Trace Element Fractional Solubility in Ultrapure Water From Samples Collected During the US GEOTRACES Eastern Tropical South Pacific Section

The US GEOTRACES section cruise to the Eastern Tropical South Pacific (GP16) embarked from Manta, Ecuador on October 25, 2013 and terminated in Papeete, Tahiti on December 22, 2013. Bulk and size fractionated aerosol samples were collected over seventeen 72-hour periods on cellulose filters using Tisch high volume samplers. The bulk samples were collected on 47mm W41 filters and the size fractionated samples on slotted impactor filters. The Sierra-style slotted cascade impactor cutoffs are >7µm, >3µm, >1.5µm, >0.95µm and >0.49µm. Particles <0.49µm were collected on a 20 x 25cm W41 backing filter. The soluble bulk aerosol fraction was extracted aboard ship by passing 100mL of ultrapure water (>18.2MΩ cm) through the sample filter under vacuum. The extract was acidified for storage and later analyzed by ICP-MS to quantify the soluble aerosol fraction. Replicate bulk filters collected simultaneously were digested and analyzed by ICP-MS to provide the total aerosol concentration. Our data will provide insight into the nature of aerosols transported across the South Pacific and describe their potential as a source for trace elements to the surface ocean. The results will aid in the interpretation of surface water trace element concentrations. We will also characterize the alteration of aerosol fractional solubility with transport in the atmosphere as well as investigate the relationship between aerosol concentration and aerosol fractional solubility. All of our observations will be discussed in the context of the larger global dataset of aerosol solubility data and compared with assumptions currently applied in global models of atmospheric deposition.