An alternative approach for atmospheric plume deposition and sedimentation

An alternative air pollution model of transport, diffusion, deposition and sedimentation has been formulated for gaseous or suspended particulate pollutants emitted from an elevated point source. The model is obtained by utilizing a continuous distribution of surface sources to replace the image source. It properly describes gradient diffusion to account for the ground deposition and gravitational settling. For practical application of the model to a variety of atmospheric stabilities, the vertical standard deviation parameter σz (x) as a function of downwind distance and stability has been incorporated in the model. The numerical algorithms and the diagrams for facilitating application of the model are present. The model has been tested and applied to particulate pollutants with gravitational settling velocity and to gases which deposit on the ground. Calculated results of concentration at the receptor height and net deposition and suspension ratios with respect to downwind distances are presented.     

高烟囱大气扩散的数值模拟

使用数值模拟的方法来计算给定源强下的高架排放点源的浓度场分布情况．通过求解复杂地形上的大气热力──动力学方程组及扩散方程，建立了三维的风场，浓度场的数值模拟模式．并结合云南开远电厂节能改建工程环境影响评价课题，对模式进行了验证．证明此方法可以成为解决复杂地形上大气污染扩散的实用方法．     

Air monitoring network program in Saudi Arabia

The Kingdom of Saudi Arabia has initiated a program to install air quality network stations throughout the country in order to measure concentration of the ambient air pollutants. The site selection of these stations is an important objective to be accomplished and must be done based on scientific and rational work. To accomplish this objective, a modified version of atmospheric transport and dispersion model, known as air resources laboratories - atmospheric transport and dispersion (ARLATAD) model, is used to evaluate long range transport and diffusion of air pollutants from major pollution causing sources such as refineries, open-air burning of associated gases of oil fields and major industries.Hourly meteorological data for a period of three years (from 1977 to 1979) on wind speed, wind direction, pressure, and temperature from 20 synoptic stations in Saudi Arabia is processed and used as model input. In addition to these, meteorological data from three upper air stations is also processed in order to determine base and top of critical inversion heights.Various pollution causing sources are identified within the study area. Air trajectories are drawn with sources as the origins of the trajectories and the dispersion characteristics is studied with distance and time. Based on long term meteorological records, the adversely affected zones are statistically identified for potential station sites.     

地下道路污染物对流扩散反问题伴随同化研究

在反问题框架内,基于偏微分方程最优化控制理论的伴随同化方法,建立了融合动力模型和观测信息的地下公路隧道污染物对流扩散反问题的计算模型,并给出了模型求解方法。以对流扩散方程中的源项为例进行了反演计算,并利用反演计算出的源项对污染物浓度进行了预测。研究表明,与传统的正问题模型相比,反问题模型反演计算得到的源项可以动态地反映隧道内车流量、车速、排放特性等因素的综合影响,并且计算得到的污染物浓度场精度更高。应用该方法,通过有效的对各类污染物观测资料进行客观利用,可以识别一些不确定参数,从而更好地实现对污染物浓度分布的分析与预测。     

确定建筑材料有害物散发量的三种传质模型

室内空气污染源散发量的确定是建立室内空气质量(IAQ)模型的重要步骤之一。目前研究建筑装饰材料和建筑涂料散发污染物的模型主要有经验模型和理论模型两类。经验模型简洁，但应用受到测试条件的限制，不具有普适性。基于传质理论而提出的理论模型目前研究较多，本文对研究建筑材料散发有害物的三个传质模型进行了评述。VB模型是一个简单的溶剂基室内涂料散发的总挥发性有机物(TVOC)的传质模型，低估了污染物的长期散发量。对流传质模型是基于界面平衡所导出的稳态模型，适用于固体和液体等材料的散发过程。Yang等提出的四层传质模型通常需与数值求解结合，计算较麻烦，但能较好地确定建筑材料散发挥发性有机物的散发量。     

