Transparent exopolymer particles (TEP) and sodium in ambient aerosol particles and cloud water at Cape Verde islands

Transparent exopolymer particles (TEP) exhibit the properties of gels and may enter the atmosphere as part of sea spray aerosol. Here, we report number concentrations of TEP (diameter> 4.5 µm) in ambient aerosol (total suspended particles, TSP) and cloud water samples from the tropical Atlantic Ocean as well as in generated aerosol particles (PM10) using a plunging waterfall tank that was filled with the ambient sea water. Samples were taken during the MarParCloud: “Marine biological production, organic aerosol particles and marine clouds: a Process chain” campaign that took place from September 13th to October 13th 2017 at the Cape Verde archipelago Island Sao Vicente located in the Eastern Tropical North Atlantic (ETNA). Total suspended aerosol particle (TSP) for TEP analysis and PM10 sampling for sodium analysis was performed on top of a 30 m sampling tower of the CVAO. TSP were sampled with a filter sampler consisting of a filter holder equipped with a 0.2 µm pore-sized, acid-cleaned polycarbonate (PC) filter mounted to a pump. Sampling usually took place for 24 h and the flow of the pump was between 5 and 10 L min-1 and frequently measured with a flowmeter. Total volumes between 10 and 15 m3 were sampled. Cloud water was sampled on Mt. Verde, which is the highest point of the São Vicente Island (744 m), situated in the northeast of the Island (16°52.11ˈN, 24°56.02ˈW) and northwest to the CVAO. Bulk cloud water was collected using a compact Caltech Active Strand Cloudwater Collectors (CASCC2) equipped with acid cleaned Teflon®strands (508 µm diameter). Cloud droplets were caught on the strands and gravitationally channelled into an acid-precleared Nalgene bottle. TSP particles were sampled from a plunging waterfall tank experiment that consists of a 1400 L basin with a 500 L aerosol chamber on top. The bubble driven transport of organic matter was induced using a skimmer on a plunging waterfall. A stainless steel inlet was inserted in the headspace of the tank and connected with three filter holders for offline aerosol particle sampling without size segregation (TSP). The filter system for TEP analysis was equipped with a 0.2 µm pore-sized, acid-cleaned polycarbonate (PC) filter mounted to a pump. Sampling usually took place for ~ 24 h, the flow of the pump was between 5 and 10 L min-1 and frequently measured with a flowmeter. Total volumes between 9 and 10 m3 were sampled. […]