Spatial and temporal variation of particle number concentration in Augsburg, Germany

Epidemiological studies on health effects of outdoor air pollution are largely based on a single monitoring site to estimate the exposure of people living in urban areas. For such an approach two aspects are important: the temporal correlation and the spatial variation of the absolute levels of concentrations measured at different sites in an urban area. Whereas many studies have shown small spatial variability of fine particles in urban areas, little is known on how well a single monitoring station could represent the temporal and spatial variation of ultrafine particles across urban areas. In our study we investigated the temporal and spatial variation of particle number concentration (PNC) at four background sites in Augsburg, Germany. Two of them were influenced by traffic, one was placed in the outskirts of the city. The average PNC levels at two urban background sites with traffic impact were 16,943 cm(-3) and 20,702 cm(-3), respectively, compared to 11,656 cm(-3) at the urban background site without traffic impact (ratio 1.5 to 1.8). The Spearman correlation coefficients between the monitoring sites were high (r>0.80). The pronounced differences in absolute PNC levels suggest that the use of a single monitoring station in long-term epidemiological studies must be insufficient to attribute accurate exposure levels of PNC to all study subjects. On the other hand, the high temporal correlations of PNC across the city area of Augsburg implicate that in epidemiological time-series studies the use of one single ambient monitoring site is an adequate approach for characterizing exposure to ultrafine particles.     

Spatial variation in nitrogen dioxide in three European areas

In order to estimate the spatial variation within well-defined study areas, nitrogen dioxide was measured with diffusion samplers (Palmes tube) in 40-42 sites each in Germany (Munich), the Netherlands and Sweden (Stockholm County). Each site was measured over four 2-week periods during 1 year (spring 1999 to summer 2000). In each country, one reference site was measured during all periods and the results were used to adjust for seasonal variability, to improve the estimates of the annual average. Comparisons between the chemiluminescence method (European reference method) and Palmes tube measurement indicated a good agreement in Germany (with a ratio of 1.0 for Palmes tube/chemiluminescence) but underestimation for Palmes tube measurement in the Netherlands and Sweden (0.8 for both countries). The r2 values were between 0.86 and 0.90 for all three countries. The annual average values for NO2 for different sampling sites were between 15.9 and 50.6 (mean 28.8 microg/m3) in Germany, between 12.1 and 50.8 (mean 28.9 microg/m3) in the Netherlands and between 6.1 and 44.7 (mean 18.5 microg/m3) in Sweden. Comparing spatial variation between similar sites in the three countries, we did not find any significant differences between annual average levels for urban traffic sites. In Sweden, annual average levels in urban background and suburban backgrounds sites were about 8 microg/m3 lower than comparable sites in Germany and the Netherlands. Comparing site types within each country only urban traffic sites and suburban background sites differed in Germany. In the Netherlands and Sweden, the urban traffic sites differed from all other sites and in Sweden also the urban background sites differed from the other background sites. The observed contribution from local traffic was similar in the Netherlands and Sweden (10 and 8 microg/m3, corresponding to 26-27% of the NO2 concentration found in the urban traffic sites). In Germany, the contribution from local traffic was only 3 microg/m3, corresponding to 9% of the NO2 concentration found in the urban traffic sites. The spatial variation was substantially larger for NO2 than the variation for PM2.5 and similar to PM2.5 absorbance, measured in the same locations.     

Spatial heterogeneity of personal exposure to airborne metals in French urban areas

The spatial distribution of urban population exposures to ambient air particles was investigated as part of the Genotox'ER study conducted in four metropolitan areas (Grenoble, Paris, Rouen and Strasbourg) in France. In each city, 60 to 90 non-smoking adult and children volunteers were selected. Subjects lived in three different urban sectors: one highly exposed to traffic emissions, one influenced by local industrial sources, and a background urban environment. The Harvard Chempass multi-pollutant personal sampler was used to sample PM10 and PM2.5 particles during 48 h during two different seasons ('hot' and 'cold'). The elemental composition of the filters was analysed by Particle-Induced X-ray Emission (PIXE). Sixteen elements were found to be over the method detection limits: Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Pb. The relative concentrations of elements of crustal origin (Si, Al, Ca) were higher in the coarse fraction of PM10 filters, while elements associated with combustion processes (traffic emissions or industrial combustion) presented higher relative concentrations in the PM2.5 fraction (S, Ni, V, Pb). Spatial heterogeneity of elemental exposures by urban sector is substantial for some metals of health concern, with 20% to 90% greater exposure values, on average, in the traffic proximity or industrial sectors, compared to the background sector, for Fe, Zn, Cu, V and Cr. This spatial heterogeneity should not be overlooked in epidemiological or risk assessment studies.     

