A51A-0020
Atmospheric trace metals in Lake Ontario Region
Particles in rural and urban air were collected at two ground sites along the Lake Ontario shoreline in Hamilton Eastport (industrial) and Pt. Petre (ambient). Weather protected filter-based high-flow PM10 and PM2.5 samplers were used. Particulate metal size distribution and abundance depends on the source and prevailing weather conditions. Trace metal content per cubic meter of air (PM10, Pt. Petre January 2005 to April 2006) was As~0.5-1.1, Cd~0.3â€"11.6, Co~0.06-0.5, Cr~1.5-10.3, Cu~50-230, Fe~50-200, Mn~1.7-6.7, Ni~0.5-3.1, Pb~2.2-7.0, Se~0.4-2.8 and Zn~14-75 ng which can generally represent ambient contributions during that time period. Annual average flux calculated (2004 dry/wet, uniform deposition velocity of 0.2 cm s-1 used for dry deposition) was 23/100, 510/2500 and 170/440 ng/m2/day for Cd, Pb & Se. Captured particulate metals from the Eastport industrial site were found to be 50-100 times ambient level. Results of particle size distribution, particulate metal content, meteorological conditions and other parameters can help to identify potential sources as well as provide better estimates of metal loading by dry/wet deposition in the Great Lakes areas of Ontario.
A51A-0021
Trace metal concentration in Trade Wind aerosols collected over Barbados and Miami.
African mineral dust aerosols are transported by trade winds to Barbados and often reach Miami. The trace metals contained in these aerosols play an important role in biogeochemical processes and thus the global carbon cycle. High-volume bulk aerosols were collected in the summer dust season (June-September) of 2003 and 2004 in Miami and Barbados on Whatman-41 filters and microwave digested using a modified version of EPA method 3051. Aliquots of digested samples were tested for trace metal concentrations by ICP-MS. Excellent agreement with gravimetrically determined ashed weights was observed with dust concentrations calculated based on Al crustal abundance. As a major component, aluminum averaged 8.7% content in agreement to 8.1% crustal abundance, and was used to examine other trace metals. Al, Fe, V, Cr, Mn, Cu, Co, Ni, Zn, As, Tl, Ba, Cd, Pb and REE's were examined and deviations from average crustal abundance are discussed in relationship to temporal variation and meteorological conditions. In addition, trace metal pollutants in Miami aerosols were examined relative to the relatively clean samples offered by Barbados.
A51A-0022
Long-Term Trends in Trace Metals Concentrations in Sediment in Lakes in Adirondack Park, NY
The industrial Midwestern states consume large quantities of fossil fuel and emit large quantities of trace elements, SO2 and other chemicals. Owing to their long residence time these pollutants can be transported hundreds of miles downwind. These chemical species are removed from the atmosphere by wet and dry deposition and are ultimately deposited in lake sediments. Through the sedimentation process the pollution records can be stored for centuries. In this work we have attempted to retrieve the deposition of 25 trace elements for the past ~170 years by analyzing lake sediment cores from lakes located in the Adirondack Mountains. Sediment cores were collected from four lakes (Clear Pond, West Pine Pond, Bear Pond and Deer Pond) located in the Adirondack Park, NY. These lakes are at high altitude and some are inaccessible except by boat, and have minimum human activity (no motor boats, no camping and away from major roads). Coring was carried out by a gravity driven coring device. The cores were sectioned, weighed, freeze-dried, ground to a fine powder, and homogenized for analysis. The sediment cores were dated using 210Pb radioactive dating. The 137Cs activity was measured for an independent verification of 210Pb technique. Trace metals concentration were determined by microwave digestion method followed by inductively coupled plasma mass spectrometric (ICP-MS) analysis. The top sixteen sections of the West Pine Pond sediment core (representing from about 1835 to 2005) were analyzed for Sr, Ba, As, Se, Mo, Cd, Sn, Sb, Co, Ni, Cu, Ag,Ti, V, Cr, Mn, Fe, Zn, K, Na, Ca, Mg, Be, Tl, and Pb. During pre industrial era the concentrations of Pb, Se and Tl were very low and constant. Pb showed a sharp increase in concentration after around 1880 and a sharp decrease in concentration after about 1990. The concentration of Se increased slowly after pre industrial era. The concentrations of about eight of these elements were determined in quarterly composites of daily aerosol samples collected at Whiteface Mountain, NY, (within about 50 km of the lakes) from 1979 through 2002. The trends during this period are elucidated.
