Séminaire
The Caribbean is an atmospherically important, but understudied region that is heavily influenced by trade winds, has frequent inputs of African dust, and occasional inputs of anthropogenic pollution from North America.
In this seminar I will present results from the chemical and physical properties of atmospheric particles measured at Cape San Juan Observatory (CPR, 18o 23' N, 65o 37' W), located in the Caribbean island of Puerto Rico. Air masses influenced by marine (M) aerosols, African dust (AD), and anthropogenic pollution (AP) from North America are our main focus. Size distributions showed a bimodal distribution (peaks around 40 and 200 nm) typical of clean maritime air. Also, typical of marine remote areas, aerosol mass concentrations (Dp < ca. 1 µm) were on average 1.6 µg m-3. The predominant aerosol species were Cl-, Na+, SO4=, and particulate organic matter (POM). The positive artifact during the sampling of OC was on average 50%. Elemental carbon (EC) was found at low-to-non detectable levels and was also found adhering to the surface of dust particles. Samples with AD influence showed an enhanced number of accumulation and coarse mode particles and an increase in Ca2+, Mg2+ and K+ concentrations. The period with AP from North America showed an enhanced number of accumulation particles, significant concentrations of SO4=, NH4+, NO3-, and POM, sea-spray acidification, and nss- SO4= concentrations of 245 ng m-3 on average. Additional results on the size-resolved chemical composition of the aerosol samples (water-soluble ions and carbonaceous aerosol) and differences in the aerosol properties between different periods will be discussed.