Semicontinuous PM2.5 sulfate and nitrate measurements at an urban and a rural location in New York: PMTACS-NY summer 2001 and 2002 campaigns

Several collocated semicontinuous instruments measuring particulate matter with particle sizes < or =2.5 microm (PM2.5) sulfate (SO4(2-)) and nitrate (NO3-) were intercompared during two intensive field campaigns as part of the PM2.5 Technology Assessment and Characterization Study. The summer 2001 urban campaign in Queens, NY, and the summer 2002 rural campaign in upstate New York (Whiteface Mountain) hosted an operation of an Aerosol Mass Spectrometer, Ambient Particulate Sulfate and Nitrate Monitors, a Continuous Ambient Sulfate Monitor, and a Particle-Into-Liquid Sampler with Ion Chromatographs (PILS-IC). These instruments provided near real-time particulate SO4(2-) and NO3- mass concentration data, allowing the study of particulate SO4(2-)/NO3- diurnal patterns and detection of short-term events. Typical particulate SO4(2-) concentrations were comparable at both sites (ranging from 0 to 20 microg/m3), while ambient urban particulate NO3- concentrations ranged from 0 to 11 microg/m3 and rural NO3- concentration was typically less than 1 microg/m3. Results of the intercomparisons of the semicontinuous measurements are presented, as are results of the comparisons between the semicontinuous and time-integrated filter-based measurements. The comparisons at both sites, in most cases, indicated similar performance characteristics. In addition, charge balance calculations, based on major soluble ionic components of atmospheric aerosol from the PILS-IC and the filter measurements, indicated slightly acidic aerosol at both locations.     

Annual evolution and generation mechanisms of particulate nitrate in Madrid

During the course of one year (March 2004–March 2005), PM_2.5 particulate nitrate concentrations were semi-continuously measured every 10 min at a Madrid suburban site using the Rupprecht and Patashnick Series 8400N Ambient Particulate Nitrate Monitor (8400N). Gaseous pollutants (NO, NO₂, O₃, HCHO, HNO₂) were simultaneously measured with a DOAS spectrometer (OPSIS AR-500) and complementary meteorological information was obtained by a permanent tower. The particulate nitrate concentrations ranged from the instrumental detection limit of around 0.2 μg m⁻³, up to a maximum of about 25 μg m⁻³. The minimum monthly average was reached during August (0.32 μg m⁻³) and the maximum during November (3.0 μg m⁻³). Due to the semi-volatile nature of ammonium nitrate, peaks were hardly present during summer air pollution episodes. A typical pattern during days with low dispersive conditions was characterized by a steep rise of particulate nitrate in the morning, reaching maximum values between 9 and 14 UTC, followed by a decrease during the evening. On some occasions a light increase was observed at nighttime. During spring episodes, brief diurnal nitrate peaks were recorded, while during the autumn and winter episodes, later and broader nitrate peaks were registered. Analysis of particulate nitrate and related gaseous species indicated the photo-chemical origin of the morning maxima, delayed with respect to NO and closely associated with secondary NO₂ maximum values. The reverse evolution of nitrate and nitrous acid was observed after sunrise, suggesting a major contribution from HNO₂ photolysis to OH formation at this time of the day, which would rapidly produce nitrate in both gaseous and particulate phase. Some nocturnal nitrate maxima appeared under high humidity conditions, and a discussion about their origin involving different possible mechanisms is presented, i.e. the possibility that these nocturnal maximum values could be related to the heterogeneous formation of nitrous and nitric acid by the hydrolysis of NO₂ on wet aerosols.     

