Air quality and its response to satellite-derived urban form in the Yangtze River Delta,China

Air pollution is one of the top environmental concerns and causes of deaths and various diseases worldwide. An important question for sustainable development is to what extent urban design can improve or degrade urban air quality. In this article, we explored the relationship between ground-based observations of air pollution and urban form in the Yangtze River Delta (YRD), the largest metropolitan region in China. We analyzed six criteria pollutants (SO₂, NO₂, PM₁₀, PM_2.5, CO, O₃) and summarized metric (air quality index, AQI) from 129 ambient air quality monitoring stations during 2015. Urban form was characterized using six spatial metrics, including the size, shape, regularity, fragmentation and traffic coupling factor of urban patches, based on satellite-derived land cover data. The results indicated that: (1) PM_2.5, PM₁₀ and O₃ were three primary pollutants in the YRD. The annual average AQI was 79, and the air quality was “moderate” for human health, with the highest and lowest AQI appeared in winter (107) and summer (60). Moreover, the air quality of the southern areas (Zhejiang province, AQI: 68) was generally better than the northern parts (Jiangsu province, AQI: 86). (2) Through the size and shape of urban patches, urban form had a significant effect on urban air quality in the YRD. PARA_MN (Mean Perimeter-area ratio), ENN_MN (Mean Euclidean Nearest Neighbor Distance), CA (Total Urban Area) and NP (Number of urban patches) had the most significant impacts on air quality. PM₁₀ and PM_2.5 were two important pollutants highly positively related to CA and NP, while negatively related to PARA_MN and ENN_MN. In addition, the polycentric urban form was associated with high air quality. (3) Land use configuration was an important indicator to describe the urban air quality. When buffer distance of spatial scale was 25 km, air quality showed the highest correlation with forest coverage. A high forest coverage rate contributed to the better air quality, increasing or preserving the forested areas would help mitigate the air pollution.     

Induction of sister chromatid exchanges in traffic policemen exposed to vehicular exhaust

In urban areas there is an explosive growth of population and the number of automobiles. The ever-increasing vehicular traffic density is posing continued threat to the ambient air quality. Traffic policemen as a group of workers are exposed occupationally to the pollutants from vehicular exhaust. Sister chromatid exchanges (SCEs) as a biomarker of the pollutant's effect, were analyzed in peripheral blood lymphocytes of 85 traffic policemen and 60 control subjects. There was a significant increase in the mean SCEs+/-S.D./cell in the exposed group (9.31+/-5.29) when compared to the controls (4.18+/-1.85). Thus the present study concludes that vehicular exhaust might induce cytogenetic damage in traffic police. Further, the more pronounced frequency of SCEs observed in the smoking traffic policemen than in the non-smoking group suggests the joint effect of smoking and vehicular exhaust.     

Polycyclic aromatic hydrocarbons (PAHs) concentration levels,pattern, source identification,and human risk assessment in foliar dust from urban to rural areas in Nanjing,China

Environmental health is an essential component of quality of life in modern societies. Foliar dust contains polycyclic aromatic hydrocarbons (PAHs) that may have harmful effects on human health. The PAHs concentration of foliar dust is useful to assess environmental air pollution. Our results indicate that: (1) the highest levels of PAHs were distributed in urban areas, with a mean of 3430.23 ng·g^?1, lower mean concentrations were found in suburban (2282.12 ng·g^?1), and rural areas (1671.06 ng·g^?1). (2) Diagnostic ratios and principal component analysis were used to identify the sources of PAHs: Gasoline vehicle traffic emissions were the predominant source in urban areas, along with coal and coke combustion. In suburban areas, the main sources were petroleum combustion (especially liquid fossil fuels) and coal combustion. Coal and wood combustion were the primary source of PAHs in foliar dust in rural areas. (3) The incremental lifetime cancer risk (ILCR), estimated based on the results of this study indicate that urban residents were potentially exposed to high cancer risk via both dust ingestion and dermal contact. We conclude that urbanization has significant effects on the PAH concentrations of foliar dust, illustrating the importance of trees in improving air quality in urban areas.     

