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

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nitric/hydrofluoric acid mixture (5 :8 volumes respectively of concentrated
acids) using high-purity acids (Aristar) for 48 hours at 140-145°C . After
cooling to room temperature, 4 grams of recrystallized reagent grade boric
acid were added, the pH was adjusted to 4 .0 with ammonia, and the digest
was then transferred quantitatively to a 125 ml separatory funnel . The heavy
metals were then complexed with ammonium pyrollidine dithicarbamate (AFDC)
(2 ml of 2% solution) and extracted 3-4 times with 30 ml of carbon tetrachloride .
The extract was collected in a 100 ml volumetric flask, and the solvent was
then removed from the extract with a Buchi Rotavapor evaporator . For this
purpose the volumetric flask was attached directly to the evaporator via a
special adaptor . Removal of solvent was carried out at relatively low temperature
(50-55°C) to prevent loss of metals in the process . The residue in the
flask was then oxidized with 5-ml of concentrated high-purity (Aristar) nitric
acid, and the solution was made up to volume with triply distilled (twice in
quartz) water . The heavy metals in this aqueous matrix were then analyzed for
Cu and Zn by flameless atomic absorption, using a heated graphite tube atomizer,
70 HGA Perkin Elmer, and a 403 Perkin Elik , Atomic Absorption Spectrophotometer
. Precision, accuracy and some operational parameters are given in
Wagemann (1975) .
The elements Si, Al and Ca were determined simultaneously on a multichannel
ARL X-ray spectrometer (University of Manitoba, using the method of
Wilson et al ., 1965) . This method consists essentially of fusing the sample
with lithium tetraborate at 1100°C, then grinding the fused bead with the
appropriate quantities of lanthanum oxide and boric acid and pressing the
mixture into discs appropriate for analysis .
Cation exchange capacity and ammonium acetate-extractible cations were
determined on Mackenzie Delta channel sediments according to methods 5A1 and
3A2a from U . S . Dept . Agriculture (1967) . These sediments were also extracted
with HC1 to determine acid- .labile elements . Oven-dried (110 °C) sediment
(15-25 g) was shaken with 100 ml of 1N NH40Ac and 1N HC1 for 8 hrs . The
solution was then filtered through Whatman GF/C filters and analyzed for Ca,
Mg, Na, K, Fe and Hn by atomic absorption spectrophotometry according . t o
Stainton et al . (1974) .
X-ray diffraction, mineral identifications and sediment particle size
determinations were done by methods given in Brunskill et al . (1973,
Appendix VII) .
Data Analysis
Instantaneous concentrations of suspended, sediment or particulate nutrients
were obtained by direct measurement or analysis . Instantaneous discharge
figures were generally taken from Water Survey of Canada (Davies, 1973 ; 1974) .
Summations of total monthly discharges, computed from the mean discharge for
each month, yielded annual discharge. Monthly rates of transport of suspended
sediment and particulate nutrients were calculated from the product
of the mean concentration during the month and the total monthly discharge .