Micrograms per Liter (ug/L) is equivalent to which unit?

Micrograms per Liter (ug/L) is equivalent to Parts Per Billion (PPB). This is based on the understanding that 1 microgram is one-millionth of a gram, and when considering concentrations in water, one liter of water weighs approximately 1,000,000 milligrams. Thus, when you have 1 microgram of a substance in 1 liter of water, this equates to 1 part per billion because there are 1 billion micrograms in a liter of water. Therefore, the relationship of micrograms per liter to parts per billion is direct and defined, making the answer correct.

In contrast, parts per million (PPM) would relate to milligrams per liter (mg/L), where 1 mg/L is equivalent to 1 PPM. This shows a clear distinction in scale compared to micrograms per liter. Moles per liter (mol/L) measures concentration in terms of the number of molecules rather than weight, creating further differentiation from the initial measurement unit.