6. Size-resolved concentrations of carbonaceous aerosol in marine and urban sites in the island of Puerto Rico

(1) Department of Chemistry, University of Puerto Rico, San Juan, P.R.

(2) Institute for Tropical Ecosystems Studies, University of Puerto Rico, San Juan, P.R.

Carbonaceous aerosols, composed mainly of organic (OC) and elemental carbon (EC), comprise a significant fraction of the submicron aerosol mass. Theses aerosols may play a significant role in radiative forcing, affecting the extinction of solar radiation and thus having an influence on climate. In the case of EC, this species has also been associated with health problems. As part of this project, we collected samples in urban and marine sites in the island of Puerto Rico. A Dekati low-pressure impactor (DLPI) with 13 stages was used to collect size-segregated particles with diameters in the range of 0.03 to 10 mm using quartz filters (volume sampled ca. 19 m3). Stacked-Filter Units (SFUs) were used parallel to the DLPI to collect particles with diameters < 1.0 µm (volume sampled ca. 33 m3). Filters collected with the DLPI and the SFUs have been analyzed with a thermo-optical analyzer for the determination of total carbon (TC), OC and EC. Results to be presented for urban and marine sites include the size-resolved mass concentrations of TC, OC, EC, water-soluble organic carbons, and the differences between day and nighttime samples. These results will provide insight in terms of the impact that tropical carbonaceous aerosols have on climate. Preliminary results for urban sites in average total concentrations are 6.2µg/m3 TC, 0.7 µg/m3 EC, and 5.5 µg/m3 OC. Preliminary results for urban sites in the fine mode average concentrations (<1 microns) are 4.0 µg/m3 TC, 0.7 µg/m3 EC, and 3.4 µg/m3 OC. Preliminary results for marine sites in total average concentrations are 1.3 µg/m3 TC, 0.0 µg/m3 EC, and 1.3 µg/m3 OC. Preliminary results for marine sites in fine mode concentrations are 0.8 µg/m3 TC, 0.0 µg/m3 EC, and 0.8 µg/m3 OC.