A51A-0023
Measurements of Gas and Particle Phase Emissions From Munitions Detonation in a Field Environment
During the Point of Fire (POF) field campaign conducted at Fort Sill Oklahoma U.S.A. in March 2007 a suite of real- time trace gas and fine (submicron) particulate matter (PM) instrumentation characterized the point of fire emission plumes from large, medium and small caliber weapons systems. Muzzle emission plumes were measured and where appropriate, breach plumes and gun crew breathing zone measurements were also conducted. Aerosol measurements were conducted with an aerosol mass spectrometer (Aerodyne CTOF-AMS) for particle composition, condensation particle counter (CPC) for particle number density and DUSTRAK aerosol monitor for particle mass. Gas phase measurements included CO, CO2, NOx and a variety of trace gas species measured by proton transfer reaction mass spectrometry (PTR-MS) including hydrogen cyanide (HCN), acetonitrile, acrylonitrile, benzene, toluene, benzonitrile and styrene. In the majority of the plume measurements, HCN was the most prominent compound measured by PTR-MS. Quantification of HCN by PTR-MS is difficult due to its proton affinity being close enough to that of water to allow a significant backward reaction of protonated HCN with water, reducing the detection sensitivity and making the response dependent on humidity. We have developed a quantification procedure for HCN based on laboratory measurements of a calibration gas standard of HCN, which allows the humidity dependence to be extracted directly from the proton hydrate ion intensities. The correction factors for HCN are quite significant varying between 10 and 30 depending on sample humidity.
A51A-0024
Temporal Variations of Elemental Carbon in Beijing
Concentrations of elemental carbon (EC) in fine mode (PM2.5) were measured at Peking University in Beijing, China in four seasons from November 2005 to October 2007. The EC concentrations were measured every one- hour with a semi-continuous thermal-optical analyzer. Carbon monoxide (CO) and carbon dioxide (CO2) concentrations were measured using non-dispersive infrared absorption (NDIR) instruments with a time resolution of 1 minute. The EC and CO concentrations decreased with the increase in the wind speed (WS). The correlations of EC with CO and CO2 were generally compact throughout the measurement period and the slopes of the EC-CO and EC-CO2 correlations (ƒ¢EC/ƒ¢CO and ƒ¢EC/ƒ¢CO2) are therefore useful parameters in investigating EC sources. The average EC concentrations for each season ranged between about 6 and 8 ƒÊg/m3. CO showed minimum values of about 1.1 ppmv in spring-summer and maximum of about 2.1 ppmv in winter. On calm days (WS < 2m/s), the average EC concentrations started to increase at around 1800 LT and continued to increase until around 0200 LT. The ƒ¢EC/ƒ¢CO ratios also showed similar diurnal patterns except for winter, when they showed little diurnal variation. These results suggest that there are strong EC source in Beijing during the nighttime, possibly from diesel vehicles. The high CO in winter indicates strong source of CO due to domestic heating and this lowered the ƒ¢EC/ƒ¢CO ratios.
