportion five different sources of fine particulate emission. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
104.
D. G. Chen 《Environmetrics》2009,20(1):101-109
The isobologram model is a commonly used and powerful graphical and statistical tool for analyzing the joint action for simple chemical mixtures. Substantial research has been done for the quantitative response and the amount of research in the qualitative framework is minuscule. In this paper, isobologram model is proposed to analyze the joint action of chemical mixtures for quantal dose‐response relationship based on the generalized linear model technique to estimate the associated parameters by the maximum likelihood estimation and then to be used to construct the isobologram so that the joint action from the chemicals can be identified both by the isobologram and the statistical inference for interaction parameter. A real dataset is used to illustrate the application of the developed approach. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
105.
Catherine A. Calder 《Environmetrics》2008,19(1):39-48
Elevated levels of particulate matter (PM) in the ambient air have been shown to be associated with certain adverse human health effects. As a result, monitoring networks that track PM levels have been established across the United States. Some of the older monitors measure PM less than 10 µm in diameter (PM10), while the newer monitors track PM levels less than 2.5 µm in diameter (PM2.5); it is now believed that this fine component of PM is more likely to be related to the negative health effects associated with PM. We propose a bivariate dynamic process convolution model for PM2.5 and PM10 concentrations. Our aim is to extract information about PM2.5 from PM10 monitor readings using a latent variable approach and to provide better space‐time interpolations of PM2.5 concentrations compared to interpolations made using only PM2.5 monitoring information. We illustrate the approach using PM2.5 and PM10 readings taken across the state of Ohio in 2000. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
106.
The exact distributions of the ratio X/Y are derived when X and Y are independent random variables and come from type I, type II or type III extreme value distributions. A detailed application of the results is provided to extreme rainfall data from Korea. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
107.
Over the past few years, Bayesian models for combining output from numerical models and air monitoring data have been applied to environmental data sets to improve spatial prediction. This paper develops a new hierarchical Bayesian model (HBM) for fine particulate matter (PM2.5) that combines U. S. EPA Federal Reference Method (FRM) PM2.5 monitoring data and Community Multi‐scale Air Quality (CMAQ) numerical model output. The model is specified in a Bayesian framework and fitted using Markov Chain Monte Carlo (MCMC) techniques. We find that the statistical model combining monitoring data and CMAQ output provides reliable information about the true underlying PM2.5 process over time and space. We base these conclusions on results of a validation exercise in which independent monitoring data were compared with predicted values from the HBM and predictions from a standard kriging model based solely on the monitoring data. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
108.
The Caroní catchment located in the south‐east of Venezuela accounts for 70 per cent of the total hydropower energy of the country. On a year to year basis, it has been shown that low frequency large scale ocean‐atmosphere phenomena are highly coupled to the hydroclimatology of the region, El Niño‐Southern Oscillation (ENSO) being a major forcing mechanism of climatic and hydrological anomalies. Regional differences in amplitude and timing are due to complex orographic interactions, land surface‐atmosphere feedback mechanisms and the evolution of dominant synoptic meteorological conditions. A detailed analysis of the relationship between rainfall and several large scale ocean‐atmospheric variables was carried out to determine the potential use of large scale climatic information as predictors of the rainfall anomalies over the region. The problem was tackled in two ways: (a) first a seasonal dynamic rainfall model was fitted to monthly rainfall for different locations. In this case rainfall is assumed as a normal variate w which has been transformed to account for its departure from normality and truncated to account for the positive probability mass of zero values, which corresponds to negative values of the normal variable. The time series of the model parameters and the macroclimatic variables are inspected for their potential relationship with local rainfall via the stochastic model. (b) Second, dynamic linear regression models between the macroclimatic variables as predictors and the rainfall anomalies as predictant were fitted to evaluate and quantify the significance of these dependencies. Consistent patterns are observed with the Tropical Atlantic and Pacific ocean temperature anomalies, in which a significant negative relationship has been present since 1976, indicating an overall decrease (increase) in rainfall when the Pacific and the Tropical Atlantic are warmer (colder) than normal. In all cases the results suggest that the relationships between rainfall anomalies and the macroclimatic variables are not constant with time. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
109.
Changbing Yang Susan D. Hovorka Michael H. Young Ramon Trevino 《Greenhouse Gases: Science and Technology》2014,4(3):384-399
Various approaches to groundwater monitoring for CO2 leakage detection and potential impacts of groundwater quality in the above potable aquifers at geological carbon sequestration sites have been reported in literature and briefly reviewed in this study. Although geochemical para‐meters have been proposed as indicators of CO2 leakage in potable aquifers, assessing sensitivity of geochemical parameters to CO2 leakage in groundwater is needed. In this study, we present a methodology, using a geochemical model, to simulate responses of aqueous geochemistry to CO2 leakage into a potable aquifer and then to assess sensitivities of the proposed monitoring geochemical parameters based on their relative changes to initial values. The geochemical model was used to simulate CO2 leakage into carbonate‐poor and carbonate‐rich aquifers. Results of calculated sensitivities show that dissolved CO2 and dissolved inorganic carbon in groundwater are most sensitive to CO2 leakage in all settings. Alkalinity is moderately sensitive, with the best response in the presence of carbonates in the aquifer sediments while groundwater pH shows best response in the aquifer sediments with little carbonates. Impacts of initial (or baseline) groundwater chemistry on sensitivity of geochemical parameters to CO2 leakage, compared to impacts of aquifer mineralogy, appear to be minor. For monitoring purpose, dissolved CO2 and dissolved inorganic carbon are better indicators than pH and alkalinity in potable aquifers at geological carbon sequestration sites. 相似文献
110.
Use of an Airborne Lidar System to Model Plant Species Composition and Diversity of Mediterranean Oak Forests 总被引：2，自引：0，他引：2
Abstract: Airborne lidar is a remote‐sensing tool of increasing importance in ecological and conservation research due to its ability to characterize three‐dimensional vegetation structure. If different aspects of plant species diversity and composition can be related to vegetation structure, landscape‐level assessments of plant communities may be possible. We examined this possibility for Mediterranean oak forests in southern Portugal, which are rich in biological diversity but also threatened. We compared data from a discrete, first‐and‐last return lidar data set collected for 31 plots of cork oak (Quercus suber) and Algerian oak (Quercus canariensis) forest with field data to test whether lidar can be used to predict the vertical structure of vegetation, diversity of plant species, and community type. Lidar‐ and field‐measured structural data were significantly correlated (up to r= 0.85). Diversity of forest species was significantly associated with lidar‐measured vegetation height (R2= 0.50, p < 0.001). Clustering and ordination of the species data pointed to the presence of 2 main forest classes that could be discriminated with an accuracy of 89% on the basis of lidar data. Lidar can be applied widely for mapping of habitat and assessments of habitat condition (e.g., in support of the European Species and Habitats Directive [92/43/EEC]). However, particular attention needs to be paid to issues of survey design: density of lidar points and geospatial accuracy of ground‐truthing and its timing relative to acquisition of lidar data. 相似文献