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.     

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.     

Concentration of atmospheric particulates during a dust storm period in central Taiwan, Taichung

In this study we monitored concentrations of particles in central Taiwan using PS-1 (GPS1 PUF Sampler) and Model 310 Universal Air Sampler (UAS) from 02/23/2001 to 03/12/2001 at two sampling sites. During this period, an Asian dust storm moved across central Taiwan from 3/3 to 3/6. The total ambient air particle concentrations during the dust storm period were than compared with previous data from this region. In general, the average total suspended particulate (TSP) concentration order was during dust storm period > after dust storm period > non-dust storm period at both HKITT (traffic) and THUC (rural) sampling sites. The ratio of PM2.5/PM10 was 60% before and after the dust storm period. However, this ratio was decreased to less than 50% during the dust storm. This demonstrates that the coarse particulate concentrations (PM2.5-10) increased during the dust storm period. In contrast the increase of ambient air particles concentrations after the Taiwan Chi-Chi Earthquake were mainly due to fine particles (PM2.5). And, the increased of ambient air particles concentrations after dust storm period were mainly coarse particle (PM2.5-10) concentrations in central Taiwan.     

The PM2.5 and PM10 particles in urban areas of Taiwan

This study conducted an atmospheric aerosol sampling to measure the PM10 (particles < 10 microns in aerodynamic diameter) and PM2.5 (particles < 2.5 microns in aerodynamic diameter) mass concentrations from October 1996 to June 1997 in northern (Taipei), central (Taichung) and southern (Kaohsiung), the three largest cities of Taiwan. Seventy-eight samples were obtained to measure the mass concentrations of PM10 and PM2.5 from nine sampling sites. According to those results, the PM10 mass concentrations in Taipei, Taichung and Kaohsiung were 42.19, 60.99 and 77.10 micrograms/m3, respectively. The corresponding PM2.5 mass concentrations were 23.09, 39.97 and 48.47 micrograms/m3, respectively. The PM2.5 fraction accounted for 61-67% of the PM10 mass in central and southern Taiwan, but was lower (54-59%) in northern Taiwan. Some samples in which the PM2.5 fraction was overwhelmingly dominant could reach as high as 80-95% of the PM10 mass. In addition, the PM2.5, PM10 levels and PM2.5/PM10-2.5 (particles with aerodynamic diameters ranging from 2.5 to 10 microns) ratios in metropolitan Taiwan significantly fluctuated from site-to-site and over time. Moreover, ambient daily PM2.5 and PM10-2.5 mass concentrations did not correlate well with each other at most of the sampling sites, indicated that they originated from different kinds of sources and emitted variedly over time.     

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。     

A combined analysis of backward trajectories and aerosol chemistry to characterise long-range transport episodes of particulate matter: the Madrid air basin, a case study

This study has investigated the influence of synoptic weather patterns and long-range transport episodes on the concentration levels of airborne particulate matter (TSP, PM10 and PM2.5) and some major ions (SO(4)(2-), NO(3)(-) and NH(4)(+)) at a background rural station in central Spain. Air mass back-trajectories arriving at the site in 1999-2005 have been analysed by statistical methods. First, cluster analysis was used to group trajectories into 8 clusters depending on their direction and speed. Meteorological scenarios associated to each cluster have been obtained and interpreted. Then, the incidence of different air mass transport patterns on particle concentrations and composition recorded at this station was evaluated. This evaluation included PM10 and PM2.5 concentrations and chemical composition data, obtained at three representative sites of the Madrid air basin during sampling campaigns carried out in the course of the 1999-2005 period. Finally, a residence time analysis of trajectories was also performed to detect remote sources and transport pathways. Significantly elevated concentrations of TSP and PM10 were observed for Northern African flows as a consequence of the transport of mineral dust. Significant inter-cluster differences were also observed for PM2.5 and secondary inorganic compounds, with the highest concentrations associated with low baric gradient situations and Southern European flows. The residence time analysis confirmed that current TSP and PM10 concentrations in central Spain are likely to be influenced significantly by long-range transport of desert dust from different desert regions in North Africa. Furthermore, emissions from continental Europe with a high time of residence in the western and central areas of the Mediterranean basin, seem to significantly influence PM2.5 and secondary inorganic aerosol concentrations in this region.     

