Urban Atmospheric Environment Research Articles

Emission Data Uncertainty in Urban Air Quality Modeling—Case Study

Air pollution models are often used to support decisions in air quality management. Due to the complexity of the forecasting system and difficulty in acquiring precise enough input data, an environmental prognosis of air quality with an analytical model of the air pollution dispersion is burdened with a substantial share of uncertainty, especially as regards urban areas. To ignore the uncertainty in the modeling would lead to incorrect policy decisions, with further negative environmental and health consequences. This paper presents a case study which shows how emission uncertainty of air pollutants generated by the industry, traffic, and the municipal sector relates to concentrations measured at receptor points. The computational experiment was implemented in the Warsaw metropolitan area, Poland. The main source of this adverse environmental impact is the transportation system, including the transit traffic. The Monte Carlo technique was used for assessing the key uncertainty factors. Several types of pollution species that are characteristic for the urban atmospheric environment (e.g., PM10, PM2.5, NO x , SO2, Pb) were included in the analysis. The results show significant spatial variability of the modeled uncertainty. The reason of this variability is discussed in detail. It depends not only on the category of the emission source but also on the contributing emission sources and their quantity.

Optimal Signal Timing of Single Intersection for Traffic Emission Control

Traffic emission is one of the main pollution sources of urban atmospheric environment. Traffic control scheme of intersection has important influence on vehicle emission. Research on low emission traffic signal control scheme has become one of focuses of Intelligent Transportation. Current typical control methods of traffic emission are based on optimizing the average delay and number of stops. However, it is extremely difficult to use mathematical formula to calculate the delay and the number of stops in the presence of initial queue length of intersection. In order to solve this problem, we proposed a traffic emission control algorithm based on reinforcement learning. The simulation experiments were carried out by using the microscopic traffic simulation software. Compared with the Hideki emission control scheme, the experimental results show that the reinforcement learning algorithm is more effective. The average vehicle emissions are reduced by 12.2% for high saturation of the intersection.

Urban atmospheric environment and human biometeorological studies in Dar es Salaam, Tanzania

The urban climate system is a complex system constituting many components including urban air pollution and the thermal climate. While air pollution modifies local climate through the composition of the air, human biometeorological condition is assessed through thermal indices in order to understand the effects of thermal climate on man. In this study, a holistic approach was applied to review the past research in urban climate of Dar es Salaam, by considering the past research in air pollution and thermal climate about the city. Dar es Salaam is one of the fastest growing cities in the world, and this study is very relevant to future research in urban climate and urban planning, especially to cities with similar environmental challenges like Dar es Salaam. It was noted that the city, as many other cities in Africa or developing world, lacks a proper air quality monitoring programme despite of air pollution being a problem many years ago. However, meteorological observation started as early as in nineteenth century with rainfall being the most sampled environmental parameter in terms of spatial distribution, hence providing a potential to future research and comprehensive understanding of the urban climate.

Study on Dust-Retention Ability of Major Afforestation Tree Species in New Industrial Zone

Dust pollution has become one of the major problems that impact unban environment. While urban vegetation plays an important role in improving the urban atmospheric environment. This study conducted a preliminary research on the dust-retention ability of 20 greening tree species, by field sampling investigating and laboratory analyzing. The 20 greening tree species in Tianjin Airport Economic Area, a new industrial zone of Tianjin, were taken as research object. The results of the study show that: (1) the dust-retention ability of shrubs is bigger than arbors; (2) the dust-retention ability per unit area of different tree species varies; (3) Among Arbors, the order of the dust-retention ability is Populus tomentosa> Sophora japonica> Paulownia tomentosa> Firmiana simplex> Platanus orientalis> Robinia pseudoacacia> Koelreuteria paniculata> Salix matsudana > Fraxinus chinensis; (4) Among shrubs, the order is Syzygium aromaticum> Kerria japonica> Sorbaria sorbifolia> Ligustrum obtusifolium> Malus micromalus> Prunus cistena> Hibiscus syriacus> Prunus cerasifera var. pissardi> Prunus cistena> Lonicera maackii (Rupr.)Maxim.> Sambucus racemosa> Cercis chinensis. The research provides a theoretical basis for choosing the tree species in reducing the atmospheric particulate matter in Tianjin Airport Economic Area and the new industrial zone of northern China. In addition, the greening activity will be in favor of improving the ecological environment of the region.

