This research assessed the environmental impact of cement silos emission on the existing concrete batching facilities in M35-Mussafah, Abu Dhabi, United Arab Emirates. These assessments were conducted using an air qua...This research assessed the environmental impact of cement silos emission on the existing concrete batching facilities in M35-Mussafah, Abu Dhabi, United Arab Emirates. These assessments were conducted using an air quality dispersion model (AERMOD) to predict the ambient concentration of Portland Cement particulate matter less than 10 microns (PM<sub>10</sub>) emitted to the atmosphere during loading and unloading activities from 176 silos located in 25 concrete batching facilities. AERMOD was applied to simulate and describe the dispersion of PM<sub>10</sub> released from the cement silos into the air. Simulations were carried out for PM<sub>10</sub> emissions on controlled and uncontrolled cement silos scenarios. Results showed an incremental negative impact on air quality and public health from uncontrolled silos emissions and estimated that the uncontrolled PM<sub>10</sub> emission sources contribute to air pollution by 528958.32 kg/Year. The modeling comparison between the controlled and uncontrolled silos shows that the highest annual average concentration from controlled cement silos is 0.065 μg/m<sup>3</sup>, and the highest daily emission value is 0.6 μg/m<sup>3</sup>;both values are negligible and will not lead to significant air quality impact in the entire study domain. However, the uncontrolled cement silos’ highest annual average concentration value is 328.08 μg/m<sup>3</sup>. The highest daily emission average value was 1250.09 μg/m<sup>3</sup>;this might cause a significant air pollution quality impact and health effects on the public and workers. The short-term and long-term average PM<sub>10</sub> pollutant concentrations at these receptors predicted by the air dispersion model are discussed for both scenarios and compared with local and international air quality standards and guidelines.展开更多
To better predict the spread of the COVID-19 outbreak, mathematical modeling and analysis of the spread of the COVID-19 outbreak is proposed based on data analysis and infectious disease theory. Firstly, the mathemati...To better predict the spread of the COVID-19 outbreak, mathematical modeling and analysis of the spread of the COVID-19 outbreak is proposed based on data analysis and infectious disease theory. Firstly, the mathematical model indicators of the spread of the new coronavirus pneumonia epidemic are determined by combining the theory of infectious diseases, the basic assumptions of the spread model of the new coronavirus pneumonia epidemic are given based on the theory of data analysis model, the spread rate of the new coronavirus pneumonia epidemic is calculated by combining the results of the assumptions, and the spread rate of the epidemic is inverted to push back into the assumptions to complete the construction of the mathematical modeling of the diffusion. Relevant data at different times were collected and imported into the model to obtain the spread data of the new coronavirus pneumonia epidemic, and the results were analyzed and reflected. The model considers the disease spread rate as the dependent variable of temperature, and analyzes and verifies the spread of outbreaks over time under real temperature changes. Comparison with real results shows that the model developed in this paper is more in line with the real disease spreading situation under specific circumstances. It is hoped that the accurate prediction of the epidemic spread can provide relevant help for the effective containment of the epidemic spread.展开更多
ADMS-Urban is the most widely used advanced dispersion model for urban areas, being used extensively in China and worldwide, providing a practical tool for assessing and managing urban air quality. In this paper we br...ADMS-Urban is the most widely used advanced dispersion model for urban areas, being used extensively in China and worldwide, providing a practical tool for assessing and managing urban air quality. In this paper we briefly describe the ADMS dispersion models and give an overview of their use in China. And it describes in more detail the use of ADMS-Urban in Fushun in Liaoning province and in Jinan in Shangdong province respectively, for studies of urban air quality. Finally the conclusions are presented.展开更多
This paper makes comparisons between Chinese Environmental Impact Assessment (EIA) Guidelines for Air dispersion modelling and the advanced air dispersion model ADMS. Since 2001 the ADMS model has been the first and o...This paper makes comparisons between Chinese Environmental Impact Assessment (EIA) Guidelines for Air dispersion modelling and the advanced air dispersion model ADMS. Since 2001 the ADMS model has been the first and only foreign model that has been approved by the Appraisal Center for Environment and Engineering (ACEE) to be used in EIA projects in China (http://www.china-eia. com/inden_content/rjrz/ rjrz_ADMS/htm). In the paper the following sections provide brief descriptions of the main features of the Chinese Guidelines for Air Dispersion (Section 2) and ADMS (Section 3); Section 4 provides a comparison of the two modelling methods for some simple cases and conclusions and discussion are given in Section 5.展开更多
An observational campaign was conducted in the street canyon of Zhujiang Road in Nanjing city in 2007. Hourly mean concentrations of PM10 were measured at street and roof levels. The Operational Street Pollution Model...An observational campaign was conducted in the street canyon of Zhujiang Road in Nanjing city in 2007. Hourly mean concentrations of PM10 were measured at street and roof levels. The Operational Street Pollution Model (OSPM) street canyon dispersion model was used to calculate the street concentrations and the results were compared with the measurements. The results show that there is good agreement between measured and predicted concentrations. The correlation coefficient R2 values (R2 is a measure of the correlation of the predicted and measured time series of concentrations) are 0.5319, 0.8044, and 0.6630 for the scatter plots of PM10 corresponding to light wind speed conditions, higher wind speed conditions, and all wind speed conditions, respectively. PM10 concentrations tend to be smaller for the higher wind speed cases and decrease rapidly with increasing wind speed. The presentations of measured and modelled concentration dependence on wind direction show fairly good agreement. PM10 concentrations measured on the windward side are relatively smaller, compared with the corresponding results for the leeward side. This study demonstrates that it is possible to use the OSPM to model PM10 dispersion rules for an urban street canyon.展开更多
