A wintertime PM2.5 episode at the Fresno,CA, supersite

A winter PM_2.5 episode that achieved a maximum 24-h average of 138 μg m⁻³ at the Fresno Supersite in California's San Joaquin Valley between 2 and 12 January, 2000 is examined using 5-min to 1-h continuous measurements of mass, nitrate, black carbon, particle-bound PAH, and meteorological measurements. Every day PM_2.5 sampling showed that many episodes, including this one, are missed by commonly applied sixth-day monitoring, even though quarterly averages and numbers of US air quality standard exceedances are adequately estimated. Simultaneous measurements at satellite sites show that the Fresno Supersite represented PM_2.5 within the city, and that half or more of the urban concentrations were present at distant, non-urban locations unaffected by local sources. Most of the primary particles accumulated during early morning and nighttime, decreasing when surface temperatures increased and the shallow radiation inversion coupled to a valleywide layer. When this coupling occurred, nitrate levels increased rapidly over a 10–30 min period as black carbon and gaseous concentrations dropped. This is consistent with a conceptual model in which secondary aerosol forms above the surface layer and is effectively decoupled from the surface for all but the late-morning and early afternoon period. Primary pollutants, such as organic and black carbon, accumulate within the shallow surface layer in urban areas where wood burning and vehicle exhaust emissions are high. Such a model would explain why earlier studies find nitrate concentrations to be nearly the same among widely separated sites in urban areas, as winds aloft of 1 to 6 m s⁻¹ could easily disperse the elevated aerosol throughout the valley.     

Dust transport in maricopa county,Arizona

Numerical simulations have been carried out for ambient supermicrometric particulate concentrations in Maricopa County, Arizona during late fall and winter periods of atmospheric stability. Results of model studies are in approximate agreement with limited field observational data. Observed high particulate concentrations in Maricopa County urban areas during late fall and winter periods of atmospheric stability are associated with local fugitive dust sources. Because of light drainage winds prevalent during these periods, advective transport of dust from countryside to the urban areas is not an important contribution to urban supermicrometric particulate concentrations. Surface roughness, dry deposition, and primary sources are among the most important determinants of ground level concentrations. An adequate and practical predictive model, along the lines of the current model, could be developed for Maricopa County as well as for the other urban areas in the high desert regions.     

Mesoscale modeling of wintertime particulate matter episodes in eastern Washington, USA

The Spokane, Washington area is classified as a non-attainment area for the 24-h PM₁₀ standard due to a history of high particulate matter concentrations. A Eulerian regional air quality model (CALMET/CALGRID) has been used to characterize the emission, transport and dispersion of PM₁₀ and PM_2.5 in Spokane. Observations from a residential site (Rockwood, RW) and an industrial site (Crown Zellerbach, CZ), spanning July 1994–August 1996 were used to evaluate the current emission inventory. Two major tasks were devised to conduct the objectives of this investigation. First, a simple and efficient urban dispersion model (WYNDValley) was used to simulate important episodes characterized by the highest PM₁₀ and PM_2.5 concentrations. The selected episodes included four days with wet conditions for which no roads would have been emitting and seven days with dry conditions for which roads would emit. In the second step, a single road-emitting event was selected from the previous predicted results for further analysis using the Eulerian regional air quality model to examine the emission inventory. The urban and regional models predicted the observed concentration distributions reasonably well for the source emissions inventoried in Spokane. The mass concentrations of PM₁₀ were well predicted for the roads emitting case examined by both models indicating that the emission inventory based primarily upon area sources including roads is reasonably well characterized, at least at the RW site. The area sources around CZ are less well characterized, so that the PM₁₀ concentrations are underpredicted at CZ. The models appear unable to reach an equilibrium mass balance status at the beginning of the simulation, and the urban model seems unable to properly resolve the nocturnal boundary layer.     