Formation and evolution mechanism of regional haze: a case study in the megacity Beijing, China

Abstract. The main objective of this study is to investigate the formation and evolution mechanism of the regional haze in megacity Beijing by analyzing the process of a severe haze that occurred 20–27 September 2011. Mass concentration and size distribution of aerosol particles as well as aerosol optical properties were concurrently measured at the Beijing urban atmospheric environment monitoring station. Gaseous pollutants (SO2, NO-NO2-NOx, O3, CO) and meteorological parameters (wind speed, wind direction, and relative humidity) were simultaneously monitored. Meanwhile, aerosol spatial distribution and the height of planetary boundary layer (PBL) were retrieved from the signal of satellite and LIDAR (light detection and ranging). Concentrations of NO, NO2, SO2, O3, and CO observed during 23–27 September had exceeded the national ambient air quality standards for residents. The mass concentration of PM2.5 gradually accumulated during the measurement and reached at 220 μg m−3 on 26 September, and the corresponding atmospheric visibility was only 1.1 km. The daily averaged AOD in Beijing increased from ~ 0.16 at λ = 500 nm on 22 September and reached ~ 3.5 on 26 September. The key factors that affected the formation and evolution of this haze episode were stable anti-cyclone synoptic conditions at the surface, decreasing of the height of PBL, heavy pollution emissions from urban area, number and size evolution of aerosols, and hygroscopic growth for aerosol scattering. This case study may provide valuable information for the public to recognize the formation mechanism of the regional haze event over the megacity, which is also useful for the government to adopt scientific approach to forecast and eliminate the occurrence of regional haze in China.

The dust retention capacities of urban vegetation—a case study of Guangzhou, South China

Urban vegetation increasingly plays an important role in the improvement of the urban atmospheric environment. This paper deals with the dust retention capacities of four urban tree species (Ficus virens var. sublanceolata, Ficus microcarpa, Bauhinia blakeana, and Mangifera indica Linn) in Guangzhou. The dust-retaining capacities of four tree species are studied under different pollution intensities and for different seasons. Remote sensing imagery was used to estimate the total aboveground urban vegetation biomass in different functional areas of urban Guangzhou, information that was then used to estimate the dust-retaining capacities of the different functional areas and the total removal of airborne particulates in urban Guangzhou by foliage. The results showed that urban vegetation can remove dust from the atmosphere thereby improving air quality. The major findings are that dust retention, or capture, vary between the four species of tree studied; it also varied between season and between types of urban functional area, namely industrial, commercial/road traffic, residential, and clean areas. Dust accumulation over time was also studied and reached a maximum, and saturation, after about 24days. The overall aboveground biomass of urban vegetation in Guangzhou was estimated to be 52.0 × 10(5)t, its total leaf area 459.01km(2), and the dust-retaining capacity was calculated at 8012.89t per year. The present study demonstrated that the foliage of tree species used in urban greening make a substantial contribution to atmospheric dust removal and retention in urban Guangzhou.

Study on Emission Characteristics of Automobile Exhaust and Control Measures with Environmental Materials

With the rapid development of automobile industry and the accelerated process of urbanization, pollution caused by automobile exhaust had become one of the major sources of urban environment and atmospheric environment pollution. According to the automobile exhaust emission characteristics in this paper, the generation mechanism of major automobile exhaust pollutants which were suspended solid particles, carbon monoxide nitrogen oxides and hydrocarbons, were described, as well as emission control measures with environmental materials.

Impact of urban atmospheric environment on hospital admissions in the elderly

OBJECTIVE: To analyze the impact of intra-urban atmospheric conditions on circulatory and respiratory diseases in elder adults. METHODS: Cross-sectional study based on data from 33,212 hospital admissions in adults over 60 years in the city of São Paulo, southeastern Brazil, from 2003 to 2007. The association between atmospheric variables from Congonhas airport and bioclimatic index, Physiological Equivalent Temperature, was analyzed according to the district's socioenvironmental profile. Descriptive statistical analysis and regression models were used. RESULTS: There was an increase in hospital admissions due to circulatory diseases as average and lowest temperatures decreased. The likelihood of being admitted to the hospital increased by 12% with 1ºC decrease in the bioclimatic index and with 1ºC increase in the highest temperatures in the group with lower socioenvironmental conditions. The risk of admission due to respiratory diseases increased with inadequate air quality in districts with higher socioenvironmental conditions. CONCLUSIONS: The associations between morbidity and climate variables and the comfort index varied in different groups and diseases. Lower and higher temperatures increased the risk of hospital admission in the elderly. Districts with lower socioenvironmental conditions showed greater adverse health impacts.