Atmospheric conversion of sulfur dioxide to particulate sulfate and nitrogen dioxide to particulate nitrate and gaseous nitric acid in an urban area

Sulfur dioxide, nitrogen dioxide, particulate sulfate and nitrate, gaseous nitric acid, ozone and meteorological parameters (temperature and relative humidity) were measured during the winter season (1999-2000) and summer season (2000) in an urban area (Dokki, Giza, Egypt). The average particulate nitrate concentrations were 6.20 and 9.80 microg m(-3), while the average gaseous nitric acid concentrations were 1.14 and 6.70 microg m(-3) in the winter and summer seasons, respectively. The average sulfate concentrations were 15.32 microg m(-3) during the winter and 25.10 microg m(-3) during the summer season. The highest average concentration ratio of gaseous nitric acid to total nitrate was found during the summer season. Particulate sulfate and nitrate and gaseous nitric acid concentrations were relatively higher in the daytime than those in the nighttime. Sulfur conversion ratio (Fs) and nitrogen conversion ratio (Fn) defined in the text were calculated from the field measurement data. Sulfur conversion ratio (Fs) and nitrogen conversion ratio (Fn) in the summer were about 2.22 and 2.97 times higher than those in the winter season, respectively. Moreover, sulfur conversion ratio (Fs) and nitrogen conversion ratio (Fn) were higher in the daytime than those in the nighttime during the both seasons. The sulfur conversion ratio (Fs) increases with increasing ozone concentration and relative humidity. This indicates that the droplet phase reactions and gas phase reactions are important for the oxidation of SO2 to sulfate. Moreover, the nitrogen conversion ratio (Fn) increases with increasing ozone concentration, and the gas phase reactions are important and predominant for the oxidation of NO2 to nitrate.     

Characterization of PM2.5 and PM10 in the South Coast Air Basin of southern California: Part 1--Spatial variations

In December 1994, the South Coast Air Quality Management District (SCAQMD) initiated a comprehensive program, the PM10 Technical Enhancement Program (PTEP), to characterize fine PM in the South Coast Air Basin (SCAB). A 1-year special particulate monitoring project was conducted from January 1995 to February 1996 as part of the PTEP. Under this enhanced monitoring, HNO3, NH3, and speciated PM10 and PM2.5 concentrations were measured at five stations (Anaheim, downtown Los Angeles, Diamond Bar, Fontana, and Rubidoux) in the SCAB and at one background station at San Nicolas Island. PM2.5 and PM10 mass and 43 individual species were analyzed for a full chemical speciation of the particle data. The PTEP data indicate that the most abundant chemical components of PM10 and PM2.5 in the SCAB are NH4+ (8-9% of PM10 and 14-17% of PM2.5), NO3- (23-26% of PM10 and 28-41% of PM2.5), SO4- (6-11% of PM10 and 9-18% of PM2.5), organic carbon (OC) (15-19% of PM10 and 18-26% of PM2.5), and elemental carbon (EC) (5-8% of PM10 and 8-13% of PM2.5). On an annual average basis, PM2.5 comprises 52-59% of the SCAB PM10. Annual average PM10 and PM2.5 concentrations showed strong spatial variations, low at coastal sites and high at inland sites. Annual average PM10 concentrations varied from 40.8 micrograms/m3 at Anaheim to 76.8 micrograms/m3 at Rubidoux, while annual average PM2.5 concentrations varied from 21.7 micrograms/m3 at Anaheim to 39.8 micrograms/m3 at Rubidoux. The chemical characterizations of the PM2.5 and PM10 concentrations, as well as their spatial variations, were examined; the important findings are summarized in this paper, and the temporal variations are discussed in the companion paper.     

Quality-assured measurements of animal building emissions: particulate matter concentrations

Federally funded, multistate field studies were initiated in 2002 to measure emissions of particulate matter (PM) < 10 microm (PM10) and total suspended particulate (TSP), ammonia, hydrogen sulfide, carbon dioxide, methane, nonmethane hydrocarbons, and odor from swine and poultry production buildings in the United States. This paper describes the use of a continuous PM analyzer based on the tapered element oscillating microbalance (TEOM). In these studies, the TEOM was used to measure PM emissions at identical locations in paired barns. Measuring PM concentrations in swine and poultry barns, compared with measuring PM in ambient air, required more frequent maintenance of the TEOM. External screens were used to prevent rapid plugging of the insect screen in the PM10 preseparator inlet. Minute means of mass concentrations exhibited a sinusoidal pattern that followed the variation of relative humidity, indicating that mass concentration measurements were affected by water vapor condensation onto and evaporation of moisture from the TEOM filter. Filter loading increased the humidity effect, most likely because of increased water vapor adsorption capacity of added PM. In a single layer barn study, collocated TEOMs, equipped with TSP and PM10 inlets, corresponded well when placed near the inlets of exhaust fans in a layer barn. Initial data showed that average daily mean concentrations of TSP, PM10, and PM2.5 concentrations at a layer barn were 1440 +/- 182 microg/m3 (n = 2), 553 +/- 79 microg/m3 (n = 4), and 33 +/- 75 microg/m3 (n = 1), respectively. The daily mean TSP concentration (n = 1) of a swine barn sprinkled with soybean oil was 67% lower than an untreated swine barn, which had a daily mean TSP concentration of 1143 +/- 619 microg/m3. The daily mean ambient TSP concentration (n = 1) near the swine barns was 25 +/- 8 microg/m3. Concentrations of PM inside the swine barns were correlated to pig activity.     