Can one use ambient air concentration data to estimate personal and population exposures to particles? An approach within the European EXPOLIS study

The objective of this paper is to devise a way to facilitate the use of fixed air monitors data in order to assess population exposure. A weighting scheme that uses the data from different monitoring sites and takes into account the time-activity patterns of the study population is proposed. PM2.5 personal monitoring data were obtained within the European EXPOLIS study, in Grenoble, France (40 adult non-smoking volunteers, winter 1997). Volunteers carried PM2.5 personal monitors during 48 h and filled in time-activity diaries. Workplaces and places of residence were classified into two categories using a Geographic Information System (GIS): some volunteers' life environments are seen as best represented by PM10 ambient air monitors located in urban background sites; others by monitors situated close to high traffic density sites (proximity sites). Measurements from the Grenoble fixed monitoring network using a TEOM PM10 sampler were available across the same period for these two types of sites (PM10block and PM10prox). These data were used to compute a translator parameter deltai that forces the measured PM2.5 personal exposures (PM2.5persoi) to equate the average PM10 urban ambient air concentrations ([PM10back + PM10prox]/2) measured the same days. Average deltai was 4.2 microg/m3 (CI95%[-3.4; 11.9]), with true average PM2.5 personal exposure being 36.2 microg/m3 (28.2; 44.1). PM10 ambient levels at the proximity site and at the background site were respectively PM10prox = 43.8 microg/m3 (37.1; 50.6) and PM10back = 37.0 microg/m3 (31.8; 42.3). In order to assess the consistency of this approach, six scenarios of 'proximity' and 'background' environments were accommodated, according to traffic intensity and road distance. Deltai was estimated for the entire EXPOLIS population and for subgroups, using terciles based on the percentage of time spent in proximity by each subject. Other similar studies need to be conducted in different urban settings, and with other pollutants, in order to assess the generalizability of this simple approach to estimate population exposures from air quality surveillance data.     

多尺度时空PM 2.5 分布特征、影响要素、方法演进的综述及 城市规划展望

精细化治理空气污染正成为改善城 市品质的重点方向,对城市多尺度PM 2.5 时 空格局与影响要素的梳理有助于从研究和 实践层面加强规划设计对公共健康的积极 影响。本文从全国、城市、社区层面较全面 地阐述了不同时空尺度下PM 2.5 的时空格局 特征,总结了土地格局、交通网络、建成环 境、蓝绿空间等不同影响因素与城市空气中 PM 2.5 的相互关联耦合作用。同时,本文分析了不同的研究方法在精细化污染治理中的应用,指出人工智能方法在高精度尺度下的时空复 杂特征融合分析中的优势。最后,结合现有的城市PM 2.5 治理经验,对精细化目标下分时分区 的城市规划提出展望：基于提升精确度的新技术方法,优化城市空间结构,构建精细化分时 分区管理策略。     

PM2.5 chemical composition in Hong Kong: urban and regional variations

Chemically speciated PM2.5 measurements were made at roadside, urban, and rural background sites in Hong Kong for 1 year during 2000/2001 to determine the spatial and temporal variations of PM2.5 mass and chemical composition in this highly populated region. Annual average PM2.5 concentrations at the urban and rural sites were 34.1 and 23.7 microg m(-3), respectively, approximately 50-100% higher than the United States' annual average National Ambient Air Quality Standard (NAAQS) of 15 microg m(-3). Daily PM2.5 concentrations exceeded the U.S. 24-h NAAQS of 65 microg m(-3) on 19 days, reaching 131+/-8 microg m(-3) at the roadside site on 02/28/2001. Carbonaceous aerosol is the largest contributor to PM2.5 mass (explaining 52-75% of PM2.5 mass at the two urban sites and 32% at the background site), followed by ammonium sulfate (ranging from 23% to 37% at the two urban sites and 51% at the background site). Ammonium sulfate and crustal concentrations showed more uniform spatial distributions, while the largest urban-rural contrasts found in carbonaceous aerosol (likely due to emissions from on-road gasoline and diesel vehicles). Marine influences accounted for 7% of the mass at the background site (more than twice as much as at the two urban sites). Ternary diagrams are utilized to illustrate the different spatial patterns.     