A51A-0025
Chemical Composition of Aerosol Particles Emitted by a Passenger Car Engine Fueled by Ethanol/Gasoline Mixtures
With concerns of national security, climate change, and human health, many people have called for oil independence for the United States and for the creation of alternative fuels. Ethanol has been widely praised as a viable alternative to petroleum-based fuels, due to the fact that it can be produced locally. A great deal of work has been done to characterize the energy balance of ethanol production versus consumption, but there have been fewer studies of the environmental and health impacts of emissions from combustion of ethanol/gasoline mixtures such as those burned in the modern vehicle fleet. To study the particulate emissions from such fuels, different ethanol/gasoline fuel mixtures with 0, 20, 40, and 85% ethanol were burned in a dynamometer-mounted automobile engine. The engine exhaust was diluted and sampled with two aerosol Time-of-Flight Mass Spectrometers (TSI 3800 ATOFMS), sampling different particle size ranges (50-500 nm and 150-3000 nm, respectively), to measure size and composition of the emitted aerosol particles. A variety of other aerosol characterization techniques were also employed to determine the size distribution of the aerosol particles, the mass emission rate from the engine, and the concentration of polycyclic aromatic hydrocarbons (PAHs) and elemental carbon (EC) in the particle emissions. Here we will focus on results from the ATOFMS, which provides us with a particle size and mass spectra - for both negative and positive ions - for each particle that is sampled. Particles being emitted were found to contain primarily PAHs, elemental carbon (EC), nitrates, and sulfates. Particles were analyzed to investigate trends in particle composition as a function of fuel ethanol content, particle size, and for the types of particles emitted. A trend in particle type as a function of fuel ethanol content was evident in smaller particles, and trends in composition as a function of particle size were visible across the entire size range sampled.
A51A-0026
Real-time Characterization of Particle-bound Polycyclic Aromatic Hydrocarbons in Ambient Aerosols and From Motor-Vehicles Exhausts
During the spring of 2007 a diffusion charger (DC), a photoelectric aerosol sensor (PAS), and a condensation particle counter (CPC) were operated a) in Wilmington (CA), an urban area near the Los Angeles port heavily influenced by a mix of industrial and gasoline- / diesel-fuelled vehicle emissions, and b) at the California Air Resource Board (CARB) Heavy-Duty Diesel Emissions Test Laboratory (HDETL), a dynamometer testing facility in downtown Los Angeles (CA). During the dynamometer tests, we characterized the exhausts of several individual types of vehicles, equipped with different emission control technologies, and operated under different driving conditions. Information about the chemical composition, active surface area, and particle number concentration from the PAS, DC, and CPC were combined to identify the main chemical and physical characteristics of the studied aerosols. In particular, the ratio between the PAS and the DC signals (PAS/DC) provided a reliable measurement of the amount of particle-bound Polycyclic Aromatic Hydrocarbon (pPAH) per unit area of the active surface of the particles. This quantity may be directly related to the amount of pPAHs transported into the human respiratory tract. Plots of the PAS/DC ratio versus the average surface particle diameter (Dp; estimated by combining DC and CPC measurements) were then used to distinguish between the presence/absence of nuclei mode particles and the presence/absence of an adsorbed layer on accumulation mode particles, for both ambient and dynamometer-tests data. All results were then complemented with measurements of the particle size distribution (SMPS) and of the black carbon (BC) aerosol content to obtain further insights on the pPAHs emitted by motor-vehicles and other sources. Integrated 24-h filter samples were also collected in Wilmington, solvent extracted and analyzed by GC/MS to determine the relative concentrations of the 11 most abundant pPAHs found at the urban site. Finally, these results were used to establish correlations between the concentrations of each individual PAH species and the measured PAS signal (from fA to μ g/m3).
A51A-0027
Reactive Oxygen Species in Combustion Aerosols
Research on airborne particulate matter (PM) has received increased concern in recent years after it was identified as a major component of the air pollution mix that is strongly associated with premature mortality and morbidity. Particular attention has been paid to understanding the potential health impacts of fine particles (PM2.5), which primarily originate from combustion sources. One group of particulate-bound chemical components of health concern is reactive oxygen species (ROS), which include molecules such as hydrogen peroxide (H2O2), ions such as hypochlorite ion (OCl-), free radicals such as hydroxyl radical (·OH) and superoxide anion (·O2-) which is both an ion and a radical. However, the formation of ROS in PM is not clearly understood yet. Furthermore, the concentration of ROS in combustion particles of different origin has not been quantified. The primary objective of this work is to study the effect of transition metals on the production of ROS in PM2.5 by determining the concentrations of ROS and metals. Both soluble and total metals were measured to evaluate their respective associations with ROS. PM2.5 samples were collected from several outdoor and indoor combustion sources, including those emitted from on-road vehicles, food cooking, incense sticks, and cigarette smoke. PM2.5 samples were also collected from the background air in both the ambient outdoor and indoor environments to assess the levels of particulate-bound transition metals and ROS with no combustion activities in the vicinity of sampling locations. Results obtained from this comprehensive study on particulate-bound ROS will be presented and discussed.