Compilation and assessment of recent positive matrix factorization and UNMIX receptor model studies on fine particulate matter source apportionment for the eastern United States

In 1997, the U.S. Environmental Protection Agency (EPA) revised its particulate matter standards to include an annual standard for fine particulate matter (PM2.5; 15 microg/m3) and a 24-hr standard (65 microg/m3). The 24-hr standard was lowered to 35 microg/m3 in 2006 in an effort to further reduce overall ambient PM2.5 concentrations. Identifying and quantifying sources of particulate matter affecting a particular location through source apportionment methods is now an important component of the information available to decision makers when evaluating the new standards. This literature compilation summarizes a subset of the source apportionment research and general findings on fine particulate matter in the eastern half of the United States using Positive Matrix Factorization. The results between studies are generally comparable when comparable datasets are used; however, methodologies vary considerably. Commonly identified source categories include: secondary sulfate/coal burning (sometimes over 50% of total mass), secondary organic carbon/mobile sources, crustal sources, biomass burning, nitrate, various industrial processes, and sea salt. The source apportionment tools and methodologies have passed the proof-of-concept stage and are now being used to understand the ambient composition of particulate matter for sites across the United States and the spatial relationship of sources to the receptor. Recommendations are made for further and standardized method development for source apportionment studies, and specific research areas of interest for the eastern United States are proposed.     

Measurement of fine particulate matter nonvolatile and semi-volatile organic material with the Sunset Laboratory Carbon Aerosol Monitor

Semi-volatile organic material (SVOM) in fine particles is not reliably measured with conventional semicontinuous carbon monitors because SVOM is lost from the collection media during sample collection. We have modified a Sunset Laboratory Carbon Aerosol Monitor to allow for the determination of SVOM. In a conventional Sunset monitor, gas-phase organic compounds are removed in the sampled airstream by a diffusion denuder employing charcoal-impregnated cellulose filter (CIF) surfaces. Subsequently, particles are collected on a quartz filter and the instrument then determines both the organic carbon and elemental carbon fractions of the aerosol using a thermal/optical method. However, some of the SVOM is lost from the filter during collection, and therefore is not determined. Because the interfering gas-phase organic compounds are removed before aerosol collection, the SVOM can be determined by filtering the particles at the instrument inlet and then replacing the quartz filter in the monitor with a charcoal-impregnated glass fiber filter (CIG), which retains the SVOM lost from particles collected on the inlet filter. The resulting collected SVOM is then determined in the analysis step by measurement of the carbonaceous material thermally evolved from the CIG filter. This concept was tested during field studies in February 2003 in Lindon, UT, and in July 2003 in Rubidoux, CA. The results obtained were validated by comparison with Particle Concentrator-Brigham Young University Organic Sampling System (PC-BOSS) results. The sum of nonvolatile organic material determined with a conventional Sunset monitor and SVOM determined with the modified Sunset monitor agree with the PC-BOSS results. Linear regression analysis of total carbon concentrations determined by the PC-BOSS and the Sunset resulted in a zero-intercept slope of 0.99 +/- 0.02 (R2 = 0.92) and a precision of sigma = +/- 1.5 microg C/m3 (8%).     