Spatial analysis and land use regression of VOCs and NO2 from school-based urban air monitoring in Detroit/Dearborn, USA

Passive ambient air sampling for nitrogen dioxide (NO₂) and volatile organic compounds (VOCs) was conducted at 25 school and two compliance sites in Detroit and Dearborn, Michigan, USA during the summer of 2005. Geographic Information System (GIS) data were calculated at each of 116 schools. The 25 selected schools were monitored to assess and model intra-urban gradients of air pollutants to evaluate impact of traffic and urban emissions on pollutant levels. Schools were chosen to be statistically representative of urban land use variables such as distance to major roadways, traffic intensity around the schools, distance to nearest point sources, population density, and distance to nearest border crossing. Two approaches were used to investigate spatial variability. First, Kruskal-Wallis analyses and pairwise comparisons on data from the schools examined coarse spatial differences based on city section and distance from heavily trafficked roads. Secondly, spatial variation on a finer scale and as a response to multiple factors was evaluated through land use regression (LUR) models via multiple linear regression. For weeklong exposures, VOCs did not exhibit spatial variability by city section or distance from major roads; NO₂ was significantly elevated in a section dominated by traffic and industrial influence versus a residential section. Somewhat in contrast to coarse spatial analyses, LUR results revealed spatial gradients in NO₂ and selected VOCs across the area. The process used to select spatially representative sites for air sampling and the results of coarse and fine spatial variability of air pollutants provide insights that may guide future air quality studies in assessing intra-urban gradients.     

Intraurban variations of PM10 air pollution in Christchurch, New Zealand: implications for epidemiological studies

Epidemiological studies relating air pollution to health effects often utilise one or few central monitoring sites for estimating wider population exposures to outdoor particulate air pollution. These studies often assume that highly correlated particulate concentrations between intraurban sites equate to a uniform concentration field. Several recent studies have questioned the universal validity of this assumption, noting that in some cities, the uniformity assumption may lead to exposure misclassification in health studies. Few studies have compared central fixed site concentrations to intraurban population background sites using actual monitored data in cities with higher levels of pollution. This research examines daily concentration variations in particulate matter less than 10 microm in diameter (PM10) at the neighbourhood scale over two winter months in Christchurch, New Zealand, a city with high winter pollution concentrations. Daily concentrations of PM10 data were collected for two winter months at ten background monitoring sites within 9.3 km of the central fixed monitoring site typically used for estimating exposure in epidemiological studies. Results indicate that while the correlation between PM10 concentrations measured at the central monitoring site and most background sites is strong (r>0.76), absolute daily concentration differences between the central monitoring site and population background sites were substantial (mean 90th percentile absolute difference=17.6 microg m-3). In Christchurch, a central monitoring site does not therefore appear to accurately depict wider area population exposures to PM10. Local intraurban variations in particulates should be well understood before applying central monitoring site concentrations as proxies for population exposure in epidemiological studies.     

基于ENVI-met模拟的不同用地类型居住小区绿地布局对PM2.5的影响

居住区绿地作为城市绿地的主要组成肌理,对改善空气质量起着重要作用.首次将ENVI-met用于居住小区绿地布局与PM2.5的模拟,选取武汉市典型的一类、二类、三类小区,定量分析不同草地、乔木布局对PM2.5的影响.研究表明,集中型的草地布局、四周型的乔木布局能更有效降低小区PM2.5浓度;分散型的草地布局、集中型的乔木布...     