Annual TSP and Trace Metal Distribution in the Urban Atmosphere of Islamabad in Comparison with Mega-Cities of the World

The objective of this work was to assess the current concentrations of total suspended particles (TSP) and trace metals in the urban atmosphere of Islamabad, Pakistan, where local industries, transportation, and urbanization are adversely affecting air quality. Air sampling was done using a high-volume sampler and the metals were estimated in TSP by Flame Atomic Absorption Spectrophotometry. An annual mean TSP of 151.9 μ g/m³ was determined for the period May 2003–April 2004, which exceeded the World Health Organization's (WHO's) primary and secondary standards of air quality. The TSP metal concentrations were compared with those reported in literature for other regions of the world and with air quality standards laid down by regulatory agencies. The levels of Na, Fe, Zn, Pb, Mn, Cr, Co, and Cd for the present study were higher than most of the levels reported for other typical industrial and urban areas of the world. The airborne Ni concentrations were higher than the WHO and the U.S. Environmental Protection Agency's standards. Cluster and Principal Component Analyses of the data were used to identify the sources of the metals and establish their mutual correlations in the local atmosphere.     

Physiological measurements from native and transplanted mussel (Mytilus galloprovincialis) in the canals of Venice. Survival in air and condition index

The Venice Lagoon has been the focus of many environmental studies due to its heavy contaminant load derived from a variety of sources, including industrial activity, oil tanker traffic, and waste runoff from the mainland. In recent years, there has been increasing concern about water quality in the urban areas of Venice related to the discharge of untreated sewage directly into canals, adding to the pollutant load already existing in these areas. One way of gauging the impact of these chemicals is monitoring the local fauna. In the search for good indicators of water quality in the Venice urban area, two physiological indices for mussels-survival in air and condition index-have been evaluated. In 2002, a seasonal study was undertaken; mussels (Mytilus galloprovincialis) were collected in three sites located in the canals of the city and a clean reference site. At the same time, two transplantation experiments were performed, deploying farmed mussels for 1,2, 4, and 12 weeks in the historic centre of Venice and also at a reference site. Data from survival in air test and the condition index of native and transplanted mussels are reported. The results suggest an impact of the complex mixture of pollutants on mussel health status. Both native mussels and those transplanted to the urban area showed reduced survivability in air and decreased condition index values, indicating a less healthy status in animals from the canals of the city. Data are discussed in relation to pollutant bioaccumulation.     

城市街道空气污染物扩散模型综述

城市街道是城市居民的活动场所,其空气质量与居民健康密切相关.空气污染扩散模型是模拟和评估街道空气质量的重要方法,近年来广受关注,但模型应用存在问题,亟待解决.本文介绍了4种常用的空气污染物扩散模型:ENVI-met、FLUENT、MISKAM和OSPM.通过工作原理、运算流程、时空分辨率等的对比分析,明确了各模型的适用范围及其对街道峡谷内空气质量模拟能力的差异,阐述了各模型在时间尺度、物理建模、天气模拟、湍流模拟及光化学污染方面处理能力的局限性,提出了模型优化途径.通过综合分析4种模型的研究案例,总结了模型应用中存在的问题,提出未来研究可以通过激光雷达等新技术提高模型参数的获得精度,并强调综合模拟污染效应与热效应等对评估城市街道空气质量的重要性.     