A51A-0028
Secondary organic aerosol formation from the oxidation of polycyclic aromatic hydrocarbons with two aromatic rings
Polycyclic aromatic hydrocarbons (PAHs) are products of incomplete combustion and are ubiquitous in the environment. In the atmosphere, gas-phase reactions of PAHs with two aromatic rings with hydroxyl radicals (OH) lead to products that partition to the aerosol phase, forming secondary organic aerosol (SOA). The main objective of this study is to quantify the conversion of gas-phase PAHs with two aromatic rings into particle-phase species through the SOA yield. Eight experiments were conducted on each of the following PAHs: naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, acenaphthalene, acenaphthylene, and fluorene. Experiments were performed in a 9-m3 Teflon chamber, at an initial hydrocarbon to nitric oxide ratio of approximately five, and using hydrogen peroxide as the OH source. The experiments were initiated by illuminating germicidal lamps to drive photochemical reactions and were terminated when the SOA formation reached a plateau. During the experiments, PAH mixing ratios, aerosol particle size distributions and number concentrations, oxides of nitrogen mixing ratios, and ozone mixing ratios were monitored by a gas chromatograph with a flame ionization detector, a scanning mobility particle sizer spectrometer, a chemiluminescence analyzer, and a photometric analyzer, respectively. Results indicate SOA yields ranging from 0.02 to 0.12 over an organic aerosol mass concentration range of 2 to 15 μ g m-3. Peak aerosol mode diameters were in the range of 60 to 80 nm. An attempt to determine the relationship between yields and PAH structure will be made.
A51A-0029
Atmospheric Aging of Semi-volatile Pesticides: Real Time Monitoring of Cypermethrin Photo- oxidation Using FTIR
Pesticides are highly toxic compounds that unlike other pollutants are intentionally introduced, in large quantities, to the environment. The vast majority of them are applied to agricultural lands, but they are also widely used in urban areas as herbicides, insecticides and fungicides. Pesticides may be promoted into the atmosphere during their application via drift of aerosols, as well as by volatilization or dust erosion from treated surfaces after application. In the atmosphere, semi-volatile pesticides may remain as pure aerosols or become adsorbed upon background aerosols or surfaces. During transport or as deposited thin films, they undergo chemical degradation processes due to interaction with atmospheric oxidants and/or solar radiation. Although previous studies indicate that a major portion of applied pesticides wind up in the atmosphere, this is the medium about which we know the least regarding pesticides' fate. Quantitative data regarding aging processes of these hazard air pollutants are important in order to asses their environmental fate and impact. The present study investigates the heterogeneous reaction of thin film of cypermethrin, a common used insecticide, with atmospheric ozone and UV radiation. The reactions are monitored in real time using novel apparatus that combines ATR/FTIR and Long-path IR gas cell for examining the condensed and gas phases, respectively. The obtained data, including oxidation rate constants and photochemical quantum yields, are used to determine atmospheric lifetime of cypermethrin and its probability to reach non-target regions. Kinetic results from the oxidation of cypermethrin with different concentrations of ozone show that its atmospheric half-life time, with regard to ozone, is in the same order of magnitude as other known degradation processes in the soil and water compartments. Also is shown that some of the condensed phase products are more water soluble than the parent molecule, hence having higher potential to be more mobile in soil and to reach groundwater. The main gas-product detected was phosgene, which is a nerve gas. This might raise a question of using cypermethrin as an indoor insecticide (as currently done), especially in poorly ventilated environments. Solar radiation was shown to have a large effect on cypermethrin with half life of only several days. Some of the condensed photo-degradation products were similar to the ozonation ones and hence, are assumed to have the same environmental impact. Photo-degradation gas products were found to be carbon dioxide, carbon monoxide and formic acid, which after their formation may participate in additional atmospheric reactions. Thus, the present results suggest that photolysis plays a dominant role in cypermethrin's outdoor environmental fate, while ozonolysis plays a larger role indoors. In both cases, some of the degradation products are toxic and are likely to further pose an environmental risk that needs to be considered.