Continuous and semicontinuous monitoring techniques for particulate matter mass and chemical components: a synthesis of findings from EPA's Particulate Matter Supersites Program and related studies

The U.S. Environmental Protection Agency (EPA) established the Particulate Matter (PM) Supersites Program to provide key stakeholders (government and private sector) with significantly improved information needed to develop effective and efficient strategies for reducing PM on urban and regional scales. All Supersites projects developed and evaluated methods and instruments, and significant advances have been made and applied within these programs to yield new insights to our understanding of PM accumulation in air as well as improved source-receptor relationships. The tested methods include a variety of continuous and semicontinuous instruments typically with a time resolution of an hour or less. These methods often overcome many of the limitations associated with measuring atmospheric PM mass concentrations by daily filter-based methods (e.g., potential positive or negative sampling artifacts). Semicontinuous coarse and ultrafine mass measurement methods also were developed and evaluated. Other semicontinuous monitors tested measured the major components of PM such as nitrate, sulfate, ammonium, organic and elemental carbon, trace elements, and water content of the aerosol as well as methods for other physical properties of PM, such as number concentration, size distribution, and particle density. Particle mass spectrometers, although unlikely to be used in national routine monitoring networks in the foreseeable future because of their complex technical requirements and cost, are mentioned here because of the wealth of new information they provide on the size-resolved chemical composition of atmospheric particles on a near continuous basis. Particle mass spectrometers likely represent the greatest advancement in PM measurement technology during the last decade. The improvements in time resolution achieved by the reported semicontinuous methods have proven to be especially useful in characterizing ambient PM, and are becoming essential in allowing scientists to investigate sources of particulate pollution and to probe into the dynamics and mechanisms of aerosol formation in the atmosphere.     

Correlation of ambient inhalable bioaerosols with particulate matter and ozone: a two-year study

In this study, we have examined the relationships between the concentrations of ambient inhalable airborne fungi and pollen with PM10, PM2.5, ozone, organic carbon, selected trace metals (cadmium, copper, lead, and zinc), temperature, and relative humidity. The database was collected in Cincinnati, Ohio, USA, during two consecutive years. Measurements of all environmental variables were performed at the same site continuously 5 days a week except during winter months. The airborne concentrations of biological and non-biological pollutants ranged as follows: total fungi: 184-16 979 spores m(-3); total pollen: 0-6692 pollen m(-3); PM10: 6.70-65.38 microg m(-3); PM2.5: 5.04-45.02 microg m(-3); and ozone: 2.54-64.17 ppb. Higher levels of total inhalable fungi and particulate matter were found during fall and summer months. In contrast, total pollen concentration showed elevated levels in spring. Peak concentrations of ozone were observed during summer and beginning of fall. Our study concluded that several types of inhalable airborne fungi and pollen, particulate matter, and ozone could be positively correlated as a result of the atmospheric temperature influence.     

Fine particulate chemical composition and light extinction at Meadview, AZ

The concentration of fine particulate nitrate, sulfate, and carbonaceous material was measured for 12-hr day-night samples using diffusion denuder samplers during the Project Measurement of Haze and Visibility Effects (MOHAVE) July to August 1992 Summer Intensive study at Meadview, AZ, just west of Grand Canyon National Park. Organic material was measured by several techniques. Only the diffusion denuder method measured the semivolatile organic material. Fine particulate sulfate and nitrate (using denuder technology) determined by various groups agreed. Based on the various collocated measurements obtained during the Project MOHAVE study, the precision of the major fine particulate species was +/- 0.6 microg/m3 organic material, +/- 0.3 microg/m3 ammonium sulfate, and +/- 0.07 microg/m3 ammonium nitrate. Data were also available on fine particulate crustal material, fine and coarse particulate mass from the Interagency Monitoring of Protected Visual Environments sampling system, and relative humidity (RH), light absorption, particle scattering, and light extinction measurements from Project MOHAVE. An extinction budget was obtained using mass scattering coefficients estimated from particle size distribution data. Literature data were used to estimate the change in the mass scattering coefficients for the measured species as a function of RH and for the absorption of light by elemental carbon. Fine particulate organic material was the principal particulate contributor to light extinction during the study period, with fine particulate sulfate as the second most important contributor. During periods of highest light extinction, contributions from fine particulate organic material, sulfate, and light-absorbing carbon dominated the extinction of light by particles. Particle light extinction was dominated by sulfate and organic material during periods of lowest light extinction. Combination of the extinction data and chemical mass balance analysis of sulfur oxides sources in the region indicate that the major anthropogenic contributors to light extinction were from the Los Angeles, CA, and Las Vegas, NV, urban areas. Mohave Power Project associated secondary sulfate was a negligible contributor to light extinction.     

