ATMOSPHERIC TURBULENCE INTENSITY AND DIFFUSION PARAMETER OVER COMPLICATED TOPOGRAPHY OF EASTERN GUANGDONG

ＡＴＭＯＳＰＨＥＲＩＣＴＵＲＢＵＬＥＮＣＥＩＮＴＥＮＳＩＴＹＡＮＤＤＩＦＦＵＳＩＯＮＰＡＲＡＭＥＴＥＲＯＶＥＲＣＯＭＰＬＩＣＡＴＥＤＴＯＰＯＧＲＡＰＨＹＯＦＥＡＳＴＥＲＮＧＵＡＮＧＤＯＮＧＷｕＹａｎｂｉａｏ（吴艳标）；ＬｉｕＳｈｕｗａｎｇ（刘树旺）ａ...

Case Study of Atmospheric Pollutant Diffusion Data Based on Gaussian Model

Air pollution as one of the major environmental issues in modern society,has already brought severe impact to human life and production,thus it is an urgent task for studying environmental and ecological science to solve this issue that has bothered human society for the last centuries.Scientists have endeavored to figure out the laws of atmospheric pollutant diffusion using various mathematical models and statistical models,and drawn some precious conclusions.This paper explored the basic model of atmospheric diffusion—modeling and solution of Gaussian Diffusion Model,clarify its principles and operation forms,then applied the model into the PM_(2.5) atmospheric diffusion cases,make the program planning base on the results of model calculation,and get the final conclusion.

Effect of Ocean Thermal Diffusivity on Global Warming Induced by Increasing Atmospheric CO_2

A global mean ocean model including atmospheric heating, heat capacity of the mixed layer ocean, and vertical thermal diffusivity in the lower ocean, proposed by Cess and Goldenberg (1981), is used in this paper to study the sensitivity of global warming to the vertical diffusivity. The results suggest that the behaviour of upper ocean temperature is mainly determined by the magnitude of upper layer diffusivity and an ocean with a larger diffusivity leads to a less increase of sea surface temperature and a longer time delay for the global warming induced by increasing CO2 than that with smaller one. The global warming relative to four scenarios of CO2 emission assumed by Intergovernmental Panel of Climate Change (IPCC) is also estimated by using the model with two kinds of thermal diffusivities. The result shows that for various combinations of the CO2 emission scenarios and the diffusivities, the oceanic time delay to the global warming varies from 15 years to 70 years.

The Characteristics of Atmospheric Ice Nuclei Measured at Different Altitudes in the Huangshan Mountains in Southeast China

The concentration of ice nuclei （IN） and the relationship with aerosol particles were measured and analyzed using three 5-L mixing cloud chambers and a static diffusion cloud chamber at three altitudes in the Huangshan Mountains in Southeast China from May to September 2011.The results showed that the mean total number concentration of IN on the highest peak of the Huangshan Mountains at an activation temperature （Ta） of-20℃C was 16.6 L-1.When the supersaturation with respect to water （Sw） and with respect to ice （Si） were set to 5％,the average number concentrations of IN measured at an activation temperature of-20℃C by the static diffusion cloud chamber were 0.89 and 0.105 L-1,respectively.A comparison of the concentrations of IN at three different altitudes showed that the concentration of IN at the foot of the mountains was higher than at the peak.A further calculation of the correlation between IN and the concentrations of aerosol particles of different size ranges showed that the IN concentration was well correlated with the concentration of aerosol particles in the size range of 1.2-20 μtm.It was also found that the IN concentration varied with meteorological conditions,such as wind speed,with higher IN concentrations often observed on days with strong wind.An analysis of the backward trajectories of air masses showed that low IN concentrations were often related to air masses travelling along southwest pathways,while higher IN concentrations were usually related to those transported along northeast pathways.