Chemical composition of PM2.5 and PM10 in Mexico City during winter 1997

PM2.5 and PM10 were measured over 24-h intervals at six core sites and at 25 satellite sites in and around Mexico City from 23 February to 22 March 1997. In addition, four 6-h samples were taken each day at three of the core sites. Sampling locations were selected to represent regional, central city, commercial, residential, and industrial portions of the city. Mass and light transmission concentrations were determined on all of the samples, while elements, ions and carbon were measured on approximately two-thirds of the samples. PM10 concentrations were highly variable, with almost three-fold differences between the highest and lowest concentrations. Fugitive dust was the major cause of PM10 differences, although carbon concentrations were also highly variable among the sampling sites. Approximately 50% of PM10 was in the PM2.5 fraction. The majority of PM mass was comprised of carbon, sulfate, nitrate, ammonium and crustal components, but in different proportions on different days and at different sites. The largest fine-particle components were carbonaceous aerosols, constituting approximately 50% of PM2.5 mass, followed by approximately 30% secondary inorganic aerosols and approximately 15% geological material. Geological material is the largest component of PM10, constituting approximately 50% of PM10 mass, followed by approximately 32% carbonaceous aerosols and approximately 17% secondary inorganic aerosols. Sulfate concentrations were twice as high as nitrate concentrations. Sulfate and nitrate were present as ammonium sulfate and ammonium nitrate. Approximately two-thirds of the ammonium sulfate measured in urban areas appears to have been transported from regions outside of the study domain, rather than formed from emissions in the urban area. Diurnal variations are apparent, with two-fold increases in concentration from night-time to daytime. Morning samples had the highest PM2.5 and PM10 mass, secondary inorganic aerosols and carbon concentrations, probably due to a shallow surface inversion and rush-hour traffic.     

Comparative PM10-PM2.5 source contribution study at rural, urban and industrial sites during PM episodes in Eastern Spain

In this study a set of 340 PM10 and PM2.5 samples collected throughout 16 months at rural, an urban kerbside and an industrial background site (affected by the emissions from the ceramic manufacture and other activities) were interpreted. On the regional scale, the main PM10 sources were mineral dust (mainly Al2O3, Fe, Ti, Sr, CaCO3, Mg, Mn and K), emissions derived from power generation (SO4=, V, Zn and Ni), vehicle exhausts (organic and elemental carbon, NO3- and trace elements) and marine aerosol (Na, Cl and Mg). The latter was not identified in PM2.5. At the industrial site, additional PM10 sources were identified (tile covering in the ceramic production, petrochemical emissions and bio-mass burning from a large orange tree cultivation area). The contribution of each PM source to PM10 and PM2.5 levels experiences significant variations depending on the type of PM episode (Local-urban mainly in autumn-winter, regional mainly in summer, African or Atlantic episode), which are discussed in this study. The results show that it would be very difficult to meet the EU limit values for PM10 established for 2010. The annual mean PM levels are 22.0 microg PM10/m3 at the rural and 49.5 microg PM10/m3 and 33.9 microg PM2.5/m3 at the urban site. The natural contribution in this region, estimated at 6 microg/m3 of natural mineral dust (resulting from the African events and natural resuspension) and 2 microg/m3 of marine aerosol, accounts for 40% of the 2010 EU annual limit value (20 microg PM10/m3). Mineral dust concentrations at the urban and industrial sites are higher than those at the rural site because of the urban road dust and the ceramic-production contributions, respectively. At the urban site, the vehicle exhaust contribution (17 microg/m3) alone is very close to the 2010 EU PM10 limit value. At the rural site, the African dust is the main contributor to PM10 levels during the highest daily mean PM10 events (100th-97th percentile range). At the urban site, the vehicle exhaust product is the main contributor to PM10 and PM2.5 levels during the highest daily mean PM events (100th-85th percentile range). Mineral dust concentrations during African dust events accounts for 20-30 microg/m3 in PM10 and 10-15 microg/m3 in PM2.5. During non-African dust events, mineral dust derived from anthropogenic activities (e.g. urban road dust) is also a significant contributor to PM10, but not to PM2.5.     