Nitrate Artifacts during PM25 Sampling in the South Coast Air Basin of California

ABSTRACT

In February 1993, the South Coast Air Basin (SCAB) was redesignated as a “serious” nonattainment area for PM10. To improve the understanding and characterization of fine particulate matter in the SCAB, the South Coast Air Quality Management District (SCAQMD) initiated a comprehensive PM₁₀ Technical Enhancement Program (PTEP). Using enhanced PTEP monitors (specially designed multichannel/multifilter samplers), a one-year fine particulate matter (PM) monitoring program was initiated in January 1995. As part of the special monitoring program, nitric acid, ammonia, and speciated PM₁₀ and PM_2.5 concentrations were measured at five locations in the SCAB (downtown Los Angeles, Anaheim, Diamond Bar, Fontana, and Rubidoux) and at one background station (San Nicolas Island). The PM2.5 data are the first spatially resolved speciated data collected in the SCAB on an annual basis. Within the SCAB, where nitrate is a major component of PM_2.5, nitrate losses have been documented. The spatial and temporal variations of the nitrate losses during PM_2.5 sampling and the uncertainties of the nitrate losses are discussed. Significant losses occur at a low mass range, between 10 and 50 ìg/m³. Significant gains occur at an even lower mass range of less than 30 ìg/m³. On an annual average basis, nitrate losses vary between 1.25 and 2.32 ìg/m³ and the SCAB-wide average value of nitrate loss is 1.8 ìg/m³ based on five PTEP stations in the SCAB. The maximum nitrate losses for each station vary from 6.4 ìg/m³ to 22.5 ìg/m ³. Theoretical prediction of the sampling efficiency of the nitrate during PM_2.5 sam - pling was compared with the PTEP data. In general, theoretical prediction was in good agreement with measured values.     

Human exposure to respirable suspended particulate and airborne lead in different roadside microenvironments

The aim of this study is to evaluate the particulate air pollution in selected roadside microenvironments of Hong Kong through an intensive field study dated from January 1997 to February 1997. The study employed the microenvironment monitoring technique to access the exposure of pedestrians to respirable suspended particulate and airborne lead (Pb) at heavily trafficked roadsides. A total of 62 roadside sites in 14 districts covering the most urbanized and densely populated areas were selected. It was found that pedestrians were exposed to a 24 h average of respirable suspended particulate, PM10, and airborne Pb (APb), typically ranged from 25.56 to 337.40 microg/m3 and 70.71 to 285.71 ng/m3, respectively. The average PM10 concentrations at different roadside microenvironments corresponding to urban residential, urban commercial, urban industrial and new town areas were 91.84, 129.08, 83.83, and 118.89 microg/m3 respectively. The corresponding values for APb were 130.01, 143.40, 127.40 and 173.17 ng/m3, respectively. It was found that measurement at EPD nearby rooftop monitoring stations might not reflect the actual roadside PM10 exposure. Most APb field study data was significantly higher than the nearby fixed station data.     

Seasonal and shorter-term variations in particulate atmospheric nitrate in Baltimore