A51A-0030
Long-Range Transport of Perchlorate Observed in the Atmospheric Aerosols Collected at Okinawa Island, Japan
The study of perchlorate has become quite active in the U.S. in the last several years. Perchlorate has been recognized as a new environmental pollutant and it attracted much attention quickly in the world. The health concern about perchlorate stems from the fact that it displaces iodide in the thyroid gland, while iodine-containing thyroid hormones are essential for proper neural development from the fetal stage through the first years of life. In this study, we determined the concentrations of perchlorate ion present in the atmospheric aerosols collected in Okinawa Island, Japan. We then examined the relationships between the perchlorate concentrations and the environmental parameters and the climatic conditions peculiar to Okinawa. Bulk aerosol samples were collected on quartz filters by using a high volume air sampler at Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS). Each sampling duration was one week. The quartz filters with aerosols were stirred with Milli-Q pure water for three hours before perchlorate ion was extracted. The extracted perchlorate ion concentrations were determined by ion chromatography (ICS-2000, DIONEX). The mean perchlorate concentration for the samples collected at CHAAMS was 1.83 ng/m3, and the minimum was 0.18 ng/m3. The samples collected during November 21-27, 2005, January 23-30, 2006 and April 24-01, 2006 had highest perchlorate concentrations. For these three samples, we performed back trajectory analysis, and found that the air mass for the three samples arrived from the Asian continent. A relatively strong correlation (r2 = 0.55) was found between perchlorate and nss-sulfate concentrations for the CHAAMS samples. Furthermore, we analyzed perchlorate in the soils and the fertilizers used for sugar cane farming around the CHAAMS area. The Milli-Q extract of the soil and the fertilizers did not contain any detectable levels of perchlorate ions. Therefore, it was suggested that perchlorate found in the atmospheric aerosols collected at CHAAMS was probably transported from the Asian continent.
A51A-0031
Light- and Heavy-Duty Vehicle Emission Factors of PM Species Based on Freeway Measurements and Comparison With Tunnel and Dynamometer Studies
Emission factors of various particle species from light- and heavy-duty vehicles (LDVs and HDVs, respectively), including organic and elemental carbon (OC and EC), sulfate, polycyclic aromatic hydrocarbons (PAHs), hopanes, steranes, trace metals, elements, and particle number (PN), were estimated based on roadway measurements. Sampling campaigns were conducted at two different roadways: the CA-110 highway (where only gasoline-powered vehicles are allowed), and the I-710 freeway (where about 20 % of the total number of vehicles are diesel-powered trucks). The PM emission factors determined in these roadways were compared to those reconstructed from recent source emission data from the Caldecott tunnel, and those from previous tunnel and chassis dynamometer studies. Very good agreement between estimated and reconstructed emission factors was found for PN, EC, sulfate, high molecular weight (MW) PAHs, hopanes and steranes. This suggests that PM speciated chemical data collected at roadsides can be used to calculate reliable emission factors for several important particulate species at other locations characterized by a similar mix of on-road motor vehicles. The agreement between our results and other studies in the emission factors of trace elements and metals varied from very good (for species such as Cu, Mo, Ba, Pb) to poor (for species such as Mg, Fe, Ca) probably because the atmospheric concentrations of the latter elements are associated with both traffic and non-traffic sources, and the relative abundances of Mg, Ca, and Fe in road dust varies considerably across locations. The emission factors of OC and EC were clearly highest for HDVs, and those of PAHs, hopanes, and steranes from our roadway measurements were well within the range of values reported in the literature from tunnel and dynamometer studies. The approach presented in this study allows for a straightforward estimation of PM emission factors from ambient, near-freeway measurements. Our results were generally in very good agreement with those in the available literature for most non-labile PM species.