城市扩张背景下城市群环境问题的区域性特征分析

作为区域空间组织的重要形式,城市群已经成为促进城市化快速发展的重要地区,同时也逐渐成为生态环境问题高度集中的地区。采用夜晚灯光影像在分析京津冀、长江三角洲和珠江三角洲城市群空间扩张进程的基础上,从空气质量、工业固体废物处置利用情况以及植被覆盖度3个方面对三大城市群环境问题的区域性特征及其敏感区进行分析。结果表明:三大城市群空间扩张进程不断加快,并逐渐形成城市用地连绵区,长江三角洲城市群城市用地连绵区范围最大,珠江三角洲城市群城市用地连绵区范围高于京津冀城市群;从城市群层面看,三大城市群在空气质量、工业固体废物综合利用率以及植被覆盖度演变方面已呈区域性特征,城市化水平与工业固体废物综合利用率呈正相关,与城市群植被覆盖度呈负相关;从城市层面来看,空间扩张较快的宁波市和北京市为长江三角洲和京津冀城市群在空气质量、工业固体废物综合利用率以及植被覆盖度方面的敏感区,中山市为珠江三角洲在工业固体废物综合利用率以及植被覆盖度方面的敏感区。环境问题的区域特征以及环境敏感区分析对环境治理工作具有一定的指导作用,对区域的可持续发展具有一定的现实意义。     

北京城区行道树国槐叶面尘分布及重金属污染特征

叶面尘分布范围广、累积时间长,能够较好地指示近地面大气颗粒物污染特征和累积状况。为揭示城市道路交通的大气颗粒物污染特征,研究了北京城区不同类型道路两侧行道树国槐(Sophora japonica)的叶面滞尘量,分析了叶面尘主要重金属的浓度和污染特征,采用相关分析和主成分分析法探讨了颗粒物重金属的主要来源。结果表明:国槐叶面滞尘量在快速路、主干路、次干路、支路上的比值为100∶84∶75∶75,受车流量影响较大。行道树国槐的平均叶面滞尘量为0.68 g/m2,庭院树国槐(远离交通)叶面滞尘量是0.51 g/m2,两者差异显著。行道树叶面尘重金属元素Cu、Zn、Pb在叶面尘中的浓度达到土壤背景值的6倍,空间分布较均匀,主要来自交通排放,庭院树叶面尘重金属污染也受到交通排放的重要影响。     

城市景观格局演变的生态环境效应研究进展

快速城市化过程剧烈影响着下垫面变化,直接带来了交通拥挤、资源短缺、环境污染、生态恶化等诸多问题,所有这些问题的出现均与景观格局演变密切相关,研究城市景观格局演变及其生态环境效应正在成为全社会关注的热点.系统总结了城市化过程对景观格局演变的影响,分析了城市景观格局演变的热环境效应、水环境效应、生态服务效应,以及城市生态用地与生态安全格局设计等方面的研究进展.指出了目前城市景观演变与生态环境效应研究中存在的问题与不足:(1)现有研究侧重于景观格局演变的量化分析和景观格局指数的计算,较少关注景观格局演变对生态环境及其区域生态安全的影响;(2)城市景观格局演变与热岛效应研究多局限于两者数理统计关系的分析,对于城市热环境形成的机理缺乏深入研究;(3)城市景观格局演变与大气环境效应方面更多研究关注绿地及其空间布局在吸收和降解大气污染物、固体颗粒物方面的作用,对城市景观格局演变的大气环境综合效应以及大气灰霾效应影响机理重视不够;(4)如何通过合理设置生态用地,有效提高城市生态服务功能和保障城市生态安全,目前仍缺乏深入而又系统的研究.下一步的研究中,需要综合多尺度的景观信息来揭示城市景观的演变机理和环境效应,构建基于城市空间扩展和生态服务效应评价的城市生态空间优化决策模型,探讨城市生态空间优化模式与安全格局.     

Pollutant dispersion in the urban environment

Flow and pollutant dispersion models are important elements for managing air quality in urban areas, to complement and, sometimes, even substitute monitoring. Developing fast and reliable parameterisations is necessary to improve the spatial and temporal resolutions of current mathematical prediction models. Recently there has been a growing interest in the so-called “neighbourhood scale” models, that offer relatively high spatial and temporal resolutions while keeping the needed computational resources at a minimum. This paper describes experimental and numerical simulations performed to explore the interaction of flow and pollutant dispersion with local building and street geometry. The methods developed may be useful as a way for cities to improve air quality management.     