As an important design factor for constructed wetlands,hydraulic retention time and its distribution will affect the treatment performance.Instantaneously injected sodium chloride tracers were used to obtain residence...As an important design factor for constructed wetlands,hydraulic retention time and its distribution will affect the treatment performance.Instantaneously injected sodium chloride tracers were used to obtain residence time distributions of the lab scale subsurface flow constructed wetland.Considering the presence of trailing and multiple peaks of the tracer breakthrough curve,the multi flow dispersion model(MFDM)was used to fit the experimental tracer breakthrough curves.According to the residual sum of squares and comparison between the experimental values and simulated values of the tracer concentration,MFDM could fit the residence time distribution(RTD)curve satisfactorily,the results of which also reflected the layered structure of wetland cells,thus to give reference for application of MFDM to the same kind of subsurface flow constructed wetlands.展开更多
Understanding the behavior of urban air pollution is important en route for sustainable urban development (SUD). Malaysia is on its mission to be a developed country by year 2020 comprehends dealing with air pollution...Understanding the behavior of urban air pollution is important en route for sustainable urban development (SUD). Malaysia is on its mission to be a developed country by year 2020 comprehends dealing with air pollution is one of the indicators headed towards it. At present monitoring and managing air pollution in urban areas encompasses sophisticated air quality modeling and data acquisition. However, rapid developments in major cities cause difficulties in acquiring the city geometries. The existing method in acquiring city geometries data via ground or space measurement inspection such as field survey, photogrammetry, laser scanning, remote sensing or using architectural plans appears not to be practical because of its cost and efforts. Moreover, air monitoring stations deployed are intended for regional to global scale model whereby it is not accurate for urban areas with typical resolution of less than 2 km. Furthermore in urban areas, the pollutant dispersion movements are trapped between buildings initiating it to move vertically causing visualization complications which imply the limitations of existing visualization scheme that is based on two-dimensional (2D) framework. Therefore this paper aims is to perform groundwork assessment and discuss on the current scenario in Malaysia in the aspect of current policies towards SUD, air quality monitoring stations, scale model and detail discussion on air pollution dispersion model used called the Operational Street Pollution Model (OSPM). This research proposed the implementation of three-dimensional (3D) spatial city model as a new physical data input for OSPM. The five Level of Details (LOD) of 3D spatial city model shows the scale applicability for the dispersion model implementtation. Subsequently 3D spatial city model data commonly available on the web, by having a unified data model shows the advantages in easy data acquisition, 3D visualization of air pollution dispersion and improves visual analysis of air quality monitoring in urban areas.展开更多
A modified Fickian plug-flow/dispersion model (P/D model) is developed in this study. In P/D model, the flow process is divided into two belts, plug flow belt and dispersion belt. P/D model is very similar to Fickian ...A modified Fickian plug-flow/dispersion model (P/D model) is developed in this study. In P/D model, the flow process is divided into two belts, plug flow belt and dispersion belt. P/D model is very similar to Fickian model and rather perfect. The prediction by P/D model can be always consistent with experimental data in river, flume, and pond, even though the data are much skew. Therefore, P/D model is better than Fickian model and other dispersion models.展开更多
We try to enhance the AERMOD industrial pollution dispersion model with remote sensing observations and climatic models based on them. In this paper, we focus on surface parameters (albedo, roughness, Bowen ratio) and...We try to enhance the AERMOD industrial pollution dispersion model with remote sensing observations and climatic models based on them. In this paper, we focus on surface parameters (albedo, roughness, Bowen ratio) and land use classification on which they depend. We model maximum hourly concentrations and the resulting acute health risk and assess the effect on them produced by using remote sensing data for local areas around industrial plants instead of global standard AERMOD parameters. We consider five real multi-source plants for the effect of classification and two of them for the effect of surface parameters. The effect on the critical pollutant is measured in three ways: a) as difference between the yearly maxima of hourly concentrations of a critical pollutant (“absolute”);b) the same limited to daytime workhours and 95% quantile instead of absolute maximum (“regulatory”);c) as maximum hourly difference over a year (“instant”). The measure of effect is divided either by the reference concentration of the pollutant, which yields the impact on health risk, or by the concentration obtained with AERMOD standards, which yields relative measure of impact. For a), the impact of roughness dominates, that of albedo is small and that of the Bowen ratio is almost zero. For b), the impact of roughness is less prominent, and that of albedo and Bowen ratio is noticeable. For c), the impact is considerable for all three parameters. The effect of land use classification is considerable in all three cases a) </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> c). We provide the figures for different measures of remote sensing data effect and discuss the perspective of using remote sensing data in regulatory context.展开更多
Odorous emissions emitted from various sources including industrial and commercial activities have particular concerns about human health. These malodors emissions are an environmental concern that affects health stat...Odorous emissions emitted from various sources including industrial and commercial activities have particular concerns about human health. These malodors emissions are an environmental concern that affects health status and social life of the neighbors. That requires the local authority to set up a management strategy to control this nuisance. The evaluation of odour emissions from fishing port is complex because these emissions depend on several factors such as multiple sources of odor emissions, meteorological conditions, topography and others. That imposes the use of complementary approaches to monitor odours. In this paper, the case of Agadir fishing port is studied, which is adjacent to the tourist area and residential neighborhoods and which hosts a number of points that can generate odors. To assess this odour impact, three methods are used such as dynamic olfactometry, dispersion modeling and mobile electronic nose (e-nose). The use of these three methods in a complementary manner to assess odour