A51A-0032
Spatial Variation and Source Characterization of Size Fractionated Particulate Matter in Long Beach
The Los Angeles Ports complex (the largest in the US) consists of the Port of Long Beach and Port of Los Angeles. Due to the high levels of particulate matter (PM) emitted from many sources (some unregulated) in the vicinity of these ports (e.g. marine vessels, diesel and gasoline vehicles, refineries, and power plants) and projected massive expansion, the ports have been the focus of future governmental regulation. The focus of this study is to characterize the composition and distribution of PM at various locations influenced by port-affiliated sources. Size fractionated PM samples were collected concurrently at seven sites in Southern California for two six-week periods in the summer and winter of 2007. Personal cascade impactor samplers (PCISs) were used to collect weekly coarse, accumulation, and quasi-ultrafine mode particles at each site. Four sites were located within the communities of Wilmington and Long Beach and two sites were located at background locations near the harbors of each port. The seventh sampler, operated at the University of Southern California (near downtown Los Angeles), was used as a reference of a typical urban site. Each PCIS was accompanied by a CPC and a meteorological station to identify local sources based on wind speed and direction correlated to particle counts. Coefficients of divergence (COD) calculated based on PM levels were highly variable between different sites (0.12 to 0.7), with higher CODs resulting from comparisons between background and inland sites. In addition, accumulation mode particles showed lower CODs compared to other size fractions, which is due to high atmospheric residence times and greater spatial dispersion of this size range. Weekly filter-based samples are being analyzed for chemical composition, including elemental and organic carbon (EC and OC, respectively) and inorganic ions. Samples will then be composited and analyzed for organic species, trace metals, and redox potential. This information will be used to decouple the source signatures of ports, local freeways and other industries. Such information is essential in the implementation of future control measures and particle standards that aim to reduce the public health risk.
A51A-0033
Insights on Sources, Growth, and Phase Partitioning of Atmospheric Particles from Hourly Measurements of Organic Marker Compounds
Atmospheric aerosols have adverse affects on human health and have direct and indirect affects on the global radiation balance. In order to implement particle concentration control strategies, we must first understand particle origins. Atmospheric aerosols have both primary sources such as combustion processes and secondary sources such as photochemically driven gas to particle phase partitioning. By monitoring changes in the molecular composition of the organic fraction of atmospheric aerosols, these various sources can be differentiated. Thermal desorption Aerosol Gas chromatography (TAG) is a new in-situ instrument capable of identifying and quantifying organic aerosol chemical composition with one hour time resolution. TAG is fully automated, offering around the clock measurements to determine diurnal, weekly, and seasonal patterns in organic aerosol composition, hence, determining aerosol sources and transformation processes. We report results from ambient measurements made in Southern California during the summer and fall of 2005 as part of the Study of Organic Aerosol at Riverside (SOAR). We use hourly measurements of over 300 individual organic compounds to define both primary and secondary particle sources. The particle sources defined include primary anthropogenic sources such as vehicle emissions, meat cooking, biomass burning, pesticide use, herbicide use, along with primary biogenic sources such as plant emissions and plant waxes. We also explore secondary particle sources (i.e. SOA) formed as a result of the oxidation of biogenic and anthropogenic precursor gases. Comparisons are made between TAG-defined sources and aerosol sources defined using Aerosol Time-Of-Flight Mass Spectrometer (ATOFMS) and Aerosol Mass Spectrometer (AMS) data. In addition to source apportionment results, we present seasonal changes in ambient phase partitioning of organic compounds as a function of carbon number for multiple compound classes.