Fine particle nitrate concentrations were measured at 10-min intervals for approximately 9.5 months beginning on 14 February 2002, at the Baltimore Supersite Ponca St. location using an R&P 8400N semi-continuous monitor. The measurement results were used to characterize seasonal and shorter-term excursions in nitrate concentrations and determine their influence on PM_2.5 concentrations. Over the 9.5-month study period, nitrate levels of 1.7±1.6 μg m⁻³ accounted for 11.4% of the PM_2.5 mass. Monthly averages ranged from 0.8 μg m⁻³ in August to 2.9 μg m⁻³ in November, and accounted for 4.7–17.3% of monthly PM_2.5 mass. Hourly averages, however, were often larger, especially in the colder months, owing to numerous relatively short-term transients, where hourly nitrate concentrations exceeded 5.0 μg m⁻³. These often occurred along with NO_x and ultrafine particle transients during the morning commute hours.A total of 275 short-term transients (31.7% of the total) exceeding 1.0 μg m⁻³ were identified. These were associated with one of three sets of conditions. The first, most typical (177, i.e. 64.4% of the 275 incidences), is characterized by high NO_x typically between 0500 and 0800EST and is attributed to early morning commute traffic activity. The second type occurred during the afternoon due to photochemical activity. The excursions in the afternoon occurred infrequently (only 9.5% of all the observed transients) during the study period and were characterized by less elevated nitrate concentrations than morning and nighttime transients. The third (72, i.e. 26.2% of the 275 transients) occurred at night, typically between 2000EST and 0200EST.Multiple linear regression analysis between nitrate excursions and volume size distributions indicates that particulate nitrate observed is closely related to the near accumulation (0.1–0.2 μm) and droplet modes (0.5–1.0 μm) in the morning hours, and associated with the droplet (0.5–1.0 μm) and coarse modes (1.0–2.5 μm) for nighttime transients, suggesting that processes governing particulate nitrate formation depend on time-of-day.     

Effects of sulfur dioxide and oxides of nitrogen emission reductions on fine particulate matter mass concentrations: regional comparisons

Two thermodynamic equilibrium models were applied to estimate changes in mean airborne fine particle (PM2.5) mass concentrations that could result from changes in ambient concentrations of sulfate, nitric acid, or ammonia in the southeastern United States, the midwestern United States, and central California. Pronounced regional differences were found. Southeastern sites exhibited the lowest current mean concentrations of nitrate, and the smallest predicted responses of PM2.5 nitrate and mass concentrations to reductions of nitric acid, which is the principal reaction product of the oxidation of nitrogen dioxide (NO2) and the primary gas-phase precursor of fine particulate nitrate. Weak responses of PM2.5 nitrate and mass concentrations to changes in nitric acid levels occurred even if sulfate concentrations were half of current levels. The midwestern sites showed higher levels of fine particulate nitrate, characterized by cold-season maxima, and were projected to show decreases in overall PM levels following decreases of either sulfate or nitric acid. For some midwestern sites, predicted PM2.5 nitrate concentrations increased as modeled sulfate levels declined, but sulfate reductions always reduced the predicted fine PM mass concentrations; PM2.5 nitrate concentrations became more sensitive to reductions of nitric acid as modeled sulfate concentrations were decreased. The California sites currently have the highest mean concentrations of fine PM nitrate and the lowest mean concentrations of fine PM sulfate. Both the estimated PM2.5 nitrate and fine mass concentrations decreased in response to modeled reductions of nitric acid at all California sites. The results indicate important regional differences in expected PM2.5 mass concentration responses to changes in sulfate and nitrate precursors. Analyses of ambient data, such as described here, can be a key part of weight of evidence (WOE) demonstrations for PM2.5 attainment plans. Acquisition of the data may require special sampling efforts, especially for PM2.5 precursor concentration data.     

Characterization of particulate matter for three sites in Kuwait

Many studies have shown strong associations between particulate matter (PM) levels and a variety of health outcomes, leading to changes in air quality standards in many regions, especially the United States and Europe. Kuwait, a desert country located on the Persian Gulf, has a large petroleum industry with associated industrial and urban land uses. It was marked by environmental destruction from the 1990 Iraqi invasion and subsequent oil fires. A detailed particle characterization study was conducted over 12 months in 2004-2005 at three sites simultaneously with an additional 6 months at one of the sites. Two sites were in urban areas (central and southern) and one in a remote desert location (northern). This paper reports the concentrations of particles less than 10 microm in diameter (PM10) and fine PM (PM2.5), as well as fine particle nitrate, sulfate, elemental carbon (EC), organic carbon (OC), and elements measured at the three sites. Mean annual concentrations for PM10 ranged from 66 to 93 microg/m3 across the three sites, exceeding the World Health Organization (WHO) air quality guidelines for PM10 of 20 microg/m3. The arithmetic mean PM2.5 concentrations varied from 38 and 37 microg/m3 at the central and southern sites, respectively, to 31 microg/m3 at the northern site. All sites had mean PM2.5 concentrations more than double the U.S. National Ambient Air Quality Standard (NAAQS) for PM2.5. Coarse particles comprised 50-60% of PM10. The high levels of PM10 and large fraction of coarse particles comprising PM10 are partially explained by the resuspension of dust and soil from the desert crust. However, EC, OC, and most of the elements were significantly higher at the urbanized sites, compared with the more remote northern site, indicating significant pollutant contributions from local mobile and stationary sources. The particulate levels in this study are high enough to generate substantial health impacts and present opportunities for improving public health by reducing airborne PM.     