Deposition of particulate matter of different size fractions on leaf surfaces and in waxes of urban forest species

Particulate matter (PM) is an air contaminant in urban and industrial areas that often exceeds limit values, creating serious problems due to its harmful effects on health. Planting trees and shrubs as air filters is a way to improve air quality in these areas. However,further knowledge on species effectiveness in air purification is essential This study compared four species of tree (Acer campestre L, Fraxinus excelsior L, Platanus x hispanica Mill. ex Muenchh. 'Acerifolia', Tilia cordata Mill.), three species of shrub (Forsythia x intermedia Zabel, Physocarpus opulifolius (L.) Maxim., Spiraea japonica L.), and one climber species (Hedera helix L) that are commonly cultivated along streets in Poland to capture fine, coarse and larger particles from air. Separate gravimetric analyses were performed to quantify PM deposited on surfaces and trapped in waxes. Significant differences were found between the plant species tested. The distribution of different particle size fractions differed between and within species and also between leaf surfaces and in waxes.     

Impacts of air pollution and climate change on forest ecosystems--emerging research needs

Outcomes from the 22nd meeting for Specialists in Air Pollution Effects on Forest Ecosystems "Forests under Anthropogenic Pressure--Effects of Air Pollution, Climate Change and Urban Development", September 10-16, 2006, Riverside, CA, are summarized. Tropospheric or ground-level ozone (O3) is still the phytotoxic air pollutant of major interest. Challenging issues are how to make O3 standards or critical levels more biologically based and at the same time practical for wide use; quantification of plant detoxification processes in flux modeling; inclusion of multiple environmental stresses in critical load determinations; new concept development for nitrogen saturation; interactions between air pollution, climate, and forest pests; effects of forest fire on air quality; the capacity of forests to sequester carbon under changing climatic conditions and coexposure to elevated levels of air pollutants; enhanced linkage between molecular biology, biochemistry, physiology, and morphological traits.     

城市绿化对空气质量的影响研究——以中国27个省会城市为例

城市间绿化程度与空气污染比较及相关差异分析是提出城市环境管理措施的重要前提。选择全国27个主要省会城市,基于网络街景照片测定绿色指数差异,对比空气主要质量指标[空气质量指数(AQI)、细颗粒物(PM_2.5)、可吸入颗粒物(PM₁₀)、二氧化硫(SO_2)、二氧化氮(NO_2)、臭氧(O_3)、一氧化碳(CO)]的基础上,探讨了二者相关关系,旨在为提升环境质量、改善绿化水平提供基础数据。结果表明:(1)济南市和重庆市的绿色指数最高,分别达到是11.70%和11.55%,呼和浩特市和拉萨市城市绿色指数最低,在4%～5%。(2)海口市的空气质量最好,AQI为39.66,郑州市和济南市的空气质量最差,AQI年均值分别为117.34和113.93。但是不同空气指标城市排序间差异较大,比如PM_2.5、PM₁₀、NO_2以及SO_2年平均最低的城市都是海口,拉萨市年平均CO含量最低(0.55 mg·m^-3),哈尔滨市年平均O_3含量最低(77.08μg·m^-3)。(3)相关关系分析发现,增加城市的绿色程度,伴随着空气质量的改善,如沈阳、南宁、合肥等城市;但对于某些城市,则存在明显的正相关,如兰州、昆明、贵阳等城市,这意味着城市越绿伴随着空气污染的加重。尽管大量研究已经表明,城市绿色植被能够起到滞尘降低污染的作用,目前我国主要城市的空气污染程度,仅依靠城市绿化改善已经远远不够,甚至某一些城市绿色植被存在阻碍空气流通的作用。上述研究结果为科学规划城市绿化、提升空气质量提供基础数据支撑。     

