R-3 Repository :: Browsing by Author "Fraser, Matthew P."

Browsing by Author "Fraser, Matthew P."

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A comprehensive study of urban gaseous and particulate air pollution in Houston, Texas: Source apportionment and the emissions inventory assessment
(2006) Buzcu Guven, Birnur; Fraser, Matthew P.
Ground-level ozone is of a growing concern in many areas of the United States. Ozone is a significant health concern, particularly for people with asthma and other respiratory diseases. Ozone is rarely emitted directly into the air but is formed by the reaction of volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the presence of sunlight. VOCs are emitted from a variety of sources, including motor vehicles, chemical plants, refineries, factories, consumer and commercial products, other industrial sources, and biogenic sources. NOx is emitted from motor vehicles, power plants, and other combustion sources. Ozone and ozone precursors also can be transported into an area from pollution sources found hundreds of miles away. In accordance with the 1990 Clean Air Act Amendments, EPA has required more extensive monitoring of ozone and its precursors in areas with persistently high ozone levels. In these areas, the States have established ambient air monitoring networks consisting of CAMS (continuous air monitoring system) sites, which collect and report detailed data for volatile organic compounds, nitrogen oxides, ozone and meteorological parameters. Analyses of these data help the regulatory agencies to better understand the underlying causes of ozone pollution, to devise effective remedies and to measure air quality trends. This thesis focuses on how to integrate these measurements of VOCs with the receptor modeling techniques in order to identify the sources of VOCs and to attribute ambient VOC concentrations to their original sources. The measurements taken from three CAMS stations in Houston, TX serve as the basis of this research. After presenting the source attribution of volatile organic compounds, where the contribution from different sources to ambient VOC levels are determined, the methods to identify the source regions associated with elevated VOC levels are described. The quantitatively reconstructed emissions from a recently prepared VOC emissions inventory are compared with the receptor model calculations of ambient VOC measurements. Finally, a separate growing concern in the US, the particulate matter pollution, is addressed. The impacts of regional wild fires in Texas on the secondary particulate matter formation are examined. The results of the laboratory investigations on the formation of the secondary sulfate particles through heterogeneous surface reactions are presented.
Atmospheric carbonyl compounds in rural and urban Texas: Formation, methodology, and statistical modeling
(2002) Friedfeld, Stephen Judah; Fraser, Matthew P.
Atmospheric carbonyl compounds, specifically aldehydes and ketones, were measured in both rural and urban regions in Texas. The biogenic or rural study examined the extent of conversion from primary biogenic hydrocarbons to secondary carbonyls. The anthropogenic or urban studies investigated techniques for measuring carbonyl compounds; statistical modeling was applied in one such study to elucidate the primary and secondary contributions to formaldehyde formation. From the biogenic study, the spatial variation of isoprene and its reaction products' concentrations are strong functions of the immediate land cover. Spatial differences between sampling sites need to include NOx data to account for urban and rural influences. Finally, both ozone attributable to biogenic hydrocarbon oxidation and ozone formation potential are predicted to be insignificant under high VOC/NOx ratios typical of rural areas, but may be important under conditions where NOx levels are elevated. From the anthropogenic studies, a daylong sampling period sufficiently captures persistent low-lying carbonyl levels, but overlooks small scale fluctuations. Furthermore, the low concentration precision limit of real-time sampling through a DFG sensor produces similar bias as time-integrated wet chemical quantification, and validates the use of the DFG system for urban atmospheric studies. Finally, two distinct statistical models attribute nearly two-thirds (ratio 1.75) of HCHO formation to secondary VOC reactions, and one-third to primary emissions.
Atmospheric organic fine particulate matter in Houston: Composition, seasonality and source apportionment
(2005) Yue, Zhiwei; Fraser, Matthew P.