Model calculating annual mean atmospheric dispersion factor for coastal site of nuclear power plant

This paper describes an atmospheric dispersion field experiment performed on the coastal site of nuclear power plant in the east part of China during 1995 to 1996. The three-dimension joint frequency are obtained by hourly observation of wind and temperature on a 100m high lower; the frequency of the 'event day of land and sea breeze' are given by observation of surface wind and land and sea breezes; the diffusion parameters are got from measurements of turbulent and wind tunnel simulation test. A new model calculating the annual mean atmospheric dispersion factor for coastal site of nuclear power plant is developed and established. This model considers not only the effect from mixing release and mixed layer but also the effect from the internal boundary layer and variation of diffusion parameters due to the distance from coast. The comparison between results obtained by the new model and current model shows that the ratio of annual mean atmospheric dispersion factor gained by the new model and the current one is about 2.0.

Study on the Total Amount Control of Atmospheric Pollutant Based on GIS

To provide effective environmental management for total amount control of atmospheric pollutants. Methods An atmospheric diffusion model of sulfur dioxide on the surface of the earth was established and tested in Shantou of Guangdong Province on the basis of an overall assessment of regional natural environment, social economic state of development, pollution sources and atmospheric environmental quality. Compared with actual monitoring results in a studied region, simulation values fell within the range of two times of error and were evenly distributed in the two sides of the monitored values. Predicted with the largest emission model method, the largest emission of sulfur dioxide would be 54 279.792 tons per year in 2010. Conclusion The mathematical model established and revised on the basis of GIS is more rational and suitable for the regional characteristics of total amount control of air pollutants.

Using Longwave Infrared Hyperspectral Imaging for a Quantitative Atmospheric Tracer Monitoring in Outdoor Environments

Quantitative real-time retrieval of concentration-lengths (CL) through gaseous plumes is an important tool for environmental monitoring, enabling remote monitoring of emissions from industrial facilities and risk assessment in scenarios of toxic gas releases. The adoption of LWIR (Long Wave InfraRed) hyperspectral imaging as a leading technique for remote gas plume detection paved the way for an introduction of a precise CL estimation and two-dimensional (2D) mapping. A novel methodology for evaluating and characterizing the performance of a retrieval algorithm is presented. The algorithm utilizes state-of-the-art retrieved hyperspectral 2D mapping and is applied on a series of localized atmospheric tracer gas (SF6) releases in monitored environmental conditions. The retrieved CL distributions are compared to a numeric atmospheric T&D (Transport and Diffusion) model. Satisfactory agreement between retrieved and simulated CL prediction is manifested, and the uncertainty involved is quantified. Possible sources for the remained discrepancies between retrieved and simulated CL values are characterized, and methods to minimize them are discussed.

Generation of X-ray Emission in Repetitive Nanosecond-pulse Discharge at Atmospheric Pressure

Pulsed discharges can generate high power densities and high equivalent electric fields in plasma to emit X-rays,which is closely related to discharge mechanism.In this paper,discharge characteristics and X-ray emission of typical nanosecond-pulse discharges(corona,diffuse,spark or arc)are reviewed.Especially,the diffuse discharges are observed at pulse repetition frequencies up to 1 kHz.Factors influencing the discharge characteristics and X-ray emission are analyzed,such as the gap spacing,parameters of the applied pulse(amplitude,pulse repetition frequency),anode and cathode materials,and curvature radius of cathode.It is concluded that the maximum X-ray intensity is obtained in a diffuse discharge,and the X-ray intensity is affected by the pulse repetition frequency,applied voltage,anode material,and curvature radius of cathode.For example,X-ray intensity increases with the pulse repetition frequency and the atomic numbers of the anode material,but it decrease with the increase of curvature radius.It is also shown that the cathode material has no obvious influence on the X-ray intensity.

Generation of Runaway Electrons in Atmospheric Pressure Air Under 30-200 kV Voltage Pulses of Rise Time 1.5 ns

A pulse generator with a voltage rise time of～1.5 ns and voltage amplitude variable from 30 kV to 200 kV was designed for generating runaway electron beams in atmospheric pressure air with different interelectrode gaps.The influence of the voltage amplitude and gap length on the generation was studied.In the gas diode geometry under study,the gap voltage at which the generation of a runaway electron beam begins was determined.Decreasing the voltage pulse amplitude does not increase the beam current pulse width measured with a time resolution of～0.1 ns.It is shown that the escape of beam electrons to the downstream of the foil is sync in time with the voltage drop across the gap,and that the delay of beam current generation increases gradually from 1.1 ns to 2.6 ns as the voltage pulse amplitude across the gap decreases from～100 kV to 40 kV.