impacts around a fishing port allowed both the quantification of the emissions using dynamic olfactometry and the evaluation of their impact on the study area with model dispersion. The results enabled also to identify the most affected areas of the city by odor emissions and to recognize the meteorological parameters maximizing odor impact. The other goal of this work is to compare the results of the odour dispersion modeling and e-nose measurements for one year in terms of frequency of overtaking the set alert thresholds over the same period. Comparison highlights the strengths and weaknesses of both approaches. Modeling can be used predicatively but it does not take into account fugitive emissions reliably in the absence of data on these emissions, modeling based on the hourly average misjudges the odor peaks, while e-nose made it possible to obtain validated data and provides accurate, affordable and real-time odour measurement capability tacking in to account the role of human perception without being able to characterize the extent of the odor nuisance caused by each source. We conclude that these three valuation methods provide complementary information about odor nuisance and reasonable estimates of odors.展开更多
This study focuses on the transient analysis of nonlinear dispersion of a polymeric pollutant ejected by an external source into a laminar pipe flow of a Newtonian liquid under axi-symmetric conditions.The influence o...This study focuses on the transient analysis of nonlinear dispersion of a polymeric pollutant ejected by an external source into a laminar pipe flow of a Newtonian liquid under axi-symmetric conditions.The influence of density variation with pollutant concentration is approximated according to the Boussinesq approximation and the nonlinear governing equations of momentum,pollutant concentration are obtained together with and Oldroyd-B constitutive model for the polymer stress.The problem is solved numerically using a semi-implicit finite difference method.Solutions are presented in graphical form for various parameter values and given in terms of fluid velocity,pollutant concentration,polymer stress components,skin friction and wall mass transfer rate.The model can be a useful tool in understanding the dynamics of industrial pollution situations arising from improper discharge of hydrocarbon pollutants into,say,water bodies.The model can also be quite useful for available necessary early warning methods for detecting or predicting the scale of pollution and hence help mitigate related damage downstream by earlier instituting relevant decontamination measures.展开更多
Footprint characteristics for passive scalar concentration in the convective boundary layer (CBL) are investigated. A backward Lagrangian stochastic (LS) dispersion model and a large eddy simulation (LES) model ...Footprint characteristics for passive scalar concentration in the convective boundary layer (CBL) are investigated. A backward Lagrangian stochastic (LS) dispersion model and a large eddy simulation (LES) model are used in the investigation. Typical characteristics of the CBL and their responses to the surface heterogeneity are resolved from the LES. Then the turbulence fields are used to drive the backward LS dispersion. To remedy the spoiled description of the turbulence near the surface, MoninObukhov similarity is applied to the lowest LES level and the surface for the modeling of the backward LS dispersion. Simulation results show that the footprint within approximately 1 km upwind predominates in the total contribution. But influence from farther distances also exists and is even slightly greater than that from closer locations. Surface heterogeneity may change the footprint pattern to a certain degree. A comparison to three analytical models provides a validation of the footprint simulations, which shows the possible influence of along-wind turbulence and the large eddies in the CBL, as well as the surface heterogeneity.展开更多
Our previous experimental studies have confirmed that viscoelastic-fluid-based nanofluid(VFBN) prepared by suspending nanoparticles in a viscoelastic base fluid(VBF, behaves drag reduction at turbulent flow state) can...Our previous experimental studies have confirmed that viscoelastic-fluid-based nanofluid(VFBN) prepared by suspending nanoparticles in a viscoelastic base fluid(VBF, behaves drag reduction at turbulent flow state) can reduce turbulent flow resistance as compared with water and enhance heat transfer as compared with VBF. Direct numerical simulation(DNS) is performed in this study to explore the mechanisms of heat transfer enhancement(HTE) and flow drag reduction(DR) for the VFBN turbulent flow. The Giesekus model is used as the constitutive equation for VFBN. Our previously proposed thermal dispersion model is adopted to take into account the thermal dispersion effects of nanoparticles in the VFBN turbulent flow. The DNS results show similar behaviors for flow resistance and heat transfer to those obtained in our previous experiments. Detailed analyses are conducted for the turbulent velocity, temperature, and conformation fields obtained by DNSs for different fluid cases, and for the friction factor with viscous, turbulent, and elastic contributions and heat transfer rate with conductive, turbulent and thermal dispersion contributions of nanoparticles, respectively. The mechanisms of HTE and DR of VFBN turbulent flows are then discussed. Based on analogy theory, the ratios of Chilton–Colburn factor to friction factor for different fluid flow cases are investigated, which from another aspect show the significant enhancement in heat transfer performance for some cases of water-based nanofluid and VFBN turbulent flows.展开更多
Deterioration of air quality due to the increase in atmospheric emissions from biomass burning(BB)is one of the major environmental problems worldwide.In this study,we estimated the contributions of BB to PM_(2.5) con...Deterioration of air quality due to the increase in atmospheric emissions from biomass burning(BB)is one of the major environmental problems worldwide.In this study,we estimated the contributions of BB to PM_(2.5) concentrations in the municipalities of Soledad and Malambo located in the Colombian Caribbean.The evaluation period ranged from February 24 to March 30,2018,a period with a high number of BB events recorded in the surroundings of the evaluated sites.The contribution of BB to the two sampling sites was estimated using the Hybrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT)dispersion model with forwarding trajectories from each of the burning points identified by satellite images(n=1089).The PM_(2.5) emissions were determined using the fire radiative power(FRP),obtained by remote-sensing data,and corresponded to the radiant energy released per time unit by burning vegetation.The average PM_(2.5) concentrations during the evaluation period were 19.91μg/m^(3) for Soledad and 22.44μg/m^(3) for Malambo.The average contribution of BB to these municipalities was 22.8%and 28.8%,respectively.The methodology used in this study allowed to estimate the contribution of this important source without knowledge of a previous tracer of BB,thereby increasing the use of the proposed procedure worldwide.This information would enable the implementation of effective mitigation,thereby diminishing the adverse impact of PM_(2.5) on the health of the population.展开更多