A51A-0034
Source and Health Implication of Diurnal Atmospheric PM Mass and Number Concentrations
Exposure to atmospheric PM has been known to be associated with adverse health effects, decreased heart-rate variability, and respiratory and cardiopulmonary related morbidity and mortality. New evidence suggests that physical characteristics (mass, size, number, surface area, and morphology) of particles are strongly associated with mortality and morbidity through acute exposure. In particular, as reported in the literature, fine or ultrafine particles are more toxic than coarse particles on an equivalent mass basis while particles of less than 30 nm or greater than 2.5 um in diameter deposit more effectively (approximately 80 percent) in lung versus approximately 18 percent for particles in the range of 100 nm and 1 um. In addition, positive association has been observed between day to day variation in PM2.5 and hospital admissions, mortality and particle surface area, or particle number concentration and oxidative stress-induced DNA damage. This presentation shows the results of a study characterizing the physical properties of PM in El Paso, Texas. Diurnal PM mass concentration peaks previously observed at several other cities along the U.S.-Mexico border and elsewhere in the world were observed in El Paso. The hourly PM particle count varied from less than 10,000 particles/cm3 to greater than 80,000 particles/cm3 during the diurnal PM mass peaks. The total number of PM particles peaked in the morning and in the evening while the mode of the particle size changed from 20 nm to 50 nm, indicating different PM sources may be responsible for the mass and number concentrations and agglomeration of particles in the atmosphere during the day may possibly plays a role. A multivariate regression analysis was performed to correlate the PM mass and number concentrations to environmental variables. Real- time wind statistics were used in conjunction with traffic data at a nearby highway for identifying sources of the PM mass and number concentration peaks. Evaluation of the diurnal variation of PM physical properties and a recent study on PM mass and mortality implies that particle number may be a better environmental indicator for mortality than PM2.5 mass. This publication was made possible by grant number 1 S11 ES013339-01A1 from the National Institute of Environmental Health Sciences (NIEHS), NIH. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS, NIH.
A51A-0035
Influence of African Dust and Volcanic Ash on the Chemical Composition of Cloud/Rain Water Collected in a Tropical Montane Cloud Forest in Puerto Rico
Some organic compounds present in aerosols are surface active and their presence in cloud condensation nuclei can affect the surface tension of cloud droplets. The nature of these surface active compounds in clouds and rainwater is not well understood and there is very little information about their content in remote tropical environments. Therefore, our study focuses on the chemical characterization of the organic component of cloud and rainwater samples collected in a tropical montane cloud forest on the island of Puerto Rico. Samples were collected during periods of varying air mass origin, including periods of influence by African dust and by volcanic ash. Cloud samples were collected using a compact version of the single-stage Caltech Active Strand Cloudwater Collector. Rain samples were collected using a passive collector. The organic fraction of collected samples was characterized using a total organic carbon and total nitrogen analyzer (TOC/TN) and nuclear magnetic resonance (1H-NMR) spectroscopy. Elemental and organic carbon (EC, OC) were determined for suspended particles contained in collected cloud and rainwater samples. These particles were also analyzed using scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) to determine their elemental compositions. Preliminary results indicate that average concentrations of cloud water TOC ranged from 0.9 to 1.2 mg/L. Lower concentrations were observed in rainwater, 0.3 to 0.7 mg/L. TN concentrations were higher than TOC in cloud water samples when air masses came from the African continent. The suspended aerosol particles had a content of 2.0 µg of OC per mL of cloud water, but EC was not detected. Suspended particle analysis by SEM-EDS showed Si, Al, and Fe, which have crustal origin, as the predominant species. The 1H-NMR spectra showed alcohols in large quantities, suggesting the presence of biogenic material or polyols when air masses arrived from the African continent. A more complete set of results including volcanic ash events from the Soufriere Hills in Montserrat will also be presented.