<b>Impact of urban atmospheric environment on hospital admissions in the elderly</b>

<b>Impact of urban atmospheric environment on hospital admissions in the elderly</b>

Influence of Weight on Ecological Security Assessment of Urban Atmospheric Environment

With the accelerated development of urbanization human’s activities are playing an increasing negative impact on ecological security of atmospheric environment especially for urban movement. In order to manage the statement of urban ecological security of air environment as well as its spatial and temporal trends, several measures and methods for resolving the issues are provided in the paper. An assessment system is established with 19 factors and 4 sub-systems based on the atmospheric environment characteristics of Changde through adopting the Pressure-State-Danger-Response (P-S-D-R) model. For guaranteeing the reliability of results two methods are used to determine the weight. The final assessment results indicate that from 2005 to 2009 the composite index for ecological security of atmospheric environment in Changde lies between 0.27-0.87 and the overall trend of quality for ecological security improves gradually which turns to fluctuate between less and more secure and the security threat is not avoided.

Dynamics and dispersion modelling of nanoparticles from road traffic in the urban atmospheric environment—A review

Reducing exposure to atmospheric nanoparticles in urban areas is important for protecting public health. Developing new or improving the capabilities of existing dispersion models will help to design effective mitigation strategies for nanoparticle rich environments. The aims of this review are to summarise current practices of nanoparticle dispersion modelling at five local scales (i.e. vehicle wake, street canyons, neighbourhood, city and road tunnels), together with highlighting associated challenges, research gaps and priorities. The review begins with a synthesis of available information about the flow and mixing characteristics in urban environments which is followed by a brief discussion on dispersion modelling of nanoparticles. Further sections cover the effects of transformation processes in dispersion modelling of nanoparticles, and a critical discussion on associated structural and parametric uncertainties in modelling. The article concludes with a comprehensive summary of current knowledge and future research required on the topic areas covered. Appropriate treatment of transformation processes (i.e. nucleation, coagulation, deposition and condensation) in existing dispersion models is essential for extending the applicability of gaseous dispersion models to nanoparticles. Some modelling studies that consider the particles down to 1 nm size indicate importance of coagulation and condensation processes on street-scale modelling whereas others neglecting either sub-10 nm particles or Van der Waals forces along with fractal geometry suggest to discard these processes due to negligible effects on particle number and size distributions. Further, it is important to consider those transformation processes e.g. at city scale or in road tunnels because of the much longer residence time or much higher concentration levels compared to the street scale processes. Structural and parametric uncertainties affect the modelled results considerably. In particular, parametric uncertainty in the form of particle number emission factors appears to be the most significant due to considerably large variations in their estimates. A consistent approach to the use of emission factors, appropriate treatment of transformation processes in particle dispersion models and the evaluation of model performance against measured data are essential for producing reliable modelled results.

A composite model for complex building street configuration in a large eddy simulation of local urban atmospheric environment

The wind field and pollutant dispersion are predicted numerically in a local urban area with crowded buildings and heavy traffic. A domain decomposition method is used in the large eddy simulation, in which the urban area is decomposed into a central area, where pollution is the major concern, and a surrounding region, where the pollutant distribution is not important. The composite model is proposed for the complex building-street layout. The fine grid mesh is used to resolve the buildings in the central area while the buildings are treated as roughness elements in the surrounding region where the coarse grids are used. The proposed numerical method is applied to simulate the wind field and pollutant dispersion from vehicle exhaust in the Rua Do Campo area of Macau. The results show that the composite model is an appropriate method for predicting wind field and pollutant dispersion in the crowded building area.