Comparison of Formation Mechanism Between Helium and Argon Atmospheric Pressure Plasma Jets

To compare the formation mechanisms of He and Ar atmospheric pressure plasma jets(APPJs),an intensified charge-coupled device(ICCD)are utilized to observe the dynamic process of APPJ.The experimental results show that,He APPJ is first ignited,which is independent of the dielectric barrier discharge(DBD)between the two wrapped electrodes when the high voltage placed at the downstream.The intensity and APPJ length under positive discharge pulses are bigger than that under negative discharge pulses due to the space charge effect.The He APPJ is formed by the DBD development when the high-voltage electrode placed at the upstream side of tube.However,the plasma plume in Ar APPJ is formed by the propagation of DBD whatever the high-voltage electrode is arranged on upstream or downstream side of ground electrode.The difference in formation mechanism between He and Ar APPJs is mainly caused by the gas properties.Moreover,during the discharges,Ar tends to lead to thermal instability and electron Maxwellian instability.

Numerical Modeling of Three-Phase Mass Transition with an Application in Atmospheric Chemistry

This work presents a software tool for modeling of mass transfer physicochemical processes occurring in the atmosphere. The implemented algorithms provide an efficient theoretical frame for the interpretation of the results obtained from Coated Wall Flow Tube (CWFT) reactor experiments, which is one of the most adequate techniques to study heterogeneous kinetics. The numerical simulations are based on the fundamental Langmuir adsorption theory by ordinary differential equations and the second Fick’s law described by partial differential equations. The main application of the system is to estimate the basic parameters that characterize the processes. The best parameter estimation is found by minimizing the difference between experimental signals from the CWFT reactors and the obtained numerical simulations. A numerical example for an experimental data fit is given.

Air Pollution Steady-State Advection-Diffusion Equation: The General Three-Dimensional Solution

Atmospheric air pollution turbulent fluxes can be assumed to be proportional to the mean concentration gradient. This assumption, along with the equation of continuity, leads to the advection-diffusion equation. Many models simulating air pollution dispersion are based upon the solution (numerical or analytical) of the advection-diffusion equation as- suming turbulence parameterization for realistic physical scenarios. We present the general steady three-dimensional solution of the advection-diffusion equation considering a vertically inhomogeneous atmospheric boundary layer for arbitrary vertical profiles of wind and eddy-diffusion coefficients. Numerical results and comparison with experimental data are shown.

森林火灾污染物质释放及其影响研究进展

森林火灾是大气中气体污染物和颗粒物的重要来源,可对全球气候系统、大气环境以及生态系统产生重要影响,对全球温室气体和含碳颗粒物释放具有重要的贡献,是推动全球气候变化的重要因素。森林火灾释放污染物已成为区域乃至全球范围内重要污染源之一,这些污染物质与辐射、能见度以及温室效应等问题直接相关。准确地描述森林火灾释放的气体和颗粒污染物释放机理、释放总量、时空分布特征、不同尺度的扩散过程模拟,以及对区域大气环境的影响,对于量化森林火灾释放污染物总量及区域影响具有重要意义。基于森林火灾污染物质释放方面的国内外文献,从火灾释放的污染物质对环境的影响、森林火灾释放污染物定量化和传输路径监测的研究方法、污染物质的扩散和运输模型以及跨区域影响等几个方面进行了综述。森林火灾释放的CO、PM_(10)和PM_(2.5)对环境和人的生命安全造成巨大威胁,而且森林火灾释放的污染物质能够随气流长距离传输,不仅对当地的空气造成污染,污染物也能够随着气团进行长距离传输,并在传输过程与当地气溶胶混合,形成跨区域污染。森林火灾释放污染物扩散、传输模拟通过不同模型相互耦合完成,包括可燃物载量估算模型、可燃物消耗和释放模型、污染物扩散传输模型,以及污染物预测和可视化模型等。总结了国内外森林火灾释放污染物质主要研究方法,并展望了今后研究重点:目前我国关于森林火灾释放物质相关的研究尚不足以支撑我国森林火灾温室气体释放、污染物释放等方面的研究,并且我国目前还没有发展出适合于我国的森林火灾污染物释放模型,以及污染物扩散、传输系统。森林火灾排放因子库大多数引用国外研究结果,在一定程度上增加不确定性,缺乏森林火灾对区域大气环境影响的定量化研究。因此,今后我国应加强对森林火灾污染物质释放与影响的研究,尤其是污染物质扩散和传输模型的预测和可视化研究以及排放因子的测量。