Characterizing air pollution in two low-income neighborhoods in Accra, Ghana

Sub-Saharan Africa has the highest rate of urban population growth in the world, with a large number of urban residents living in low-income "slum" neighborhoods. We conducted a study for an initial assessment of the levels and spatial and/or temporal patterns of multiple pollutants in the ambient air in two low-income neighborhoods in Accra, Ghana. Over a 3-week period we measured (i) 24-hour integrated PM(10) and PM(2.5) mass at four roof-top fixed sites, also used for particle speciation; (ii) continuous PM(10) and PM(2.5) at one fixed site; and (iii) 96-hour integrated concentration of sulfur dioxide (SO(2)) and nitrogen dioxide (NO(2)) at 30 fixed sites. We also conducted seven consecutive days of mobile monitoring of PM(10) and PM(2.5) mass and submicron particle count. PM(10) ranged from 57.9 to 93.6 microg/m(3) at the four sites, with a weighted average of 71.8 microg/m(3) and PM(2.5) from 22.3 to 40.2 microg/m(3), with an average of 27.4 microg/m(3). PM(2.5)/PM(10) ratio at the four fixed sites ranged from 0.33 to 0.43. Elemental carbon (EC) was 10-11% of PM(2.5) mass at all four measurement sites; organic matter (OM) formed slightly less than 50% of PM(2.5) mass. Cl, K, and S had the largest elemental contributions to PM(2.5) mass, and Cl, Si, Ca, Fe, and Al to coarse particles. SO(2) and NO(2) concentrations were almost universally lower than the US-EPA National Ambient Air Quality Standards (NAAQS), with virtually no variation across sites. There is evidence for the contributions from biomass and traffic sources, and from geological and marine non-combustion sources to particle pollution. The implications of the results for future urban air pollution monitoring and measurement in developing countries are discussed.     

Particulate matter exposure along designated bicycle routes in Vancouver, British Columbia

An instrumented bicycle was used to elucidate particulate matter exposures along bicycle routes passing through a variety of land uses over 14 days during summer and fall in a mid-latitude traffic dominated urban setting. Overall, exposures were low or comparable to those found in studies elsewhere (mean PM(2.5) and PM(10) concentrations over each daily bicycle traverse varied between 7-34 microg m(-3) and 26-77 microg m(-3) respectively). Meteorological factors were responsible for significant day-to-day variability with PM(2.5) positively correlated with air temperature, PM(10) negatively correlated with precipitation, and ultrafine particles negatively correlated with both air temperature and wind speed. On individual days, land use and proximity to traffic were factors significantly affecting exposure along designated bicycle routes. While concentrations of PM(2.5) were found to be relatively spatially uniform over the length of the study route, PM(10) showed a more heterogeneous spatial distribution. Specifically, construction sites and areas susceptible to the suspension of road dust have higher concentrations of coarse particles. Ultrafine particles were also heterogeneously distributed in space, with areas with heavy traffic volumes having the highest concentrations. Observations show qualitative agreement in terms of spatial patterns with a land-use regression (LUR) model for annual PM(2.5) concentrations.     

城市绿地空间形态对PM2.5的消减影响——以武汉市为例

缓解大气颗粒物污染、营造清洁健康的城市环境是中国绝大部分城市须解决的问题之一。城市绿地能有效缓解PM_(2.5),然而当前对绿地空间形态的研究不足,导致能在规划设计中直接应用的成果不多。基于武汉市9个城市绿地空间形态要素量化差异与实地测量的PM_(2.5)浓度大小,探索二者深层的量化关系规律。结果显示:1)PM_(2.5)消减量随绿地规模的增加呈增长趋势,当规模大于5～10 hm~2消减量减缓;2)绿地面积、周长及形状指数与PM_(2.5)的消减量显著正相关,分维指数与近圆形形状指数相关性不显著;3)PM_(2.5)的消减效率随绿地规模的增加急剧下降,当绿地规模超过5～10 hm~2,消减效率变化不明显。通过量化分析,揭示对PM_(2.5)消减具有显著影响的城市绿地空间形态指标,提出适当的规模、不规则或复杂的绿地形态及分散式的布局等绿地优化策略。     

Intense winter atmospheric pollution episodes affecting the Western Mediterranean

The geographic location of the Western Mediterranean Basin and its peculiar topography, the climatic conditions and the intense anthropogenic and natural emissions of atmospheric pollutants are key factors necessary to interpret the atmospheric aerosol phenomenology over this area. During the cold season it is common to have severe atmospheric particulate matter (PM) pollution episodes (of an anthropogenic origin) affecting this region, not only in the urban and industrial areas but also in the regional and rural sites. During these episodes, the midday hourly PM₁ levels at regional background sites are in many cases higher than those at urban areas. Around 10% of the days under winter anticyclonic conditions registered similar PM₁ levels at the regional background than at the urban area and, sporadically the daily PM₁ levels at the regional background sites may exceed those at urban sites. Furthermore, the very high hourly PM₁ levels measured at regional background sites during these episodes are not regularly attained in the closest urban areas, which leads to the hypothesis that an important formation of secondary aerosols occurs during the transport of the polluted air masses towards the elevated rural sites.The interpretation of the variability of PM levels and composition (2002-2008) at one urban site (Barcelona) and at one regional background site (Montseny) allows us to illustrate the phenomenology of these scenarios, to quantify the mean annual contributions to the PM levels and to identify their main tracers. Ammonium nitrate appears to be the most abundant compound during these scenarios, although organic species and trace metals also increase markedly. Owing to the intensity, composition and recurrence of these atmospheric pollution episodes, important health, climatic and ecological implications may be derived.     

