Case studies of Asian dust storm impacts on a coastal site: implication of a good dust storm tracer

Significant dust storm impacts have seldom been recorded and reported in Hong Kong. Herein, four cases which occurred in Hong Kong during the spring times of recent years are examined using back-trajectory computation and chemical analysis of air-borne samples. All of the cases show that the dust was transported from the source to Hong Kong in 2–5 days and that PM₁₀ concentrations approached or exceeded the European Union air quality criteria and the USA National Ambient Air Quality Standard. The chemical characteristics of the samples taken in these events agreed both with those from the source regions and with those archived from selected Hong Kong datasets. The concentrations of the crustal constituents (Al, Fe, Mn, Ca) of the Hong Kong samples on the episode days were at least three times higher than the concentrations measured on non-episode days. The mass ratios of Fe/Al and Mn/Al (but not Ca/Al) can act as good tracers of Asian dust storms to this coastal site where sea-salt and other anthropogenic species are normally dominant. Furthermore, unusually high Mg levels indicated a mainly crustal origin for this element, rather than the marine origin normally found at this coastal location. Particulate nitrate exhibited more elevated concentrations in all of the dust storm samples than in non-dust-storm and local samples.     

A Comparison of Trace Gases and Particulate Matter over Beijing (China) and Delhi (India)

Air pollution represents a significant fraction of the total mortality estimated by the World Health Organization (WHO) global burden of disease projec?t (GBD). The present paper discusses the characteristics of trace gases (O₃, NO, NO₂, and CO) and particulate matter (PM₁₀ and PM_2.5) in two Asian megacities, Delhi (India) and Beijing (China). A continuous measurement of trace gases and particulate matter are considered from 12 measuring sites in Beijing and 8 sites in Delhi. Over Beijing, the annual average of PM_2.5, PM₁₀, O₃, NO₂, and CO is, respectively, 85.3, 112.8, 58.7, and 53.4 μg/m³ and 1.4 mg/m³, and, respectively, over Delhi 146.5, 264.3, 24.7,and 19.8 μg/m³ and 1.73 mg/m³. From the spatial variations of pollutants, the concentrations of particulate matter and trace gases are observed to be much higher in the urban areas compared to the suburban areas. The higher average concentrations of PM₁₀ and PM_2.5 over Delhi and Beijing are observed during winter season compared with other seasons. The maximum diurnal variation of PM₁₀ concentration is observed during winter season over Beijing and Delhi. The comparison of trace gases shows that the O₃ concentrations during daytime are obviously higher compared with nighttime, and the highest diurnal variation of O₃ is observed during summer. The concentrations of CO are highest during winter season, and higher concentrations are observed during nighttime compared to daytime. The O₃ and CO show negative correlation over Beijing and Delhi. The negative correlation between O₃ and NO₂ is merely observed over Beijing, while CO and NO₂ concentrations, in contrast, show positive correlation over Beijing.     

Concentration and Sources of PM10 and its Constituents in Alsasua, Spain

Ambient concentrations of PM₁₀ were measured every fifteen minutes from November 2002 to October 2003 at Alsasua (Northern Spain) using a laser particle counter. A high volume sampler was also used to collect 24-h integrated PM₁₀ samples at a frequency of three running days per week (i.e. three consecutive PM₁₀ samples followed by five days without sampling) for gravimetric determination of PM₁₀ mass concentrations followed by chemical analysis of its chemical components. The annual mean PM₁₀ concentration obtained using the laser particle counter with gravimetric correction was 22.7 μg m^?3 (365 days), while the mean for the gravimetric samples was 29.5 μg m^?3 (134 days). A total of 94 integrated PM₁₀ samples were analyzed for 60 chemical species using a combination of inductively coupled plasma spectrometry (ICP) and ion chromatography (IC). The concentrations of the main PM₁₀ components were found to be generally in agreement with the values reported for other Spanish cities. Bilinear Positive Matrix Factorization (PMF2) was used to study the sources of PM₁₀ and its constituents. Six main sources of PM₁₀ were identified (average contribution to total PM₁₀ mass in parentheses): crustal material (35%), secondary sulfate (21%), secondary nitrate (14%), motor vehicles (12%), sea-salt aerosol (12%) and metallurgical industries (3%).     