大气边界层参数化方案在核电厂址扩散参数计算中的应用研究

在核电厂环境污染影响评价、环境质量管理、应急等工作中,需对核电厂排放的放射性污染物在大气中迁移扩散特征进行评价,而扩散参数是核电厂环评、设计、应急相关评价软件中重要的参数。由边界层参数化方案计算扩散参数的方法应用较为普遍,文章对两种常用大气边界层参数化方案在核电厂址扩散参数计算中的效果进行了讨论。与核电厂址湍流观测数据的比较显示:Mellor-Yamada 2层方案模拟结果具有较好的相关性,但方差更大;Hanna方案模拟结果相关性相对较弱,但其方差也较小,在应用中可根据两种方案各自的特点选用具体的扩散参数计算方案。

气载核素迁移扩散模型LPAM对SF_(6)示踪实验的模拟分析

为了验证国产核事故后果评价系统中的拉格朗日粒子模型LPAM在我国滨海核电厂使用的有效性,本研究采用影响扩散因素相对单一的大气扩散示踪实验对LPAM的模拟结果进行了验证。结果表明LPAM模型模拟的结果与示踪实验结果偏差合理,吻合度与欧洲核事故后果评价系统JRODOS中DIPCOT对示踪实验模拟的表现基本一致,同时4次模拟结果与采样结果的相关性也较好,说明核事故后果评价系统中所采用的拉格朗日粒子模型LPAM模拟结果具有合理性。同时,在后续研究中增加相应物理资料的使用,可以进一步对模型有效性进行研究判断,本研究可为后续有效性验证工作提供借鉴。

恶臭污染的测定方法与预测模型研究进展

随着人们对环境问题的认识,恶臭污染已经成为一类典型的环境公害。我国的恶臭污染来源广泛,臭气浓度的测定成本昂贵,构建基于简易输入参数的臭气预测模型降低恶臭污染判定与控制的难度,是目前恶臭污染研究的热点问题。本研究从臭气定义的基本概念入手,总结对比了不同的臭气标准和测定方法。综述了目前常用的臭气预测模型,包括基于污染物浓度的多元线性回归法和不同的臭气浓度/强度预测模型,发现不同研究或者不同模型得到的结果差异较大。其中,为预测模型提供准确的嗅觉阈值是优化模型的关键。另外,作为一种环境问题,本研究也对臭气的大气扩散以及排放速率进行了综述研究,研究中使用不同的大气扩散模型对臭气的大气扩散过程进行预测。但不同模型需要的基础数据和知识背景不同,因此需要根据实际的应用场景选择合适的模型。排放速率作为大气扩散模型中的重要输入参数,可以通过不同的方法和装置进行测定,不同方法的测定结果存在差异,后续研究中需要依据更多的现场数据对预测结果进行验证。基于以上综述,本研究将为恶臭污染的识别和控制提供科学指导。

