Transport and Reaction of Heavy Metals in Alaskan Fjord-Estuaries. Annual Report, July 1, 1978-June 30, 1979 Page: 29 of 126
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(0, 205, 635 particles/counts per ml) are used progressively to set the
threshold settings on the particle counter; however, for the two separate
high count bottles, agreement between the stated figure (637, 635) and the
instrument has never been achieved (the manufacturers admit their inability
to do the same).
The manufacturers further imply that the original counting of the standard
solutions was simply performed on a similar instrument; i.e., there is no inde-
pendent external check on the counting accuracy. This process of "internal"
calibration becomes more doubtful when one calibrates the particle sizing
attachment, a multichannel analyzer with digital display and paper printout.
Standard settings (threshold, gain) are adjusted until the particle
count readings on both instruments agree to within 5% for particles greater
than 3 y. The standard settings, however, have originally been determined
to provide size intervals of 5 y in 16 different channels so that any change
in the gain setting alters this size interval. The manufacturer.cannot pro-
vide information as to size intervals obtained for different settings of the
gain knob thus introducing considerable uncertainty into the size distribution
data (e.g., is the interval.4 y or 6 y or 7 y).
ii. No significant.difference detected between different seawater samples,
apparently primarily due to lack of sensitivity and high count rates.
Although the lack of "absolute" calibration was suspected initially,
it was hoped that relative size distributions could be used to distinguish
different particle populations in different seawater samples. Analysis
of the size distribution data has shown that the variation between samples
is similar to the variation, between duplicates; this is true for samples
collected in two different localities over three seasons. Furthermore,
when seawater samples were "spiked" with concentrations of standard size
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Burrell, D.C. Transport and Reaction of Heavy Metals in Alaskan Fjord-Estuaries. Annual Report, July 1, 1978-June 30, 1979, report, June 1, 1979; Albany, New York. (https://digital.library.unt.edu/ark:/67531/metadc1093222/m1/29/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.