Electrical Conductance — A Versatile Guide in Freshwater Science

Abstract

Abstract Attention is directed to the many potential uses of specific electrical conductance (‘conductivity’) in the study of inland waters. Its measurement is capable of a precision useful in the detection of differences in a standing or flowing water-mass, but cannot be translated into measures of chemical concentration with equivalent absolute accuracy. Reasons — not infrequently neglected — include approximations in temperature correction, in allowance for a depression effect at higher ionic strength (salinity), and especially in the differences of specific conductance of chemically different ions. The last can be reduced by treating ionic concentration in chemical equivalents (e.g. meq L-1) rather than the usual units of mass (e.g. mg L-1) or molarity (e.g. mmol L-1); also by making allowance for the exceptionally high equivalent conductance of H+and OH- ions of significance in markedly acid and alkaline waters. Measurement in the field has been helped by the development of small portable instruments...