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[1] During the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) intensive experiment in the spring of 2001 we used a total aerosol sampler (TAS) and a micro-orifice impactor (MOI) to collect dust and pollution aerosols for ion chromatographic analysis. An aerodynamic particle sizer (APS) was used to estimate the total coarse-mode volume. We conducted postexperiment passing efficiency measurements on the APS, the MOI, and their delivery tubing to constrain the inevitable (and sometimes large) artifacts associated with sampling supermicron particles from an aircraft. We have combined TAS and corrected MOI data to estimate ambient coarse and fine sulfate, ammonium, nitrate, calcium, sodium, chloride, potassium, magnesium, and oxalate. We found significant differences between aerosol composition in the free troposphere (FT) and boundary layer (BL). The molar ratio of nitrate to soluble calcium averaged 1.8 in the BL, but only 0.2 in the FT. Nitrate and calcium frequently had identical coarse size distributions, while sulfate and ammonium often had identical fine distributions. Dust clearly directs NO y toward coarse-mode nitrate. Sulfate in the FT was closest to ammonium bisulfate (half neutralized), while non-sea-salt sulfate (NSS) in the BL was usually completely neutralized to ammonium sulfate. In the presence of dust, up to half the NSS was found in the coarse mode, probably the result of SO 2 uptake by CaCO 3 in the dust. Soluble calcium averaged 5-8% of the coarse dust mass inferred from the APS. BL aerosol chemistry was seldom a good indicator of ionic composition in the FT.

[1] Physical and optical properties of inorganic aerosols have been extensively studied, but less is known about carbonaceous aerosols, especially as they relate to the non-urban settings such as our nation's national parks and wilderness areas. Therefore an aerosol characterization study was conceived and implemented at one national park that is highly impacted by carbonaceous aerosols, Yosemite. The primary objective of the study was to characterize the physical, chemical, and optical properties of a carbon-dominated aerosol, including the ratio of total organic matter weight to organic carbon, organic mass scattering efficiencies, and the hygroscopic characteristics of a carbon-laden ambient aerosol, while a secondary objective was to evaluate a variety of semi-continuous monitoring systems. Inorganic ions were characterized using 24-hour samples that were collected using the URG and Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring systems, the micro-orifice uniform deposit impactor (MOUDI) cascade impactor, as well as the semi-continuous particle-into-liquid sampler (PILS) technology. Likewise, carbonaceous material was collected over 24-hour periods using IMPROVE technology along with the thermal optical reflectance (TOR) analysis, while semi-continuous total carbon concentrations were measured using the Rupprecht and Patashnick (R&P) instrument. Dry aerosol number size distributions were measured using a differential mobility analyzer (DMA) and optical particle counter, scattering coefficients at near-ambient conditions were measured with nephelometers fitted with PM 10 and PM 2.5 inlets, and ''dry'' PM 2.5 scattering was measured after passing ambient air through Perma Pure Nafion 1 dryers. In general, the 24-hour ''bulk'' measurements of various aerosol species compared more favorably with each other than with the semi-continuous data. Semi-continuous sulfate measurements correlated well with the 24-hour measurements, but were biased low by about 0.15 mg/m 3 . Semi-continuous carbon concentrations did not compare favorably with 24-hour measurements. Fine mass closure calculations suggested that the factor for estimating organic mass from measurements of carbon was approximately 1.8. Furthermore, fine scattering closure calculations showed that the use of 4.0 m 2 /g for the fine organic mass scattering coefficient was an underestimate by at least 30% for periods with high organic mass concentrations.

[1] Atmospheric deposition of nitrogen (N) and base cations was measured for 5-7 years on the island of Hawaii and for 1.