Long-term visibility trends in one highly urbanized, one highly industrialized, and two rural areas of Taiwan

Visibility trends on the island of Taiwan were investigated employing visibility and meteorological (1961-2003), and air pollutant (1994-2003) data from one highly urbanized center (Taipei), one highly industrialized center (Kaohsiung), and two rural centers (Hualien and Taitung). Average annual visibility (1961-2003) was significantly higher at the rural centers. Unlike at the other centers, visibility in Taipei improved between 1992 (6.6 km) and 2003 (9.9 km), and this can be linked to the construction and expansion of a mass transit rail system in Taipei, the use of which has helped reduce emissions of traffic related air pollutants, particles, and NO2. This has left Kaohsiung with the lowest annual visibility since 1994, despite its 1961-2003 average being superior to that of Taipei. Precipitation lowers visibility, as demonstrated by the all-centers correlation coefficient for visibility and precipitation of -0.92. Hence, frequency of precipitation is one of the factors contributing to the average annual visibility number. The poorest air quality category ('episode'), most commonly experienced in Taipei and Kaohsiung, was characterized by relatively high concentrations of PM10 and NOx at those centers, with comparatively high atmospheric pressure and comparatively low visibility and wind speed. Excepting O3, pollutant concentrations were slightly higher during weekdays, although there was no consistent, significant difference in weekday-weekend visibility. Principal component analysis demonstrated that visibility was markedly reduced in Taipei, Kaohsiung, and Hualien by increased vehicular emissions, road traffic dust, and industrial activity, but not in Taitung, where visibility was as a result superior to that at the other centers and degradation in visibility was likely a response to long-range transport of pollutants rather than local sources. Optimal empirical regression models indicated a negative impact on visibility for each of PM10, SO2 and NO2, particularly so for PM10, and validity of these models for Taipei, Kaohsiung, and Hualien was confirmed by correlation coefficients of simulated and observed average visibility of 0.63-0.72 for daily visibility and 0.85-0.88 for monthly visibility. For Taitung these figures were only 0.46 and 0.50, respectively, indicating that simulations for Taitung should include long-range transport as a pollutant source.     

Simulation of long-range transport aerosols from the Asian Continent to Taiwan by a southward Asian high-pressure system

Aerosol is frequently transported by a southward high-pressure system from the Asian Continent to Taiwan and had been recorded a 100% increase in mass level compared to non-event days from 2002 to 2005. During this time period, PM2.5 sulfate was found to increase as high as 155% on event days as compared to non-event days. In this study, Asian emission estimations, Taiwan Emission Database System (TEDS), and meteorological simulation results from the fifth-generation Mesoscale Model (MM5) were used as inputs for the Community Multiscale Air Quality (CMAQ) model to simulate a long-range transport of PM2.5 event in a southward high-pressure system from the Asian Continent to Taiwan. The simulation on aerosol mass level and the associated aerosol components were found within a reasonable accuracy. During the transport process, the percentage of semi-volatile PM2.5 organic carbon in PM2.5 plume only slightly decreased from 22-24% in Shanghai to 21% near Taiwan. However, the percentage of PM2.5 nitrate in PM2.5 decreased from 16-25% to 1%. In contrast, the percentage of PM2.5 sulfate in PM2.5 increased from 16-19% to 35%. It is interesting to note that the percentage of PM2.5 ammonium and PM2.5 elemental carbon in PM2.5 remained nearly constant. Simulation results revealed that transported pollutants dominate the air quality in Taipei when the southward high-pressure system moved to Taiwan. Such condition demonstrates the dynamic chemical transformation of pollutants during the transport process from continental origin over the sea area and to the downwind land.     

