Lowell L. Ashbaugh

Similarities and differences in PM10 chemical source profiles for geological dust from the San Joaquin Valley, California

A systematic sampling and analysis approach was followed to acquire chemical source profiles for six types of geological dust in California’s San Joaquin Valley. Forty-seven samples from 37 locations included: (1) urban and rural paved roads, (2) residential and agricultural unpaved roads and parking areas, (3) almond, cotton, grape, safflower, and tomato fields, (4) dairy and feedlot surfaces, (5) salt-laden lake and irrigation canal drainage deposits, and (6) building and roadway construction/earthmoving soil. These samples were dried, sieved, resuspended, sampled through a PM10 inlet onto filters, and chemically analyzed to construct PM10 source profiles (fractional mass abundances and uncertainties) for 40 elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Zr, Mo, Pd, Ag, Cd, In, Sn, Sb, Ba, La, Au, Hg, Tl, Pb, and U), 7 ions (Cl � ,N O 3 ,P O 4� ,S O 4� ,N a + ,K + , and NH4 ), organic and elemental carbon (OC and EC), 8 carbon fractions (OC1, OC2, OC3, OC4, OP, EC1, EC2, and EC3), and carbonate carbon. Individual source profiles with analytical precisions were averaged and compared to quantify differences in chemical abundances for: (1) duplicate laboratory resuspension sampling, (2) multiple sampling within the same agricultural field, (3) sampling at different locations for the same land-use activity, (4) sampling of different activities regardless of location, and (5) grouping of different activities into generalized emission inventory source categories. Distinguishing features were found among composite source profiles of six source types. Elemental carbon and Pb marked paved road dust; Na + , Na, S, and SO4� marked salt deposits; OC, PO4� ,P , K + , K, and Ca characterized animal husbandry; and several metals (Ti, V, Mn) marked construction soil, with abundances 2–10 times higher than those of other profiles. High-sensitivity X-ray fluorescence analysis resulted in detectable alkali and rare earth elements. Ga, Zr, Sn, and Ba were found in some of the paved road dust profiles; toxic species such as As, Mo, Cd, Sb, and U were found in salt deposits from canal drainage; and Pd, Rb, Sr, and Tl were found in construction dust. The profile-compositing methodology can be used for evaluating similarities and differences for other source characterization studies. r 2003 Elsevier Science Ltd. All rights reserved.

Characterization of organic aerosol in Big Bend National Park, Texas

The Big Bend Regional Aerosol and Visibility Observational (BRAVO) Study was conducted in Big Bend National Park, Texas, July through October 1999. Daily PM2.5 organic aerosol samples were collected on pre-fired quartz fiber filters. Daily concentrations were too low for detailed organic analysis by gas chromatography-mass spectrometry (GC-MS) and were grouped based on their air mass trajectories. A total of 12 composites, each containing 3–10 daily samples, were analyzed. Alkane carbon preference indices suggest primary biogenic emissions were small contributors to primary PM2.5 organic matter (OM) during the first 3 months, while in October air masses advecting from the north and south were more strongly influenced by biogenic sources. A series of trace organic compounds previously shown to serve as particle phase tracers for various carbonaceous aerosol source types were examined. Molecular tracer species were generally at or below detection limits, except for the wood smoke tracer levoglucosan in one composite, so maximum possible source influences were calculated using the detection limit as an upper bound to the tracer concentration. Wood smoke was found not to contribute significantly to PM2.5 OM, with contributions for most samples at <1% of the total organic particulate matter. Vehicular exhaust also appeared to make only minor contributions, with maximum possible influences calculated to be 1–4% of PM2.5 OM. Several factors indicate that secondary organic aerosol formation was important throughout the study, and may have significantly altered the molecular composition of the aerosol during transport.

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.

