What constitutes PPT of freshwater?

PPT, or parts per thousand, is a measurement used to express the concentration of dissolved substances in water, including freshwater. In freshwater contexts, PPT typically refers to the salinity or the amount of salt content present in the water, with freshwater usually defined as having a salinity of less than 0.5 PPT. This low concentration of dissolved salts differentiates freshwater from saline water bodies like oceans. Thus, freshwater PPT is a key indicator of water quality and ecosystem health.