Robert G. Flocchini

Analysis of respirable fractions in atmospheric particulates via sequential filtration

It has long been recognized that information on particle size distributions in atmospheric aerosals is necessary for meaningful evaluations of potential health hazards. Such information is also important in establishing particulate sources, transport, transformations, and sinks, especially in combination with elemental and chemical data. While instruments exist to collect size segregated samples of particulates, they are too complex and expensive to encourage use of multiple units in field situations.

Composition of PM2.5 and PM10 Aerosols in the IMPROVE Network

Abstract PM2.5 and PM10 particulate concentrations measured at 42 sites in the Interagency Monitoring of Protected Visual Environments(IMPROVE) network at Class I visibility areas throughout the United States over the 1993 seasonal year showed well-defined regional patterns. The PM2.5 concentration had a large gradient from West to East, averaging 3 μg/m3 in most of the West compared to 13 μg/m3 in the Appalachian region. Coarse particle concentration (2.5-10 μm) exhibited a small gradient from North to South, but no gradient from West to East. No change in PM2.5 or PM10 was observed from 1988 to 1993 for sites with complete records. The elemental concentration (H, Na-Pb) was determined from all PM2.5 Teflon filters and from the PM10 filters from four sites: an eastern and western urban site (Washington, D.C. and South Lake Tahoe) and the nearest Class I site (Shenandoah and Bliss). Soil was the largest component of the coarse particle concentration. Sulfur accounted for 3% of the coarse particle concentr...

Characterization of particles in the arid west

Abstract This paper describes spatial and temporal variations of airborne paniculate matter in the eight western states included in the western fine particle network (WFPN). The samples were generated by a 40-site monitoring network of remotely sited dichotomous samplers of the stacked filter and virtual design, with a coarse fraction between 15 μm and 2.5 μm dia. and a fine fraction below 2.5 μm dia. The units operate for two 72 h period each week, delivering samples analyzed gravimetrically for mass and by particle induced X-ray emission (PIXE) for elements sodium and heavier. Results are presented for the period October 1979 to May 1980, showing regional patterns of particles especially in the fine modes. A sulfur episode which occurred in the southwest is examined via trajectory analysis, while factor analysis is applied to the entire data set to generate information on particulate sources.

Sensitivity versus target backings for elemental analysis by alpha excited X-ray emission

Abstract The sensitivity of elemental analysis by charged-particle induced X-ray fluorescence is examined by measuring characteristic X-ray cross sections for K α , K β , L α , L β , L γ , and M transitions for many elements and bremsstrahlung backgrounds from thin mylar, kapton, and teflon films between 0.7 and 8 mg/cm 2 thickness. Sensitivities are given as a function of target atomic number, backing thickness, incident beam charge, energy and flux, and detector configuration. An evaluation of the strengths and weaknesses of charged-particle induced X-ray emission for elemental analysis is included.

Reactive organic gas emissions from livestock feed contribute significantly to ozone production in central California.

The San Joaquin Valley (SJV) in California currently experiences some of the highest surface ozone (O(3)) concentrations in the United States even though it has a population density that is an order of magnitude lower than many urban areas with similar ozone problems. Previously unrecognized agricultural emissions may explain why O(3) concentrations in the SJV have not responded to traditional emissions control programs. In the present study, the ozone formation potentials (OFP) of livestock feed emissions were measured on representative field samples using a transportable smog chamber. Seven feeds were considered: cereal silage (wheat grain and oat grain), alfalfa silage, corn silage, high moisture ground corn (HMGC), almond shells, almond hulls, and total mixed ration (TMR = 55% corn silage, 16% corn grain, 8% almond hulls, 7% hay, 7% bran + seeds, and 5% protein + vitamins + minerals). The measured short-term OFP for each gram of reactive organic gas (ROG) emissions from all livestock feed was 0.17-0.41 g-O(3) per g-ROG. For reference, OFP of exhaust from light duty gasoline powered cars under the same conditions is 0.69 +/- 0.15 g-O(3) per g-ROG. Model calculations were able to reproduce the ozone formation from animal feeds indicating that the measured ROG compounds account for the observed ozone formation (i.e., ozone closure was achieved). Ethanol and other alcohol species accounted for more than 50% of the ozone formation for most types of feed. Aldehydes were also significant contributors for cereal silage, high moisture ground corn, and total mixed ration. Ozone production calculations based on feed consumption rates, ROG emissions rates, and OFP predict that animal feed emissions dominate the ROG contributions to ozone formation in the SJV with total production of 25 +/- 10 t O(3) day(-1). The next most significant ROG source of ozone production in the SJV is estimated to be light duty vehicles with total production of 14.3 +/- 1.4 t O(3) day(-1). The majority of the animal feed ozone formation is attributed to corn silage. Future work should be conducted to reduce the uncertainty of ROG emissions from animal feeds in the SJV and to include this significant source of ozone formation in regional airshed models.

