Sea-Bird Scientific SUNA V2, Руководство пользователя

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CDOM sample QSD per mg/L
particle
Absorbance at
225 nm (10 mm) per
mg/L particle
NO
3
change, µM, in
seawater per mg/L
particle
NO
3
change, µM, in
seawater per mg/L
particle
Pony Lake Fulvic Acid
reference (1R109F) N/A 0.017 0.4 (5.6 e -3) 0.6 (8.4 e -3)
Suwannee River Fulvic Acid
standard (1S101F) N/A 0.027 < 0.1 (1.4 e -3) < 0.1 (1.4 e -3)
Pahokee Peat Humic Acid
reference (1R103H-2) 42 0.003 < 0.01 (1.4 e -4) < 0.1 (1.4 e -3)
An interfering species causes an incorrect nitrate concentration when its spectral
characteristics are almost the same as nitrate. The root mean square error (RMSE) value
is the square root of the mean of the sum of the squared differences between the
measured and the fitted absorbance. The RMSE is a measure of the quality of the fit.
Independent measurements of turbidity and CDOM, and an analysis of the absorption
spectrum help the impact analysis.
7.4.4 Sensor function
The lamp and other optical components in the sensor change with time. This causes
nitrate measurements to change, or "drift." Do regular updates to the reference, or
baseline, spectrum to minimize this change.
The output of the lamp is related to its temperature. The manufacturer recommends that
the user collect the reference (baseline) spectrum in conditions that are almost the same
as a deployment.
7.5 CDOM absorption
Figure 4 Fulvic acid, mg/L
Note that the CDOM spectral shape overlaps with the nitrate processing region.
The model to calculate nitrate fits for four parameters: nitrate, bromide, a temperature
coefficient and a linear baseline correction that accounts for all additional absorbing
species. If the absorption of the sample is high (default cut-off = 1.3 AU), the model can
no longer be used effectively to fit parameters or calculate nitrate concentration. The
SUNA V2 data output is an RMSE parameter that indicates the quality of the fit of the
models to the absorption curves.
Reference
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