Polyphenol inhibition of calcite precipitation in Lake Powell 1

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Abstract
Laboratory studies of calcite precipitation kinetics in waters of simulated Lake Powell composition have verified that precipitation occurs by a spiral dislocation growth mechanism. But waters from the lake and laboratory solutions containing tannic acid and plant polyphenols at low and very low levels showed calcite growth rates proportional to the fourth power of the carbonate ion concentration. The results indicate the operation of a surface polynuclear growth process that becomes effective when polyphenol adsorption blocks spiral dislocation growth sites and causes precipitation rates to diminish with increasing polyphenol concentration and to fall drastically as pH is lowered. The effects of these factors are dominant controls on the calcium carbonate geochemistry of Lake Powell. Significant amounts of calcite precipitation occur only in the surface waters of the downstream portion of the reservoir and, even there, only during the warm (6 months) portion of the year.