Polypropylene(PP)/ethylene-octene copolymer(POE) blends were prepared with a twin-screw extruder.Their dynamic mechanical behavior were systematically investigated.The results show that PP/POE blends are heterogen...Polypropylene(PP)/ethylene-octene copolymer(POE) blends were prepared with a twin-screw extruder.Their dynamic mechanical behavior were systematically investigated.The results show that PP/POE blends are heterogeneities with a partial compatible two-phase structure,the glass transition temperature of PP phases in the blends tends to shift towards high temperature with increasing the POE content,and the glass transition temperature of POE phases shifts towards the low temperature with increasing the PP content.The Kerner's dispersed phase model and co-continuous phase model can reasonably predict the visco-elasticity of PP/POE blends with different compositions.Additionally,the morphological structure of the blends can be estimated via comparing the predicted DMA behavior with the experimental data.展开更多
This is an analytical study on the time develop- ment of hydrodynamic dispersion of an inert species in elec- troosmotic flow through a rectangular channel. The objec- tive is to determine how the channel side walls m...This is an analytical study on the time develop- ment of hydrodynamic dispersion of an inert species in elec- troosmotic flow through a rectangular channel. The objec- tive is to determine how the channel side walls may affect the dispersion coefficient at different instants of time. To this end, the generalized dispersion model, which is valid for short and long times, is employed in the present study. An- alytical expressions are derived for the convection and dis- persion coefficients as functions of time, the aspect ratio of the channel, and the Debye-Htickel parameter representing the thickness of the electric double layer. For transport in a channel of large aspect ratio, the dispersion may undergo several stages of transience. The initial, fast time develop- ment is controlled by molecular diffusion across the narrow channel height, while the later, slower time development is governed by diffusion across the wider channel breadth. For a sufficiently large aspect ratio, there can be an interlude between these two periods during which the coefficient is nearly steady, signifying the resemblance of the transport to that in a parallel-plate channel. Given a sufficiently long time, the dispersion coefficient will reach a fully-developed steady value that may be several times higher than that with- out the side wall effects. The time scales for these periods of transience are identified in this paper.展开更多
The International Space Station(ISS) employs catalytic wet oxidation carried out in a Volatile Reactor Assembly (VRA) for water recycling. Previous earth gravity experiments show that the VRA is very effective at ...The International Space Station(ISS) employs catalytic wet oxidation carried out in a Volatile Reactor Assembly (VRA) for water recycling. Previous earth gravity experiments show that the VRA is very effective at removing polar, low molecular weight organics. To compare the reactor performance under micro-gravity and Earth gravity conditions, a tracer study was performed on a space shuttle in 1999 by using 0.2% potassium carbonate as the chemical tracer. In this paper, the experimental data were analyzed and it is indicated that the reactor can be considered as a plug flow one under both micro-gravity and earth gravity experimental conditions. It has also been proved that dispersion is not important in the VRA reactor under the experimental conditions. Tracer retardation was observed in the experiments and it is most likely caused by catalyst adsorption. It is concluded that the following reasons may also have influence on the retardation of mean residence time : (1) the liquid can be held by appurtenances, which will retard the mean residence time; (2) the pores can hold the tracer, which can also retard the mean residence time.展开更多
As the simple dispersion model tested is not sufficiently accurate to predict the SO2 concentration in complex terrain commonly encountered amongst high rise buildings in Hong Kong, and the lack of comprehensive local...As the simple dispersion model tested is not sufficiently accurate to predict the SO2 concentration in complex terrain commonly encountered amongst high rise buildings in Hong Kong, and the lack of comprehensive local wind data at most sites prevents the use of more advanced dispersion model to assess the impact of major air pollutant sources, a receptor model approach is adopted for the apportionment of air pollution sources in Hong Kong. The preliminary results obtained are presented and discussed.展开更多
Mercury contamination was found to be widespread in soils at a property in Upstate New York. Historical site use suggested that the mercury did not result from prior industrial use of the property. Soil contamination ...Mercury contamination was found to be widespread in soils at a property in Upstate New York. Historical site use suggested that the mercury did not result from prior industrial use of the property. Soil contamination may have resulted from atmospheric deposition of mercury released from properties in close proximity to the contaminated property. The purpose of this forensics investigation was to examine to what extent atmospheric deposition of elemental mercury may have influenced mercury levels found in surficial soils on the contaminated property and further to identify the source(s) of the mercury. Work efforts included an examination of historical records available for a chlor-alkali plant (CAP) upwind of the contaminated property to establish historical use and disposal practices for elemental mercury. Mercury emissions test data from the Upstate New York chlor-alkali facility were modeled (USEPA ISC3) as a means of estimating impacts on ambient air and soils vicinal to the facility. Mercury emissions from the facility were modeled as both a point source and volume source. For example, at a location 305 meters to the east and 30 meters to the north of the modeled source centerline elemental mercury concentrations in ambient air were estimated at 270 ng/m<sup>3</sup> (average results based upon 5 years of meteorological data). This value is contrasted to a background concentration of 1.6 ng/m<sup>3</sup> (USEPA Report to Congress 1997). As a result of the modeling data in combination with findings related to mercury use and disposal practices at the NY CAP documented from the records review, it was concluded that emissions from the CAP facility during the period of operation (1897-1991) most likely accounted for the concentrations of elemental mercury found in surficial soils at properties situated downwind of the CAP. These findings were further corroborated by information available in the open literature for CAPs world-wide.展开更多
