Dissolved Mn, Al, Cd and Cu concentrations were determined across a series of
horizontal surface transects along the Northeast Pacific Ocean from the coast off Big Sur,
California to Vancouver Island, British Columbia. This region of coastline allows the relative
importance of different modes of input of trace metals to California Current surface waters to be
assessed. In particular, the impact on dissolved concentrations of fluvial input from the Columbia
River, diffusion from reducing shelf sediments and/or sediment resuspension coupled with
upwelling, and the width of the continental shelf were examined. In addition, Mn, Al, Cd and Cu
distributions were compared with Fe and Ga data from the same region.
Background California Current surface water values were determined for Mn (3-
5nmol/kg), Al (0.38-0.65mnol/kg), Cd (0.08-0.30nmol/kg) and Cu (0.79-1.51nmol/kg). These
data agree well with previous work.
According to this study, the Columbia River is a considerable source of Mn and Al to
California Current surface waters, with the highest levels of Mn and Al for all transects observed
coincident with the lowest salinity waters sampled (Mn up to 117nmol/kg; Al up tol.lnmol/kg).
Metal versus salinity plots for both Mn and Al indicate non-conservative mixing and removal as
the water ages. Al is removed significantly faster than Mn and Ga. This agrees well with
previous estimates of surface ocean residence times for these elements. In contrast to Mn and Al,
Cd does not show enrichment in low salinity waters. However, it is possible that the Columbia
may well be providing small quantities of Cd to California Current waters, but in this area the
input is masked by relatively higher background signals. No data for Cu were available for the
Columbia River area.
Summer upwelling off the coasts of Oregon, Washington and California supplied
significant quantities of Mn (4.6-39.5nmol/kg), Cd (0.32-0.92nmol/kg) and Cu (1.66-
4.52nmol/kg) to California Current surface waters. For Mn and Cu, diagenic remobilization
and/or sediment resuspension coupled with upwelling explains the elevated signals for these
metals. For Cd, the elevation is attributable to transport of enriched bottom water to the surface
by upwelling. For Al, either sediments in this area are not a significant source of this metal, or Al
is indeed supplied by sediments but is then stripped out of the water at a dramatic rate.
Mn and Cu (as well as Cd and Al to a lesser extent) showed high elevation coincident
with transects overlying areas where the continental shelf is wide, and significantly lower
elevation coincident with transects overlying areas where the continental shelf is narrow. This
again emphasizes the potential impact of sediments on trace metals concentrations in surface
waters.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/13662 |
| Date | 11 1900 |
| Creators | Merrin, Claire |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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