Biomedical subjects

Michael J Kleeman

Publications and source records attributed to Michael J Kleeman.

8 recordsLinked to original sources

PubMed2006

LC-MS analysis of carbonyl compounds and their occurrence in diesel emissions.

Liquid chromatography coupled with atmospheric pressure chemical ionization (APCI) ion trap mass spectrometry (ITMS) is applied to atmospheric aerosol relevant carbonyls. Characterization of positive and negative ion detection mass spectra are presented for 24 model compounds analyzed in their underivatized and O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) oxime forms. The addition of PFBHA derivatization enhanced the detection and sensitivity for many of the carbonyls investigated. For all but five of the carbonyls examined, a pseudomolecular (M + H)+ ion is the base peak in the APCI positive ion mass spectra of PFBHA oxime derivatives and is observed in four of the five exceptions. Application of the evaluated analysis methodology to heavy-duty diesel source emissions facilitated the quantification of 10 aliphatic carbonyls (5 C5-C9 ketones, 4 C6 unsaturated ketones, 1 C6 dicarbonyl) and 14 aromatic carbonyls (1 C9 aldehyde, 5 C8-C13 ketones, 8 C6-C14 quinones). Diesel truck engine emission factors spanning 0.55-540 microg km(-1) were measured for gas- and particle-phase carbonyls. Good agreement was observed for gas-phase emission factors with results obtained by gas chromatography with ITMS.

Chromatography, Liquid↗

PubMed2006

Measuring the trace elemental composition of size-resolved airborne particles.

A new method to measure the trace elemental composition of size-resolved airborne particles that uses acetone extraction followed by ICPMS analysis is compared to three other established methods: copper anode XRF, molybdenum anode XRF, and an ICPMS method that uses HF digestion. The method detection limit (MDL), accuracy, and precision of each method is studied through the analysis of ambient samples collected in California. The MDLs of the new acetone-ICPMS method are similar to MDLs for the established HF-ICPMS method. Both sets of ICPMS MDLs are 1-3 orders of magnitude lower than XRF MDLs for approximately 50 elements other than the light crustal elements such as silicon, sulfur, calcium, and zinc. The accuracy of the acetone-ICPMS method was verified by comparison to measurements made using ion chromatography and the HF-ICPMS method. The acetone-ICPMS analysis method was more precise than the conventional HF-ICPMS method for collocated measurements. Both ICPMS methods were more precise than XRF for most elements. The size distribution of 21 elements contained in ambient particles collected with cascade impactors could be measured with good precision using the new acetone-ICPMS analysis method: lithium, sulfur, potassium, titanium, vanadium, manganese, iron, gallium, germanium, arsenic, selenium, bromine, rubidium, strontium, cadmium, tin, antimony, barium, thallium, lead, and bismuth. It is likely that the size distribution of an additional 9 elements could also be measured when concentrations are sufficiently high: phosphorus, molybdenum, niobium, palladium, cesium, europium, holmium, platinum, and uranium. None of the conventional methods were able to measure the size distribution of these elements with acceptable precision under the conditions studied. The new acetone-ICPMS method should provide useful data for the study of the health effects of airborne particles.

Air Pollution↗

PubMed2005

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.

Air Movements↗

PubMed2004

Source apportionment of visibility impairment using a three-dimensional source-oriented air quality model.

A three-dimensional source-oriented Eulerian air quality model is developed that can predict source contributions to the visibility reduction. Particulate matter and precursor gases from 14 different sources (crustal material, paved road dust, diesel engines, meat cooking, noncatalyst-equipped gasoline engines, catalyst-equipped gasoline engines, high-sulfur fuel, sea salt, refrigerant losses, residential production, animals, soil and fertilizer application, other anthropogenic sources, and background sources) are tracked though a mathematical simulation of emission, chemical reaction, gas-to-particle conversion, transport, and deposition. A visibility model based on Mie theory is modified to use the calculated source contributions to airborne particulate matter size and composition as well as gas-phase pollutant concentrations to quantify total source contributions to visibility impairment. The combined air quality-visibility model is applied to predict source contributions to visibility reduction in southern California for a typical air pollution episode (September 23-25, 1996). The model successfully predicts a severe visibility reduction in the eastern portion of the South Coast Air Basin where the average daytime visibility is measured to be less than 10 km. In the relatively clean coastal portion of the domain, the model successfully predicts that the average daytime visibility is greater than 65 km. Transportation-related sources directly account for approximately 50% of the visibility reduction (diesel engines approximately 15-20%, catalyst-equipped gasoline engines approximately 10-20%, noncatalyst-equipped gasoline engines approximately 3-5%, crustal and paved road dust approximately 5%) in the region with the most severe visibility impairment. Ammonia emissions from animal sources account for approximately 10-15% of the visibility reduction.

Air Movements↗

PubMed2002

Source apportionment of secondary airborne particulate matter in a polluted atmosphere.