Mineralogy of Inhalable Particulate Matter (PM10) in the Atmosphere of Beijing, China

The study of mineral components in respirable particles (particulate matter with diameter less than 10 μm, PM₁₀) in ambient air is important in understanding and improving air quality. In this study, PM₁₀ samples were collected in various areas around Beijing during 2002～2003, including an urban setting, a satellite city and a rural area. The mineralogical composition of these PM₁₀ samples was studied by X-ray diffraction (XRD), environmental scanning electron microscopy / and energy-dispersive X-ray analyzer (ESEM/EDX). The results indicated that mineral composition of PM₁₀ in different seasons and in different region varied significantly. Mineral mass concentration in Beijing PM₁₀ reached the highest percentage in the spring and fell to the lowest level in the autumn. The minerals in the spring PM₁₀ were dominated by clay minerals and quartz, followed by plagioclase, K-feldspar, calcite, dolomite, hematite, pyrite, magnesite, gypsum and laumontite as well as some unidentified materials. Fewer mineral types were collected in summer, however some new components, including K(NH₄)Ca(SO4)₂·H₂O, NH₄Cl and As₂O₃·SO₃ were noted to be present, suggesting that atmospheric chemical reaction in Beijing air were more active in summer than in other seasons. Mineral components in Beijing urban air were at a higher percentage with fewer phases than that in satellite city air. In conclusion, there was considerable variation in mineral components in PM₁₀ samples collected in different seasons and areas, which reflects the related air quality of sampling areas.     

A Study of PM2.5 and PM2.5-Associated Polycyclic Aromatic Hydrocarbons at an Urban Site in the Po Valley (Bologna, Italy)

PM_2.5 and PAHs bound to PM_2.5 were investigated in downtown Bologna, from January to June 2003, in order to determine the burden of the fine fraction in the aerosol of a typical urban environment of the Po Valley, a critical area in Northern Italy in terms of atmospheric pollution. The sampling campaign was divided into three parts: a winter sub-campaign, an intermediate campaign where PM_2.5 and PM₁₀ were simultaneously sampled and which identified PM_2.5 as the major component of PM₁₀, and a summer sub-campaign. Critical concentrations of both PM_2.5 and PAHs were observed in winter time; for example, in January 2003 the mean value for the 24-h average PM_2.5 concentration was 58 μg/m³, much higher than the annual arithmetic mean of 15 μg/m³ established by the US ambient air quality standard (NAAQS). Correspondingly, the mean value for benzo[a]pyrene (BAP) in PM_2.5 was 1.79 ng/m³, again higher than the annual mean of 1 ng/m³, required by European regulations for BAP in PM₁₀. In summer time the BAP concentration considerably decreases to 0.10 ng/m³ as the likely effect of photolysis and dilution on a higher boundary layer; PM_2.5 decreases too, but the mean concentration (22 μg/m³) is still higher than the NAAQS value. Further analysis included TEM microscopy of collected particles and correlations between PM_2.5, PAHs and gases (benzene, O₃, CO, NO₂, SO₂). All these observations identified on-road mobile sources as the main source of emissions and, in general, of the poor air quality level in the city of Bologna.     

Particle-associated Polycyclic Aromatic Hydrocarbons in the Atmosphere of Hong Kong