A51A-0036
Single-Particle Composition Measured in an Alpine Valley: Wood Smoke, EC and BC
Particulate pollution is an issue of concern in today's society. Current regulations focus on the mass of particulate matter (PM) per volume of air, and not the source or chemical composition of the PM. Here we will present results from the AEROWOOD campaign in Roveredo, Switzerland where we investigated the PM composition measured using a single-particle mass spectrometer (TSI 3800 ATOFMS) to identify the sources of ambient particles. The goal was to differentiate wood smoke particles from diesel emissions. Roveredo is located in a deep alpine valley with strong wintertime thermal inversions, trapping the emissions. Local homes are predominantly heated by wood fires, and the village is located along a motorway that crosses the Swiss alps, providing two distinct particle sources. The particles sampled with the ATOFMS have been analyzed in a variety of ways with a focus on the temporal trends of the different particle types identified. Of particular interest is the distinction made between elemental carbon (EC) and black carbon (BC). During AEROWOOD, EC was measured chemically using real- time thermo/optical methods. BC was recorded directly by absorption, using an aethalometer. Regression models have been constructed to predict the EC and BC values using the single-particle mass spectra, providing chemical insight into the differences in these quantities. Additionally, comparing the timeline plots of EC, BC and the particle types found from the ATOFMS data should provide an idea as to the sources of EC and BC in this location.
A51A-0037
Aerosol Monosaccharide Anhydrides as Tracer Species for Identifying Wildfire Smoke Transport to California's Central Valley in August 2002
The Biscuit fire burned close to 2,000 km2 of forested land in southwestern Oregon in July and August, 2002. August, 2002 also was a time in which PM2.5 concentrations were higher than typical in California Central Valley cities located several hundred kilometers to the southeast. The concentrations of two monosaccharide anhydrides, levoglucosan and mannosan, were measured in aerosol samples collected at four California Air Resource Board sites in Central Valley cities for the purpose of determining how the wildfire smoke affected air quality. Levoglucosan concentrations ranged from the detection limit of 18 ng m-3 to about 400 ng m-3. While days with high levoglucosan concentrations generally had above average to high PM2.5 concentrations, there were also days with high PM2.5 concentrations with low levoglucosan concentrations. Although mannosan was only detected in a small number of samples, the levoglucosan to mannosan ratios in these samples were consistent with smoke from softwood combustion. A wildfire source levoglucosan to PM2.5 concentration ratio was used to estimate the PM2.5 concentration originating from smoke. From this method, smoke was found to be a significant (greater than 10% of the total PM2.5 concentration) on occassions. The estimated smoke PM2.5 concentration always remained less than 10 μg m-3 and contributed to less than a third of the total PM2.5 concentration. Because the PM2.5 concentrations were higher than typical August values, either there were other factors leading to high PM2.5 concentrations in August 2002, or the smoke estimation method underestimated the smoke concentration.
A51A-0038
Impact of prescribed fire emission on air quality over the southeastern US
Prescribed burning is a large aerosol source in the southeastern United States. Its air quality impact is investigated using EPA model-3 system. Fire emissions are calculated based on a recent developed emission inventory by the Visibility Improvement - State and Tribal Association of the Southeast (VISTAS) program. Two scenarios with and without prescribed fire emissions are investigated for the 10 southeastern states in the base year of 2002 of VISTAS. Large impact has been found with the inclusion of prescribed fire emissions. It significantly improved model performance in spring by reducing the mean biases of organic carbon (OC) and elemental carbon (EC). CO enhancements in the free troposphere in spring for some fire events can be confirmed by the Measurements Of Pollution In The Troposphere (MOPITT) satellite CO observations. Model results show that prescribed burning leads to ~30% enhancements of OC and EC in spring, respectively. We found a moderate correlation between local burning areas and the enhancement of EC and OC. Long-range transport leads to some episodes of PM2.5 increase at some sites in the low fire emission areas. In summer, model underestimated carbonaceous aerosols even after the consideration of prescribed fire emission. Scaled fire emitted EC to MODIS observed seasonality of fire counts in summer cannot account for the underestimation. Under-predicted EC in summer indicates missing or underestimated EC sources in the southeastern US.