DO_salinity_correction: Salinity correction factor for dissolved oxygen concentration...

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Salinity correction factor for dissolved oxygen concentration measurements

Description

Salinity correction factor for dissolved oxygen concentration measurements

Usage

DO_salinity_correction(dat.wide, Sal = NULL, method = "garcia-gordon")

Arguments

dat.wide	Dataframe with at least one column: Temperature. Corresponding salinity (psu) data may be included in column Salinity. Additional columns will be ignored and returned.
Sal	A single value of salinity (psu). This value must be specified if there is no Salinity column in dat.wide. Default is Sal = NULL. Note: if Sal is specified when there is a Salinity column in dat.wide, the function will stop with an error.
method	Equation to use to calculate salinity correction factor. Options are method = "garcia-gordon" (the default) and method = "benson-krause".

Details

Dissolved oxygen concentration measured by HOBO sensors needs to be corrected for salinity (see manual: https://www.onsetcomp.com/files/manual_pdfs/15603-B-MAN-U26x.pdf).

The salinity correction factor can be calculated using the Benson and Krause 1984 equations or the Garcia and Gordon 1992 equations. These equations should only be used when 0 < Temperature < 40 degrees Celcius, 0 < Salinity < 40 PSU and 0.5 < Pressure < 1.1 atm.

Benson & Krause, 1984:

Used by the USGS DOTables (USGS, 2011).

Results from this equation should match those from the USGS DOTABLES (part C) at https://water.usgs.gov/water-resources/software/DOTABLES/.

Final term in Equation 32:

F_{s} = exp(-Salinity * (0.017674 - 10.754 / T_{Kelvin} + 2140.7 / T_{Kelvin}^2))

Garcia & Gordon, 1992:

Garcia & Gordon re-fit the Benson & Krause data with a higher order polynomial and defined a scaled temperature (T_{s}).

This correction factor is used in the SCOR WG 142 (Part C).

Results from this equation are very similar to the Benson & Krause correction factor (to ~4 decimal places).

B0 = -6.24523E-3

B1 = -7.37614E-3

B2 = -1.03410E-2

B3 = -8.17083E-3

C0 = -4.88682E-7

F_{s} = exp(Salinity * (B0 + B1 * T_{s} + B2 * T_{s}^2 + B3 * T_{s}^3) + C0 * Salinity^2)

T_{s} = log((298.15 - Temperature) / (273.15 + Temperature))

Note: the HOBO Dissolved Oxygen Assistant Software salinity correction factor uses the same form as the Garcia and Gordon equation, but different coefficients (although the results are similar).

References

Benson, Bruce B., Krause, Daniel, (1984), The concentration and isotopic fractionation of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere, Limnology and Oceanography, 3, doi: 10.4319/lo.1984.29.3.0620.

Bittig, H. &.-J. (2016). SCOR WG 142: Quality Control Procedures for Oxygen and Other Biogeochemical Sensors on Floats and Gliders. Recommendations on the conversion between oxygen quantities for Bio-Argo floats and other autonomous sensor platforms. https://repository.oceanbestpractices.org/handle/11329/417.

Garcia, H., and L. Gordon (1992), Oxygen solubility in seawater: Better fitting equations, Limnol. Oceanogr., 37(6).

USGS. Change to Solubility Equations for Oxygen in Water. Technical Memorandum 2011.03. USGS Office of Water Quality, 2011.

Value

Returns dat.wide with additional column(s), F_s and Salinity.

See Also

Other Dissolved Oxygen: DO_pressure_correction(), calculate_DO_concentration(), calculate_DO_percent_saturation(), calculate_cp()

Centre-for-Marine-Applied-Research/strings documentation built on Aug. 21, 2023, 8 a.m.