One part per million (ppm) denotes 1 part of solute per 1,000,000 parts of solution.
What does 1mg/L mean?
1mg/L denotes 1 mg of solute per 1 liter of solution.
If the solvent is water, then 1L = 1kg (the density of water is equals to one kilogram per liter at the temperature 4C).
1L= 1kg= 1000 g= 1,000,000 mg
In this way 1mg/L= 1mg/1,000,000mg= 1ppm
More correct to say, that 1ppm is approximately equal to 1mg/L, because 1kg not always equals to 1 liter.
Answer: 1ppm= 1mg/L.