Laura Lewis

Fine particulate chemical composition and light extinction at Canyonlands National Park using organic particulate material concentrations obtained with a multisystem, multichannel diffusion denuder sampler

The concentration of fine particulate carbonaceous material has been measured over a 1-year period at the Interagency Monitoring of Protected Visual Environments (IMPROVE) Canyonlands National Park, Utah sampling site using a Brigham Young University organic sampling system (BOSS) multisystem, multichannel diffusion denuder sampler. Samples were collected on the IMPROVE schedule of a 24-hour sample every Wednesday and Saturday. The concentrations of particulate C, determined using only a quartz filter pack sampling system, were low by an average of 39%, as a result of the loss of semi-volatile organic compounds from the particles collected on quartz filters during sampling. The loss was higher during the summer than during the winter sampling periods. The BOSS and IMPROVE quartz filter carbon measurements were in agreement except for a few samples collected during the summer. The fine particulate carbonaceous material concentrations determined using the BOSS have been combined with concentrations of particulate elemental C (soot), sulfate, nitrate, crustal material, and fine and coarse particulate mass from the IMPROVE sampling system, as well as relative humidity, light absorption, and transmissometer measurements of light extinction from IMPROVE. Extinction budgets have been calculated using multilinear regression analyses of the data set. Literature data were used to estimate the change in the mass extinction coefficients for the measured species as a function of relative humidity. The results show carbonaceous material to be the principal contributor to light extinction due to particles during the study period, with the major contributor to light extinction being light-absorbing carbonaceous material. However, the periods of maximum light extinction are associated with high humidity and the associated increased scattering of light due to particulate sulfate during the winter. The effect of particulate organic compounds on light extinction is greatest in the summer and smallest in the winter.

Determination of semivolatile organic compounds in particles in the Grand Canyon area

Several diffusion denuder-filter-sorbent bed and filter-sorbent bed sampling systems with varying selectivity for the collection of different classes of organic compounds have been used for the collection and determination of atmospheric organic material present at Hopi Point in the Grand Canyon. The data show that the amount of semivolatile organic compounds in particles in the atmosphere in the Southwest United States has been underestimated by sampling with only a filter. The collection of gas-phase organic compounds by the filter causes a small positive artifact. However, a much larger, negative error results from the loss of 40%–80% of the organic material in the particles collected by the filter. The concentration of organic particulate matter present at the Hopi Point site is probably about 2 μg/m3 larger than inferred from previous data.

Fine Particulate Organic Material at Meadview During the Project MOHAVE Summer Intensive Study

The Brigham Young University (BYU) organic sampling system (BOSS) and the high flow rate multi-system BYU organic sampling system (BIG BOSS), which use multichannel diffusion denuder sampling techniques, were both used to collect samples of atmospheric fine particulate organic material. Both systems were used at the Meadview sampling site located at the western boundary of the Grand Canyon National Park in northwestern Arizona for the Project MOHAVE summer intensive sampling program in August 1992. The concentrations of total fine particulate carbonaceous material determined by temperature programmed volatilization for BOSS collocated replicate samples were in agreement with an uncertainty of ±14%. A comparable agreement was seen between the BOSS and BIG BOSS samples. Carbonaceous material collected by the second of two sequential quartz filters was shown to have originated from organic material lost from particles during sampling. About one-half of the fine particulate organic material was lost from particles during sample collection. These semi-volatile organic compounds lost from particles during sampling were characterized by GC/MS analysis. The concentrations of n-alkanes, n-fatty acids, n-fatty methyl esters, and phthalic acid as a function of fine particulate size were obtained for compounds both retained by and lost from particles during sampling. The possible sources of fine particulate semi-volatile organic material collected at Meadview, and the particle size distribution of fine particulate organic material, n-alkanes, n-fatty acids, and n-fatty esters are discussed.

The Contribution of Sulfate and Nitrate to Atmospheric Fine Particles During Winter Inversion Fogs in Cache Valley, Utah

Abstract Air pollutants were collected in Logan, Cache County, UT, in February 1993 during two periods of atmospheric inversion accompanied by fog. The following atmospheric species were determined: (1) gaseous SO2, NO2 (semi-quantitatively),HNO3, NH3, and HF; (2) fine particulate SO4 =, NO3 -, NH4 +, F–, H+, C, Si, S, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Pb, Se, Br, and Sr, and; (3) fine particulate mass, which was calculated. The major components of fine particulate matter were carbonaceous material, ammonium nitrate, and ammonium sulfate, while the soil component was small. Calculated, fine particulate mass averaged 80 μg/m3 and reached concentrations as high as 120 μg/m3. SO2/Sox and NO2/NOy mole ratios generally varied between 0.2 and 0.1 during inversions. These ratios also showed moderate but consistent diurnal patterns. The emission inventory for Cache County indicates sources of SO2 and NOx but not significant amounts of primary sulfate and nitrate. The observations reported here indicate there is sign...