Organic matter is one of the major components of the fine particles in Houston. In the present study, fine particulate samples collected at three sites (plus one temporary site) in Houston have been investigated to determine the molecular composition and seasonal variation patterns of individual organic compounds, including n-alkanes, PAH compounds, petroleum biomarkers, alkanoic and alkenoic acids, dicarboxylic acids and levoglucosan. Next, chemical mass balance (CMB) model has been applied to calculate quantitative contributions from major primary emission sources to ambient PM2.5 levels. These emission sources include diesel engine trucks, gasoline powered vehicles, wood combustion, paved road dust, food preparation process, vegetative detritus and natural gas combustion. Source profiles suitable for the present CMB model have been developed based on source test results published in literature and our road dust resuspension experiment. Source apportionment shows diesel and gasoline vehicle exhaust to be the major primary contributors to ambient PM2.5 collected in Houston. Moreover, 52% of annual average PM2.5 mass measured in the present study can be attributed to secondary formation in the atmosphere.
Characterization of simple saccharides and other organic compounds in atmospheric particulate matter and source apportionment using positive matrix factorization
(2010) Jia, Yuling; Fraser, Matthew P.; Griffin, Robert J.
Ambient particulate matter samples were collected at various sites in Texas, Arizona, and Austria from 2005 to 2009 to characterize the organic compositions and local PM sources. The primary biologically derived carbon sources, specifically the atmospheric entrainment of soil and associated biota and primary biological aerosol particles (PBAPs), are major sources contributing to ambient PM. This dissertation work proposes simple saccharides as well-suited tracers to characterize the contribution to ambient PM from these primary biologically derived carbon sources. Saccharide concentrations in ambient PM were determined from various locations and various seasons. Aerosol saccharide compounds displayed seasonal variations, inter-correlations, and size fractionations (fine vs. coarse) that were consistent between samples and that can be used to determine sources. The difference in aerosol saccharide concentrations and relative species abundances was reflective of different climate patterns and ecosystems. Selected saccharide compounds including an established marker (levoglucosan) and novel markers (glucose, sucrose, trehalose, mannitol, and arabitol) were used along with other markers to model the major source contributions to ambient PM using a positive matrix factorization (PMF) model. Major local PM sources were resolved at three Texas sites (San Augustine, Dallas, and Big Bend National Park) and one Arizona site (Higley), with two source factors enriched in the proposed novel saccharide markers that can be related to the primary biologically derived carbon sources. The contribution to PM from the saccharide-rich primary biological sources was estimated to range from 16% (remote area) to 36% (rural and suburban area) at the four sampling sites studied. Other PM sources identified by PMF included motor vehicles, secondary aerosol formation, meat cooking, biogenic wax, sea salt, crustal material, and road dust. To further characterize the primary biologically derived carbon sources, different soil and source samples representing PBAPs (plants and spores) were collected at Higley (AZ) to study their saccharide compositions in particle sizes equivalent to PM2.5 and PM10. It was found that the total measured non-levoglucosan saccharide content relative to PM mass in ambient aerosols (0.2% on average in PM2.5 and 0.11% in PM10) was much higher than the soil samples (<0.02% in both PM2.5 and PM10) but much lower than in the PBAP source samples (2% on average in plant PBAP samples and 16% in spore PBAP samples). The measured PBAP samples contained a concentration of sucrose and glucose that is consistent with the saccharide-rich source profiles resolved from ambient aerosol data analyzed by PMF while the measured soil samples did not. This can be interpreted as confirmation that PBAPs are an important PM source in additional to soil and associate biota at Higley, AZ. However, the saccharide levels in the measured PBAP samples were several orders of magnitude higher than the PMF results, suggesting that the ambient aerosol samples are a combination of high saccharide concentration PBAPs and lower saccharide concentration soils at Higley, AZ.
Characterization of sugars in fine particles – Biomass burning and soil organic matter as two major sources
(2008) Jia, Yuling; Fraser, Matthew P.
Fine particulate matter samples were collected at two rural sites and one urban site in Texas from November 2005 to July 2006 for quantification of sugars. Several extraction methods were applied to optimize sugar recovery, and the combination of dichloromethane and methanol was found to extract sugars with greater efficiency than other solvent suites. Concentrations of total fine particle sugars ranged from 22 to 164 ng/m 3 , with levoglucosan, glucose, mannitol, arabitol and glycerol measured at the largest concentrations at all sites. The presence of sugars in fine particle samples can be tied to both biomass burning and soil organic matter. Smaller influence of reintrainment of local soils to the atmosphere was found at the urban site than at the rural sites. Several sugar compounds were proposed as potential molecular markers for soil organic matter input into the atmosphere.