Polycyclic aromatic hydrocarbons (PAHs) in total suspended particulates (TSP) collected at six rural and urban stations in Hong Kong from 1993–1995 using high volume air samplers were identified using GC-MS (gas chromatography-mass spectrometry). The results showed that the PAHs exhibited distinct spatial and seasonal variability. The total PAH content (ΣPAH) in the samples ranged from 0.41 to 48 ng m^-3. The unsubstituted analogs are the characteristic products of high temperature combustion processes. The highest average ΣPAH was measured at the street-level station in Mong Kok indicating that vehicles were high PAHs contributors. The rural station at Hok Tsui exhibited the lowest PAH level, however; influences of city plumes could be seen when northerly or northeasterly winds prevailed in the winter. All stations experienced the highest loading of PAHs in autumn and the lowest in summer; the former was 2.8 times greater than the latter. This seasonal variability is due to the Asian monsoon system, precipitation, micrometeorology, and the rate of photodegradation. In summer, Hong Kong experiences relatively clean oceanic air and high rates of precipitation and photodegradation, while upon the onset of the winter monsoon, local air mass is replaced by polluted air streams from the Asian continent. Benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(e)pyrene, indeno(1,2,3-cd)pyrene and benzo(ghi)perylene were the dominant species in the samples. The PAH distribution patterns at different stations were similar within each season. However, seasonal variations existed. For example, phenanthrene contributed up to 14% of the total PAH in summer, while the dominance of benzo(b)fluoranthene, benzo(k)fluoranthene was more significant in autumn and winter.     

Evaluation of Spatial Variability of PM10 Concentrations in London

This study aims to apply principal component analysis (PCA) to identify monitoring sites with similar variations of PM₁₀ concentrations in the London Air Quality Monitoring Network. This statistical methodology was applied to hourly average concentrations measured at 27 monitoring sites during the period from January 2000 to December 2009. The monitoring sites were selected according their efficiency in the study period (greater than 75% for each year). It was observed that the hourly average PM₁₀ concentrations were decreasing along the selected period at almost all monitoring sites. PCA was performed for each year, selecting the number of principal components (PCs) that had at least 95% of the original data variance. Analysing the frequency with which each pair of monitoring sites gave a significant contribution to the same PC, nine city areas with specific PM₁₀ behaviour were identified. Thus, monitoring sites with redundant measurements during the studied period were identified, being possible to remove them to decrease the costs relative to their maintenance or replace them to increase the monitored area.     

Modeling Urban PM<Subscript>2.5</Subscript> Concentration by Combining Regression Models and Spectral Unmixing Analysis in a Region of East China

Understanding the spatial distribution of PM_2.5 concentration and its contributing environmental variables is critical to develop strategies of addressing adverse effects of the particulate pollution. In this study, a range of meteorological and land use factors were incorporated into a linear regression (LR) model and a logistic model-based regression (LMR) model to simulate the annual and winter PM_2.5 concentrations. The vegetation cover, derived from a linear spectral unmixing analysis (LSUA), and the normalized difference built-up index (NDBI), were found to improve the goodness of fit of the models. The study shows that (1) both the LR and the LMR agree on the predicted spatial patterns of PM_2.5 concentration and (2) the goodness of fit is higher for the models established based on the annual PM_2.5 concentration than that based on the winter PM_2.5. The modeling results show that higher PM_2.5 concentration coincided with the major urban area for the annual average but focused on the suburban and rural areas for the winter. The methods introduced in this study can potentially be applied to similar regions in other developing countries.     

PM10 and PM2.5 Levels in the Eastern Mediterranean (Akrotiri Research Station, Crete, Greece)

Particulate matter measurements (PM₁₀, PM_2.5) using a beta radiation attenuation monitor were performed at the Akrotiri research station (May 2003–March 2006) on the island of Crete (Greece). The mean PM₁₀ concentration during the measuring period (05/02/03–03/09/04) was equal to 35.0?±?17.7 μg/m³ whereas the mean PM_2.5 concentration (03/10/04–04/02/06) was equal to 25.4?±?16.5 μg/m³. The aerosol concentration at the Akrotiri station shows a large variability during the year. Mean concentrations of particulate matter undergo a seasonal change characterised by higher concentrations during summer [PM₁₀, 38.7?±?10.8 μg/m³ (2003); PM_2.5, 27.9?±?8.7 μg/m³ (2004) and 27.8?±?9.7 μg/m³ (2005)] and lower concentrations during winter [PM₁₀, 28.7?±?22.5 μg/m³ (2003/2004); PM_2.5, 21.0?±?13.0 μg/m³ (2004/2005) and 21.4?±?21.9 μg/m³ (2005/2006)]. Comparative measurements of the PM₁₀ concentration between the beta radiation attenuation monitor, a standardized low volume gravimetric reference sampler and a low volume sequential particulate sampler showed that PM₁₀ concentrations measured by the beta radiation attenuation monitor were higher than values given by the gravimetric samplers (mean ratio 1.17?±?0.11 and 1.21?±?0.08, respectively). Statistical and back trajectory analysis showed that elevated PM concentrations (PM₁₀, 93.8?±?49.1 μg/m³; PM_2.5: 102.9?±?59.9 μg/m³) are associated to desert dust events. In addition regional transport contributes significantly to the aerosol concentration levels whereas low aerosol concentrations were observed during storm episodes.     