Source apportionment of population representative samples of PM(2.5) in three European cities using structural equation modelling

Apportionment of urban particulate matter (PM) to sources is central for air quality management and efficient reduction of the substantial public health risks associated with fine particles (PM(2.5)). Traffic is an important source combustion particles, but also a significant source of resuspended particles that chemically resemble Earth's crust and that are not affected by development of cleaner motor technologies. A substantial fraction of urban ambient PM originates from long-range transport outside the immediate urban environment including secondary particles formed from gaseous emissions of mainly sulphur, nitrogen oxides and ammonia. Most source apportionment studies are based on small number of fixed monitoring sites and capture well population exposures to regional and long-range transported particles. However, concentrations from local sources are very unevenly distributed and the results from such studies are therefore poorly representative of the actual exposures. The current study uses PM(2.5) data observed at population based random sampled residential locations in Athens, Basle and Helsinki with 17 elemental constituents, selected VOCs (xylenes, trimethylbenzenes, nonane and benzene) and light absorbance (black smoke). The major sources identified across the three cities included crustal, salt, long-range transported inorganic and traffic sources. Traffic was associated separately with source categories with crustal (especially Athens and Helsinki) and long-range transported chemical composition (all cities). Remarkably high fractions of the variability of elemental (R(2)>0.6 except for Ca in Basle 0.38) and chemical concentrations (R(2)>0.5 except benzene in Basle 0.22 and nonane in Athens 0.39) are explained by the source factors of an SEM model. The RAINS model that is currently used as the main tool in developing European air quality management policies seems to capture the local urban fraction (the city delta term) quite well, but underestimates crustal particle levels in the three cities of the current study. Utilizing structural equation modelling parallel with traditional principal component analysis (PCA) provides an objective method to determine the number of factors to be retained in a model and allows for formal hypotheses testing.     

Particle size distribution and composition in a mechanically ventilated school building during air pollution episodes

Particle count-based size distribution and PM(2.5) mass were monitored inside and outside an elementary school in Salt Lake City (UT, USA) during the winter atmospheric inversion season. The site is influenced by urban traffic and the airshed is subject to periods of high PM(2.5) concentration that is mainly submicron ammonium and nitrate. The school building has mechanical ventilation with filtration and variable-volume makeup air. Comparison of the indoor and outdoor particle size distribution on the five cleanest and five most polluted school days during the study showed that the ambient submicron particulate matter (PM) penetrated the building, but indoor concentrations were about one-eighth of outdoor levels. The indoor:outdoor PM(2.5) mass ratio averaged 0.12 and particle number ratio for sizes smaller than 1 microm averaged 0.13. The indoor submicron particle count and indoor PM(2.5) mass increased slightly during pollution episodes but remained well below outdoor levels. When the building was occupied the indoor coarse particle count was much higher than ambient levels. These results contribute to understanding the relationship between ambient monitoring station data and the actual human exposure inside institutional buildings. The study confirms that staying inside a mechanically ventilated building reduces exposure to outdoor submicron particles. PRACTICAL IMPLICATIONS: This study supports the premise that remaining inside buildings during particulate matter (PM) pollution episodes reduces exposure to submicron PM. New data on a mechanically ventilated institutional building supplements similar studies made in residences.     