Characterization, seasonality and source apportionment of fine particulate organic matter at urban an d rural sites
(2007) Bhat, Shagun; Fraser, Matthew P.
To better understand the sources of organic PM and the effect of secondary organic aerosols (SOA) on PM levels, samples of fine particulate matter were collected outside Durham, NC in the Duke Research Forest as part of the CELTIC study in July 2003. Among compounds analyzed, oxidation products of α-pinene, namely pinic acid and pinonic acid, were identified in all samples. Pinic acid and pinonic acid have low vapor pressures, of the order of 10 -7 Torr, and are expected to contribute significantly to secondary organic aerosol (SOA) formation from the oxidation of α-pinene (Koch et al. , 2000). Source contribution estimates from primary organic aerosol emissions were computed using measured organic species as molecular markers with the chemical mass balance (CMB) model. The unapportioned organic carbon (OC) was determined as the difference between measured OC and OC apportioned to primary sources. This unapportioned OC was then correlated with pinic and pinonic acid. The correlations between unapportioned OC and pinic and pinonic acids were r 2 = 0.33 (p-value = 0.64) and r 2 = 0.42 (p-value = 0.16), respectively. Given the large number of possible SOA precursors this moderate to good fit between pinic acid and pinonic acid concentrations with unapportioned OC is indicative of the major contribution of α—pinene oxidation products to secondary formation at this sampling site. The results are significant considering the role of monoterpene emissions to global atmospheric chemistry. These results were used as a basis of a second study investigating the use of pinic acid and pinonic acid as molecular markers for secondary formation using source apportionment. This hypothesis was explored for an urban and a rural site in Texas as part of the second sampling campaign, the Texas Air Quality (TexAQS) II study. In the TexAQS II study, fine PM sources were first characterized more broadly, creating a framework to evaluate the effectiveness of pinic and pinonic acid as SOA markers. Five factors were identified for both Dallas and San Augustine with differing contributions to PM 2.5 mass and OC. The factors identified are (1) motor vehicles, including gasoline and diesel-powered vehicles, (2) wood combustion, (3) secondary organic aerosols (SOA) identified using pinic and pinonic acids as markers, (4) plant wax and (5) meat cooking. PMF parameters and residuals were within the acceptable Q-values, indicating valid model performance. The Chemical Mass Balance (CMB) model was used to estimate sources contributions to OC in Dallas and San Augustine airsheds. These source contribution estimates were in turn used to calculate the unapportioned OC based on OC contributions to each source. A strong correlation was observed between measured ambient concentrations and concentrations calculated using CMB. The average r 2 of 0.74 and chi-squared value of 7.8 was acceptable. Mobile sources were a major contributor at Dallas, which is expected for an urban site, followed by meat cooking, plant wax and wood combustion. In these two studies, pinic acid and pinonic acid were effective as molecular markers for secondary formation in North Carolina where α-pinene emissions were dominant among all monoterpenes, but not in Dallas and San Augustine, where other sources dominated SOA mass. (Abstract shortened by UMI.)
