| dc.contributor.author | Moran, Stephen Bradley. | en_US |
| dc.date.accessioned | 2014-10-21T12:34:53Z | |
| dc.date.available | 1990 | |
| dc.date.issued | 1990 | en_US |
| dc.identifier.other | AAINN64507 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55202 | |
| dc.description | The aim of this study is to improve our understanding of the sources and removal processes that control the oceanographic distribution of dissolved Al. The focus of this thesis is on: (1) the removal of Al from oceanic waters; (2) the distribution of colloidal (10,000 NMW-0.45 $\mu$m) Al, organic C, and $\sp{234}$Th tracer in oceanic waters; (3) the distribution of dissolved Al in the Southern Ocean; and (4) distributions of dissolved and particulate Al in the western North Atlantic. | en_US |
| dc.description | Time-series measurements of Al obtained during phytoplankton blooms from a coastal inlet and a mesocosm tank clearly show that temporal changes in biological activity can significantly alter the surface water distribution of dissolved and particulate Al. The flux of particulate Al subsequent to a diatom bloom was dominated by a weak acid leachable fraction; this suggests that the removal of dissolved Al by diatom particles involves surface complexation and/or incorporation of Al into the soft tissues of diatoms. Kinetic experiments conducted with dead diatoms show that, as for particle-reactive Th, the removal of Al from sea water occurs at a rate directly proportional to the particle concentration $(C\sb{p})$. These kinetic data are consistent with a model that assumes a pseudo-first-order reversible reaction between dissolved Al and the particle surface. A positive relationship is shown to exist between the reciprocal of oceanic residence times (1/$\tau)$ of dissolved Al and in-situ $C\sb{p}$ for various oceanic regimes. This positive relationship provides additional evidence in support of a surface complexation rather than an active biological removal mechanism for dissolved Al on a global ocean scale. | en_US |
| dc.description | Measurements of colloidal Al and organic C in coastal and open ocean waters off Nova Scotia show that $<$5% to 15% and 10-15% of "dissolved" ($<$0.45 $\mu$m) Al and organic C, respectively, is associated with colloids. There is a higher percentage of colloidal $\sp{234}$Th tracer in nearshore (50%) relative to shelf (4%) and open ocean surface waters (1%). These results are used to examine the relationship between the apparent distribution coefficient $(K\sbsp{d}{\prime})$ for metals and $C\sb{p}$ in oceanic waters. Model predictions show that for most of the global ocean $K\sbsp{d}{\prime}$ is independent of $C\sb{p}$, consistent with oceanic and laboratory $K\sbsp{d}{\prime}$ values for Al. | en_US |
| dc.description | Dissolved Al concentrations in the Weddell Sea, the first reported for the Southern Ocean, are low, ranging from 1 to 5 nM. The combination of the low atmospheric input and the seasonally high rate of biological productivity is suggested to account for the low levels of dissolved Al in these polar waters. | en_US |
| dc.description | Release of dissolved Al from resuspended sediments associated with nepheloid layers in high-energy Deep Western Boundary Currents (DWBC) is proposed as a source of dissolved Al to the North Atlantic Deep Water. This hypothesis is supported by: (1) sediment resuspension experiments that show low concentrations of terrigenous sediments can act as a source of dissolved Al to sea water; and (2) increases in dissolved Al with proximity to the DWBC. The continued recycling of bottom sediments within nepheloid layers is suggested to increase the lability of particulate Al and cause a net increase in dissolved Al. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1990. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Biogeochemistry. | en_US |
| dc.title | The marine geochemistry of aluminum. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