Secondary airborne particulate matter formed from gas-phase pollutants contributes significantly to the most severe particulate air quality events that occur in the United States each year. In this study, a mechanistic air quality model is demonstrated that can predict source contributions to the size distribution of secondary airborne particulate matter. Calculations performed for a typical air quality episode in Southern California show that NOx released from diesel engines and catalyst-equipped gasoline engines account for the majority of the secondary particulate nitrate aerosol measured at inland locations. NH3 released from catalyst-equipped gasoline engines, farm animals, and residential sources account for the majority of the secondary particulate ammonium ion at inland locations in the region. When both tailpipe and road dust emissions are considered, transportation sources dominate the size distribution of total (primary plus secondary) airborne particulate matter in the South Coast Air Basin during the episode studied. These findings suggest that the public health risk associated with air pollution released from transportation sources is significant relative to other public health threats such as traffic accidents.

Air Pollutants↗

PubMed2002

Evaluation of an air quality model for the size and composition of source-oriented particle classes.

Air quality model predictions of the size and composition of atmospheric particle classes are evaluated by comparison with aerosol time-of-flight mass spectrometry (ATOFMS) measurements of single-particle size and composition at Long Beach and Riverside, CA, during September 1996. The air quality model tracks the physical diameter, chemical composition, and atmospheric concentration of thousands of representative particles from different emissions classes as they are transported from sources to receptors while undergoing atmospheric chemical reactions. In the model, each representative particle interacts with a common gas phase but otherwise evolves separately from all other particles. The model calculations yield an aerosol population, in which particles of a given size may exhibit different chemical compositions. ATOFMS data are adjusted according to the known particle detection efficiencies of the ATOFMS instruments, and model predictions are modified to simulate the chemical sensitivities and compositional detection limits of the ATOFMS instruments. This permits a direct, semiquantitative comparison between the air quality model predictions and the single-particle ATOFMS measurements to be made. The air quality model accurately predicts the fraction of atmospheric particles containing sodium, ammonium, nitrate, carbon, and mineral dust, across all particle sizes measured by ATOFMS at the Long Beach site, and in the coarse particle size range (Da > or = 1.8 microm) atthe Riverside site. Given thatthis model evaluation is very likely the most stringent test of any aerosol air quality model to date, the model predictions show impressive agreement with the single-particle ATOFMS measurements.

Aerosols↗

PubMed2002

Measurement of emissions from air pollution sources. 5. C1-C32 organic compounds from gasoline-powered motor vehicles.

Gas- and particle-phase organic compounds present in the tailpipe emissions from an in-use fleet of gasoline-powered automobiles and light-duty trucks were quantified using a two-stage dilution source sampling system. The vehicles were driven through the cold-start Federal Test Procedure (FTP) urban driving cycle on a transient dynamometer. Emission rates of 66 volatile hydrocarbons, 96 semi-volatile and particle-phase organic compounds, 27 carbonyls, and fine particle mass and chemical composition were quantified. Six isoprenoids and two tricyclic terpanes, which are quantified using new source sampling techniques for semi-volatile organic compounds, have been identified as potential tracers for gasoline-powered motor vehicle emissions. A composite of the commercially distributed California Phase II Reformulated Gasoline used in these tests was analyzed by several analytical methods to quantify the gasoline composition, including some organic compounds that are found in the atmosphere as semi-volatile and particle-phase organic compounds. These results allow a direct comparison of the semi-volatile and particle-phase organic compound emissions from gasoline-powered motor vehicles to the gasoline burned by these vehicles. The distribution of n-alkanes and isoprenoids emitted from the catalyst-equipped gasoline-powered vehicles is the same as the distribution of these compounds found in the gasoline used, whereas the distribution of these compounds in the emissions from the noncatalyst vehicles is very different from the distribution in the fuel. In contrast, the distribution of the polycyclic aromatic hydrocarbons and their methylated homologues in the gasoline is significantly different from the distribution of the PAH in the tailpipe emissions from both types of vehicles.

Air Pollutants↗

PubMed2002

Measurement of emissions from air pollution sources. 4. C1-C27 organic compounds from cooking with seed oils.

The emission rates of gas-phase, semivolatile, and particle-phase organic compounds ranging in carbon number from C1 to C27 were measured from institutional-scale food cooking operations that employ seed oils. Two cooking methods and three types of seed oils were examined: vegetables stir-fried in soybean oil, vegetables stir-fried in canola oil, and potatoes deep fried in hydrogenated soybean oil. The emission rates of 99 organic compounds were quantified, and these include n-alkanes, branched alkanes, alkenes, n-alkanoic acids, n-alkenoic acids, carbonyls, aromatics, polycyclic aromatic hydrocarbons (PAH), and lactones. Carbonyls and fatty acids (n-alkanoic and n-alkenoic acids) make up a significant portion of the organic compounds emitted from all three seed oil cooking procedures. The compositional differences in the organic compound emissions between the different cooking operations are consistent with the differences in the organic composition of the various cooking oils used. The distribution of the n-alkanoic acids between the gas and particle phases was found to be in good agreement with gas/particle partitioning theory. The relative importance of emissions from commercial deep frying operations to the total emissions of C16 and C18 n-alkanoic acids in the Los Angeles urban area was estimated using the available information and is estimated to account for approximately 7% of the total primary emissions of these acids. Additional emissions of these n-alkanoic acids from stir-frying and grill frying operations are expected. Estimates also indicate that seed oil cooking may make up a significant fraction of the emissions of lighter n-alkanoic acids such as nonanoic acid.

Air Pollutants↗