Collaborative Proposal: GEOTRACES Pacific Section: Collection and analysis of atmospheric deposition

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During the 2013 GEOTRACES Eastern Pacific zonal transect, a gradient in aerosol inputs to surface waters will be encountered with higher inputs near Peru and decreasing offshore. This zonal section contrasts sharply to the high aerosol deposition areas found and sampled during the GEOTRACES North Atlantic Zonal Section in the fall of 2010 and 2011. As such, this Pacific section represents a unique opportunity to characterize aerosol and rainfall chemistry in a low deposition environment. Scientists from the University of Alaska and Florida State University plan to collect and characterize aerosol and rainfall samples along this transect, as well as distribute samples to the community. Bulk and size-fractionated aerosol samples collected on a 24 to 48-hour integrated basis and event-based rain samples will be analyzed for trace elements and isotopes (TEIs) to quantify their atmospheric input. The TEIs to be analyzed will be aluminum, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium, lead, and thorium, as well as the major ions sodium, magnesium, potassium, calcium, nitrate, phosphate, chlorine, and fluorine. Other efforts to be carried out as part of this study include (1) aerosol leaches to determine seawater-soluble and ultrapure-water-soluble TEI fractions: (2) determine the size fractionation and redox speciation of seawater-soluble iron: (3) obtain subsamples of water column samples from other GEOTRACES scientists for the analysis of the TEIs of interest to help interpret the atmospheric deposition data; and (4) collaborate with researchers from other institutions to characterize and constrain estimates of atmospheric deposition. This project will contribute towards the overall goal of the GEOTRACES Program by establishing the range of fractional aerosol solubility and better quantify deposition across the global ocean. One graduate student from the University of Alaska would be supported and trained as part of this project. Relying on a cruise blog, email, and project website updates, the scientist from the University of Alaska plans to continue her interactions with students in Alaska, Arizona, and Florida and results from the study would be incorporated into class curricula, as well as disseminated via public outreach and web dissemination.