Fine particle concentrations and composition during wintertime inversions in Logan,Utah, USA

During Winter 2004, a series of elevated PM_2.5 events occurred in Logan, Utah, coinciding with strong winter inversions. This period resulted in 17 exceedances of the 24-h PM_2.5 standard, and some of the highest PM_2.5 mass loadings recorded in the United States, including 9 days of 24-h PM_2.5 measurements over 100 μg m⁻³. During the 3-month period, we monitored the size and mass concentrations of airborne particles using an aerosol mass spectrometer. PM_2.5 concentrations were dominated by the formation of ammonium nitrate, accounting for over 50% of the non-refractory aerosol matter throughout the study and 80% on the highest pollution days. Another 15–20% of the particulate matter was composed of organic carbon. The high particle concentration loadings in Utah's Cache Valley result from a combination of unfavorable meteorology dominated by a severe cold-temperature inversion, a mix of rural and urban emission sources, and a confined geographical area. As a rapidly growing formerly rural area, the Cache Valley is representative of future air pollution problems facing areas of the interior west undergoing rapid urbanization.     

Dispersion modelling of a wintertime particulate pollution episode in Christchurch,New Zealand

This paper examines the inter-suburb dispersion of particulate air pollution in Christchurch, New Zealand, during a wintertime particulate pollution episode. The dispersion is simulated using the RAMS/CALMET/CALPUFF modelling system, with data from a detailed emissions inventory of home heating, motor vehicles and industry. During the period 27 July–1 August 1995, peak 1 h and 24 h PM₁₀ concentrations of 368 and 107 μg m⁻³, respectively, were observed. Peak concentrations occurred at night, when particulate emissions from wood- and coal-burning domestic heating appliances were at a maximum and emitted into a stable boundary layer. The model is generally able to reproduce the observed PM₁₀ time series recorded at surface monitors located throughout the urban area. For this simulation, the fractional gross error ranges between 0.69 and 0.99, and the fractional bias ranges between −0.17 and 0.30. Strong horizontal concentration gradients of 100 μg m⁻³ km⁻¹, both in the observational record and model predictions, are apparent. Three emission reduction options, designed to reduce the severity of particulate pollution episodes in Christchurch, are simulated. When both domestic open-hearth fires and all coal burning are removed, the 24 h average peak concentration is reduced by 55%. The number of guideline exceedences of PM₁₀ in the modelled period is reduced from five to one. Removing open-hearth fires results in 42% reduction in PM₁₀ concentration, resulting in three exceedences of the guideline, and removing coal-burning fires yields a 32% reduction in PM₁₀, resulting in four exceedences of the guideline.     

A study of winter variability in carbon dioxide and Arctic haze aerosols at Barrow,Alaska

Relationships among atmospheric CO₂ concentration, excess sulfate and vanadium, and meteorological analyses for one winter at Barrow, Alaska were investigated. The results provided a basis for understanding the causes of short term CO₂ variability. The study indicated that peaks in CO₂ concentration were related to direct atmospheric transport of industrial pollutants from Eurasia. Evidence that background Arctic concentrations contained a pollution component was also found. Lowest CO₂ concentrations occurred with intrusions of Pacific air above the surface-based polluted Arctic air mass.     

Ammonium Nitrate,Nitric Acid,and Ammonia Equilibrium in Wintertime Phoenix,Arizona

A secondary aerosol equilibrium model, SEQUILIB, is applied to evaluate the effects of emissions reductions from precursor species on ambient concentrations during the winter in Phoenix, Arizona. The model partitions total nitrate and total ammonia to gas-phase nitric acid and ammonia and to particle-phase ammonium nitrate. Agreement between these partitions and ambient measures of these species was found to be satisfactory. Equilibrium isopleths were generated for various ammonium nitrate concentrations corresponding to high and low humidity periods which occurred during sampling. These diagrams show that ammonia is so abundant in Phoenix that massive reductions in its ambient concentrations would be needed before significant reductions in particulate ammonium nitrate would be observed. When total nitrate is reduced by reductions in its nitrogen oxides precursor, proportional reductions in particulate nitrate are expected. Many of the complex reactions in SEQUILIB do not apply to Phoenix, and its ability to reproduce ambient data in this study does not guarantee that it will be as effective in areas with more complex chemistry. Nevertheless, the nitrate chemistry in SEQUILIB appears to be sound, and it is a useful model for addressing the difficult apportionment of secondary aerosol to its precursors.     

