WSP05652

• File Number: 8273.300
• Description: Colorado River Basin Salinity Control - Federal Agency Reports - USGS
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1997
• Author: USGS
• Title: Interim Results of Quality-Control Sampling of Surface Water for the Upper Colorado River National Water - Quality Assessment Study Unit - Water Years 1995-96
• Water Supply Pro - Doc Type: Report/Study

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[Lowest roundmg unif is equal 10 nl:lgnilUde of the lowesl significant figurej

Table 16. Summary of differences between post-processing split-replicate samples for nutrients and organic carbon

Constituent

Percent 01 samples Percent of samples Percent of samples
within plus or minus 1 within plus or mir'lus 2
with no difference lowest rounding unit lowest rounding unit
tOO tOO loo
iOO tOO tOO
62 88 88
100 100 100
38 62 75
4.1 72 86
50 75 100
25 62 75
88 100 tOO

Ammonia
Dissoked ammonia plus organic
TOlaJ ammoniJ plus organic
Nilrite
Nitrite plus nitrafe
Dissolved organic c.1rbon
Dissol....ed phmrhorus
Total phosphorus
Onhopho..:;phate

Field Blanks

A field blank is a sample prepared using waler
that is free of Ihe analyles of ioterest. The blank waler
is passed through all sampling equipment and then
processed as a typical water-quality sample. Results of
analysis of field blanks are used to te51 for bias that
could resull from the contamination of environmental
samples as a resuh of sample collection. processing.
handling. shipping. and analysis. Specifically. field
blanks demonstrale that equipment has been properly
cleaned to remove contamination from other samples.
tbal sample collection and processing do not contami-
nate samples. and that sample handling. Iranspon.
and analysis have not contaminmed Ihe sample.
Twelve field-blank samples were collected during
water years 1995-96. The distribution of collection
of tield-blank samples by site and date is shown in
figure 5.

General Chemical Constituents

Analytical results of field blanks for walcr
years 1995-96 for general chemical constituents are
lis led in table 17. Any concenlration that was greater
than twice the laboratory reporting limit is shown
in a shaded cell. Silica and. 10 some extent, chloride
indicate some systematic contamination. The silica
contamination can for the most part be explaincd
as the result of the use of contaminated blank water.
Independenl analyses of the 10ls of blank water
used al French. East. and State Line sites showed
silica concentralions of 0.11 mglL. Analyses of
the lots of blank water suspecled of being used at
Gore and Dotsero showed a silica concentration of
0.30 mgfL (lot numbers were nol recorded for these
sample.s). Interpretation of the silica data collected
at network sites should not be affected by the silica
blank results because the conlamination was intro-
duced by the blank water.

QUALITY-CONTROL SAMPLING PROGRAM 31