An integral analysis of Air Pollution in the Gulf of Mexico was made considering pollutants emissions assessment and diagnosis;air pollution monitoring;and modeling of air pollution dispersion. Combustion sources cons...An integral analysis of Air Pollution in the Gulf of Mexico was made considering pollutants emissions assessment and diagnosis;air pollution monitoring;and modeling of air pollution dispersion. Combustion sources considered in this work were: thermoelectric power plants and open flares;and pollutants considered were sulfur dioxide, nitrogen dioxides, particulate matter (PM<sub>10</sub> and PM<sub>2.5</sub>), Total suspended particles (TSP) and carbon monoxide (CO). This study made evident a lack of more recent information and a homogenization in emissions factors in order to know the conditions of air pollution in the Gulf of Mexico in a more reliable way.展开更多
文摘This research assessed the environmental impact of cement silos emission on the existing concrete batching facilities in M35-Mussafah, Abu Dhabi, United Arab Emirates. These assessments were conducted using an air quality dispersion model (AERMOD) to predict the ambient concentration of Portland Cement particulate matter less than 10 microns (PM<sub>10</sub>) emitted to the atmosphere during loading and unloading activities from 176 silos located in 25 concrete batching facilities. AERMOD was applied to simulate and describe the dispersion of PM<sub>10</sub> released from the cement silos into the air. Simulations were carried out for PM<sub>10</sub> emissions on controlled and uncontrolled cement silos scenarios. Results showed an incremental negative impact on air quality and public health from uncontrolled silos emissions and estimated that the uncontrolled PM<sub>10</sub> emission sources contribute to air pollution by 528958.32 kg/Year. The modeling comparison between the controlled and uncontrolled silos shows that the highest annual average concentration from controlled cement silos is 0.065 μg/m<sup>3</sup>, and the highest daily emission value is 0.6 μg/m<sup>3</sup>;both values are negligible and will not lead to significant air quality impact in the entire study domain. However, the uncontrolled cement silos’ highest annual average concentration value is 328.08 μg/m<sup>3</sup>. The highest daily emission average value was 1250.09 μg/m<sup>3</sup>;this might cause a significant air pollution quality impact and health effects on the public and workers. The short-term and long-term average PM<sub>10</sub> pollutant concentrations at these receptors predicted by the air dispersion model are discussed for both scenarios and compared with local and international air quality standards and guidelines.
文摘To better predict the spread of the COVID-19 outbreak, mathematical modeling and analysis of the spread of the COVID-19 outbreak is proposed based on data analysis and infectious disease theory. Firstly, the mathematical model indicators of the spread of the new coronavirus pneumonia epidemic are determined by combining the theory of infectious diseases, the basic assumptions of the spread model of the new coronavirus pneumonia epidemic are given based on the theory of data analysis model, the spread rate of the new coronavirus pneumonia epidemic is calculated by combining the results of the assumptions, and the spread rate of the epidemic is inverted to push back into the assumptions to complete the construction of the mathematical modeling of the diffusion. Relevant data at different times were collected and imported into the model to obtain the spread data of the new coronavirus pneumonia epidemic, and the results were analyzed and reflected. The model considers the disease spread rate as the dependent variable of temperature, and analyzes and verifies the spread of outbreaks over time under real temperature changes. Comparison with real results shows that the model developed in this paper is more in line with the real disease spreading situation under specific circumstances. It is hoped that the accurate prediction of the epidemic spread can provide relevant help for the effective containment of the epidemic spread.
文摘ADMS-Urban is the most widely used advanced dispersion model for urban areas, being used extensively in China and worldwide, providing a practical tool for assessing and managing urban air quality. In this paper we briefly describe the ADMS dispersion models and give an overview of their use in China. And it describes in more detail the use of ADMS-Urban in Fushun in Liaoning province and in Jinan in Shangdong province respectively, for studies of urban air quality. Finally the conclusions are presented.
文摘This paper makes comparisons between Chinese Environmental Impact Assessment (EIA) Guidelines for Air dispersion modelling and the advanced air dispersion model ADMS. Since 2001 the ADMS model has been the first and only foreign model that has been approved by the Appraisal Center for Environment and Engineering (ACEE) to be used in EIA projects in China (http://www.china-eia. com/inden_content/rjrz/ rjrz_ADMS/htm). In the paper the following sections provide brief descriptions of the main features of the Chinese Guidelines for Air Dispersion (Section 2) and ADMS (Section 3); Section 4 provides a comparison of the two modelling methods for some simple cases and conclusions and discussion are given in Section 5.
基金supported by the Natural Science Foundation of Jiangsu Province(No.BK2004216)
文摘An observational campaign was conducted in the street canyon of Zhujiang Road in Nanjing city in 2007. Hourly mean concentrations of PM10 were measured at street and roof levels. The Operational Street Pollution Model (OSPM) street canyon dispersion model was used to calculate the street concentrations and the results were compared with the measurements. The results show that there is good agreement between measured and predicted concentrations. The correlation coefficient R2 values (R2 is a measure of the correlation of the predicted and measured time series of concentrations) are 0.5319, 0.8044, and 0.6630 for the scatter plots of PM10 corresponding to light wind speed conditions, higher wind speed conditions, and all wind speed conditions, respectively. PM10 concentrations tend to be smaller for the higher wind speed cases and decrease rapidly with increasing wind speed. The presentations of measured and modelled concentration dependence on wind direction show fairly good agreement. PM10 concentrations measured on the windward side are relatively smaller, compared with the corresponding results for the leeward side. This study demonstrates that it is possible to use the OSPM to model PM10 dispersion rules for an urban street canyon.