Climatology and forecast modeling of ambient carbon monoxide in Phoenix, Arizona

We perform a climatology of factors influencing ambient carbon monoxide (CO), in which we examine the relationships between meteorology, traffic patterns, and CO at seasonal, weekly, and diurnal time scales in Phoenix, Arizona. From this analysis we identify a range of potentially important variables for statistical CO modeling. Using stepwise multivariate regression, we create a suite of models for hourly and 8-h ambient CO designed for daily operational forecasting purposes. The resulting models include variables and interaction terms related to anticipated nocturnal atmospheric stability as well as antecedent and climatological CO behavior. The models are evaluated using a range of error statistics and skill measures. The most successful approach employs a two-stage modeling strategy in which an initial prediction is made that may, depending on the forecast value, be followed by a second prediction that improves upon the first. The best models provide accurate daily forecasts of CO, with explained variances approaching 0.9 and errors under 1 ppm.     

Transport and dispersion during wintertime particulate matter episodes in the San Joaquin Valley, California

Data analysis and modeling were performed to characterize the spatial and temporal variability of wintertime transport and dispersion processes and the impact of these processes on particulate matter (PM) concentrations in the California San Joaquin Valley (SJV). Radar wind profiler (RWP) and radio acoustic sounding system (RASS) data collected from 18 sites throughout Central California were used to estimate hourly mixing heights for a 3-month period and to create case studies of high-resolution diagnostic wind fields, which were used for trajectory and dispersion analyses. Data analyses show that PM episodes were characterized by an upper-level ridge of high pressure that generally produced light winds through the entire depth of the atmospheric boundary layer and low mixing heights compared with nonepisode days. Peak daytime mixing heights during episodes were -400 m above ground level (agl) compared with -800 m agl during nonepisodes. These episode/nonepisode differences were observed throughout the SJV. Dispersion modeling indicates that the range of influence of primary PM emitted in major population centers within the SJV ranged from -15 to 50 km. Trajectory analyses revealed that little intrabasin pollutant transport occurred among major population centers in the SJV; however, interbasin transport from the northern SJV and Sacramento regions into the San Francisco Bay Area (SFBA) was often observed. In addition, this analysis demonstrates the usefulness of integrating RWP/RASS measurements into data analyses and modeling to improve the understanding of meteorological processes that impact pollution, such as aloft transport and boundary layer evolution.     

A case study for wintertime observation of atmospheric particulates by an eye-safe laser radar

Atmospheric particulates were monitored on a typical high concentration day in early winter in Osaka, Japan, using a compact and portable eye-safe laser radar system. The height of mixing layer was about 0.4 km at 8:00 and gradually increased to 0.8 km at 14:00. The development of the layer was in inverse proportion to the decrease of particulates near the ground surface. Analysis of particulates collected with high-volume air samplers showed that concentrations of elemental carbon (EC), lead and ammonium ion near the surface decreased significantly from morning to midday, while concentrations of sulfate, nitrate, sodium and calcium ions were almost constant. The results obtained in the preliminary study suggest that anthropogenic particulates such as EC and lead are on the rise with development of mixing layer from morning to midday.     

A wintertime study of polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air in a big student residence in Algiers,Algeria

The wintertime concentrations and diel cycles of n-alkanes and polycyclic aromatic hydrocarbons (PAHs) associated to atmospheric particulate matter with aerodynamic diameter lesser than 10 μm were determined at the biggest student residence in Algeria located in Bab-Ezzouar, 15 km southeast from Algiers city area. Samplings were carried out from December 2009 to March 2010, and organic compounds were characterized using gas chromatography coupled with mass spectrometric detection. Volatile PAHs were also monitored inside some student residence rooms in order to evaluate the impact of indoor air pollution to student health. For the sake of comparison, aerial concentrations of n-alkanes and PAHs were determined in parallel in the Oued Smar industrial zone and two suburban areas, all located in Algiers. Total concentrations recorded in CUB1 student residence ranged from 101 to 204 ng?m^?3 for n-alkanes and from 8 to 87 ng?m^?3 for PAHs. Diel cycles have shown that, while concentrations of n-alkanes peaked at morning and afternoon–evening and dropped at night, those of PAHs exhibited higher levels at morning and night and lower levels at afternoon–evening, likely due to the reactivity of some PAHs. As expected, the indoor levels of PAHs were larger than in the outdoor of the student residence and were of serious health concern. Overall, the concentrations of n-alkanes and PAHs were as high as those observed in the industrial zone and higher than the two suburban sites.     

