In water sample
– 1 gr/L = 1 part per thousand (ppth)
– 1 mg/L = 10-3 gr/L = 1 part per million (ppm)
– 1 µg/L = 10-6 gr/L = 1 part per billion (ppb)
– 1 ng/L = 10-9 g/L = 1 part per trillion (ppt)
– 1 pg/L = 10-12 g/L = 1 part per quadrillion (ppq)
In soil sample
– 1 gr/kg = 1 part per thousand (ppth)
– 1 mg/kg = 10-3 gr/kg = 1 part per million (ppm)
– 1 µg/kg = 10-6 gr/kg = 1 part per billion (ppb)
– 1 ng/kg = 10-9 g/kg = 1 part per trillion (ppt)
– 1 pg/kg = 10-12 g/kg = 1 part per quadrillion (ppq)
– 1 fg/kg = 10-15 g/kg = 1 part per quintillion
In air sample
– Percent (parts per hundred) by volume (%v)
– Parts per million by volume (ppmv)
– Weight of pollutant per cubic meter of air (mg/m3, µg/m3, ng/m3, etc.)
– Molecules of a pollutant gas per cubic centimeter of air (molecules/cc or molecules/cm3)
– Moles of pollutant gas per liter of air (mol/L)
– Partial pressure of pollutant gas
– Mole fraction of pollutant gas
Reference
Eugene R. Weiner. Application of Environmental Aquatic Chemistry. A Practical Guide. Third edition. CRC Press