城市街区形态对PM10、PM2.5的影响 研究——以武汉为例

构成城市肌理的普遍街区的空间形态与颗粒物浓度存在显著差异。基于武汉市18个空气质量监测点的PM_(10)、PM_(2.5)数据与二维、三维街区形态指标,揭示不同街区形态与PM_(10)、PM_(2.5)之间的深层关系规律,以期为城市规划管控提供参考。双变量相关分析与一元回归分析揭示了街区形态与PM_(10)、PM_(2.5)的相关性及其影响规律,多元线性回归分析揭示不同街区形态对PM_(10)、PM_(2.5)变化的贡献度。结果表明,街区之间的平均PM_(10)、PM_(2.5)浓度分别在城市平均水平55%～106%、59%～117%之间浮动,绿化覆盖率、道路面积率和相对高程对PM_(10)、PM_(2.5)具有显著影响,相对高程与绿化覆盖率对PM_(10)变化的贡献度达83.0%,绿化覆盖率对PM_(2.5)变化的贡献度达72.5%,道路面积率对PM_(10)、PM_(2.5)变化的贡献度分别为17.0%、27.5%。     

Seasonal variations and mass closure analysis of particulate matter in Hong Kong

The chemical characteristics of ambient particulate matters in urban and rural areas of Hong Kong were determined in this study. A monitoring program starting from November 2000 to February 2001 (winter) and June 2001 to August 2001 (summer) for PM10 and PM2.5 was performed at three monitoring stations in Hong Kong. Twenty-four-hour PM10 and PM2.5 samples were collected once every 6 days at two urban sites, PolyU and KT, and every 12 days at a background site, HT, with Hi-Vol samplers. High concentrations of OC, EC (except in PolyU), water-soluble ions and elements were observed in winter among the three sampling sites for PM10 and PM2.5 fractions. Seasonal variations were significant in background HT. Dilution effect due to the increase in mixing depth and precipitation in summer reduced the concentrations of particulate matters. Long-range transport could contribute to the higher concentrations of particulate matter in the winter. Chemical mass closure calculations were performed for PM10 and PM2.5 observed. Mass closure improved when separate factors (1.4 and 1.9 respectively) were used to convert water-soluble organic carbon (WSOC) and water-insoluble organic carbon (WINSOC) into corresponding organic masses. The urban sites showed high percentages of water-soluble ions in winter and high percentages of carbonaceous species in summer. Better results were obtained for the chemical mass closure analysis in winter than in summer. High temperature and solar radiation in summer increased the rate of the complex photochemical reaction in the atmosphere. Therefore the chemical mass closure analysis would underestimate the volatized species and secondary aerosols during summer.     

Modeling for point-non-point source effluent trading: perspective of non-point sources regulation in China

The high levels of fine particulate matter in Mexico City are of concern since they may induce severe public health effects as well as the attenuation of visible light. Sequential filter samplers were used at six different sites from 23 February to 22 March 1997. The sampling campaign was carried out as part of the project 'Investigación sobre Materia Particulada y Deterioro Atmosferico-Aerosol and Visibility Evaluation Research'. This research was a cooperative project sponsored by PEMEX and by the US Department of Energy. Sampling sites represent the different land uses along the city, the northwest station, Tlalnepantla, is located in a mixed medium income residential and industrial area. The northeast station, Xalostoc, is located in a highly industrialized area, Netzahualcoyotl is located in a mixed land use area, mainly commercial and residential. Station La Merced is located in the commercial and administrative district downtown. The southwest station is located in the Pedregal de San Angel, in a high-income neighborhood, and the southeast station located in Cerro de la Estrella is a mixed medium income residential and commercial area. Samples were collected four times a day in Cerro de la Estrella (CES), La Merced (MER) and Xalostoc (XAL) with sampling periods of 6 h. In Pedregal (PED), Tlalnepantla (TLA) and Netzahualcoyot1 (NEZ) sampling periods were every 24 h. In this paper the basic statistics of PM2.5 and PM10 mass concentrations are presented. The average results showed that 49, 61, 46, 57, 51 and 44% of the PM10 consisted of PM2.5 for CES, MER, XAL, PED, TLA and NEZ, respectively. The 24-h average highest concentrations of PM25 and PM10 were registered at NEZ (184 and 267 microg/m3) and the lowest at PED (22 and 39 microg/m3). The highest PM10 correlations were between XAL-CES (0.79), PED-TLA (0.80). In contrast, the highest PM2.5 correlations were between CES-PED (0.74), MER-CES (0.73) and TLA-PED (0.72), showing a lower correlation than the PM10 one. The results of the PM10 from 12.00 to 18.00 h at CES and MER presented the highest variability and also the highest median concentrations, meanwhile XAL showed them from 06.00 to 12.00 h. The highest variability and median concentrations of PM2.5 were from 06.00 to 12.00 h for the three stations.