城市群空气污染综合评估范式与应用——以京津冀城市群PM2.5污染为例

城市群已成为中国城市发展的主要形式,城市化发展引发的一系列环境污染问题成为目前的研究重点之一,尤其是近年来明显的空气污染问题。由于传统的针对某一城市地区进行细致研究,难以解决在城市聚集的城市群下形成的区域性空气污染来源和影响机制等问题,使区域性空气污染造成的负面效应难以评估。通过构建综合评估模型范式,并运用空间分析,对京津冀168个区县2000年,2005年,2010年,2015年PM_2.5人口暴露风险、人类活动对PM_2.5的贡献、以及5种土地利用类型的"源汇"特征进行了实证研究。结果发现:(1)2000—2015年,京津冀城市群的人口暴露风险、空气污染分布、综合评估结果总体呈现北低南高的现象。(2)2000—2015年,各县域的人口暴露风险和空气污染的程度、范围呈上升趋势。不同的土地利用类型具有不同的源汇特征,且对污染的贡献不同。本研究通过综合评估模型范式对城市群或区域城市发展与空气质量的权衡关系模式开展量化解析,为城市的可持续发展提供了科学的范式和初步的实证示范。     

Noisy human neighbours affect where urban monkeys live

Urban areas and many natural habitats are being dominated by a new selection pressure: anthropogenic noise. The ongoing expansion of urban areas, roads and airports throughout the world makes the noise almost omnipresent. Urbanization and the increase of noise levels form a major threat to living conditions in and around cities. Insight into the behavioural strategies of urban survivors may explain the sensitivity of other species to urban selection pressures. Here, we show that urban black-tufted marmosets (Callithrix penicillata) living in noisy urban areas may select their home-range based primarily on ambient noise level. We have tested the hypothesis that the noise from vehicular traffic and visitors in an urban park in Brazil influences the use of home-range (space) by urban marmosets. Marmosets even avoided noisy areas with high food availability. In addition, they systematically preferred the quieter areas even with dynamic changes in the acoustic landscape of the park between weekdays and Sundays (no observations were made on Saturdays). These data provide evidence that the use of home-range by wild animals can be affected by a potential aversive stimulus such as noise pollution.     

A review of the mutagenicity and rodent carcinogenicity of ambient air

Although ambient air was first shown to be carcinogenic in 1947 and mutagenic in 1975, no overarching review of the subsequent literature has been produced. Recently, Claxton et al. [L.D. Claxton, P.P. Matthews, S.H. Warren, The genotoxicity of ambient outdoor air, a review: Salmonella mutagenicity, Mutat. Res./Rev. Mutat. Res. 567 (2004) 347-399] reviewed the literature on the mutagenicity of urban air in the Salmonella mutagenicity assay. Here, we review the literature on the mutagenicity of urban air in other test systems and review the carcinogenicity of urban air in experimental systems. Urban air was carcinogenic in most of the reports involving rodents. Studies ascribed carcinogenic activity primarily to PAHs, nitroarenes, and other aromatic compounds. Atmospheric conditions, along with the levels and types of pollutants, contributed to the variations in carcinogenic and mutagenic activity of air from different metropolitan areas. The majority of the mutagenesis literature was in the Salmonella assay (50%), with plant systems accounting for most of the rest (31%). The present data give little support to the use of plant systems to compare air mutagenicity among multiple sites or studies. Studies in mice have shown that particulate air pollution causes germ-cell mutations. Air sheds contain similar types and classes of mutagens; however, the levels of these compounds vary considerably among air sheds. Combustion emissions were associated with much of the mutagenicity and carcinogenicity of urban air. Most studies focused on the particulate fraction; thus, additional work is needed on the volatile and semi-volatile fractions, metals, and atmospheric transformation. Smaller particles have greater percentages of extractable organic material and are more mutagenic than larger particles. Although hundreds of genotoxic compounds have been identified in ambient air, only a few (<25) are routinely monitored, emphasizing the value of coupling bioassay with chemistry in the monitoring of air for carcinogenic and mutagenic activities and compounds.     

