#include <cmath>

Include dependency graph for dissolved_oxygen_compensation.h:

Functions
double	pressure_correction (double pressure_mmhg=760.0)
	Approximates the effect of barometric pressure on dissolved oxygen (DO) solubility. More...

double	salinity_correction (double temperature_k, double salinity_ppt)
	Computes the salinity correction factor for dissolved oxygen solubility. More...

double	calculate_do_saturation_fresh (double temperature_k)
	Calculates the saturation concentration of dissolved oxygen in freshwater at 1 atm and 0 ppt salinity. More...

double	calculate_dissolved_oxygen_solubility (double temperature_celsius, double salinity_ppt, double pressure_mmhg=760.0)
	Calculates the dissolved oxygen (DO) solubility in mg/L, corrected for temperature, salinity, and pressure. More...

double	calculate_do_saturation_percent (double do_raw, double do_max)
	Calculates dissolved oxygen (DO) percent saturation. More...

Function Documentation

◆ calculate_dissolved_oxygen_solubility()

double calculate_dissolved_oxygen_solubility	(	double	temperature_celsius,
		double	salinity_ppt,
		double	pressure_mmhg = `760.0`
	)

Calculates the dissolved oxygen (DO) solubility in mg/L, corrected for temperature, salinity, and pressure.

This function estimates the maximum amount of oxygen that water can hold under the given conditions. It uses the Weiss (1970) equation for DO saturation at 0 ppt salinity and 1 atm pressure, then applies salinity and pressure correction factors to reflect real-world conditions.

The result represents oxygen solubility at equilibrium with the atmosphere — useful for calculating % saturation or comparing measured DO values to environmental capacity.

Parameters

temperature_celsius	Water temperature in degrees Celsius.
salinity_ppt	Salinity in parts per thousand (ppt).
pressure_mmhg	Barometric pressure in mmHg (default is standard: 760 mmHg).

Returns: DO solubility in mg/L under the specified conditions.

References:

Weiss, R. F. (1970). The solubility of nitrogen, oxygen and argon in water and seawater.
USGS WQ.2011.03: https://water.usgs.gov/water-resources/memos/documents/WQ.2011.03.pdf
USGS DO Tables: https://water.usgs.gov/water-resources/software/DOTABLES/

Definition at line 98 of file dissolved_oxygen_compensation.h.

◆ calculate_do_saturation_fresh()

double calculate_do_saturation_fresh ( double temperature_k )

Calculates the saturation concentration of dissolved oxygen in freshwater at 1 atm and 0 ppt salinity.

This is based on the Benson & Krause (1984) equation recommended by USGS for high-accuracy DO solubility estimates. It returns the maximum possible DO (mg/L) at a given temperature in °C.

Parameters

temperature_k Water temperature in degrees Kelvin.

Returns: DO saturation in mg/L at standard atmospheric pressure and zero salinity.

Reference:

Weiss, R. F. (1970). The solubility of nitrogen, oxygen and argon in water and seawater.
USGS WQ.2011.03 memo: https://water.usgs.gov/water-resources/memos/documents/WQ.2011.03.pdf

Definition at line 60 of file dissolved_oxygen_compensation.h.

◆ calculate_do_saturation_percent()

double calculate_do_saturation_percent	(	double	do_raw,
		double	do_max
	)

Calculates dissolved oxygen (DO) percent saturation.

This function expresses the measured DO concentration as a percentage of the theoretical maximum solubility under current temperature, salinity, and pressure conditions.

Percent saturation >100% indicates supersaturation (e.g., from photosynthesis), while <100% indicates undersaturation (e.g., from respiration or pollution).

Parameters

do_raw	Measured dissolved oxygen concentration in mg/L.
do_max	DO solubility in mg/L under current environmental conditions.

Returns: Percent saturation (%).

Definition at line 124 of file dissolved_oxygen_compensation.h.

◆ pressure_correction()

double pressure_correction ( double pressure_mmhg = 760.0 )

Approximates the effect of barometric pressure on dissolved oxygen (DO) solubility.

This function applies a simple linear scaling based on the ratio of the measured pressure to standard sea-level pressure (760 mmHg). It is suitable for most field applications where high-precision correction is not required.

For more precise calculations, especially at high elevations or in scientific contexts, a more complex model accounting for non-ideal gas behavior, water vapor pressure, and oxygen mole fraction is available in equations (9)–(11) of the USGS WQ.2011.03 memo.

Parameters

pressure_mmhg Barometric pressure in mmHg (default: 760 mmHg).