Trace Element Analysis of Aerosol and Seawater Samples Collected on the A16N, P02, and P16S CLIVAR Cruises

Florida State University, Tallahassee FL

Investigators

Abstract

The trace metals component of the CLIVAR Repeat Hydrography program has provided an unprecedented opportunity to determine the distributions of total and soluble aerosol iron (Fe) and aluminum (Al) and for measuring the water column profiles of dissolved and particulate Fe and Al across entire ocean basins. The samples collected at one-degree profile spacing have revealed fine-scale features in the distributions of dissolved and particulate Fe and Al that were previously unrecognized. Because of the broad interest in developing geochemical tracers of oceanographic processes (e.g. GEOTRACES), it is effective to use the archived samples from the three cruises to identify and quantify the processes that control the distribution of other trace elements and their sensitivity to changing environmental conditions. A researcher from Florida State University will analyze archived aerosol filters, archived (acidified) aerosol leach solutions, and the archived (acidified) seawater samples collected during three CLIVAR cruises (A16N-Iceland to Brazil; P02-Japan to San Diego; and P16S-Tahiti to New Zealand) for trace metals, metalloids, and rare earth elements, and complete the Fe and Al data set. Aerosol samples will be digested and analyzed for at least 42 trace elements using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). The distilled, deionized water aerosol leach solutions will be analyzed for these same elements plus silicon. Water column samples (and the seawater aerosol leach solutions) will be analyzed for iron, nickel, copper, zinc, cadmium and lead using a newly developed method for multi-element isotope dilution high resolution inductively coupled plasma mass spectrometry after extraction and elution using a small 8-hydroxyquinoline column. Information gathered from these basin-wide sections of dissolved trace elements and total and soluble aerosol trace elements will lead to a better understand of how global ocean biogeochemical cycles operate. The iron data will feed directly into coupled ocean/atmosphere nutrient and carbon cycling models, and permit a more accurate prediction of the role played by atmospheric iron deposition across various biogeographic zones of the world's major ocean basins. In addition, the scientist will participate in the P16N leg (Tahiti-Alaska) of the CLIVAR Repeat Hydrography cruise scheduled for February through May of 2006, an effort that will complete the N-S section across the Pacific Ocean. As regards broader impacts, this study will contribute to the goals of the upcoming GEOTRACES Program, greatly enhance the global trace element database that will lead to an improved understanding of oceanic biogeochemical cycles, and the data will improve coupled ocean/atmosphere models. Two graduate students will participate in the upcoming P16N CLIVAR Repeat Hydrography cruise and will also gain experience in analyzing aerosol and seawater samples for trace elements.