Indoor/outdoor relationships for PM2.5 and associated carbonaceous pollutants at residential homes in Hong Kong - case study

Six residences were selected (two roadside, two urban, and two rural) to evaluate the indoor-outdoor characteristics of PM(2.5) (aerodynamic diameter <2.5 microm) carbonaceous species in Hong Kong during March and April 2004. Twenty-minute-averaged indoor and outdoor PM(2.5) concentrations were recorded by DustTrak samplers simultaneously at each site for 3 days to examine diurnal variability of PM(2.5) mass concentrations and their indoor-to-outdoor (I/O) ratios. Daily (24-h average) indoor/outdoor PM(2.5) samples were collected on pre-fired quartz-fiber filters with battery-powered portable mini-volume samplers and analyzed for organic and elemental carbon (OC, EC) by thermal/optical reflectance (TOR) following the Interagency Monitoring of Protected Visual Environments (IMPROVE) protocol. The average indoor and outdoor concentrations of 24 h PM(2.5) were 56.7 and 43.8 microg/m(3), respectively. The short-term PM(2.5) profiles indicated that the penetration of outdoor particles was an important contributor to indoor PM(2.5), and a household survey indicated that daily activities were also sources of episodic peaks in indoor PM(2.5). The average indoor OC and EC concentrations of 17.1 and 2.8 microg/m(3), respectively, accounted for an average of 29.5 and 5.2%, respectively, of indoor PM(2.5) mass. The average indoor OC/EC ratios were 5.8, 9.1, and 5.0 in roadside, urban, and rural areas, respectively; while average outdoor OC/EC ratios were 4.0, 4.3, and 4.0, respectively. The average I/O ratios of 24 h PM(2.5), OC, and EC were 1.4, 1.8, and 1.2, respectively. High indoor-outdoor correlations (r(2)) were found for PM(2.5) EC (0.96) and mass (0.81), and low correlations were found for OC (0.55), indicative of different organic carbon sources indoors. A simple model implied that about two-thirds of carbonaceous particles in indoor air are originated from outdoor sources. PRACTICAL IMPLICATIONS: Indoor particulate pollution has received more attentions in Asia. This study presents a case study regarding the fine particulate matter and its carbonaceous compositions at six residential homes in Hong Kong. The characteristics and relationship of atmospheric organic and elemental carbon were discussed indoors and outdoors. The distribution of eight carbon fractions was first reported in indoor samples to interpret potential sources of indoor carbonaceous particles. The data set can provide significant scientific basis for indoor air quality and epidemiology study in Hong Kong and China.     

Zones of representation for PM10 measurements along the US/Mexico border

The 'Imperial/Mexicali Valley Cross-Border PM10 Transport Study' acquired a database of meteorological and air quality measurements to determine source contributions to elevated PM10 concentrations and to estimate transport of PM10 between the US and Mexico. The study was conducted from 13 March 1992 to 29 August 1993, in a 80-km long by 20-km wide area spanning the US/Mexico border approximately 200 km inland from the coast of the Pacific Ocean, with monitoring sites located in the Imperial Valley on the US side and in the Mexicali Valley on the Mexico side. Measurements of PM 10 (particles with aerodynamic diameters less than 10 microm) mass, elements, water-soluble cations (i.e. sodium, potassium, ammonium) and anions (i.e. chloride, nitrate, sulfate), organic and elemental carbon and particle light absorption were acquired at two base sites on an every-sixth-day schedule supplemented by daily monitoring during winter and 4 times per day monitoring during intensive periods. Measurements were also taken at as many as 30 neighborhood (satellite) sites during week-long intensive monitoring periods in spring, summer and winter. This paper examines the zones of representation of long-term PM10 monitors by comparing their measurements with those from a spatially dense network of satellite sites. PM10 concentrations at the Mexicali site were consistently 30 to 50% higher than those observed at the Calexico site, even though the two sites were only 12 km apart. Distinct diurnal variations were found, with 6-h average PM10 concentrations often varying by a factor of 2 throughout the day - lowest during afternoon (12.00-18.00 h PST) and highest during night time (18.00-24.00 h PST). On average, crustal material accounted for 32-35% of annual-average PM10, carbonaceous aerosol for 20-30%, and ionic species for 8-10%. Levels of trace elements and sea salt were in the range of 1-4% of PM10. Significant concentration variations were found within the study area. PM10 concentrations in Mexico were double those in the US, decreasing with increasing northerly distance.     