基金Under the auspices of the Creative Group Foundation of the National Natural Science Foundation of China(50721006)the National Basic Research Program of China(2006CB403402-3)+1 种基金the National Water Resource and Environment Special Item(2008ZX07207-006-04)the Natural Science Foundation of Shanghai(10ZR1400300)
文摘As an important design factor for constructed wetlands,hydraulic retention time and its distribution will affect the treatment performance.Instantaneously injected sodium chloride tracers were used to obtain residence time distributions of the lab scale subsurface flow constructed wetland.Considering the presence of trailing and multiple peaks of the tracer breakthrough curve,the multi flow dispersion model(MFDM)was used to fit the experimental tracer breakthrough curves.According to the residual sum of squares and comparison between the experimental values and simulated values of the tracer concentration,MFDM could fit the residence time distribution(RTD)curve satisfactorily,the results of which also reflected the layered structure of wetland cells,thus to give reference for application of MFDM to the same kind of subsurface flow constructed wetlands.
基金Major funding for this research was provided by the Ministry of Higher Education Malaysia and partially funded by the Land Surveyors Board of Malaysia.
文摘Understanding the behavior of urban air pollution is important en route for sustainable urban development (SUD). Malaysia is on its mission to be a developed country by year 2020 comprehends dealing with air pollution is one of the indicators headed towards it. At present monitoring and managing air pollution in urban areas encompasses sophisticated air quality modeling and data acquisition. However, rapid developments in major cities cause difficulties in acquiring the city geometries. The existing method in acquiring city geometries data via ground or space measurement inspection such as field survey, photogrammetry, laser scanning, remote sensing or using architectural plans appears not to be practical because of its cost and efforts. Moreover, air monitoring stations deployed are intended for regional to global scale model whereby it is not accurate for urban areas with typical resolution of less than 2 km. Furthermore in urban areas, the pollutant dispersion movements are trapped between buildings initiating it to move vertically causing visualization complications which imply the limitations of existing visualization scheme that is based on two-dimensional (2D) framework. Therefore this paper aims is to perform groundwork assessment and discuss on the current scenario in Malaysia in the aspect of current policies towards SUD, air quality monitoring stations, scale model and detail discussion on air pollution dispersion model used called the Operational Street Pollution Model (OSPM). This research proposed the implementation of three-dimensional (3D) spatial city model as a new physical data input for OSPM. The five Level of Details (LOD) of 3D spatial city model shows the scale applicability for the dispersion model implementtation. Subsequently 3D spatial city model data commonly available on the web, by having a unified data model shows the advantages in easy data acquisition, 3D visualization of air pollution dispersion and improves visual analysis of air quality monitoring in urban areas.
文摘A modified Fickian plug-flow/dispersion model (P/D model) is developed in this study. In P/D model, the flow process is divided into two belts, plug flow belt and dispersion belt. P/D model is very similar to Fickian model and rather perfect. The prediction by P/D model can be always consistent with experimental data in river, flume, and pond, even though the data are much skew. Therefore, P/D model is better than Fickian model and other dispersion models.
文摘We try to enhance the AERMOD industrial pollution dispersion model with remote sensing observations and climatic models based on them. In this paper, we focus on surface parameters (albedo, roughness, Bowen ratio) and land use classification on which they depend. We model maximum hourly concentrations and the resulting acute health risk and assess the effect on them produced by using remote sensing data for local areas around industrial plants instead of global standard AERMOD parameters. We consider five real multi-source plants for the effect of classification and two of them for the effect of surface parameters. The effect on the critical pollutant is measured in three ways: a) as difference between the yearly maxima of hourly concentrations of a critical pollutant (“absolute”);b) the same limited to daytime workhours and 95% quantile instead of absolute maximum (“regulatory”);c) as maximum hourly difference over a year (“instant”). The measure of effect is divided either by the reference concentration of the pollutant, which yields the impact on health risk, or by the concentration obtained with AERMOD standards, which yields relative measure of impact. For a), the impact of roughness dominates, that of albedo is small and that of the Bowen ratio is almost zero. For b), the impact of roughness is less prominent, and that of albedo and Bowen ratio is noticeable. For c), the impact is considerable for all three parameters. The effect of land use classification is considerable in all three cases a) </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> c). We provide the figures for different measures of remote sensing data effect and discuss the perspective of using remote sensing data in regulatory context.
文摘Odorous emissions emitted from various sources including industrial and commercial activities have particular concerns about human health. These malodors emissions are an environmental concern that affects health status and social life of the neighbors. That requires the local authority to set up a management strategy to control this nuisance. The evaluation of odour emissions from fishing port is complex because these emissions depend on several factors such as multiple sources of odor emissions, meteorological conditions, topography and others. That imposes the use of complementary approaches to monitor odours. In this paper, the case of Agadir fishing port is studied, which is adjacent to the tourist area and residential neighborhoods and which hosts a number of points that can generate odors. To assess this odour impact, three methods are used such as dynamic olfactometry, dispersion modeling and mobile electronic nose (e-nose). The use of these three methods in a complementary manner to assess odour impacts around a fishing port allowed both the quantification of the emissions using dynamic olfactometry and the evaluation of their impact on the study area with model dispersion. The results enabled also to identify the most affected areas of the city by odor emissions and to recognize the meteorological parameters maximizing odor impact. The other goal of this work is to compare the results of the odour dispersion modeling and e-nose measurements for one year in terms of frequency of overtaking the set alert thresholds over the same period. Comparison highlights the strengths and weaknesses of both approaches. Modeling can be used predicatively but it does not take into account fugitive emissions reliably in the absence of data on these emissions, modeling based on the hourly average misjudges the odor peaks, while e-nose made it possible to obtain validated data and provides accurate, affordable and real-time odour measurement capability tacking in to account the role of human perception without being able to characterize the extent of the odor nuisance caused by each source. We conclude that these three valuation methods provide complementary information about odor nuisance and reasonable estimates of odors.