Estimation of air quality degradation due to Saharan dust at Nouakchott, Mauritania, from horizontal visibility data

It is now irrefutable that air pollution caused by large amounts of Total Suspended Particulates (TSP) and respiratory particulates or Particulate Matter less than 10 μm in aerodynamic diameter (PM₁₀) has numerous undesired consequences on human health. Air quality degradation far from the African continent, in the US and in Europe, caused by high concentrations of African dust, is seen as a major threat even though most of these countries are very distant from the Sahara. Surprisingly, no estimates of TSP or PM₁₀ levels near the Saharan dust source are available. Based on horizontal visibility observations which are reduced by the presence of dust in the atmosphere, TSP and PM₁₀ levels are estimated throughout the year 2000 at Nouakchott-Airport, Mauritania, using relations found in the literature. It appears that concentrations of particles are significant both in terms magnitude and frequency, as the 24-hour PM₁₀ thresholds established by the US EPA National Ambient Air Quality Standards and the EU Limits Values for Air Quality were exceeded 86 and 137 times, respectively. The average annual concentration is far above air quality standards and estimated at 159 μg m^?3 for TSP and 108 μg m^?3 for PM₁₀. These very high particulate levels are likely to represent an important public health hazard and should be considered as a major environmental risk.     

Identification of Fine Particle Sources in Mid-Atlantic US Area

The U.S. Environmental Protection Agency (EPA) designated 20 urban areas including major cities located in mid-Atlantic US area as being in non-attainment of the new national ambient air quality standards for PM_2.5 (particulate matter ≤2.5 μm in aerodynamic diameter). To support the development of effective State Implementation Plans for PM_2.5 in the non-attainment area, 24-h integrated Speciation Trends Networks data collected in the mid-Atlantic US urban area were analyzed through the application of the positive matrix factorization (PMF). A total of 117 to 235 samples and 27 to 29 chemical species collected at the four monitoring sites between 2001 and 2003 were analyzed and six to nine sources were identified. Secondary particles provided the highest contributions to PM_2.5 mass concentrations (38–50% for secondary sulfate; 9–18% for secondary nitrate). Potential source contribution function analyses show the potential source areas and pathways of secondary particles contributing to this region, especially the regional influences of the biogenic as well as anthropogenic secondary particles. Motor vehicle emissions contributed 21–33% to the PM_2.5 mass concentration. In four sites in southern New Jersey and Delaware, gasoline vehicle and diesel emissions were tentatively separated by different abundances of organic and elemental carbons. The compositional profiles for gasoline vehicle and diesel emissions are similar across this area. In addition, other combustion sources, aged sea salt, and intercontinental dust storms were identified.     

Effects of Landfill Gas on Growth and Nitrogen Fixation of Two Leguminous Trees (Acacia Confusa,Leucaena Leucocephala)

A study was made on the effects of landfill gas on ARA (acetylene reducing activity) of nodules of two woody legumes (Acacia confusa and Leucaena leucocephala) widespread on landfill sites in Hong Kong. The effects of the three main components of landfill gas, O₂, CO₂ and CH4, were first measured separately over a 1-hr period. Maximum ARA was found at 20% O₂ (close to atmospheric partial pressure) and ARA decreased as the O₂ decreased in the range of 16–1%. Acacia confusa nodular ARA was significantly inhibited at 30–50% CO₂, but not Leucaena leucocephala nodular ARA. CH₄ had no significant effect on ARA of either species. As the landfill gas concentrations in the landfill topsoil were mostly > 10% O₂ and < 10% CO₂, root nodules should fix N₂ effectively over these ranges of gases. A four-week test was conducted to assess the long-term influence of landfill gas on seedlings of the two legumes. Landfill gas and elevated CO₂ both suppressed their growth and their nodular ARA. Even under the influence of the gases, however, seedlings with nodules formed a higher biomass than seedlings lacking nodules. The growth of the two legumes under actual landfill conditions was investigated by transplanting non-inoculated and pre-inoculated seedlings to two landfill sites in Hong Kong: Junk Bay and Shuen Wan Landfill. After six months, most of the non-inoculated seedlings became infected: Acacia confusa 63 and 70%, Leucaena leucocephala 17 and 89%, respectively, at the test sites. The results indicate that there were free rhizobia at these landfill sites to infect the legumes and they had formed effective nodules to fix N₂ under landfill conditions.     