Real‐Time Estimation of Pollution Emissions and Dispersion from Highway Traffic

Traffic‐related air pollution is a serious problem with significant health impacts in both urban and suburban environments. Despite an increased realization of the negative impacts of air pollution, assessing individuals' exposure to traffic‐related air pollution remains a challenge. Obtaining high‐resolution estimates are difficult due to the spatial and temporal variability of emissions, the dependence on local atmospheric conditions, and the lack of monitoring infrastructure. This presents a significant hurdle to identifying pollution concentration hot spots and understanding the emission sources responsible for these hot spots, which in turn makes it difficult to reduce the uncertainty of health risk estimates for communities and to develop policies that mitigate these risks. We present a novel air pollution estimation method that models the highway traffic state, highway traffic‐induced air pollution emissions, and pollution dispersion, and describe a prototype implementation for the San Francisco Bay Area. Our model is based on the availability of real‐time traffic estimates on highways, which we obtain using a traffic dynamics model and an estimation algorithm that augments real‐time data from both fixed sensors and probe vehicles. These traffic estimates combined with local weather conditions are used as inputs to an emission model that estimates pollutant levels for multiple gases and particulates in real‐time. Finally, a dispersion model is used to assess the spread of these pollutants away from the highway source. Maps generated using the output of the dispersion model allow users to easily analyze the evolution of individual pollutants over time, and provides transportation engineers and public health officials with valuable information that can be used to minimize health risks.     

浅析如何控制交通污染

论述了公路交通排放的各种污染物的成分及其危害性、污染物的运动与扩散，提出了控制汽车排放污染物的几个措施并作了具体阐述，以期使道路交通发展要合乎生态环境的要求，与环境相协调。     

A numerical model of acidification of raindrops by oxidation of SO2

A numerical model for the washout of sulphur dioxide from the atmosphere by rain has been developed by incorporating mass transfer of SO₂ into well‐mixed drops. The absorption of SO₂ by water droplets is a complex mechanism involving the transport to the air‐water interface. The washout of sulphur dioxide from the atmosphere is a phenomenon which is contributed to the production of acid rain and at the same time helps in cleaning the atmosphere. The mathematical model presented in this paper describes that the pollutants undergo chemical reaction in gas‐phase and liquid‐phase. The variation of the size of raindrops with height has also been incorporated. The model is used to simulate acid formation under different atmospheric conditions.     

城市规划中绿地布局对气象环境的影响——以成都城市绿地规划方案为例

城市规划气象环境多尺度数值模式系统为城市规划气象环境影响定量评估提供了有效的模式工具。本文利用该模式模拟了绿地布局为集中型和分散型、绿地面积百分比分别为8%、16%、32%、48%和60%条件下,城市大气温度、湿度、风速、城市大气扩散条件的变化,并以成都城市绿地规划为例,模拟分析了绿地规划前后城市气象环境的差异,揭示了城市绿地对气象环境影响的可能机制。     

Structural Disparities of Urban Traffic in Southern California: Implications for Vehicle‐Related Air Pollution Exposure in Minority and High‐Poverty Neighborhoods

Abstract: Structural inequalities provide an important context for understanding and responding to the impact of high traffic densities on disadvantaged neighborhoods. Emerging atmospheric science and epidemiological research indicates hazardous vehicle‐related pollutants (e.g., diesel exhaust) are highly concentrated near major roadways, and the prevalence of respiratory ailments and mortality are heightened in these high‐traffic corridors. This article builds on recent findings that low‐income and minority children in California disproportionately reside in high‐traffic areas by demonstrating how the urban structure provides a critical framework for evaluating the causes, characteristics, and magnitude of traffic, particularly for disadvantaged neighborhoods. We find minority and high‐poverty neighborhoods bear over two times the level of traffic density compared to the rest of the Southern California region, which may associate them with a higher risk of exposure to vehicle‐related pollutants. Furthermore, these areas have older and more multifamily housing, which is associated with higher rates of indoor exposure to outdoor pollutants, including intrusion of motor vehicle exhaust. We discuss the implications of these patterns on future planning and policy strategies for mitigating the serious health consequences of exposure to vehicle‐related air pollutants.     

城市规划与空气质量关系研究

针对城市规划与大气环境关系在定量化方面建立研究,即通过空间数据、气象数据等将城市规划、气象条件和生态环境三者相互对应,紧密结合起来,并通过精细的城市信息资料确立数学物理模型和数值计算,实现支撑技术保障。以沈阳市为例,采用不同尺度气象模式与大气化学输送扩散模式联结,运用科学合理的大气环境评估指标,建立城市规划大气环境影响评估系统,用以分析各种空气污染物对城市的影响,掌握了城市及周边地区的大气环境特征,为城市规划建设总体布局及人居环境的综合评价提供了科学依据。     

建筑物周围风绕流水平运动的数值模拟

在二维直角坐标系下,采用湍流流动的k—ε双方程模型和通用的SIMPLE算法,应用Visual Ba-sic6.0计算机语言,模拟了建筑物周围风绕流水平方向上的运动。数值模拟表明了风遇到建筑物时的绕流情况,研究成果可为城市规划和住宅小区建筑物的优化设计以及分析建筑物周围空气污染物的扩散和累积提供参考和应用基础。     

