Water and Wastewater Terms Beginning S

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SAR (sodium adsorption ratio)

A ratio that expresses the relative activity of sodium ions in the exchange reactions with soil. The ratio is defined as:

SAR = NA / [1/2(Ca + Mg)]^1/2

where Na, Ca, and Mg are concentrations of the respective ions in milliequivalents per liter of water.

Na [meq/L] = (Na[mg/L]) / (23.0[mg/meq])

Ca [meq/L] = (Ca[mg/L]) / (20.0[mg/meq])

Mg [meq/L] = (Mg[mg/L]) / (12.15[mg/meq])