Visibility, air quality and daily mortality in Shanghai, China

This study was designed to assess the association between visibility and air quality, and to determine whether the variations in daily mortality were associated with fluctuations in visibility levels in Shanghai, China. Mortality data were extracted from the death certificates, provided by Shanghai Municipal Center of Disease Control and Prevention, and visibility data were obtained from Shanghai Municipal Bureau of Meteorology. Air quality data (PM₁₀, PM_2.5, PM_10-2.5, SO₂, NO₂ and O₃) were obtained from Shanghai Environmental Monitoring Center. Generalized additive model (GAM) with penalized splines was used to analyze the mortality, visibility, air pollution, and covariate data. Among various pollutants, PM_2.5 showed strongest correlation with visibility. Visibility, together with humidity, was found appropriate in predicting PM_2.5 (R-squared: 0.64) and PM₁₀ (R-squared: 0.62). Decreased visibility was significantly associated with elevated death rates from all causes and from cardiovascular disease in Shanghai; one inter-quartile range (8 km) decrease in visibility corresponded to 2.17% (95%CI: 0.46%, 3.85%), 3.36% (95%CI: 0.96%, 5.70%), and 3.02% (95%CI: − 1.32%, 7.17%) increase of total, cardiovascular and respiratory mortality, respectively. The effect estimates using predicted PM_2.5 and PM₁₀ concentrations were similar to those assessed using actual concentrations. This is the first study in Mainland China assessing the association between visibility and adverse health outcomes. Our findings suggest the possibility of using visibility as a surrogate of air quality in health research in developing countries where air pollution data might be scarce and not routinely monitored.     

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.     

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.     

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.     

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.     

Chemical characteristics of airborne particulate matter near major roads and at background locations in Macao, China

PM10 and PM2.5 samples were collected near major roads and at the background locations in Macao using a TEOM1400a+ACCU system. The chemical analysis of these particles indicated the presence of 36 elements, water-soluble ions and carbonaceous species. The greatest contributors to total PM10 and PM2.5 mass were OC, sulfate, nitrate, ammonium, EC, Na, Cl and crustal elements including Si, Ca, Al, Fe, K and Mg. Organic material is the largest single fraction of airborne particulate matter in Macao. It contributes 32.8-41.5% and 38.2-48.4% of PM10 and PM2.5 at the roadsides, and as high as 29.7% and 33.4-39.4% of PM10 and PM2.5 at background locations, respectively. EC contributes 3.7-7.8% and 8.0-12.9% of PM10 and PM2.5, and crustal material is 10.2-15.4% and 7.6-12.2% of PM10 and PM2.5 near major roads, respectively. The share of EC at background locations is much lower than that at the roadsides, however, the contribution of crustal material is the same in both locations. At the roadsides, secondary aerosols, including sulfate, nitrate and ammonium, account for 16.6-29.0% and 15.8-38.0% of the total PM10 and PM2.5, respectively, as compared to 29.1-36.2% and 23.2-33.8% of total PM10 and PM2.5, respectively, at background locations. In PM2.5, Na and Cl contribute 1-3%, while the average amount of these two elements increase to 1-15% of the total PM10 in Macao.     

Aerosol optical depth, aerosol composition and air pollution during summer and winter conditions in Budapest

The dependence of aerosol optical depth (AOD) on air particulate concentrations in the mixing layer height (MLH) was studied in Budapest in July 2003 and January 2004. During the campaigns gaseous (CO, SO(2), NO(x), O(3)), solid components (PM(2.5), PM(10)), as well as ionic species (ammonium, sulfate and nitrate) were measured at several urban and suburban sites. Additional data were collected from the Budapest air quality monitoring network. AOD was measured by a ground-based sun photometer. The mixing layer height and other common meteorological parameters were recorded. A linear relationship was found between the AOD and the columnar aerosol burden; the best linear fit (R(2)=0.96) was obtained for the secondary sulfate aerosol due to its mostly homogeneous spatial distribution and its optically active size range. The linear relationship is less pronounced for the PM(2.5) and PM(10) fractions since local emissions are very heterogeneous in time and space. The results indicate the importance of the mixing layer height in determining pollutant concentrations. During the winter campaign, when the boundary layer decreases to levels in between the altitudes of the sampling stations, measured concentrations showed significant differences due to different local sources and long-range transport. In the MLH time series unexpected nocturnal peaks were observed. The nocturnal increase of the MLH coincided with decreasing concentrations of all pollutants except for ozone; the ozone concentration increase indicates nocturnal vertical mixing between different air layers.     

