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Brown, M.T., 2009

The distribution and behavior of dissolved and particulate aluminum in coastal waters of the northeast Pacific off Oregon and Washington and in the northern Gulf of Alaska

Bibliographic Reference

Brown, M.T., 2009, The distribution and behavior of dissolved and particulate aluminum in coastal waters of the northeast Pacific off Oregon and Washington and in the northern Gulf of Alaska: University of California, Santa Cruz, Ph.D. dissertation, 136 p., illust., maps.

Abstract

The behavior of Al in high-productivity coastal regions dominated by freshwater inputs of terrestrial material is not well characterized. Investigating the sources of both dissolved and particulate Al in coastal waters of Oregon and Washington as well as in the northern Gulf of Alaska and gaining insight into the behavior of these Al fractions in both surface waters and at depth were the goals of this dissertation research. To this end, significant modifications to an existing flow-injection analysis method were carried out that resulted in a portable, shipboard analysis method that utilized a commercially-available preconcentration resin, had a lower detection limit, and was easy to use. The coastal waters of Oregon and Washington are significantly influenced by freshwater input from the Columbia River plume. Dissolved and particulate Al concentrations were significantly greater in the river than in the coastal waters that mixed to form the plume while riverine dissolved Al concentrations were low relative to other major world rivers. Dissolved Al within the Columbia River estuary showed a significant removal (? 60%) at salinities between 0 and 10 with salt-induced flocculation colloidal Al complexes and enhanced particle scavenging being probable explanations for Al removal. Dilution of the plumes advecting from near-field to far-field with lower dissolved Al surface waters as well as particle scavenging along the flow path appeared to be controlling dissolved Al distributions. In northern Gulf of Alaska coastal waters, glacial/riverine inputs were correlated with extremely high dissolved and particulate Al concentrations in low-salinity coastal plumes with the dissolved Al existing entirely in the soluble (< 0.03 µm) fraction. The endmember Al characteristics of fresh glacial melt was found to be significantly different than that of riverine input that had interacted with soil/vegetation. A consistency in Si:Al ratios from different samplings was attributed to the chemical weathering of biotite. Finally, an extreme decreasing gradient of dissolved Al in surface waters was observed moving offshelf where some of the lowest dissolved Al concentrations in the world oceans was observed. The residence time of dissolved Al in coastal shelf waters was estimated to be ? 10 days.

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