AN ASSESSMENT OF THE RESULTS OF THE IAEA INTERLABORATORY COMPARISONS FOR GEOTHERMAL WATER CHEMISTRY

Abstract

Since 1985 the International Atomic Energy Agency, Vienna (IAEA) has conducted four interlaboratory calibrations for geothermal water chemistry. Two water samples in each calibration (i.e. eight samples in total) were analyzed in the geochemistry laboratories involved in geothermal developments all over the world. The parameters, pH, Li+, Na+, K+, Ca2+, Mg2+, Cl-, SO42-, HCO3- and SiO2 were analyzed in all samples together with some analyses of electrical conductivity, B, As and F-. A statistical evaluation suggests that the analytical error increases with decreasing concentration for all the chemical parameters except for SiO2 and is of same order of magnitude for concentration less than 1 ppm. The overall error in the analytical data for geothermal waters is ±13%.

There are systematic errors in the data from some laboratories, which is one of the reasons for higher analytical errors in the results of interlaboratory calibrations. Thus to improve the analytical quality of the participating laboratories it is necessary to run some common commercial standards in all the laboratories together with the geothermal water samples, as has been established in case of stable isotope mass spectrometry by the IAEA.

A brief discussion is also presented on the uncertainty in the geochemical interpretation of these data due to the analytical errors to understanding the deep reservoir processes in the hydrothermal systems.