Characteristic of polycyclic aromatic hydrocarbon concentrations and source identification for fine and coarse particulates at Taichung Harbor near Taiwan Strait during 2004-2005

Fine (PM(2.5)) and coarse (PM(2.5-10)) particulate concentrations of ambient air polycyclic aromatic hydrocarbons (PAHs) were measured simultaneously from February 2004 to January 2005 at the Taichung Harbor (TH) sampling site near Taiwan of central Taiwan. Particle-bound polycyclic aromatic hydrocarbons (PAHs) were collected on quartz filters; the collected sample was Soxhlet extracted with a dichloromethane (DCM)/n-hexane mixture (50/50, v/v) for 24 h, and then the extracts were analyzed by gas chromatography-mass spectrometry (GC-MS). The results indicated that vehicle emissions, coal combustion, incomplete combustion and pyrolysis of fuel and oil burning were the main source of PAHs near Taiwan Strait of central Taiwan. Diagnostic ratios and principal component analysis (PCA) were also used to characterize and identify PAHs emission sources in this study.     

Comparison of the Revised Air Quality Index with the PSI and AQI indices

Air pollution indices are commonly used to indicate the level of severity of air pollution to the public. The Pollution Standards Index (PSI) was initially established in response to a dramatic increase in the number of people suffering respiratory irritation due to the deteriorating air quality. The PSI was subsequently revised and implemented by the USEPA in 1999, and became known as the Air Quality Index (AQI) that includes data relating to particle suspension, PM2.5, and a selective options of either 8-hour or 1-hour ozone concentration during increased O3 periods. Yet, the costs of launching a network of PM2.5 monitoring stations are prohibitively high for many countries to implement the AQI from the PSI system in the foreseeable future. Therefore, the purpose of this research is to discuss the optimal method of assessing air quality using the latest developed Revised AQI (RAQI), a system that serves as an alternative to the PSI and AQI systems. The feasibility, effectiveness, and the differences between RAQI, AQI, and PSI in their applications to several air pollution conditions are also studied in this research. The results show that southern Taiwan's suspended particulates have significantly greater impact on PM2.5/PM10 ratios than in central and northern metropolitan areas, and that the ratios are higher in Taiwan as a whole compared to many other countries. We also found that the RAQI shows more significant results compared to the PSI and AQI as it has a wider coverage of the range of pollutant concentration levels.     

广州城乡老年人住宅夏季室内环境调查与实测

广州夏季高温高湿,基于广州城乡老年人的室内环境差异,通过问卷调查了解了116 名广州城乡老年人的室内居住环境, 并对5 户典型城市及5 户典型农村65 岁以上居民住宅的夏季室内环境进行了对比实测研究,测量每户住宅的客厅,卧室和卫 生间的温度、相对湿度及CO2、CO、PM2.5、挥发性有机物浓度。研究表明,广州农村住户夏季主要使用风扇降温,仅有约三 分之一住户同时使用空调,而城市住户均使用空调,大部分住户同时使用风扇;广州农村住户夏季室内平均空气温度比城市住 户低0.8 ℃,平均相对湿度比城市住户高21.6%;通风较差的住户室内CO2 浓度相对较高,所有实测城市及农村住户的CO、 PM2.5 的浓度都低于国家标准规定的极限值;广州城市住户的室内外PM2.5 浓度及室内总挥发性有机物的浓度总体高于农村住户。 广州农村老年人住宅应加强防潮处理,城市老年人住宅应加强通风换气,优选环保家具。