GIS-Based Emission Inventory, Dispersion Modeling, and Assessment for Source Contributions of Particulate Matter in an Urban Environment

The Industrial Source Complex Short Term (ISCST3) model was used to discern the sources responsible for high PM₁₀ levels in Kanpur City, a typical urban area in the Ganga basin, India. A systematic geographic information system-based emission inventory was developed for PM₁₀ in each of 85 grids of 2?×?2 km. The total emission of PM₁₀ was estimated at 11 t day^?1 with an overall breakup as follows: (a) industrial point sources, 2.9 t day^?1 (26%); (b) vehicles, 2.3 t day^?1 (21%); (c) domestic fuel burning, 2.1 t day^?1 (19%); (d) paved and unpaved road dust, 1.6 t day^?1 (15%); and the rest as other sources. To validate the ISCST3 model and to assess air-quality status, sampling was done in summer and winter at seven sampling sites for over 85 days; PM₁₀ levels were very high (89?C632 ??g m^?3). The results show that the model-predicted concentrations are in good agreement with observed values, and the model performance was found satisfactory. The validated model was run for each source on each day of sampling. The overall source contribution to ambient air pollution was as follows: vehicular traffic (16%), domestic fuel uses (16%), paved and unpaved road dust (14%), and industries (7%). Interestingly, the largest point source (coal-based power plant) did not contribute significantly to ambient air pollution. The reason might be due to release of pollutant at high stack height. The ISCST3 model was shown to produce source apportionment results like receptor modeling that could generate source apportionment results at any desired time and space resolution.     

Application of LIDAR Technique and MM5-CMAQ Modeling Approach for the Assessment of Winter PM10 Air Pollution: A Case Study in Beijing, China

This paper reports the use of LIDAR technique, vertical wind profiler (VWP) and the coupled MM5-CMAQ air quality modeling system to investigate a high PM₁₀ concentration episode occurred in Beijing, China during January 8–9, 2004. Through the regression analysis between the observed PM₁₀ concentrations and the observed extinction coefficients, the converting formulas from the LIDAR records to the PM₁₀ mass concentrations in Beijing have been found. Further, a 2-level-nested grid domain with spatial resolutions of 36 and 12 km have been designed and employed for this study, and the coupled MM5-CMAQ modeling system has then been evaluated using both the ground-level PM₁₀ observations and the vertical profiles of PM₁₀ deduced from the measured LIDAR extinction coefficients. Based on the verified modeling system, two emission scenarios were designed to quantitatively assess the trans-boundary PM₁₀ contributions from the surrounding provinces of Beijing. The results illustrated that the particulate matter buildup over the Beijing region was due to a number of factors, including pollutants brought in from its surrounding provinces by the southwest winds and the emission from local sources within Beijing. It indicates that while Beijing needs to take positive steps to reduce its own pollution emissions, much effort should also be placed on demanding more pollution reduction and better environmental performance from its surrounding provinces.     

