Chemical Characterization of Carbonaceous Aerosols in the Tropical Trade Winds During RICO

Aerosol organic carbon (OC) and its water soluble fraction (WSOC) together with inorganic soluble species play an important role on Earth's radiative budget by modifying cloud condensation nuclei (CCN) concentrations. Although organic aerosols can be a major, and sometimes dominant, component of both anthropogenic and natural aerosol particles, relatively little is known about them in the marine environment. In addition, the exact role of OC and its WSOC in CCN activity and the specific species that make organic carbon CCN active are still unknown. To have a better understanding of the role of these aerosols in cloud processes, chemical characterization of the organic (carbonaceous) fraction is needed. As part of the Rain in Cumulus over the Ocean Experiment (RICO), size-resolved aerosol samples were collected in the islands of Antigua (Dian Point) and Puerto Rico (Cape San Juan, Fajardo) during December 2004 and January 2005. The samples were collected with two low-pressure impactors (13-stage DLPI and 8-stage MOUDI) and with filter-based samplers. Thermal-optical analysis (EC/OC analyzer) and total organic carbon analysis (TOC) were used to determine aerosol total carbon (TC), OC, elemental carbon (EC) y WSOC. Back trajectories calculated using the HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) model from NOAA showed two possible sources for the air masses that influence our aerosols samples: air masses coming from North America and coming from the North Atlantic Ocean (trade winds). Results, including the concentrations of aerosol TC, OC, EC, and WSOC together with the fraction WSOC forms of the TC, will be presented.