Size and composition distribution of airborne particulate matter in northern California: I--particulate mass, carbon, and water-soluble ions

The San Joaquin Valley (SJV) in California has one of the most severe particulate air quality problems in the United States during the winter season. In the current study, measurements of particulate matter (PM) smaller than 10 microm in aerodynamic diameter (PM10), fine particles (PM18), and ultrafine particles (PM0.1) made during the period December 16, 2000-February 3, 2001, at six locations near or within the SJV are discussed: Bodega Bay, Davis, Sacramento, Modesto, Bakersfield, and Sequoia National Park. Airborne PM1.8 concentrations at the most heavily polluted site (Bakersfield) increased from 20 to 172 microg/m3 during the period December 16, 2000-January 7, 2001. The majority of the fine particle mass was ammonium nitrate driven by an excess of gas-phase ammonia. Peak PM0.1 concentrations (8-12 hr average) were approximately 2.4 microg/m3 measured at night in Sacramento and Bakersfield. Ultrafine particle concentrations were distinctly diurnal, with daytime concentrations approximately 50% lower than nighttime concentrations. PMO.1 concentrations did not accumulate during the multiweek stagnation period; rather, PMO.1 mass decreased at Bakersfield as PM1.8 mass was increasing. The majority of the ultrafine particle mass was associated with carbonaceous material. The high concentrations of ultrafine particles in the SJV pose a potential serious public health threat that should be addressed.     

Source apportionment of ambient total suspended particulates and coarse particulate matter in urban areas of Jiaozuo, China

Approximately 750 total suspended particulates (TSPs) and coarse particulate matter (PM10) filter samples from six urban sites and a background site and >210 source samples were collected in Jiaozuo City during January 2002 to April 2003. They were analyzed for mass and abundances of 25 chemical components. Seven contributive sources were identified, and their contributions to ambient TSP/PM10 levels at the seven sites in three seasons (spring, summer, and winter days) and a "whole" year were estimated by a chemical mass balance (CMB) receptor model. The spatial TSP average was high in spring and winter days at a level of approximately 530 microg/m(3) and low in summer days at 456 microg/m(3); however, the spatial PMo0 average exhibited little variation at a level of approximately 325 microg/m(3), and PM10-to-TSP ratios ranged from 0.58 to 0.81, which suggested heavy particulate matter pollution existing in the urban areas. Apportionment results indicated that geological material was the largest contributor to ambient TSP/PM10 concentrations, followed by dust emissions from construction activities, coal combustion, secondary aerosols, vehicle movement, and other industrial sources. In addition, paved road dust and re-entrained dust were also apportioned to the seven source types and found soil, coal combustion, and construction dust to be the major contributors.     

Modifications to the Sunset Laboratory Carbon Aerosol Monitor for the Simultaneous Measurement of PM2.5 Nonvolatile and Semi-Volatile Carbonaceous Material

Abstract

Semi-volatile organic carbonaceous material (SVOC) in fine particles is not reliably measured with conventional semicontinuous carbon monitors because semi-volatile carbonaceous material is lost from the collection media during sample collection. Two modifications of a Sunset Laboratory carbon aerosol monitor allowing for the determination of semi-volatile fine particulate organic material are described. Collocated conventional and modified instruments were operated simultaneously using a common inlet. Comparisons were made with integrated PC-BOSS data for quartz filter retained nonvolatile organic carbon (NVOC) and elemental carbon (EC), SVOC, and total carbon (TC = SVOC + NVOC + EC) and good agreement was observed between TC concentrations during studies conducted in Rubidoux, CA. Precision of the comparison was σ=±1.5 μg-C/m³ (±8%). On the basis of experiments performed with the modified Sunset monitor, a dual-oven Sunset monitor was developed and extensively tested in Lindon, UT; Riverside, CA; and in environmental exposure chambers. The precision for the measurement of TC with the dual-oven instrument was σ = ±1.4 μg-C/m³ (±13%).     

