Measure of the total concentration of both organic and inorganic, microscopic particles suspended in a given liquid. Usually applied only to freshwater systems and measured using a conductivity or total dissolved solids meter with results expressed in units of mg per unit volume of water (e.g., mg/L) or parts per million (ppm). Soft water with low pH generally has low levels of total dissolved solids whereas harder water with higher pH tends to contain correspondingly increased concentrations. Often abbreviated to TDS.