Salinity: Electrical Conductivity and Total Dissolved Solids

This chapter describes prevalent laboratory methods for determining salinity based on measurements of electrical conductivity (EC) or total dissolved solids after evaporation at 180°C. It discusses various methods for determining the concentrations of individual inorganic solutes in waters and soil extracts in common use in laboratories having modern instrumentation. The extraction ratios are easier to make than that of saturation, but they are less well related to field soil water composition and content. More importantly, salinity and compositional errors from dispersion, hydrolysis, cation exchange, and mineral dissolution increase as the water/soil ratio increases. Soil salinity may be estimated from measurement of the EC of the saturated soil-paste and estimates of saturation percentage. The amount of total dissolved solids in a sample is determined by weighing the residue obtained after evaporating a sample that has been filtered to remove particulate matter.

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