MOTOR VEHICLE EMISSIONS VARIABILITY

Test-to-test variability has been observed by many current testing methods, including the Federal Test Procedure, the IM240 dynamometer test, the idle test common to many Inspection and Maintenance programs, and on-road remote sensing. The variability is attributable to the vehicle, not to the testing procedure. Because the vehicles are the dominant source of variability, the only way such vehicles can be reliably identified is through the use of multiple tests. The emissions variability increases with increasing average emissions, and it appears to be prevalent among the few newer technology vehicles with defective, but untampered, closed-loop emissions control systems (1981 and newer models). In one fleet the variable emitters constitute 2.2% to 4.8% of the vehicles and contribute 8.5% to 22% of the total carbon monoxide emissions. Scheduled I/M programs that fail to ensure repair of these vehicles allow a significant portion of vehicles with excess emissions to escape reduction measures.

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.

Soil sample collection and analysis for the Fugitive Dust Characterization Study

A unique set of soil samples was collected as part of the Fugitive Dust Characterization Study. The study was carried out to establish whether or not source profiles could be constructed usingnovel analytical methods that could distinguish soil dust sources from each other. The soil sources sampled included fields planted in cotton, almond, tomato, grape, and safflower, dairy and feedlot facilities, paved and unpaved roads (both urban and rural), an agricultural staging area, disturbed land with salt buildup, and construction areas where the topsoil had been removed. The samples were collected usinga systematic procedure desig ned to reduce samplingbias, and were stored frozen to preserve possible organic signatures. For this paper the samples were characterized by particle size (percent sand, silt, and clay), dry silt content (used in EPA-recommended fugitive dust emission factors), carbon and nitrogen content, and potential to emit both PM10 and PM2.5. These are not the ‘‘novel analytical methods’’ referred to above; rather, it was the basic characterization of the samples to use in comparinganalytical methods by other scientists contracted to the California Air Resources Board. The purpose of this paper is to document the methods used to collect the samples, the collection locations, the analysis of soil type and potential to emit PM10, and the sample variability, both within field and between fields of the same crop type. r 2003 Elsevier Science Ltd. All rights reserved.

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.

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.

Loss of Particle Nitrate from Teflon Sampling Filters: Effects on Measured Gravimetric Mass in California and in the IMPROVE Network

Abstract The extent of mass loss on Teflon filters caused by ammonium nitrate volatilization can be a substantial fraction of the measured particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5)or 10 μm (PM10) mass and depends on where and when it was collected. There is no straightforward method to correct for the mass loss using routine monitoring data. In southern California during the California Acid Deposition Monitoring Program, 30-40% of the gravimetric PM2.5 mass was lost during summer daytime. Lower mass losses occurred at more remote locations. The estimated potential mass loss in the Interagency Monitoring of Protected Visual Environments network was consistent with the measured loss observed in California. The biased mass measurement implies that use of Federal Reference Method data for fine particles may lead to control strategies that are biased toward sources of fugitive dust, other primary particle emission sources, and stable secondary particles (e.g., sulfates). This analysis clearly supports the need for speciated analysis of samples collected in a manner that preserves volatile species. Finally, although there is loss of volatile nitrate (NO3 −) from Teflon filters during sampling, the NO3 − remaining after collection is quite stable. We found little loss of NO3 − from Teflon filters after 2 hr under vacuum and 1 min of heating by a cyclotron proton beam.

Silicon in submicron particles in the southwest

Silicon in the fine particle size range (less than about 2 μm) was investigated. Elemental and microscopical analysis of size segregated, ambient particulate and suspended soil samples from the rural southwest indicate that the particles are earth crust material. The composition of the soil related materials changes with changing particle size. Smaller particles tend to vary more in their elemental makeup than corresponding large particles. Numerous thin mineral plates with diameters of several micrometers are aerodynamically sized in the smallest sample size range (< 0.5 μm). Since silicon accounts for one-quarter to one-half the total mass in the fine particle size range, it may be a significant causal factor in regional visibility degradation.