Douglas H. Lowenthal

Descriptive analysis of PM2.5 and PM10 at regionally representative locations during SJVAQS/AUSPEX

SJVAQS/AUSPEX acquired PM2.5 and PM10 samples at ten sites in Central California for five ozone episodes over 14 intensive sampling days. Four sample sets per day were acquired for 5 and 7 h durations and measured for particle mass; elements; water-soluble chloride, nitrate, sulfate, ammonium, sodium, and potassium ions; and organic and elemental carbon. Gaseous ammonia, nitric acid, and sulfur dioxide concentrations were acquired with absorbent filter material. To guard against contamination of these gases after sampling, the filter packs were sealed and refrigerated prior to analysis. Crustal species such as aluminum, silicon, calcium, titanium, iron, and calcium, were found in coarse particles at most sites. Substantial amounts of sodium and chloride were detected in the coarse particle fraction at the coastal Point Reyes site. Organic carbon and sulfate were the most abundant species in the PM2.5 fraction. Elemental carbon concentrations were low at all sites. Only one 24 h average PM0 concentration exceeded the U.S. PM10 standard of 150 μg m−3 during the study period, and this occurred at the agricultural-oriented Buttonwillow site. The highest concentrations of most chemical species were found at sites in the Southern San Joaquin Valley.

Differences in the carbon composition of source profiles for diesel- and gasoline-powered vehicles

Abstract Filter samples of diesel-fueled heavy-duty and gasoline-fueled light-duty vehicle exhaust were acquired under controlled conditions associated with the State of Arizonas motor vehicle inspection and maintenance program. Samples of a mixture of emissions from these vehicles were also acquired at roadside sites. These samples were analysed for mass, elements, ions, and carbon. The carbon which evolved at temperatures of 120, 250, 450, and 550 C in a pure helium atmosphere, and at temperatures of 550, 700, and 800 C in a 2°0 oxygen 98°0 helium (by volume) atmosphere was measured with a flame ionization detector. The fraction of carbon which evolved at 700 C in the 2°0 oxygen atmosphere was found to be nearly 10-times as abundant (as a fraction of PM2.5 mass emissions) in the heavy-duty diesel-fueled vehicle emissions relative to the light-duty gasoline-fueled vehicle emissions. The organic carbon which evolved at 120 C was twice as abundant in diesel exhaust. The fraction of carbon which evolved at 550 C in an oxidizing atmosphere was twice as abundant in gasoline-fueled vehicle exhaust as it was in diesel exhaust. These differences in relative composition may be sufficient to allow diesel- and gasoline-fueled vehicle exhaust contributions to be distinguished from each other in ambient samples through the use of receptor models.

Elemental Tracers of Distant Regional Pollution Aerosols

A seven-element tracer system shows that regional pollution aerosols of both North America and Europe have characteristic signatures that can be followed into remote areas up to several thousand kilometers downwind. In aerosols of mixed origin, regional contributions to the tracer elements can be resolved by least-squares procedures. After transport of several hundred kilometers, secondary sulfate can also be apportioned satisfactorily. Regional elemental tracers thus offer a way to determine the sources of pollution aerosol in important areas such as the northeastern United States, Scandinavia, and the Arctic.

Chemical Mass Balance Source Apportionment of PM10 during the Southern California Air Quality Study

The chemical mass balance (CMB) receptor model was applied to the chemically speciated diurnal particulate matter samples acquired at nine locations in Californias South Coast Air Basin (SoCAB) during the summer and fall of 1987 as part of the Southern California Air Quality Study (SCAQS). Source profiles applicable to the Los Angeles area were used to apportion PM2.5 and PM10 (particles with aerodynamic diameters < 2.5 and 10 μm, respectively) to primary paved road dust, primary construction dust, primary motor vehicle exhaust, primary marine aerosol, secondary ammonium nitrate, and secondary ammonium sulfate. Suspended dust was the major contributor to PM10 during the summer, whereas secondary ammonium nitrate and primary motor vehicle exhaust contributions were high during the fall. Secondary ammonium sulfate contributions were uniform across the SoCAB, with average contributions during the fall less than half those found during the summer. Marine aerosol contributions were lower during the fall than ...

