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At-sea ICPMS measurement for continuous observation in dynamic coastal environments

Alan M. Volpe, Ph.D.
Lawrence Livermore National Laboratory

Wednesday, January 24, 2001
3:00 p.m.—Pacific Forum

Analytical iso-van being loaded aboard the R/V Revelle
 and interior view of the iso-van.

Mankind is exerting tremendous pressure on coastal oceans through land runoff, waste disposal, spills and destruction of habitats. Until recently, geochemical measurements of ocean waters were made on discrete bottle samples. Though important for first-order characterization, such a sampling strategy provides a record that is discontinuous in time and space. In dynamic coastal environments, this record is inadequate for understanding the provenance of water masses, and for quantifying the fluxes and impact of anthropogenic inputs on the coastal biosphere. We developed an in situ capability based on commercially available Inductively Coupled Plasma Mass Spectrometry (ICPMS) instrumentation. The challenge we met was extended operation of a mass spectrometer under extremely harsh vibration and corrosion conditions to deliver high sensitivity measurements at a rate rapid enough to acquire large spatially and temporally continuous data sets. It is part of an integrated system coupled with hydrographic instrumentation and satellite ocean color imagery.

The first experiment was conducted over a regional area and provides insight to water mass mixing off the coast of Baja, California and the extent to which the trace element barium serves as a proxy for biologic productivity. The second involved in situ trace transition metal characterization of San Diego Bay water, and real-time tracking of this effluent plume offshore. A real-time, integrated ocean chemistry capability provides important ground-truth data about sediment load, chemical parameters and biologic productivity.

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