Aerosol Chemical and Physical Properties Observed over Puerto Rico in the Tropical North Atlantic Ocean

Tropospheric aerosols that originate in Africa and are transported over the Atlantic Ocean have potential impacts over the Caribbean region. To investigate aerosol properties over this region, air sampling was conducted at San Juan Cape (18.46°N, 66.12°W), Puerto Rico during the summer months in 2006. Aerosol samples were collected by both commercial PM2.5 sampler and in-house fabricated TSP sampler. Analyses of aerosols were made through the use of the following instrumental methods: (1)Ion Chromatography for the determinations of water-soluble cations (sodium, ammonium, potassium, magnesium and calcium) and anions (fluoride, acetate, propionate, methanesulfonate, chloride, nitrate, succinate, malonate, sulfate and oxalate); (2)Inductively Coupled Plasma Mass Spectrometry for the concentrations of selected trace elements (Al, Fe, Mn, Sc, Cd, Pb, Sb, Ni, Co, Cr, Cu, Zn and V); (3)Scanning Electron Microscopy for individual aerosol particle characterization. Crustal enrichment factors were calculated to determine the strength of crustal source. Preliminary results indicate that sodium (22 - 99 μg m- 3) and ammonium (1.1 - 50 μg m-3) were the major cations and chloride (1.5 - 99 μg m-3) and sulfate (35 μg m-3) were the dominant anions. Malonate (3.8 - 6.9 μg m- 3) was the most abundant organic anion. Atmospheric concentrations of iron ranged 0.30 - 3.3 ng m- 3. The elements, Sc, Cd, Pb, Sb, Ni, Co, Cr, Cu, Zn and V, were enriched by factors of 600 to 40,000 relative to their natural abundance in crustal soil. Principal components analysis indicates six assemblages of fifteen types of aerosol particles, dominated by Si - rich particles.