Diurnal Characteristics of Suspended Particulate Matter and PM<Subscript>2.5</Subscript> in the Urban and Suburban Atmosphere of the Kanto Plain,Japan

Suspended particulate matter (SPM) and PM_2.5 in the urban and suburban atmosphere of the Kanto Plain of Japan, which includes the Tokyo metropolitan area, during the period 22–26 July 2002 were characterized. Samples of SPM and PM_2.5 were collected by low-volume samplers at 6-h intervals at Suginami, Saitama, and Kisai. At all the sites, the major components of SPM and PM_2.5 were organic carbon (OC), elemental carbon (EC), and sulfate. The ion balance, the size distributions of the ionic species, and the high correlation between SO₄ ^2? and NH₄ ⁺ indicated that the main chemical form of sulfate was (NH₄)₂SO₄. The OC/EC ratios were larger in the daytime than in the nighttime. The correlation coefficients of OC, OC/EC, and SO₄ ^2? with ozone concentrations at inland sites (Saitama, Kisai) were higher than those at the coastal site (Suginami). Bound water and hydrogen and oxygen atoms associated with OC, the amounts of which were estimated with a mass closure model, contributed substantially to the total particle mass. The chemical characteristics of the particles indicated that two mechanisms led to high concentrations of SPM and PM_2.5: (i) an active photochemical process produced high concentrations of OC and sulfate, leading to a high concentration of (NH₄)₂SO₄ in the particles and to production of secondary organic aerosols; (ii) stable meteorological conditions resulted in accumulation of primary particles, mainly emitted from vehicle exhaust, resulting in high concentrations of OC and EC.     

Characterization of Elemental Species in PM2.5 Samples Collected in Four Cities of Northeast China

A monitoring program of particulate matter was conducted at eight sampling sites in four highly industrialized cities (Shenyang, Anshan, Fushun, and Jinzhou) of Liaoning Province in Northeast China to identify the major potential sources of ambient PM_2.5. A total of 814 PM_2.5 and PM_2.5–10 samples were collected between 2004 and 2005. All PM samples were collected simultaneously in four cities and analyzed gravimetrically for mass concentrations. A sum of 16 elemental species concentrations in the PM samples were determined using inductively coupled plasma atomic emission spectroscopy. Annual means of PM_2.5 concentrations ranged from 65.0 to 222.0 μg m^?3 in all the eight sampling sites, and the spatial and seasonal variations were discussed. Enrichment factors were calculated, and Cr, Cu, Zn, As, Cd, and Pb will be pollution-derived elements. Site-to-site comparisons of PM_2.5 species in each city were examined using coefficient of divergence, revealing that the two sites in each city are similar in elemental species. Principle component analysis was used for preliminary source analysis of PM_2.5. Three or four factors in each city were isolated, and similar sources (crustal source, coal combustion, vehicle exhaust, iron making, or some other metallurgical activities) were identified at four cities.     

Particle Number Size Distribution and Weight Concentration of Background Urban Aerosol in a Po Valley Site

Measurements of particle size distributions and PM_2.5 from an urban background site in the Central Po Valley are analysed; the site is one of the medium–small-size cities in the central valley, without the direct influence of the metropolitan and industrial area of Milan and of the Adriatic Sea. The data comprise number concentration of particle with diameters ranging between 10 and 700 nm, PM_2.5 and main meteorological variables from February to August 2008. Daily cycles of the observed pollutants are analysed, along with auto-correlation function for particle number concentration and principal component analysis (PCA) of all the available variables; finally, the diurnal pattern of PM_2.5 low-, medium- and high-pollution events has been investigated. Total particle number concentration showed a daily pattern both in winter and summer, although different between weekdays and Sundays and with wider variations during the cold season. A daily cycle is present for the geometric mean diameter of nucleation mode particles in winter and of nucleation and Aitken mode particles in summer. PM_2.5 showed a slight daily pattern for weekdays and Sundays, similar, but lagged, to total particle count cycle. Mixing layer depth resulted the main process controlling PM_2.5, although also human activities contribute to PM_2.5 concentration and allow some deposition and (re-)mobilisation at the first hours of the day and morning rush hour, respectively, while particle number concentration responds immediately to anthropogenic sources. PCA confirmed the dependence of particle number concentration also on meteorological variables, e.g. mixing layer height, wind speed or atmospheric pressure, showing the important influence of regional meteorology on local pollution conditions. Modena can be considered a representative test area of the effect of the meteorological regime for the Central Po Valley on atmospheric particle concentration patterns, characterised by steady high-background concentration.     

