Emissions of metals and other particle-phase species from on-road motor vehicles were measured in two tunnels in Milwaukee, WI during the summer of 2000 and winter of 2001. Emission factors were calculated from measurements of fine (PM2.5) and coarse (PM10) particulate matter at tunnel entrances and exits, and effects of fleet composition and season were investigated. Cascade impactors (MOUDI) were used to obtain size-resolved metal emission rates. Metals were quantified with inductively-coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence (XRF). PM10 emission rates ranged from 38.7 to 201 mg km(-1) and were composed mainly of organic carbon (OC, 30%), inorganic ions (sulfate, chloride, nitrate, ammonium, 20%), metals (19%), and elemental carbon (EC, 9.3%). PM10 metal emissions were dominated by crustal elements Si, Fe, Ca, Na, Mg, Al, and K, and elements associated with tailpipe emissions and brake and tire wear, including Cu, Zn, Sb, Ba, Pb, and S. Metals emitted in PM2.5 were lower (11.6% of mass). Resuspension of roadway dust was dependent on weather and road surface conditions, and increased emissions were related to higher traffic volumes and fractions of heavy trucks. Emission of noble metals from catalytic converters appeared to be impacted by the presence of older vehicles. Elements related to brake wear were impacted by enriched road dust resuspension, but correlations between these elements in PM2.5 indicate that direct brake wear emissions are also important. A submicrometer particle mode was observed in the emissions of Pb, Ca, Fe, and Cu.

A laboratory intercomparison of organic carbon (OC) and elemental carbon (EC) measurements of atmospheric particulate matter samples collected on quartz filters was conducted among eight participants of the ACE-Asia field experiment The intercomparison took place in two stages: the first round of the intercomparison was conducted when filter samples collected during the ACE-Asia experiment were being analyzed for OC and EC, and the second round was conducted after the ACE-Asia experiment and included selected samples from the ACE-Asia experiment Each participant operated ECOC analyzers from the same manufacturer and utilized the same analysis protocol for their measurements. The precision of OC measurements of quartz fiber filters was a function of the filter's carbon loading but was found to be in the range of 4-13% for OC loadings of 1.0-25 microg of C cm(-2). For measurements of EC, the precision was found to be in the range of 6-21% for EC loadings in the range of 0.7-8.4 microg of C cm(-2). It was demonstrated for three ambient samples, four source samples, and three complex mixtures of organic compounds that the relative amount of total evolved carbon allocated as OC and EC (i.e., the ECOC split) is sensitive to the temperature program used for analysis, and the magnitude of the sensitivity is dependent on the types of aerosol particles collected. The fraction of elemental carbon measured in wood smoke and an extract of organic compounds from a wood smoke sample were sensitive to the temperature program used for the ECOC analysis. The ECOC split for the three ambient samples and a coal fly ash sample showed moderate sensitivity to temperature program, while a carbon black sample and a sample of secondary organic aerosol were measured to have the same split of OC and EC with all temperature programs that were examined.