Large eddy simulation of wind field and pollutant dispersion in downtown Macao

This paper investigates numerical method for predicting wind field and pollutant dispersion in an urban area with crowded buildings and heavy traffic. Large eddy simulation is employed in numerical computation with Lagrangian dynamic model to close the subgrid scale stress. The fine grids are required in numerical simulation of micro-atmospheric flows in an urban area with crowded and complex building-streets. To realize the numerical simulation on available computer resources a domain decomposition method and a combined model for the building-street layout are proposed that the computed domain of an urban area is decomposed into a central area, where the pollution is the major concern and a surrounding region where the pollutant distribution is not concerned. The combined flow model is proposed for the complex building-street layout that the fine grid mesh and exact flow boundary conditions are prescribed in the central area while the buildings are treated as roughness elements in the surrounding region where the coarse grids are used. The proposed numerical method is applied to simulate the wind field and pollutant dispersion from vehicle exhaust in the Rua Do Campo area of Macau (referred to the site hereafter). The wind speed and temperature fields are computed from 7 am on September 6 2005 to 7 am of the next day and the pollutant concentration field is computed from 7 am to 6 pm on September 6 2005. The results show fairly good agreement with the field observation. The wind field and pollutant concentration distribution are demonstrated in the site by proposed combined model and they are compared with those computed by drag element model in whole computational domain. The results show that the combined model is an appropriate method for predicting wind field and pollutant dispersion in the crowded building area. The paper also reveals the relevance of buoyancy effect in the prediction of urban atmospheric environment.

Prediction of dust fall concentrations in urban atmospheric environment through support vector regression

Support vector regression (SVR) method is a novel type of learning machine algorithms, which is seldom applied to the development of urban atmospheric quality models under multiple socio-economic factors. This study presents four SVR models by selecting linear, radial basis, spline, and polynomial functions as kernels, respectively for the prediction of urban dust fall levels. The inputs of the models are identified as industrial coal consumption, population density, traffic flow coefficient, and shopping density coefficient. The training and testing results show that the SVR model with radial basis kernel performs better than the other three both in the training and testing processes. In addition, a number of scenario analyses reveal that the most suitable parameters (insensitive loss function ɛ, the parameter to reduce the influence of error C, and discrete level or average distribution of parameters σ) are 0.001, 0.5, and 2 000, respectively.

Levels of PM 10 and PM 2.5 in Taipei Rapid Transit System

The PM 10 and PM 2.5 levels have been measured inside trains on four routes and on platforms at five stations in the Taipei Rapid Transit System using TSI Model 8520 DustTrak monitors. In this study, the TSI DustTrak was calibrated with a Met One E-BAM sampler within the metro station. Experimental results suggest that the TSI DustTrak overestimated PM 10 and PM 2.5 levels by about 2.0 and 2.2 times, respectively, compared with those measured by the Met One E-BAM sampler. Measurement results show that average PM 10 levels inside trains and on station platforms were 10–97 μg m −3 and 11–137 μg m −3, respectively, and average PM 2.5 levels were 8–68 μg m −3 and 7–100 μg m −3, respectively. Moreover, experimental results demonstrate that PM levels inside trains and on platforms were lower than those measured for other subway systems worldwide. Additionally, the PM 10 and PM 2.5 levels measured by ambient air-quality monitoring stations near selected metro stations correspond to PM levels in the urban atmospheric environment in Taipei. Statistical results demonstrate that average PM 10 and PM 2.5 levels in metro stations were about 0.65–1.53 times and 0.89–1.75 times, respectively, those for urban ambient air. The PM levels inside stations and outdoors are positively correlated, indicating that PM levels in the metro system are influenced significantly by outdoor ambient PM levels.

Sampling artefacts, concentration and chemical composition of fine water-soluble organic carbon and humic-like substances in a continental urban atmospheric environment

Water-soluble organic carbon (WSOC) and atmospheric humic-like substances (HULIS) were investigated for urban PM2.5-fraction aerosol samples, which were collected with the tandem filter method on quartz fibre filters over a non-heating spring season. Sampling artefacts were of importance for all organic chemical fractions, and the back-to-front-filter concentration ratios were on average 28% for WSOC and 17% for HULIS and organic carbon (OC). The difference in the ratios indicates that the water-soluble organics play a more important role in adsorptive artefacts than the organic matter (OM) in general. The results emphasize the need for an appropriate sampling and/or correction method for measuring particulate organic substances in urban environments. The corrected atmospheric concentration of HULIS, obtained by subtracting the back-filter from the front-filter data, was on average 2 μg m −3; which represented 6% of the mean PM2.5 particulate mass, and it made up 45% of the secondary OC. The HULIS carbon accounted for 20% of the OC and 62% of the WSOC, while WSOC made up 32% of OC. The major element composition of HULIS, expressed in molar ratios, was C:H:O:N=22:32:10:1. The molar H/C ratio of 1.49 implies the presence of unsaturated organic compounds, although these were depleted in comparison with rural aerosol or standard fulvic acids. The molar O/C ratio of 0.47 indicates the existence of oxygenated functional groups; comparison to rural aerosol suggests that the (fresh) urban-type aerosol is less oxidized (and, therefore, less water soluble as well) than the rural one. The OM/OC mass conversion factor for the isolated (water-soluble) HULIS was derived to be 1.81. It was inferred from comparisons with published data that there are substantial differences in abundance and chemical composition of HULIS for different environments.