文摘This study focuses on the transient analysis of nonlinear dispersion of a polymeric pollutant ejected by an external source into a laminar pipe flow of a Newtonian liquid under axi-symmetric conditions.The influence of density variation with pollutant concentration is approximated according to the Boussinesq approximation and the nonlinear governing equations of momentum,pollutant concentration are obtained together with and Oldroyd-B constitutive model for the polymer stress.The problem is solved numerically using a semi-implicit finite difference method.Solutions are presented in graphical form for various parameter values and given in terms of fluid velocity,pollutant concentration,polymer stress components,skin friction and wall mass transfer rate.The model can be a useful tool in understanding the dynamics of industrial pollution situations arising from improper discharge of hydrocarbon pollutants into,say,water bodies.The model can also be quite useful for available necessary early warning methods for detecting or predicting the scale of pollution and hence help mitigate related damage downstream by earlier instituting relevant decontamination measures.
基金the National Natural Science Foundation of China under Grant Nos.40275005 , 40233030 the National Basic Research and Development Program under Grant 2002CB410802.
文摘Footprint characteristics for passive scalar concentration in the convective boundary layer (CBL) are investigated. A backward Lagrangian stochastic (LS) dispersion model and a large eddy simulation (LES) model are used in the investigation. Typical characteristics of the CBL and their responses to the surface heterogeneity are resolved from the LES. Then the turbulence fields are used to drive the backward LS dispersion. To remedy the spoiled description of the turbulence near the surface, MoninObukhov similarity is applied to the lowest LES level and the surface for the modeling of the backward LS dispersion. Simulation results show that the footprint within approximately 1 km upwind predominates in the total contribution. But influence from farther distances also exists and is even slightly greater than that from closer locations. Surface heterogeneity may change the footprint pattern to a certain degree. A comparison to three analytical models provides a validation of the footprint simulations, which shows the possible influence of along-wind turbulence and the large eddies in the CBL, as well as the surface heterogeneity.
基金supported by the National Natural Science Foundation of China(Grant No.51276046)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20112302110020)+1 种基金the China Postdoctoral Science Foundation(Grant No.2014M561037)the President Fund of University of Chinese Academy of Sciences,China(Grant No.Y3510213N00)
文摘Our previous experimental studies have confirmed that viscoelastic-fluid-based nanofluid(VFBN) prepared by suspending nanoparticles in a viscoelastic base fluid(VBF, behaves drag reduction at turbulent flow state) can reduce turbulent flow resistance as compared with water and enhance heat transfer as compared with VBF. Direct numerical simulation(DNS) is performed in this study to explore the mechanisms of heat transfer enhancement(HTE) and flow drag reduction(DR) for the VFBN turbulent flow. The Giesekus model is used as the constitutive equation for VFBN. Our previously proposed thermal dispersion model is adopted to take into account the thermal dispersion effects of nanoparticles in the VFBN turbulent flow. The DNS results show similar behaviors for flow resistance and heat transfer to those obtained in our previous experiments. Detailed analyses are conducted for the turbulent velocity, temperature, and conformation fields obtained by DNSs for different fluid cases, and for the friction factor with viscous, turbulent, and elastic contributions and heat transfer rate with conductive, turbulent and thermal dispersion contributions of nanoparticles, respectively. The mechanisms of HTE and DR of VFBN turbulent flows are then discussed. Based on analogy theory, the ratios of Chilton–Colburn factor to friction factor for different fluid flow cases are investigated, which from another aspect show the significant enhancement in heat transfer performance for some cases of water-based nanofluid and VFBN turbulent flows.
文摘Deterioration of air quality due to the increase in atmospheric emissions from biomass burning(BB)is one of the major environmental problems worldwide.In this study,we estimated the contributions of BB to PM_(2.5) concentrations in the municipalities of Soledad and Malambo located in the Colombian Caribbean.The evaluation period ranged from February 24 to March 30,2018,a period with a high number of BB events recorded in the surroundings of the evaluated sites.The contribution of BB to the two sampling sites was estimated using the Hybrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT)dispersion model with forwarding trajectories from each of the burning points identified by satellite images(n=1089).The PM_(2.5) emissions were determined using the fire radiative power(FRP),obtained by remote-sensing data,and corresponded to the radiant energy released per time unit by burning vegetation.The average PM_(2.5) concentrations during the evaluation period were 19.91μg/m^(3) for Soledad and 22.44μg/m^(3) for Malambo.The average contribution of BB to these municipalities was 22.8%and 28.8%,respectively.The methodology used in this study allowed to estimate the contribution of this important source without knowledge of a previous tracer of BB,thereby increasing the use of the proposed procedure worldwide.This information would enable the implementation of effective mitigation,thereby diminishing the adverse impact of PM_(2.5) on the health of the population.