Causes of haze in the Columbia River Gorge

Visibility impairment in the Columbia River Gorge National Scenic Area is an area of concern. A field study conducted from July 2003 to February 2005 was followed by data analysis and receptor modeling to better understand the temporal and spatial patterns of haze and the sources contributing to the haze in the Columbia River Gorge in the states of Washington and Oregon. The nephelometer light scattering and surface meteorological data at eight sites along the gorge showed five distinct wind patterns, each with its characteristic diurnal and spatial patterns in light scattering by particles (bsp). In summer, winds were nearly always from west to east (upgorge) and showed decreasing bsp with distance into the gorge and a pronounced effect of the Portland, OR, metropolitan area on haze, especially in the western portions of the gorge. Winter often had winds from the east with very high levels of bsp, especially at the eastern gorge sites, with sources east of the gorge responsible for much of the haze. The major chemical components responsible for haze were organic carbon, sulfate, and nitrate. Positive matrix factorization (PMF) using chemically speciated Interagency Monitoring of Protected Visual Environments data indicated seven source factors in the western gorge and five factors in the eastern gorge. Organic mass is a large contributor to haze in the gorge in all seasons, with a peak in fall. The PMF analysis suggests that approximately half of the organic mass is biomass smoke, with mobile sources as the second largest contributor. PMF analysis showed nitrates (important in fall and winter) mainly attributed to a generic secondary nitrate factor, with the next largest contributor being oil combustion at Mt. Zion, WA and mobile sources at Wishram, WA. Sulfate is a significant contributor in all seasons, with peak sulfate concentrations in summer.     

Acidic precipitation in southeastern Arizona: Sulfate,nitrate and trace-metal deposition

Precipitation was collected during 1984 and 1985 at two sites in southeastern Arizona within 100 km of two copper smelters. The precipitation-depth-weighted mean pH was 4.63 and wet sulfate deposition was 8.9 kg ha⁻¹ over a 13-month period. High acidity and sulfate concentration occurred when upper-level winds were from the directions of the smelters. A smelter ‘fingerprint’, based on antimony, arsenic, cadmium, copper, lead and zinc, was identified, and used to evaluate the smelter contribution to precipitation sulfate on an annually-averaged basis. The variations in the relative proportions of these trace metals were too large to permit application of the method to individual precipitation events.     

Characterization and source apportionment of wintertime aerosol in a wood-burning community

The continuing upsurge in residential wood combustion has raised questions about potential adverse effects on ambient air quality. A study to investigate the effects of wood-burning emissions on ambient aerosol concentrations was conducted in Waterbury, Vermont, from January to March 1982. Data on total, inhalable and respirable particles (24-h averages) were collected at a central monitoring site and augmented with similar measurements at two auxiliary stations. Mass concentrations were determined gravimetrically and selected samples were analyzed for elemental composition (XRF), polycyclic aromatic hydrocarbons (GC/MS, HPLC), and organic and elemental carbon (thermal-optical method). In addition, continuous data from an integrating nephelometer and a meteorological data acquisition system were collected at the central site. This paper presents results of organic and elemental characterization of wintertime aerosol and examines several different source-apportionment methods, focusing on the contribution of residential wood combustion to measured ambient concentrations.     