Revised Algorithm for Estimating Light Extinction from IMPROVE Particle Speciation Data

Abstract The Interagency Monitoring of Protected Visual Environments (IMPROVE) particle monitoring network consists of approximately 160 sites at which fine particulate matter (PM2.5) mass and major species concentrations and course particulate matter (PM10) mass concentrations are determined by analysis of 24-hr duration sampling conducted on a 1-day-in-3 schedule. A simple algorithm to estimate light extinction from the measured species concentrations was incorporated in the 1999 Regional Haze Rule as the basis for the haze metric used to track haze trends. A revised algorithm was developed that is more consistent with the recent atmospheric aerosol literature and reduces bias for high and low light extinction extremes. The revised algorithm differs from the original algorithm in having a term for estimating sea salt light scattering from Cl - ion data, using 1.8 instead of 1.4 for the mean ratio of organic mass to measured organic carbon, using site-specific Rayleigh scattering based on site elevation and mean temperature, employing a split component extinction efficiency associated with large and small size mode sulfate, nitrate and organic mass species, and adding a term for nitrogen dioxide (NO2) absorption for sites with NO2 concentration information. Light scattering estimates using the original and the revised algorithms are compared with nephelometer measurements at 21 IMPROVE monitoring sites. The revised algorithm reduces the underprediction of high haze periods and the overprediction of low haze periods compared with the performance of the original algorithm. This is most apparent at the hazier monitoring sites in the eastern United States. For each site, the PM10 composition for days selected as the best 20% and the worst 20% haze condition days are nearly identical regardless of whether the basis of selection was light scattering from the original or revised algorithms, or from nephelometer-measured light scattering.

PM10 source apportionment in California's San Joaquin valley

Abstract A PM10 (particulate matter with aerodynamic diameter equal to or less than 10 μm) aerosol study was carried out at six sites in Californias San Joaquin Valley (SJV) from 14 June 1988 to 9 June 1989, as part of the 1988–1989 Valley Air Quality Study (VAQS). Concentrations of PM10 and PM2.5 (particles with aerodynamic diameters equal to or less than 2.5 μm) mass, organic and elemental carbon, nitrate, sulfate, ammonium and elements were determined in 24-h aerosol samples collected at three urban (Stockton, Fresno, Bakersfield) and three non-urban (Crows Landing, Fellows, Kern Wildlife Refuge) locations during this period. The sources which contributed to ambient concentrations of PM10 were determined by applying the Chemical Mass Balance (CMB) receptor model using the source profiles determined specifically for that study area. The VAQS data indicates the federal 24-h PM10 standard of 150 μg m−3 was exceeded at four out of the six sites and for reasons which differ by season and by spatial region of influence. The annual average source contributions to the PM10 at Bakersfield, the site with the highest annual average, were 54% from primary geological material, 15% from secondary ammonium nitrate, 10% from primary motor vehicle exhaust, 8% from primary construction; the remaining 4% was unexplained. The results of the source apportionment at all sites show that geological contributions (fugitive dust from tilling, roadways and construction) are largest in summer and fall months, while secondary ammonium nitrate contributions (deriving from direct emissions of ammonia and oxides of nitrogen from agricultural activities and engine exhaust) are largest during winter months.

Characterization of heavy-duty diesel vehicle emissions

Abstract Emissions of heavy duty diesel-powered vehicles were measured at the Phoenix Transit Yard in South Phoenix between 31 March 1992 and 25 April 1992 using the West Virginia University Transportable Heavy-Duty Vehicle Emissions Testing Laboratory (Mobile Lab). Thirteen heavy-duty trucks and buses were tested over this period. The vehicles were operated with diesel No. 2 and Jet A fuels, with and without a fuel additive, and with and without particulate control traps. The chassis dynamometer Mobile Lab tested vehicles over the Central Business District (CBD) driving cycle. Particulate matter in the diluted exhaust was sampled proportionally from a total-exhaust dilution tunnel. Emission rates and compositions of PM 2.5 particulate mass, elements, ions, bulk organic and elemental carbon, and gaseous and particulate polycyclic aromatic hydrocarbons were averaged for various classes of fuels and particulate matter control. Emission rates for PM 2.5 mass averaged 0.2 and 1 g mile −1 for trucks and buses with and without particulate traps, respectively. Emission rates for elemental carbon averaged 0.02 and 0.5 g mile −1 for trucks and buses with and without particulate traps, respectively. Diesel particulate exhaust was comprised mainly of organic and elemental carbon (80–90%) and sulfate (up to 14%). The new diesel source composition profiles are similar to one determined earlier in Phoenix. Polycyclic aromatic hydrocarbons comprised no more than a few percent of the particulate organic carbon but their relative abundances may be useful for distinguishing diesel emissions from those of other combustion sources.

