Various concentration units used in ground water geochemistry:
– Molality: moles of solute per kilogram of solvent
– Molarity: moles of solute per liter of solution
- Molarity = Molality for dilute solutions. Not valid for brines.
– ppm: parts per million
– ppb: parts per billion
– Conc. in ppm = Conc. in mmol/kg x formula weight
Note: 1 ppm = 1 g / 10^6 g = 1 mg/kg = 1 mg/l (in most cases for dilute solution)