An Assessment of the Mobile Source Contribution to PM10 and PM2.5 in the United States

Mobile sources are significant contributors to ambient particulate matter (PM) in the United States. As the emphasis shifts from PM₁₀ to PM_2.5, it becomes particularly important to account for the mobile source contribution to observed particulate levels since these sources may be the major contributor to the fine particle fraction. This is due to the fact that most mobile source mass emissions have an aerodynamic diameter less than 2.5 µm, while the particles of geological origin that tend to dominate the PM₁₀ fraction generally have an aerodynamic diameter greater than 2.5 µm. A common approach to assess the relative contributions of sources to observed particulate mass concentrations is the application of source apportionment methods. These methods include material balance, chemical mass balance (CMB), and multivariate receptor models. This paper describes a number recent source attribution studies performed in the United States in order to evaluate the range of the mobile source contribution to observed PM. In addition, a review of the methods used to apportion source contributions to ambient particulate loadings is presented.     

PM10-bound Polycyclic Aromatic Hydrocarbons (PAHs) and Cancer Risk Estimation in the Atmosphere Surrounding an Industrial Area of Shanghai, China

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in the urban atmosphere. In particular, atmospheric pollution has increasingly become severe in China due to its rapid urbanization and industrialization. In recent years, a few studies have presented information about POPs (such as PAHs, PCBs, OCPs) in aerosols at a molecular level in a limited number of cities such as Beijing, Qingdao and Guangzhou, as well as Hong Kong. Whereas, these cities are located in northern and southern China, respectively, where characteristics of atmospheric pollution might be different from those in the eastern cities, such as Shanghai. Atmospheric particle pollution is a persistent problem in Shanghai, a typical metropolis of China, which has several huge industrial regions. In order to gain a comprehensive understanding of the present state, properties and sources of PAHs pollution in Shanghai, PM₁₀ samples were collected at Coal-Fired Power Plant (CFP), Chlor-Alkali Chemical factory (CAC) and Coking and Chemical factory (CCF) in an industrial area, during the period, November 2004–September 2005. The concentrations of 16 PAHs were analyzed using the HPLC with UV visible detector. The results showed that the mean value of total PAHs in the industrial area was 64.85 ng m^?3; 3-ring PAHs were found at low levels, while 4-, 5- and 6-ring PAHs were found at high levels. The levels of BaP were 3.07 and 7.16 ng m^?3 at Chlor-Alkali Chemistry Factory and Coking and Chemistry Factory sites, respectively. PAHs levels exhibited distinct seasonal variation, with the highest level in autumn and the lowest in summer. The major source of PAHs at the industrial area was fossil fuel combustion, coal-burning, industrial furnaces including others. There was a very significant correlation of PAHs levels between CCF and CAC (R ²?=?0.91). The average concentration of BaP in the industrial area during the sampling period was 5.95 ng m^?3. It could be concluded the local population appears to be exposed to significantly high cancer risk (exceeding 2 ng m^?3 in autumn and winter) as compared to the population of other areas.     

Calcium CO-Amendments Modify Extractable Orthophosphate Levels in Fresh and Composted Cattle Manure

The Hong Kong Environmental ProtectionDepartment (HK EPD) monitoring data for SO₂, NO, NO₂and O₃ from 1995 and 1996 at three stations spanning thelength of Hong Kong have been analyzed in the contexts ofselected meteorological parameters, and the types of synopticweather system. High level and episode days were definedaccording to two criteria. Higher pollutant gas concentrationswere found for systems involving the transport of continentalair masses to Hong Kong (cold front (type CF), north/northeastmonsoon (type NE)), or when tropical cyclones approached (typeAC) Hong Kong. Lower concentrations were observed when thecleaner maritime southerly (type S) airstreams were incidentat Hong Kong. Most notably, tropical cyclones (type C)ventilated and diluted local pollution. Days with high levelsof SO₂, NO and NO₂ were generally characterized bylow windspeed and lower relative humidity conditions. Bycontrast, high concentrations of O₃ occurred both underlow windspeed conditions (type AC) and under the advection ofa continental air mass, generally at high windspeeds. Thediurnal variation of O₃ levels is discussed: destructionis more important than production in determining local levels.