Organic and Elemental Carbon Measurements during ACE-Asia Suggest a Longer Atmospheric Lifetime for Elemental Carbon

Abstract

During the ACE-Asia intensive field campaign (March 14-April 20, 2001), PM1.0 organic (OC) and elemental carbon (EC) concentrations were measured onboard the NOAA R/V Ronald H. Brown over the Northwest Pacific Ocean using a semi-continuous automated carbon analyzer downstream of a carbon-impregnated filter denuder. This OC and EC measurement achieved a mean time resolution of about 200 min over the Pacific Ocean, substantially lower than that achieved previously (24 h). The semi-continuous measurements, in which the adsorption artifact was substantially reduced using the denuder, showed good agreement with integrated artifact-corrected measurements made without a denuder. Mean particulate OC and EC concentrations were 0.21 and 0.09, 0.70 and 0.29, 1.00 and 0.27, and 2.43 and 0.66 microg of C m(-3) over the background Pacific Ocean, Asian-influenced Pacific Ocean, offshore of Japan, and Sea of Japan, respectively. On April 11, 90-min average OC and EC concentrations peaked at 4.0 and 1.3 microg of C m(-3), respectively, offshore of Korea over the Sea of Japan. The OC/EC ratio of 3.7 over the Sea of Japan and offshore of Japan was substantially higher than that of 2.5 over the Asian-influenced Pacific Ocean, even though backward air mass trajectories put the "Asian-influenced Pacific Ocean" sample downwind. The OC/EC ratio decreased with increasing time since the air mass encountered the source regions of China, Japan, and Korea. This suggests a longer atmospheric residence time for EC than for OC.

Fine organic particulate matter dominates indoor-generated PM2.5 in RIOPA homes

“…Differences in 48-h mean temperature did not help explain the remaining variance (not shown). The sampling artifact findings are consistent with previous outdoor studies in magnitude and functional dependence (Turpin et al, 2000;Lim et al, 2003;Polidori et al, 2006). Clearly, if uncorrected an artifact of this magnitude would result in substantial bias in the reported particulate OC concentrations.…”

Characterization of carbonaceous aerosols over the East China Sea: The impact of the East Asian continental outflow

“…The relatively low OC/EC ratios observed in spring, fall, and winter compared to summer suggest a possible longer residence time for EC than OC under long-range transport from the continent. The OC/EC ratios in the present study were higher than those observed in cities of the Pearl River Delta Region, which were between 1.0 and 4.0 in summer (Cao et al, 2004), but comparable to values from observations from other islands (Feng et al, 2007;Simoneit et al, 2004), and a cruise traversing the Northwest Pacific Ocean (Lim et al, 2003, Table 3). …”

Indoor/Outdoor Relationships, Trends, and Carbonaceous Content of Fine Particulate Matter in Retirement Homes of the Los Angeles Basin

“…These values are quite close to the detection limit for EC for semicontinuous carbon measurements, typically around 0.15-0.35 gC/m 3 (as determined by Lim et al 21 ), and suggest that indoor sources of EC were not an important contributor to measured indoor EC during CHAPS. These outcomes are consistent with I/O EC ratios close to or slightly lower than unity obtained in several previous studies conducted both in California 50,51 and around the world.…”

“…Carbon data corresponding with time periods affected by rain were not considered in the determination of a and b because of the possibility of differential wet scavenging. 21,23 The average coefficient of determination (R 2 ) for all monthly regressions was 0.87 Ϯ 0.06 (1), which adds confidence to our results.…”