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Citation Voss, BM et al. 2015. Seasonal hydrology drives rapid shifts in the flux and composition of dissolved and particulate organic carbon and major and trace ions in the Fraser River, Canada. Biogeosciences 12: 5597-5618.
Organization University of Fraser Valley
URL http://www.biogeosciences.net/12/5597/2015/bg-12-5597-2015.pdf
Abstract/Description or Keywords Rapid changes in the volume and sources of discharge
during the spring freshet lead to pronounced variations
in biogeochemical properties in snowmelt-dominated
river basins. We used daily sampling during the onset of the
freshet in the Fraser River (southwestern Canada) in 2013 to
identify rapid changes in the flux and composition of dissolved
material, with a focus on dissolved organic matter
(DOM). Previous time series sampling (at twice monthly frequency)
of dissolved inorganic species in the Fraser River
has revealed smooth seasonal transitions in concentrations of
major ions and tracers of water and dissolved load sources
between freshet and base flow periods. In contrast, daily sampling
reveals a significant increase in dissolved organic carbon
(DOC) concentration (200 to 550 µmol L−1
) occurring
over a matter of days, accompanied by a shift in DOM optical
properties, indicating a transition towards higher molecular
weight, more aromatic DOM composition. Comparable
changes in DOM composition, but not concentration,
occur at other times of year, underscoring the role of seasonal
climatology in DOM cycling. A smaller data set of
total and dissolved Hg concentrations also showed variability
during the spring freshet period, although dissolved Hg
dynamics appear to be driven by factors beyond DOM as
characterized here. The time series records of DOC and particulate
organic carbon (POC) concentrations indicate that
the Fraser River exports 0.25–0.35 % of its annual basin net
primary productivity. The snowmelt-dominated hydrology,
forested land cover, and minimal reservoir impoundment of
the Fraser River may influence the DOC yield of the basin,
which is high relative to the nearby Columbia River and of
similar magnitude to that of the Yukon River to the north.
Anticipated warming and decreased snowfall due to climate
changes in the region may cause an overall decrease in DOM
flux from the Fraser River to the coastal ocean in coming
Information Type article
Regional Watershed Lower Fraser
Sub-watershed if known Fraser River
Aquifer #
Project status complete
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