Conversions and Units

1 ppm = 1 mg/L = 1 part per million
1 ppm = 1 mg/kg
1 percent concentration = 10,000 ppm
1mmolc = 1 meq/L (Hanson et al., 1999)
meq/L = 10 x EC in mmhos/cm
OP (osmotic pressure) = -0.36 x EC in mmhos/cm
TDS mg/L = 640 x EC in millimhos/cm
1 mhos/cm = 1000 mmhos/cm
1 mmhos/cm = 1000 (µhos/cm
1 Siemen/meter (S/m) = 10 mmhos/cm
1 deci-Siemen/meter (dS/m) = 1 mmhos/cm
1 dS/cm = 1 mhos/cm
(Ayers and Westcot, 1976)

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