Mass, Composition, Source Identification and Impact Assessment for Fine and Coarse Atmospheric Particles in the Desert Southwest
(2013-06-05) Clements, Andrea; Griffin, Robert J.; Fraser, Matthew P.; Cohan, Daniel S.; Siemann, Evan; Herckes, Pierre
A year-long study was conducted in Pinal County, Arizona to characterize fine and coarse particulate matter as a means of furthering our understanding of ambient concentrations and composition in rural, arid environments. Detailed measurement of ambient fine and coarse mass, ion, metal, and carbon concentrations at one-in-six day resolution was conducted at three sites from February 2009 to February 2010. Detailed organic carbon speciation was collected at 5-week resolution. A series of samples representing native soil, agricultural soil, road dust, and cattle feed lot material was collected, resuspended in the laboratory, and analyzed to provide a chemical source profile for each soil type yielding insights into unique source signatures. Observations within the chemical speciation data and subsequent modeling analysis show a strong impact from local sources at the Cowtown site where mass concentrations are highest. Source apportionment results confirm the significant impact from the cattle feedlot adjacent to the site. Chemical analysis of ambient particles and local feedlot material shows the presence of chemical marker species including phosphate which is unique to this source. Fugitive dust is a significant contributor to ambient particulate matter concentrations at all monitoring locations. Seasonal observations show higher concentrations during tilling and harvesting indicating the large role agricultural sources play on particle concentrations in this area. Chemical characterization and modeling show that re-entrained road dust is a significant factor. Fine particle modeling results indicate that concentrations are influenced significantly by motor vehicles including impacts from direct emissions including brake wear and indirect emissions including resuspended road dust. A significant fraction is also associated with crustal sources while about 5 g/m3 appears to be transported into the region from beyond the air shed. Detailed analysis of the local monsoon season indicates that monsoon rains serve to clean the atmosphere resulting in a marked decrease in ambient coarse mass and resulted in a period where local coarse PM concentrations measured at all sites became more uniform. The monsoon season also featured localized high wind events which severely increased coarse PM concentrations and often caused exceedences of the PM National Ambient Air Quality Standard.
Measurements of fine particulate matter in Houston
(2000) Lakshmanan, Kalyan Raman; Fraser, Matthew P.
The Rice University Fine Particulate Matter Air Sampling Study (1999--2000) identified and quantified the fine particulate matter (PM2.5) in an urban setting in Houston, Texas. The study lasted over two time periods to characterize the seasonal changes; the summer period was between August 16, 1999 and October 1, 1999 and the winter period was between December 18, 1999 and January 31, 2000. PM2.5 was isolated with a cyclone separator and quantified through gravimetric analysis. The major gaseous species (SO 2, gaseous NO3, NH3) and chemical species (organic carbon, elemental carbon, SO42--, NO3 --, NH4+, Na +, K+, and Cl--) were collected by multiple types of filter media and analyzed by ion chromatography, gas chromatography, mass spectrometry, and thermal/optical carbon analysis. PM 2.5 concentration during the summer and winter periods was 8.2 +/- 0.6mug/m3 and 6.2 +/- 0.6mug/m3 respectively and did not exceed the NAAQS PM2.5 standard. The major particulate species (in terms of mass fractions in the summer/winter) were OC (39%/36%), SO4 (20%/9%), NH4 (8%/4%), EC (3%/3%), and NO3 (1%/7%). In both time periods, a large mass fraction was attributed to unknown materials (28%/38%). The OC, SO4, and NH4 mass fraction decreased from the summer to the winter while the NO3 and EC mass fraction increased. The organic fraction of the particulate matter contained n-alkanes and polycyclic aromatic hydrocarbons.
Source identification and apportionment of fine particulate matter in Houston, Texas by receptor modeling
(2003) Buzcu, Birnur; Fraser, Matthew P.
Samples of atmospheric particles were analyzed for organic and elemental analysis at three sites in Houston, TX. Samples for the quantification of individual organic compounds were collected during August 2000--September 2000 and analyzed for molecular speciation. A chemical mass balance (CMB) model was applied to the organic speciation data to estimate the contributions of the eight possible sources to the fine particulate matter mass in Houston. Major contributors to PM2.5 included gasoline vehicles, diesel vehicles, meat cooking and wood combustion with smaller contributions from vegetative detritus. It was found that PM2.5 mass was also dominated by other organics and secondary sulfate. Samples for airborne metal analysis were collected and analyzed by two different chemical analysis methods; Inductively Coupled-Plasma Mass Spectrometry (ICP-MS) and X-Ray Fluorescence (XRF). Positive matrix factorization (PMF) was applied to the elemental concentration data for source identification and apportionment. PMF resolved five physically interpretable factors at each site of which four were found to be common at all sites: crustal material, road dust, wood burning, and sea salt. The composition of the remaining factor was similar, but not identical at the three sites and had an elemental composition similar to industrial combustion. Crustal material is the most important contributor at each site.

Browsing by Author "Fraser, Matthew P."

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