基金Supported by the National Natural Science Foundation of China(No.20490220)Open Fund of State Key Laboratory of Plastic Forming Simulation and Die & Mould Technology,China(No.05-10)+1 种基金Open Fund of Hubei Key Laboratory of Materials Chemistry and Service FailureProgram for New Century Excellent Talents in Universities of China(No.NCET-05-0640)
文摘Polypropylene(PP)/ethylene-octene copolymer(POE) blends were prepared with a twin-screw extruder.Their dynamic mechanical behavior were systematically investigated.The results show that PP/POE blends are heterogeneities with a partial compatible two-phase structure,the glass transition temperature of PP phases in the blends tends to shift towards high temperature with increasing the POE content,and the glass transition temperature of POE phases shifts towards the low temperature with increasing the PP content.The Kerner's dispersed phase model and co-continuous phase model can reasonably predict the visco-elasticity of PP/POE blends with different compositions.Additionally,the morphological structure of the blends can be estimated via comparing the predicted DMA behavior with the experimental data.
基金supported by the Research Grants Council of the Hong Kong Special Administrative Region,China (HKU715510E)the University of Hong Kong through the Seed Funding Programme for Basic Research (200911159024)
文摘This is an analytical study on the time develop- ment of hydrodynamic dispersion of an inert species in elec- troosmotic flow through a rectangular channel. The objec- tive is to determine how the channel side walls may affect the dispersion coefficient at different instants of time. To this end, the generalized dispersion model, which is valid for short and long times, is employed in the present study. An- alytical expressions are derived for the convection and dis- persion coefficients as functions of time, the aspect ratio of the channel, and the Debye-Htickel parameter representing the thickness of the electric double layer. For transport in a channel of large aspect ratio, the dispersion may undergo several stages of transience. The initial, fast time develop- ment is controlled by molecular diffusion across the narrow channel height, while the later, slower time development is governed by diffusion across the wider channel breadth. For a sufficiently large aspect ratio, there can be an interlude between these two periods during which the coefficient is nearly steady, signifying the resemblance of the transport to that in a parallel-plate channel. Given a sufficiently long time, the dispersion coefficient will reach a fully-developed steady value that may be several times higher than that with- out the side wall effects. The time scales for these periods of transience are identified in this paper.
文摘The International Space Station(ISS) employs catalytic wet oxidation carried out in a Volatile Reactor Assembly (VRA) for water recycling. Previous earth gravity experiments show that the VRA is very effective at removing polar, low molecular weight organics. To compare the reactor performance under micro-gravity and Earth gravity conditions, a tracer study was performed on a space shuttle in 1999 by using 0.2% potassium carbonate as the chemical tracer. In this paper, the experimental data were analyzed and it is indicated that the reactor can be considered as a plug flow one under both micro-gravity and earth gravity experimental conditions. It has also been proved that dispersion is not important in the VRA reactor under the experimental conditions. Tracer retardation was observed in the experiments and it is most likely caused by catalyst adsorption. It is concluded that the following reasons may also have influence on the retardation of mean residence time : (1) the liquid can be held by appurtenances, which will retard the mean residence time; (2) the pores can hold the tracer, which can also retard the mean residence time.
文摘As the simple dispersion model tested is not sufficiently accurate to predict the SO2 concentration in complex terrain commonly encountered amongst high rise buildings in Hong Kong, and the lack of comprehensive local wind data at most sites prevents the use of more advanced dispersion model to assess the impact of major air pollutant sources, a receptor model approach is adopted for the apportionment of air pollution sources in Hong Kong. The preliminary results obtained are presented and discussed.
文摘Mercury contamination was found to be widespread in soils at a property in Upstate New York. Historical site use suggested that the mercury did not result from prior industrial use of the property. Soil contamination may have resulted from atmospheric deposition of mercury released from properties in close proximity to the contaminated property. The purpose of this forensics investigation was to examine to what extent atmospheric deposition of elemental mercury may have influenced mercury levels found in surficial soils on the contaminated property and further to identify the source(s) of the mercury. Work efforts included an examination of historical records available for a chlor-alkali plant (CAP) upwind of the contaminated property to establish historical use and disposal practices for elemental mercury. Mercury emissions test data from the Upstate New York chlor-alkali facility were modeled (USEPA ISC3) as a means of estimating impacts on ambient air and soils vicinal to the facility. Mercury emissions from the facility were modeled as both a point source and volume source. For example, at a location 305 meters to the east and 30 meters to the north of the modeled source centerline elemental mercury concentrations in ambient air were estimated at 270 ng/m<sup>3</sup> (average results based upon 5 years of meteorological data). This value is contrasted to a background concentration of 1.6 ng/m<sup>3</sup> (USEPA Report to Congress 1997). As a result of the modeling data in combination with findings related to mercury use and disposal practices at the NY CAP documented from the records review, it was concluded that emissions from the CAP facility during the period of operation (1897-1991) most likely accounted for the concentrations of elemental mercury found in surficial soils at properties situated downwind of the CAP. These findings were further corroborated by information available in the open literature for CAPs world-wide.
文摘An integral analysis of Air Pollution in the Gulf of Mexico was made considering pollutants emissions assessment and diagnosis;air pollution monitoring;and modeling of air pollution dispersion. Combustion sources considered in this work were: thermoelectric power plants and open flares;and pollutants considered were sulfur dioxide, nitrogen dioxides, particulate matter (PM<sub>10</sub> and PM<sub>2.5</sub>), Total suspended particles (TSP) and carbon monoxide (CO). This study made evident a lack of more recent information and a homogenization in emissions factors in order to know the conditions of air pollution in the Gulf of Mexico in a more reliable way.