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Sodium Adsorption Ratio (SAR) ​

see also CEC, ESP and dispersion

SAR is a measure of the relative proportions of sodium, calcium and magnesium ions in a water or wastewater. It is defined as:

SAR=Na12(Ca+Mg)

where Na, Ca, and Mg refer to the concentration of Sodium, Calcium, and Magnesium respectively.

WARNING

The concentrations must be expressed in units of milliequivalents/L. To convert from mg/L to milliequivalents/L, multiply Na by 0.0435, Ca by 0.025, and Mg by 0.041.

For example, 100 mg/L of Na is the same as 4.35 milliequivalents/L of Na.

Typical domestic wastewaters have SAR's in the range 2 to 5. Because SAR is a ratio and not a measure of concentration, high- and low-salinity waters may exhibit similar SAR's.

INFO

Trench will not calculate SAR until you enter concentrations for sodium, calcium and magnesium in the appropriate locations.