海工混凝土的氯离子扩散性与寿命评估

通过现场海洋曝露试验和实验室海水浸泡试验,采取分层取样和化学分析方法,应用氯离子三维扩散理论,研究了普通混凝土和高性能混凝土在海洋大气区、潮汐区、水下区和实验室海水浸泡下的C1-扩散系数变化规律.结果表明,混凝土的C1-一扩散系数随着曝露时间的增加而降低,高性能混凝土的抗C1-扩散性优于普通混凝土.在Khatri计算模型的基础上,提出了考虑劣化效应系数的海工混凝土使用寿命计算模型.该模型计算结果与Clear经验模型基本吻合,解决了Khatri计算模型结果与实际寿命不相符的问题.     

The effect of field conditions on low Reynolds number flow in a wetland

Stormwater runoff has been an environmental concern since the 1980s. Green infrastructure, such as constructed stormwater wetlands (CSWs), is a tool in stormwater management, however, little is known about the hydraulic diffusion processes that impact water quality in low flow, laminar (i.e. baseflow) conditions. Diffusion provides the mechanisms that distribute and mix water through a CSW and therefore how pollutants will be spread through the CSW impacting the water quality. Laboratory experiments were performed by Nepf, H.M., Sullivan, J.A., Zavistoski, R.A. [1997. A model for diffusion within emergent vegetation. Limnology and Oceanography, 42(8), 1735-1745], and Serra, T., Fernando, H.J.S., Rodriquez, R.V. [2004. Effects of emergent vegetation on lateral diffusion in wetland. Water Research, 38(1), 139-147] to examine the effect of plant density on diffusion in laminar flow conditions. Nepf, H.M. [1999. Drag, turbulence, and diffusion in flow through emergent vegetation. Water Resources Research, 35(2), 479-489] proposed a model predicting the diffusion coefficient based upon the plant density for both laminar and turbulent flow conditions. The present study examines the effect of field conditions on diffusion in a laminar flow field and verifies the diffusion model created by Nepf, H.M. [1999. Drag, turbulence, and diffusion in flow through emergent vegetation. Water Resources Research, 35(2), 479-489]. The results from the present study show that the laminar flow model, based solely on mechanical diffusion, is not sufficient for field conditions and the total diffusion model must be used. The variability in flow conditions and stem diameter found in the field produce pockets of turbulence and dead zones that must be considered to predict the diffusion coefficients in low flow CSWs. A sensitivity analysis of the dead zone term shows that the laboratory, field and diffusion models lie within an acceptable theoretical range for the observed or predicted diffusion coefficient. In addition, a model was created using the Danish Hydraulic Institutes Mike 21 software. Model results indicate that non-uniform velocities significantly affect the diffusion coefficient and a range of diffusion coefficients should be considered when designing CSWs.     

Three‐dimensional analytical model of atmospheric dispersion of pollutant in a stable boundary layer

A three‐dimensional atmospheric dispersion model of a heavy admixture emitted from an elevated continuous point source is presented. Appropriate boundary conditions have been employed to model the effects of various removal mechanisms like deposition, settling and leakage of pollutants. This model takes care of variation of mixing layer height with heat flux, geostrophic drag by terrain and several meteorological parameters. A realistic form of variable eddy diffusivity is used in this model for a stable atmospheric condition. It has been found that the effect of settling of large particles is to reduce pollutant concentration always far away (horizontally as well as vertically) from the source. Whereas, in the lower part of the boundary layer near the source its effect is to increase concentration for small values of settling velocity and to decrease for larger values. The present model, being three dimensional in nature, is more suitable to assess the impact of point source emission.     

Air quality impact assessment of at-berth ship emissions: Case-study for the project of a new freight port

This work is intended to assess the impact on local air quality due to atmospheric emissions from port area activities for a new port in project in the Mediterranean Sea. The sources of air pollutants in the harbour area are auxiliary engines used by ships at berth during loading/offloading operations. A fleet activity-based methodology is first applied to evaluate annual pollutant emissions (NO_X, SO_X, PM, CO and VOC) based on vessel traffic data, ships tonnage and in-port hotelling time for loading/offloading operations. The 3-dimensional Calpuff transport and dispersion model is then applied for the subsequent assessment of the ground level spatial distribution of atmospheric pollutants for both long-term and short-term averaging times. Compliance with current air quality standards in the port area is finally evaluated and indications for port operation are provided.Some methodological aspects of the impact assessment procedure, namely those concerning the steps of emission scenario definitions and model simulations set-up at the project stage, are specifically addressed, suggesting a pragmatic approach for similar evaluations for small new ports in project.     