Source Apportionment: Findings from the U.S. Supersites Program

Abstract Receptor models are used to identify and quantify source contributions to particulate matter and volatile organic compounds based on measurements of many chemical components at receptor sites. These components are selected based on their consistent appearance in some source types and their absence in others. UNMIX, positive matrix factorization (PMF), and effective variance are different solutions to the chemical mass balance (CMB) receptor model equations and are implemented on available software. In their more general form, the CMB equations allow spatial, temporal, transport, and particle size profiles to be combined with chemical source profiles for improved source resolution. Although UNMIX and PMF do not use source profiles explicitly as input data, they still require measured profiles to justify their derived source factors. The U.S. Supersites Program provided advanced datasets to apply these CMB solutions in different urban areas. Still lacking are better characterization of source emissions, new methods to estimate profile changes between source and receptor, and systematic sensitivity tests of deviations from receptor model assumptions.

Regional sources of pollution aerosol at Barrow, Alaska during winter 1979–1980 as deduced from elemental tracers

Abstract A seven-element tracer system for regional pollution aerosol has been applied to 100 daily samples of aerosol from Barrow, Alaska during winter 1979–1980, using regional signatures from eastern N America, Europe, and the Soviet Union. The results suggest that approximately 70% of most tracer elements came from the U.S.S.R., 25 % came from Europe, and the rest came from N America. The large contribution from the U.S.S.R. is consistent with large-scale atmospheric flow patterns for that winter, in which air came strongly and persistently from central Asia northward to the Arctic. The small contribution from eastern N America agrees with previous circumstantial evidence. Apportionment of sulfate between Europe and the Soviet Union suggested that each contributed roughly 50%, however. The greater contribution of Europe to sulfate than to tracer elements is consistent with other data, including emission inventories for SO 2 and elements in the Soviet Union and Europe.

Air Quality Measurements from the Fresno Supersite

ABSTRACT The Fresno Supersite intends to 1) evaluate non-routine monitoring methods, establishing their comparability with existing methods and their applicability to air quality planning, exposure assessment, and health effects studies; 2) provide a better understanding of aerosol characteristics, behavior, and sources to assist regulatory agencies in developing standards and strategies that protect public health; and 3) support studies that evaluate relationships between aerosol properties, co-factors, and observed health end-points. Supersite observables include in-situ, continuous, short-duration measurements of 1) PM2.5, PM10, and coarse (PM10 minus PM2.5) mass; 2) PM2.5 SO4 -2, NO3 -, carbon, light absorption, and light extinction; 3) numbers of particles in discrete size bins ranging from 0.01 to ~10μm; 4) criteria pollutant gases (O3, CO, NOx); 5) reactive gases (NO2, NOy, HNO3, peroxyacetyl nitrate [PAN], NH3); and 6) single particle characterization by time-of-flight mass spectrometry. Field sampling and laboratory analysis are applied for gaseous and particulate organic compounds (light hydrocarbons, heavy hydrocarbons, carbonyls, polycyclic aromatic hydrocarbons [PAH], and other semi-volatiles), and PM2.5 mass, elements, ions, and carbon. Observables common to other Supersites are 1) daily PM2.5 24-hr average mass with Federal Reference Method (FRM) samplers; 2) continuous hourly and 5-min average PM2.5 and PM10 mass with beta attenuation monitors (BAM) and tapered element oscillating microbalances (TEOM); 3) PM2.5 chemical specia-tion with a U.S. Environmental Protection Agency (EPA) speciation monitor and protocol; 4) coarse particle mass by dichotomous sampler and difference between PM10 and PM2.5 BAM and TEOM measurements; 5) coarse particle chemical composition; and 6) high sensitivity and time resolution scalar and vector wind speed, wind direction, temperature, relative humidity, barometric pressure, and solar radiation. The Fresno Supersite is coordinated with health and toxicological studies that will use these data in establishing relationships with asthma, other respiratory disease, and cardiovascular changes in human and animal subjects.