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Ref. No. [UMCES] CBL 2015-014
ACT VS15-07
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A cross-plot of the matched observations of EXO-pH1 and reference pH is given in
figure 15. The linear regression was not statistically significant (p=0.07, r
2
=0.04) with a slope of
0.24 and an intercept of 6.23.
Figure 15.
MLML field response plot of the Xylem EXO-pH1 instrument compared to reference pH
Total
samples. Fine dotted line represents 1:1 correspondence, coarse dotted line represents correspondence
predicted based on difference between pH
NBS
and pH
Total
in seawater (pH
NBS
= pH
Total
+ 0.13).
Time series results of the EXO-pH2 and corresponding reference pH results are given in
figure 16. Ambient pH measured by the EXO-pH2 ranged from 8.10 to 8.48, compared to the
range captured by the reference samples of 7.933 to 8.077. The bottom panel presents the time
series of the difference between instrument and reference pH measurements for each matched
pair (n=84 observations). The average and standard deviation of the difference between EXO-