Climate change impacts on streamflow and non‐point source pollutant loads in the 3S Rivers of the Mekong Basin

Changes in non‐point source (NPS) pollutants are of particular concern in developing countries. This study investigated the responses of streamflow and NPS pollutant loads to climate change in the 3S River Basin, a trans‐boundary basin of the Mekong River, using Soil and Water Assessment Tool (SWAT). Firstly, the SWAT model in simulations of streamflow and NPS pollutant loads was calibrated and validated against observed data to prove the reliability of the simulation results. Then, the calibrated SWAT model was used to simulate changes in streamflow and NPS pollutants under the impact of climate change. The simulation results indicated that the streamflow and NPS pollutant loads are predicted to increase in the future. Moreover, water shortage in the dry season and soil degradation in the wet season are emphasized to occur in the future.     

Arctic atmospheric contaminants in NE Greenland: levels, variations, origins, transport, transformations and trends 1990-2001

This review is based on the results obtained from the Danish AMAP programme for the Arctic atmosphere during the 1990s. The purpose of the programme is to quantify the pollution, apportion source contributions, follow the trends, and identify midlatitude source areas and transport pathways. The project has been carried out in North Greenland as integrated monitoring, which is an interacting combination of field measurements and model calculations of atmospheric transport and transformation in the Northern Hemisphere. At the monitoring site at Station Nord the large and seasonally recurrent variations in the pollutant concentrations are testimony to the influence in this region of the phenomenon of Arctic Haze. These results can only be understood in terms of long range transport from distant pollution sources. The measurements also comprise a large number of particle-born elements. These results are used to build receptor models, which show that the ambient concentrations and their variations to a high degree can be explained by the influence of only four source types of both natural and anthropogenic nature. The challenging phenomena of atmospheric ozone and mercury depletion around Polar sunrise have been studied at Station Nord over several years. The results show that these two phenomena are closely connected, presumably through photochemical reactions with atmospheric halogens released from sea ice. A large-scale Eulerian model system for the Northern Hemisphere has been developed in this AMAP project. The validity of the model is illustrated by comparisons between measured and calculated air concentrations. The model has been used to calculate both the vertical distribution and the atmospheric depositions for several pollutants at various locations in Greenland and split into quantified contributions from different and geographically distant source areas. Mercury deposition estimates for the Northern Hemisphere are also presented. They show that the mercury depletion events are accompanied by very intense depositions to land and sea of reactive mercury that may seriously affect the Arctic ecosystems. Finally, measurement and model data are combined to demonstrate, despite considerable meteorological noise, that ambient air concentrations in North-eastern Greenland have decreased during the last decade. Quantified trends, attributable to emission reductions in distant source areas, are presented for several pollutants.     

热强化有机污染物自土中挥发过程的试验与理论研究

为了研究热强化条件下有机污染物自土中挥发去除规律及挥发过程的影响因素,设计了室内挥发模型试验,研究了不同温度、不同初始污染物浓度的挥发去除规律。研究结果表明,有机污染物自土中的挥发过程曲线可分成三个阶段:快速挥发期,稳定增长期和平衡挥发期;另外,初始污染物浓度越大,自由相污染物分子的比例越高,挥发速率越大;温度由40℃升高至80℃时,砂土的平均挥发速率提高了4.0～4.8倍;综合考虑拟合方程的相关性发现,有机污染物自土中的挥发去除过程符合一级动力学模型。     

城市地表水体径流污染模拟分析:以苍海湖为例

在我国城市持续推进绿色发展理念的背景下,为科学支撑海绵城市规划编制工作,以梧州市苍海湖为研究实例,结合国内外相关研究经验和属地化的测量参数,应用InfoWorks ICM构建研究区水量水质数学模型。设计旱季和雨季两种模拟情景,分别对苍海湖汇水区内的污染物径流冲刷效应和湖体内污染物迁移扩散规律进行模拟分析,计算不同设计情景下地表污染物随雨水径流进入苍海湖及在湖内扩散的演进过程,并基于计算结果为苍海湖水动力条件改善、湖泊水质保护等提出工程指引建议,以期为水量水质数学模型在海绵城市规划中的应用提供参考。