Back-trajectory analysis and source-receptor relationships: particulate matter and nitrogen isotopic composition in rainwater

The southeastern portion of North Carolina features a dense crop and animal agricultural region; previous research suggests that this agricultural presence emits a significant portion of the state's nitrogen (i.e., oxides of nitrogen and ammonia) emissions. These findings indicate that transporting air over this region can affect nitrogen concentrations in precipitation at sites as far as 50 mi away. The study combined nitrate nitrogen isotope data with back-trajectory analysis to examine the relationship between regional nitrogen emission estimates independent of pollutant concentration information. In 2004, the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to determine potential sources of nitrogen in rainwater collected at an urban receptor site in Raleigh, NC. The delta 15N isotope ratio signatures of each sample were used to further differentiate between sources of the rainwater nitrate. This study examined the importance of pollution sources, including animal agricultural activity, and meteorology on rainfall chemistry as well as the implications in fine particulate matter (PM2.5) formation. Samples that transited the dense crop and animal (swine) agricultural region of east-southeastern North Carolina (i.e., the source region) had lower delta 15N isotope ratios in the nitrate ion (average = -2.1 +/- 1.7 per thousand) than those from a counterpart nonagricultural region (average = 0.1 +/- 3 per thousand.) An increase in PM2.5 concentrations in the urban receptor site (yearly average = 15.1 +/- 5.8 microg/m3) was also found to correspond to air transport over the dense agricultural region relative to air that was not subjected to such transport (yearly average = 11.7 +/- 5.8 microg/m3).     

Roadside particulate air pollution in Bangkok

Airborne fine particles of PM(2.5-10) and PM2.5 in Bangkok, Nonthaburi, and Ayutthaya were measured from December 22, 1998, to March 26, 1999, and from November 30, 1999, to December 2, 1999. Almost all the PM10 values in the high-polluted (H) area exceeded the Thailand National Ambient Air Quality Standards (NAAQS) of 120 microg/m3. The low-polluted (L) area showed low PM10 (34-74 microg/m3 in the daytime and 54-89 microg/m3 at night). PM2.5 in the H area varied between 82 and 143 microg/m3 in the daytime and between 45 and 146 microg/m3 at night. In the L area, PM2.5 was quite low both day and night and varied between 24 and 54 microg/m3, lower than the U.S. Environmental Protection Agency (EPA) standard (65 microg/m3). The personal exposure results showed a significantly higher proportion of PM2.5 to PM10 in the H area than in the L area (H = 0.80 +/- 0.08 and L = 0.65 +/- 0.04). Roadside PM10 was measured simultaneously with the Thailand Pollution Control Department (PCD) monitoring station at the same site and at the intersections where police work. The result from dual simultaneous measurements of PM10 showed a good correlation (correlation coefficient: r = 0.93); however, PM levels near the roadside at the intersections were higher than the concentrations at the monitoring station. The relationship between ambient PM level and actual personal exposures was examined. Correlation coefficients between the general ambient outdoors and personal exposure levels were 0.92 for both PM2.5 and PM10. Bangkok air quality data for 1997-2000, including 24-hr average PM10, NO2, SO2, and O3 from eight PCD monitoring stations, were analyzed and validated. The annual arithmetic mean PM10 of the PCD data at the roadside monitoring stations for the last 3 years decreased from 130 to 73 microg/m3, whereas the corresponding levels at the general monitoring stations decreased from 90 to 49 microg/m3. The proportion of days when the level of the 24-hr average PM10 exceeded the NAAQS was between 13 and 26% at roadside stations. PCD data showed PM10 was well correlated with NO2 but not with SO2, suggesting that automobile exhaust is the main source of the particulate air pollution. The results obtained from the simultaneous measurement of PM2.5 and PM10 indicate the potential environmental health hazard of fine particles. In conclusion, Bangkok traffic police were exposed to high levels of automobile-derived particulate air pollution.