GEOTRACES: Intercalibration for Aerosol Preservation and Analysis

The international GEOTRACES program is pursuing a series of enabling activities to ensure the accuracy and precision of analytical methodology before sampling transects across ocean basins are started. The importance of measuring trace element and isotope (TEI) concentrations and deposition to the oceans for aerosols is described in the GEOTRACES Science Plan (2006). NSF has already funded several US scientists involved in GEOTRACES intercalibration experiments to establish protocols for sample collection and analysis. These protocols will be developed in collaboration with international scientists so that the GEOTRACES research cruises will yield a data set that is accurate, precise and internally-consistent.

In this project, researchers at the University of California at Santa Cruz will augment a previously funded project at the Florida State University to acquire, test, and intercalibrate equipment and methods for the collection of aerosols and rainwater on the GEOTRACES cruises. The FSU funded work does not stress intercomparison of analytical methods for measuring aerosol TEI solubility, the impact of filter type on solubility and analytical accuracy (blanks), or the effect of sample storage on solubility. In addition, the range in solubility that may depend on sample source and composition is not addressed. This project will enhance the FSU project by adding these important aspects.

The Santa Cruz team will use a unique set of aerosol filters collected using trace-metal clean methods since 2004 and ongoing to 2010 to achieve five objectives: (1) test several different leaching protocols on parallel samples (collected simultaneously thus of the same composition); (2) evaluate the effect of storage time on samples using our archived samples and ongoing collection; (3) test the effect of different filter types on solubility, blank and collection efficiency (four different filter types could be tested simultaneously);(4) measure the impacts of different aerosol chemistries, mineralogy, particle sizes, and trajectories on TEI solubility; and (5) prepare 'handbooks' describing the analytical protocols for use on GEOTRACES cruises; to be shared with our US and international GEOTRACES colleagues.

Broader Impacts: Education and training of a young researcher is an essential components of this research. Additional graduate and undergraduate students will be involved in this work but will be funded separately (REU supplements and Honors thesis). The data will be submitted in a timely manner according to the requirements of the GEOTRACES program.