Predictability of Road Traffic and Congestion in Urban Areas

Mitigating traffic congestion on urban roads, with paramount importance in urban development and reduction of energy consumption and air pollution, depends on our ability to foresee road usage and traffic conditions pertaining to the collective behavior of drivers, raising a significant question: to what degree is road traffic predictable in urban areas? Here we rely on the precise records of daily vehicle mobility based on GPS positioning device installed in taxis to uncover the potential daily predictability of urban traffic patterns. Using the mapping from the degree of congestion on roads into a time series of symbols and measuring its entropy, we find a relatively high daily predictability of traffic conditions despite the absence of any priori knowledge of drivers'' origins and destinations and quite different travel patterns between weekdays and weekends. Moreover, we find a counterintuitive dependence of the predictability on travel speed: the road segment associated with intermediate average travel speed is most difficult to be predicted. We also explore the possibility of recovering the traffic condition of an inaccessible segment from its adjacent segments with respect to limited observability. The highly predictable traffic patterns in spite of the heterogeneity of drivers'' behaviors and the variability of their origins and destinations enables development of accurate predictive models for eventually devising practical strategies to mitigate urban road congestion.     

Evaluation of Anticipated Performance Index,biochemical, and physiological parameters of Cupressus arizonica Greene and Juniperus excelsa Bieb for greenbelt development and biomonitoring of air pollution

Abstract

Plants can be used naturally to mitigate environmental pollution, such as air pollution; however, it is important to evaluate plant susceptibility to air pollution when considering green space creation in urban areas. In this study, we investigated the biochemical and physiological parameters, including pH, and ascorbic acid, relative water, total chlorophyl, proline, soluble sugar, protein, and free amino acid contents of two gymnosperm tree species, Cupressus arizonica Greene and Juniperus excelsa Bieb. Using these data, we computed the Air Pollution Tolerance Index (APTI) and Anticipated Performance Index (API) of the trees at five sites in Isfahan, Iran, to determine their applicability for greenbelt establishment. Our results indicated that these evergreen species are good indicators of air pollution and can be used as an early warning tool for air pollution level that is harmful to human health.     

Mismatches between ecosystem services supply and demand in urban areas: A quantitative assessment in five European cities

Assessing mismatches between ecosystem service (ES) supply and demand can provide relevant insights for enhancing human well-being in urban areas. This paper provides a novel methodological approach to assess regulating ES mismatches on the basis of environmental quality standards and policy goals. Environmental quality standards (EQS) indicate the relationship between environmental quality and human well-being. Thus, they can be used as a common minimum threshold value to determine whether the difference between ES supply and demand is problematic for human well-being. The methodological approach includes three main steps: (1) selection of EQS, (2) definition and quantification of ES supply and demand indicators, and (3) identification and assessment of ES mismatches on the basis of EQS considering certain additional criteria. While ES supply indicators estimate the flow of an ES actually used or delivered, ES demand indicators express the amount of regulation needed in relation to the standard. The approach is applied to a case study consisting of five European cities: Barcelona, Berlin, Stockholm, Rotterdam and Salzburg, considering three regulating ES which are relevant in urban areas: air purification, global climate regulation and urban temperature regulation. The results show that levels of ES supply and demand are highly heterogeneous across the five studied cities and across the EQS considered. The assessment shows that ES supply contributes very moderately in relation to the compliance with the EQS in most part of the identified mismatches. Therefore, this research suggests that regulating ES supplied by urban green infrastructure are expected to play only a minor or complementary role to other urban policies intended to abate air pollution and greenhouse gas emissions at the city scale. The approach has revealed to be appropriate for the regulating ES air purification and global climate regulation, for which well-established standards or targets are available at the city level. Yet, its applicability to the ES urban temperature regulation has proved more problematic due to scale and user dependent constraints.