Impact of haze and air pollution-related hazards on hospital admissions in Guangzhou,China

Guangzhou is a metropolitan in south China with unique pollutants and geographic location. Unlike those in western countries and the rest of China, the appearance of haze in Guangzhou is often (about 278 days per year on average of 4 years). Little is known about the influence of these hazes on health. In this study, we investigated whether short-term exposures to haze and air pollution are associated with hospital admissions in Guangzhou. The relationships between haze, air pollution, and daily hospital admissions during 2008–2011 were assessed using generalized additive model. Studies were categorized by gender, age, season, lag, and disease category. In haze episodes, an increase in air pollutant emissions corresponded to 3.46 (95 % CI, 1.67, 5.27) increase in excessive risk (ER) of total hospital admissions at lag 1, 11.42 (95 % CI, 4.32, 18.99) and 11.57 (95 % CI, 4.38, 19.26) increases in ERs of cardiovascular illnesses at lags 2 and 4 days, respectively. As to total hospital admissions, an increase in NO₂ was associated with a 0.73 (95 % CI, 0.11, 1.35) and a 0.28 (95 % CI, 0.11, 0.46) increases in ERs at lag 5 and lag 05, respectively. For respiratory illnesses, increases in NO₂ was associated with a 1.94 (95 % CI, 0.50, 3.40) increase in ER at lag 0, especially among chronic obstructive pulmonary disease. Haze (at lag1) and air pollution (for NO₂ at lag 5 and for SO₂ at lag3) both presented more drastic effects on the 19 to 64 years old and in the females. Together, we demonstrated that haze pollution was associated with total and cardiovascular illnesses. NO₂ was the sole pollutant with the largest risk of hospital admissions for total and respiratory diseases in both single- and multi-pollutant models.     

Fine particulate matter and visibility in the Lake Tahoe Basin: chemical characterization, trends, and source apportionment

Speciated PM2.5 (particulate matter with an aerodynamic diameter相似文献   

An intensive two-week study of an urban CO2 dome in Phoenix,Arizona, USA

Atmospheric CO₂ concentrations were measured prior to dawn and in the middle of the afternoon at a height of 2 m above the ground along four transects through the metropolitan area of Phoenix, Arizona on 14 consecutive days in January 2000. The data revealed the existence of a strong but variable urban CO₂ dome, which at one time exhibited a peak CO₂ concentration at the center of the city that was 75% greater than that of the surrounding rural area. Mean city-center peak enhancements, however, were considerably lower, averaging 43% on weekdays and 38% on weekends; and averaged over the entire commercial sector of the city, they were lower still, registering 30% on weekdays and 23% on weekends. Over the surrounding residential areas, on the other hand, there are no weekday–weekend differences in boundary-layer CO₂ concentration. Furthermore, because of enhanced vertical mixing during the day, near-surface CO₂ concentrations in the afternoon are typically reduced from what they are prior to sunrise. This situation is additionally perturbed by the prevailing southwest-to-northeast flow of air at that time of day, which lowers afternoon CO₂ concentrations on the southern and western edges of the city still more, as a consequence of the importation of pristine rural air. The southwest-to-northeast flow of air also sometimes totally compensates for the afternoon vertical-mixing-induced loss of CO₂ from areas on the northern and eastern sides of the city, as a consequence of the northeastward advection of CO₂ emanating from the central, southern and western sectors of the city. Hence, although complex, the nature of the urban CO₂ dome of Phoenix, Arizona, is readily understandable in terms of basic meteorological phenomena and their interaction with human activities occurring at the land/air interface.     

An Urban Airshed Model for Predicting Carbon Monoxide Concentrations in Tucson,Arizona

ABSTRACT

The Electric Power Research Institute (EPRI) is conducting research to investigate mercury removal in utility flue gas using sorbents. Bench-scale and pilot-scale tests have been conducted to determine the abilities of different sor-bents to remove mercury in simulated and actual flue gas streams. Bench-scale tests have investigated the effects of various sorbent and flue gas parameters on sorbent performance. These data are being used to develop a theoretical model for predicting mercury removal by sorbents at different conditions. This paper describes the results of parametric bench-scale tests investigating the removal of mercuric chloride and elemental mercury by activated carbon.