Sampling artifacts in the determination of particulate sulfate and SO2(g) in the desert Southwest using filter pack samplers

Particles collected in the desert Southwest on Teflon filters using an annular denuder sampling system absorb SO 2 (g) in a subsequential exposure to SO 2 (g) in the laboratory if the concentration of fine particulate sulfate measured with a filter pack sampling system is greater than the concentration of sulfate measured with the annular denuder sampling system. If the concentrations of sulfate determined using the two sampling systems agreed, no absorption of SO 2 (g) by the denuder-collected particles occurs. These results show that SO 2 (g) may be collected by Southwest desert fine particles during sampling, resulting in measured concentrations of fine particulate sulfate that are higher than the correct concentrations. The magnitude of this filter pack sampling artifact, 0.1-0.4 μg SO 4 2- /m 3 , is small. However, the artifact is important relative to the concentration of particulate sulfate present in the desert Southwest, typically 0.5-2 μg SO 4 2- /m 3 . The magnitude of the filter pack sulfate sampling artifact is not related to either the atmospheric particulate sulfate or SO 2 (g) concentrations.

Apportionment of sulfur oxides at Canyonlands during the winter of 1990. I: Study design and particulate chemical composition

Abstract Spherical aluminosilicate (SAS) particles, total fluoride and particulate trace elements are potential endemic tracers for determining and quantifying the presence of coal-fired power plant and other sulfur oxide source emissions at far downwind distances. These endemic tracers, and sulfate and SO 2 were collected at Canyonlands National Park, at seven ambient sampling sites located in air mass transport paths to Canyonlands and from the stacks of coal-fired power plants in central Utah during January-March of 1990 for use in source apportionment analyses. These data have been combined with results obtained in concurrent studies by the National Park Service (EPIC study) and Salt River Project to provide a complete data set for the characterization of the regional and point sources that can influence air quality in the Canyonlands area. This paper gives details on the study design and on the chemical composition of fine particulate matter in the study area. While concentrations of SO x (SO 2 (g) plus particulate sulfate) were in good agreement among the various studies, accurate concentrations for sulfate and SO 2 were only obtained using a diffusion denuder sampling system because of the absorption of SO 2 (g) by particles in all filter pack sampling systems. Concentrations of FT Total (HF(g) plus particulate fluoride), and particulate Se, As, and Pb determined by multiple techniques were generally in good agreement. Sulfate (assumed present as ammonium sulfate) and nitrate (assumed present as ammonium nitrate) accounted for an average of 19 and 4%, respectively, of the fine particulate mass collected at Canyonlands and 8 and 2% of the fine particulate mass at Green River, Utah. Data were available at the Edge of the Cedars, Utah, sampling site to estimate the complete chemical composition of the fine particles. The average concentration of fine particles at Edge of the Cedars was 15 μg m −3 . Sulfate (as the ammonium salt) averaged 15% of the fine particulate mass, comparable to Canyonlands. Nonsulfate inorganic compounds averaged 58% of the mass. The majority of these inorganic species are background desert particles. The remainder of the mass, 27%, is presumably water, and organic and elemental carbon.

Regional Source Profiles of Sources of SOx at the Grand Canyon During Project Mohave

Total fluoride (gas plus fine particle), spherical aluminosilicate particles, particulate selenium, arsenic, lead, bromine, and absorption of light by fine particles have been used to characterize chemical profiles for sources of sulfur oxides impacting the Grand Canyon National Park Class I Visibility Region. During the Project MOHAVE (Measurement of Haze and Visual Effects) winter and summer intensive studies in 1992, these various species were determined at seven sampling sites in and around the Grand Canyon. Extensive upper air and surface-based meteorological measurements were examined to determine probable geographical origins of the air mass present during a given sampling period for each sampling site. Samples corresponding to air masses dominated by transport from a single major source region were used to determine a source profile for each region. Source regions which have been characterized by this analysis include the San Joaquin Valley area, the southern California coastal urban area, the Baja, California-Imperial Valley area, the Arizona and Mexico area (including major smelters) south of the Grand Canyon, the area southeast of the Grand Canyon, the Colorado Plateau area, the Wasatch Front in Utah, and the area in Nevada to the west and northwest of the Grand Canyon. Source profiles giving the ratio of each endemic marker to SO x for each identified regional source in these areas have been determined. The source profiles for the various regional sources are all statistically different and distinguishable from those for other geographically adjoining sources.

