The chemistry, mineralogy, and rates of transport of sediments in the ...

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Stream and river bottom sediments were sampled by hand and with Lane
buckets, Ekman and Ponar dredges . . Shore, and bank sediments were sampled
with a shovel . Water velocity was measured with Gurley flow meters, and
steel tapes were used to measure stream cross-section area . Discharge and
suspended sediment concentrations were also taken from the data of Davies
(1973 ; 1974) .-
Oxygen-demand of Harris bank sediments was estimated in the field and
laboratory . Harris River bank sediments, identical to those sediments used
in the experiments of Rosenberg and Snow (1975), were added to 300 ml glass
stoppered 02 bottles to yield suspended sediment concentrations of 2 to 300 mg/L
of Harris River water . These stoppered bottles, with sediment-free controls,
were suspended in the stream current for 1-4 hours . Oxygen was measured by
the Winkler method (APHA, 1965) at the beginning and the end of the period to
estimate changes in 02 concentrations caused by sediments . Similar experiments
were done in the Freshwater Institute laboratory by adding Harris River
bank sediments to oxygenated water in glass stoppered bottles to yield sediment
concentrations of 100-18,500 mg/L . These bottles were wrapped in tinfoil
and agitated on an automatic shaker for 16-60 hours . Oxygen was measured as
above .
SampleAnalyses
-Suspended sediment samples were usually filtered on ignited, preweighed
Whatman GF/C 45 mm filters at field camps in Ft . Simpson and Inuvik, usually
on the day of sampling, but sometimes_ as late as one week after sampling .
Alternately, large volume (20 L . carboy) samples were centrifuged in Yellowknife
on a Sorval RC2B centrifuge with a continuous-flow unit . A comparison
of the precision of these methods is given in Campbell and Elliott (1975)
which indicates that filtration of 1-2 L . of sample gives reasonable (±5%)
results, even in very low suspended sediment (2-5 mg/L) waters . For analytical
reasons, it was necessary to have large (10 g) samples of suspended sediments,
which required the use of the continuous-flow centrifuge . The precision of
suspended sediment determination by centrifugation was 15-20% for low suspended
sediment waters (Campbell and Elliott, 1975) . The sediment collected by
centrifugation was dried at 110°C in the centrifuge tube, weighed, removed
from the tube, ground with mortar and pestle, and shipped to Freshwater
Institute laboratories for mineralogical and chemical analyses . Sediment
on filters was dried, weighed, and stored in a freezer until analysis . Particulate
phosphorus (PP) was analyzed in the Yellowknife laboratory from filter
samples according to Stainton et aZ . (1974) . Particulate carbon (PC) and
particulate nitrogen (PN) were determined from filters or subsamples of
centrifuged sediment on a CHN elemental analyzer according to Stainton et OZ .
(1974) and Hauser (1973) .
For the analysis of copper and zinc, sediments were dried for 1 hour at
100°C, .cooled to room temperature in a desiccator, and a quantity in the range
of 0 .1-0 .2 grams was weighed accurately into the teflon insert of an acid
digestion bomb (Parr 4745) . The sediment was digested in the bomb with a