Results obtained to date indicate that the adsorption capacity of a given sorbent is dependent on many factors, including the type of mercury being adsorbed, flue gas composition, and adsorption temperature. These data provide insight into potential mercury adsorption mechanisms and suggest that the removal of mercury involves both physical and chemical mechanisms. Understanding these effects is important since the performance of a given sorbent could vary significantly from site to site depending on the coal- or gas-matrix composition.     

Identification and chemical characterization of industrial particulate matter sources in southwest Spain

A detailed physical and chemical characterization of coarse particulate matter (PM10) and fine particulate matter (PM2.5) in the city of Huelva (in Southwestern Spain) was carried out during 2001 and 2002. To identify the major emission sources with a significant influence on PM10 and PM2.5, a methodology was developed based on the combination of: (1) real-time measurements of levels of PM10, PM2.5, and very fine particulate matter (PM1); (2) chemical characterization and source apportionment analysis of PM10 and PM2.5; and (3) intensive measurements in field campaigns to characterize the emission plumes of several point sources. Annual means of 37, 19, and 16 microg/m3 were obtained for the study period for PM10, PM2.5, and PM1, respectively. High PM episodes, characterized by a very fine grain size distribution, are frequently detected in Huelva mainly in the winter as the result of the impact of the industrial emission plumes on the city. Chemical analysis showed that PM at Huelva is characterized by high PO4(3-) and As levels, as expected from the industrial activities. Source apportionment analyses identified a crustal source (36% of PM10 and 31% of PM2.5); a traffic-related source (33% of PM10 and 29% of PM2.5), and a marine aerosol contribution (only in PM10, 4%). In addition, two industrial emission sources were identified in PM10 and PM2.5: (1) a petrochemical source, 13% in PM10 and 8% in PM2.5; and (2) a mixed metallurgical-phosphate source, which accounts for 11-12% of PM10 and PM2.5. In PM2.5 a secondary source has been also identified, which contributed to 17% of the mass. A complete characterization of industrial emission plumes during their impact on the ground allowed for the identification of tracer species for specific point sources, such as petrochemical, metallurgic, and fertilizer and phosphate production industries.     

Threshold dependence of mortality effects for fine and coarse particles in Phoenix, Arizona

Daily data for fine (< 2.5 microns) and coarse (2.5-10 microns) particles are available for 1995-1997 from the U.S. Environmental Protection Agency (EPA) research monitor in Phoenix, AZ. Mortality effects on the 65 and over population were studied for both the city of Phoenix and for a region of about 50 mi around Phoenix. Coarse particles in Phoenix are believed to be natural in origin and spatially homogeneous, whereas fine particles are primarily vehicular in origin and concentrated in the city itself. For this reason, it is natural to focus on city mortality data when considering fine particles, and on region mortality data when considering coarse particles, and most of the results reported here correspond to those assignments. After allowing for seasonality and long-term trend through a nonlinear (B-spline) trend curve, and also for meteorological effects based on temperature and specific humidity, a regression of mortality was performed on PM using several different measures for PM. Based on a linear PM effect, we found a statistically significant coefficient for coarse particles, but not for fine particles, contrary to what is widely believed about the effects of coarse and fine particles. An analysis of nonlinear pollution-mortality relationships, however, suggests that the true picture is more complicated than that. For coarse particles, the evidence for any nonlinear or threshold-based effect is slight. For fine particles, we found evidence of a threshold, most likely with values in the range of 20-25 micrograms/m3. We also found some evidence of interactions of the PM effects with season and year. The main effect here is an apparent seasonal interaction in the coarse PM effect. An attempt was made to explain this in terms of seasonal variation in the chemical composition of PM, but this led to another counterintuitive result: the PM effect is highest in spring and summer, when the anthropogenic concentration of coarse PM is lowest as determined by a principal components analysis. There was no evidence of confounding between the fine and coarse PM effects. Although these results are based on one city and should be considered tentative until replicated in other studies, they suggest that the prevailing focus on fine rather than coarse particles may be an oversimplification. The study also shows that consideration of nonlinear effects can lead to real changes of interpretation and raises the possibility of seasonal effects associated with the chemical composition of PM.