A principal component analysis of sulfur concentrations in the Western United States

Abstract Data from a 40 site network of air samplers in the western United States were used in a principal components analysis to obtain spatial patterns of the inter-site correlations of sulfur concentrations. After rotation of the initial eigenvectors, two large regions were identified which accounted for 33.1% of the variance in the data. Three other smaller regions were identified which also had significant variance. The first eigenvector included all sites in the southern part of the network and was attributed to copper smelter emissions in Arizona and New Mexico. The second eigenvector included sites in the northern great plains and was attributed to episodic incursions of sulfur from the east. The third, fourth and fifth eigenvectors were attributed to locally important conditions.

Local meteorological, transport, and source aerosol characteristics of late autumn Owens Lake (dry) dust storms☆

Abstract The time evolution of aerosol generation in the saltation dominated fine particle production from Owens (dry) Lake, California, was measured by size and elemental composition for four dust events in November–December 1991. Time resolved aerosol size distributions were measured during all storm periods from genesis to cessation at the township of Keeler, less than 1 km from the border of one of the dust-producing regions. The size distributions of aerosols showed a much greater concentration of soil elements in very fine modes than is usual in typical soils, with a PM10 mass median diameter in the 2.5–5 μm size range. Four meteorological stations on and around the lake, time lapse photography of the northern lake bed, and nephelometers located 100 km to the south allowed for the continuous monitoring of local meteorology as well as transport patterns during storm periods. Local meteorological and transport patterns observed are discussed.

Regional analysis of factors affecting visual air quality

The U.S. Environmental Protection Agency, National Park Service, Visibility Research Center, and University of California at Davis are currently operating a monitoring program in national parks and monuments throughout much of the western United States. Project VIEW, the Visibility Investigative Experiment in the West, includes measurement of visibility parameters using manual telephotometers, and measurement of particle concentrations averaged over 72 h. Variation of these parameters occurs in both space and time. To better understand these variations, several techniques including principal component analysis and data comparisons among sites are applied to Fall, 1979 data for much of the network. Then the Grand Canyon is chosen for additional analysis. Best and worst case visibility days are determined and compared with particle concentrations. Finally, hypothetical causes for visibility reduction are further verified by computing wind trajectories back in time for these special case days. Highlights of this preliminary investigation include evidence that fine sulfur and fine particles are responsible for visibility variation at the VIEW sites; that fine particle copper may be suitable as a tracer for copper smelter impact and that at the Grand Canyon, the majority of trajectories for days of visibility greater than 310km come from the north and west, over Utah and Nevada.

Ammonia Flux from Open-Lot Dairies: Development of Measurement Methodology and Emission Factors

Abstract Ammonia emissions contribute to the formation of secondary particulate matter (PM) and violations of the National Ambient Air Quality Standard. Ammonia mass concentration measurements were made in February 1999 upwind and downwind of an open-lot dairy in California, using a combination of active bubbler and passive filter samplers. Ammonia fluxes were calculated from concentrations measured at 2, 4, and 10 m above ground at three locations on the downwind edge of the dairy, using micrometeorological techniques. A new method was developed to interpolate fluxes at six additional locations from ammonia concentrations measured at a single height, providing measurements at sufficient spatial resolution along the downwind border of the dairy to account for the heterogeneity of the source. PM measured up- and downwind of the dairy demonstrated insignificant ammonium particle formation in the immediate vicinity of the dairy and negligible contribution of dissociated ammonium nitrate to measured ammonia concentrations. Ammonium nitrate concentrations measured downwind of the dairy ranged from 26 to 0.26 μg m−3 and from 2 to 43% of total PM2.5 mass concentrations. Measured ammonia fluxes showed that liquid manure retention ponds represented relatively minor sources of ammonia in winter on the dairy studied. Ammonia emission factors derived from the measurements ranged from 19 to 143 g head−1 day−1, showing an increase with warmer, drier weather and a decrease with increased relative humidity and lower temperatures.

A multivariate statistical analysis of visibility degradation at four California cities

Abstract Multiple regression analysis is used to interpret the relationship between visibility reduction, pollutants and meteorological conditions. Results indicate that multiple regression is a useful technique for air pollution analysis. Four California sites were analyzed : Los Angeles, Los Alamitos, Bakersfield and Oakland. Each site had site specific variables which reduced visibility. However, sulfur in the 0.65–3.6 μm size range showed a significant relationship to reduced visibility at all sites. The study also indicated that the elemental composition and the particle size were both important in determining the effect of paniculate aerosols on visibility reduction.