Apportionment of sulfur oxides at canyonlands during the winter of 1990 — II. fingerprints of emissions from point and regional sources impacting canyonlands

Abstract During January-March of 1990 a study was conducted to determine the sources of sulfur oxides present at Canyonlands and Green River, Utah. Samples were collected at these two receptor sites and at several sites intended to characterize the chemical composition of air masses reaching the receptor sites from various geographical regions. The results of the sampling program have been given in the first paper in a series of three papers. In this paper, the concentrations of spherical aluminosilicate (SAS) particles, total fluoride, and particulate selenium, arsenic and lead are combined with meteorological data to obtain source fingerprints for the ratios of these species to SO x , from the various regional sources that can influence the Canyonlands sampling site. The results indicate that the variability in the ratios of these various species to SO x , from the various regional sources is large enough to provide useful input to a receptor based, chemical mass balance source apportionment of SO, at the receptor sites. The chemical mass balance analysis is given in the final paper of this series. The ratio of SAS: SO x , varies by a factor of 25 in emissions from various coal-fired power plants. The concentrations of lead and arsenic relative to sulfur oxides is also variable in emissions from different coal-fired power plants. The ratio of particulate selenium and total fluoride to SO x , in emissions from these coal-fired sources is relatively constant. Emissions from source regions containing smelters are high in Se, As and Pb. Emissions from source regions containing fluoride ore processing industries have a high F Tots; : SO x , ratio.

Determination of fluoride in atmospheric samples using macrocycle -based ion chromatography

Abstract The analysis of fluoride in atmospheric samples poses challenges to current available methods. Ion cnromatographic methods often suffer from interferences due to elution of the fluoride peak in the water dip and coelution of weakly retained organic acid anions. A separation system using a macrocycle-based ion cnromatographic column provides a fast, effective method for the separation of fluoride in complex matrices. The macrocycle-based system shows better resolution of fluoride than traditional ion cnromatographic methods, separating fluoride from both the water dip and the organic acid anions. Isocratic elution with a hydroxide eluent allows for a detection limit of 0.15 μM with a linear response between 0.4 and 150 μM. Results compare favorably with known values and those obtained by ion selective electrode analysis.

Precision and accuracy in the determination of sulfur oxides, fluoride, and spherical aluminosilicate fly ash particles in Project MOHAVE

The precision and accuracy of the determination of particulate sulfate and fluoride, and gas phase S02 and HF are estimated from the results obtained from collocated replicate samples and from collocated comparison samples for highland low-volume filter pack and annular diffusion denuder samplers. The results of replicate analysis of collocated samples and replicate analyses of a given sample for the determination of spherical aluminosilicate fly ash particles have also been compared. Each of these species is being used in the chemical mass balance source apportionment of sulfur oxides in the Grand Canyon region as part of Project MOHAVE, and the precision and accuracy analyses given in this paper provide input to that analysis. The precision of the various measurements reported here is ±1.8 nmol/m3 and ±2.5 nmol/m3 for the determination of S02 and sulfate, respectively, with an annular denuder. The precision is ±0.5 nmol/m3 and ±2.0 nmol/m3 for the determination of the same species with a high-volume or low-volume filter pack. The precision for the determination of the sum of HF(g) and fine particulate fluoride is +0.3 nmol/m3. The precision for the determination of aluminosilicate fly ash particles is ±100 particles/m3. At high concentrations of the various species, reproducibility of the various measurements is ±10% to ±14% of the measured concentration. The concentrations of sulfate determined using filter pack samplers are frequently higher than those determined using diffusion denuder sampling systems. The magnitude of the difference (e.g., 2-10 nmol sulfate/m3) is small, but important relative to the precision of the data and the concentrations of particulate sulfate present (typically 5-20 nmol sulfate/m3). The concentrations of S02(g) determined using a high-volume cascade impactor filter pack sampler are correspondingly lower than those obtained with diffusion denuder samplers. The concentrations of SOx (SOz(g) plus particulate sulfate) determined using the two samplers during Project MOHAVE at the Spirit Mountain, NV, and Hopi Point, AZ, sampling sites were in agreement. However, for samples collected at Painted Desert, AZ, and Meadview, AZ, the concentrations of SOx and S02(g) determined with a high-volume cascade impactor filter pack sampler were frequently lower than those determined using a diffusion denuder sampling system. These two sites had very low ambient relative humidity, an average of 25%. Possible causes of observed differences in the S02(g) and sulfate results obtained from different types of samplers are given.