This approach defines dissolved versus particulate solids by the effective pore size of the filter, because any very small particulates that pass through the filter become part of the TDS weight. Conductivity and salinity are essentially measures of the salts dissolved in a sample. Conductivity measures how well the water sample conducts an electrical current, a property which is proportional to the concentration of ions in solution. The advantage of using conductivity over TDS is the ease with which measurements can be made. However, some instruments will, by changing scales, permit conductivity measurements in saline waters.
Salinity is a special measure of dissolved solids based upon concentration of ocean salts.
Technically, the measurement of salinity requires comparing a sample's TDS, conductivity, or other physico-chemical property with that of a standard sea water. Salinity is the usual measure of salts in sea water and in brackish water derived from mixing of fresh and sea water. A conversion program for conductivity to salinity is posted at the Cerrito Creek Monitoring Program website. Further Reading Web reading resources are arranged from least to most technical. Occupational training, standard operating procedures.