Comparison of Empirical, Physical and Chemical Methods in Determination of TDS Conversion Factor from ECdw of Leached Low Dust Samples

Total Dissolved Solids (TDS, mg/L) indicates the amount of soluble salts in water or in a solution, and usually calculates by measuring the electrical conductivity (ECdw, μS/cm) and then multiplied by 0.64. This is a general conversion factor (CF) and its amount varies depending on the water-soluble components. In fact, TDS meters determine TDSvalueby measuring of the EC solution and default or user-selected CF. Hence, the precise method is to calculate this coefficient according to the solute type. In this research, to determine precisely the amount of soluble solids along with suspended dust in MDCO sediments traps installed in the northof the Yazd-Ardakan plain. To obtain the TDS calculation coefficient from ECdw resulting from leaching of small amounts of dust, three methods including of an experimental coefficient of 0.64, physical vapor deposition weighing and measuring the concentration of ions affecting chemical salinity were compared. Comparison of mean of the CFs obtained from the three methods showed that the TDS valueof the method of coefficient of 0.64 for determination of TDS from ECdw, was significantly lower than the other two methods. Hence, applying of this method, leads to a low level of solute content with dust in the study area. The average of the TDS conversion factor obtained by the physical and chemical methods without significant differences were 1.03 and 0.90 respectively, compared to 0.64 in the experimental method, that makes it possible to calculate more precisely the TDS from the measured ECdw data that derived from leached dust, and it can be used to adjust the TDS conversion factor in EC and TDS simultaneous measurement devices.