Characterization of individual complex particles in urban atmospheric environment

The origins of carrier particles of complex particles (iron-rich particles) collected from the urban atmospheric environment near to road traffic and a railroad were investigated from the detailed surface information using FE-SEM/EDS and TOF-SIMS analyses. From the FE-SEM/EDS analyses, the iron-rich particles were classified into two typical types (spherical type and non-spherical type). From the TOF-SIMS measurements, the characteristic secondary ions of spherical type of iron-rich particles were 23Na + and 39K +. The minor components of non-spherical type were Al, Ca and Ba. On the other hand, we carried out TOF-SIMS measurement to materials of rail origin and brake origin. From the comparison of these spectra pattern, it seemed that the spherical type of iron-rich particles was emitted from the rail origin. We concluded that the origin of non-spherical type of iron-rich particles were brake pad of vehicles.

Atmospheric Path Radiation Map Generated from Remote Sensing Digital Image Based on Heterogeneous Surface Reflectance

The state of the atmospheric environment is related to the values of atmospheric path radiation in remote sensing data. As an important information resource, an atmospheric path radiation image derived from remotely sensed data can be used in many research fields. These include the research in the transmission properties of the atmosphere, the atmospheric modification of remote sensing image, the study of both regional and urban atmospheric environment, and the monitoring of the atmospheric environmental qualities. The principle and methodology for generating the heterogeneous atmospheric path radiation image are described in detail. It is based on known surface reflectance. Using remote sensing images from Shanghai City as a demonstration example, we briefly analyzed the properties of the resulting image of atmospheric path radiation.

Evaluation of diesel exhaust particle pollution using the source apportionment of PM2.5 in an urban atmospheric environment

We performed a source apportionment for particulate matter under 2.5 μm with the diameter (PM2.5) based on individual particle analyses using an electron probe microanalyzer (FE-SEM/EPMA). The analyzed particles were collected from the air environment near to a traffic route in June (before diesel vehicle emissions control regulations) and December (after regulations) 2003. From the results of the size, shape, and components of the particles, five or more sources of the particles were estimated. The rates for the contribution of diesel exhaust particle (DEP) were higher than that of the other sources. DEPs were further classified based on information concerning light elements according to the X-ray spectrum patterns. The X-ray spectrum patterns of DEPs collected before diesel vehicle emissions control regulations were different from that collected after the regulations. We could obtain this information about PM2.5 and DEPs, which could not be obtained by the conventional method. Therefore, it is concluded that the combination of individual particle analysis based on FE-SEM and EPMA is one of the most powerful techniques for obtaining detailed information about PM2.5.

Occurence and Distribution of Polycyclic Aromatic Hydrocarbons in Ankara Precipitation

Urban atmospheric environment contains many trace organic pollutants that are related to the incomplete fuel combustion in domestic heating, industrial plants and automobile traffic. Removal of these pollutants from the atmosphere takes place through wet and dry deposition as well as chemical transformations. In this study, concentrations of polycyclic aromatic hydrocarbons (PAHs) in wet deposition samples were determined at an urban site of Turkey. Wet and dry deposition samples were collected using Andersen Rain Sampler. The sampler was modified accordingly for the collection of organic pollutants. Collected samples were preconcentrated by using solid phase extraction (SPE) disks and consecutively analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). Among the 13 compounds quantified in this study, anthracene, fluoranthene, and pyrene were found more frequently and at elevated concentrations (202, 271 and 260 ng L-1 mean concentrations, respectively).Concentrations of PAHs were found to be high in winter period.