Electrical conductivity method for natural waters

A new method is presented for calculating the electrical conductivity of a wide range of natural waters including acid mine waters, geothermal waters, seawater, dilute mountain waters, and river water impacted by municipal wastewater. The method has several advantages over previously published methods. New electrical conductivity measurements for electrolytes commonly found in natural waters provide a basis for improved calculation of ionic molal conductivities. In addition, the method is coupled to a geochemical speciation model that is used to calculate the speciated concentrations required for accurate conductivity calculations. The method can be used to calculate the electrical conductivity of most natural water compositions and is accurate over a large range of effective ionic strengths (0.0004-0.7 m), temperature (0-95 degrees C), pH (1.0-9.8), and conductivity (30-70,000 mu S cm (1)). For the wide range of natural waters tested in this study, transport numbers were calculated and the ions that contribute significantly to the specific conductance were identified as H(+). Na(+), Ca(2+), Mg(2+), NH(4)(+), K(+), Cl , SO(4)(2-), HCO(3)(-), CO(3)(2-), F , Al(3+), Fe(2+), NO(3)(-) and HSO(4)(-). Transport numbers can also be used to better predict the concentrations of ions in natural waters. Another important application of the specific conductance method is checking the accuracy of water analyses by coupling charge imbalance and specific conductance imbalance. Either the major cation or anion concentrations for 50 different water samples were artificially adjusted and the constituent most likely in error was easily identified. Considering the importance of accurate chemical analyses, the ability to identify inaccurate determinations is critical. Published by Elsevier Ltd.