工业气氛下电流场辅助Ni-ZrO_(2)陶瓷扩散焊

目的研究电流驱动下金属Ni向ZrO_(2)陶瓷的定向扩散以及界面化学反应,实现两者在工业气氛下的快速连接。方法在1200℃下采用独特的电流场耦合扩散焊连接系统制备Ni-ZrO_(2)扩散偶样品。利用扫描电子显微镜(SEM)、能谱仪(EDS)对不同直流电参数(电流密度0~5.09 mA/mm^(2))下制备的样品界面焊缝形貌以及原子分布进行观察和解析;测试Ni-ZrO2扩散偶的剪切强度,并结合不同样品的界面微观结构演变初步揭示电流场辅助Ni-ZrO_(2)的连接机制。结果电流场有效地促进了工业气氛下金属-陶瓷界面的交互作用,当电子流由金属Ni指向ZrO_(2)陶瓷时,界面反应层厚度随着电流密度的增大而持续增大;样品接头的连接强度随着电流强度的增大呈先升高后降低的趋势,在1200℃下通电(电流密度为3.82 mA/mm^(2))5 min时得到最佳剪切强度164 MPa。结论施加直流电场引发的金属电迁移效应和固体电解质陶瓷中氧离子的定向运动是促进界面互扩散以及化学反应的重要原因,而局部的过度“失氧”容易导致陶瓷结构和功能特性丧失。与高真空环境相比,在工业气氛下界面附近较高的氧浓度抑制了陶瓷变质,使焊接接头在电流强度较大时仍然保持了较高的剪切强度。

某油田挥发性有机物扩散模拟系统开发与应用

针对目前小尺度大气扩散模型欠缺和油气田站点挥发性有机物(VOCs)大气污染特点,文章基于空间分析方法和高斯烟羽模型,开发了多物种、多排放方式的小尺度反应性大气扩散模型体系,分别为点源无化学反应、点源有化学反应、面源无化学反应、面源有化学反应四种模型;并选用SharpDev项目开发框架进行系统搭建,Python语言开发后台计算过程,使其能根据用户输入参数自动计算油气田站点源及面源污染扩散情况、并完成可视化展示,该软件系统的开发和应用为类似油气田站点大气污染物扩散、迁移和预判提供了方法基础。

基于FLEXPART模型的复杂地形大气扩散能力研究——以山西省孝义市和古县为例

基于2012—2021年地面气象观测资料,采用无人机观测气温廓线,计算分别位于开阔盆地和狭长山谷地形的山西省孝义市和古县大气混合层厚度、大气自净能力指数、逆温层厚度;利用FLEXPART模型模拟两地不同时期(清洁期、重污染期)大气中颗粒物传输路径及高度.结果表明:孝义市和古县大气自净能力指数分别为13.4和6.2,大气自净能力等级分别为二级和四级,春季大气自净能力最强,冬季最弱.冬季古县逆温强度大于孝义市,不利于大气污染物的扩散.清洁时期,两地污染物均沿西北方向传输,孝义市大气中粒子传输高度较高,传输距离更远;重污染期,两地空气中粒子传输高度均偏低,传输距离受地形影响,易造成当地大气污染.因此,开阔盆地相较于狭长山谷地区,大气污染物更易清除;开阔盆地大气污染物传输高度高于狭长山谷地区,且传输距离也更远.

基于不同气象数据的山地城市大气环境敏感性评估对比

以典型低纬高原山地城市云南省德宏州为例,利用WRF_CALPUFF模型开展大气环境敏感性评估并以此为依据进行敏感区识别,分别采用WRF模拟结果和地面气象站观测资料作为模型输入地面气象数据,通过对比分析基于两种不同数据的评估结果,讨论适用于山地城市大气环境敏感性评估的数据和方法。结果表明:2种方法模拟计算的扩散指数均能反映出地形差异所致的扩散能力空间差异性,弱扩散区识别均较可靠。气象背景场采用WRF高空模拟数据和地面气象站观测数据相结合的方法,评估结果可靠,具有基础数据获取较难、技术难度较低、时间成本较低的特点,若能获取站点数据则推荐此法。气象背景场均采用WRF模拟结果的方法,在识别布局敏感区时不确定性较高,主要因地形复杂地区风场模拟不确定性较高所致,但此法具有基础数据获取较容易、技术难度较高、时间成本较高的特点,若采用此法,需提高模拟准确性以保障评估结果的可靠性。