Ar. Hoch et al., Calcite crystal growth inhibition by humic substances with emphasis on hydrophobic acids from the Florida Everglades, GEOCH COS A, 64(1), 2000, pp. 61-72
The crystallization of calcium carbonate minerals plays an integral role in
the water chemistry of terrestrial ecosystems. Humic substances, which are
ubiquitous in natural waters, have been shown to reduce or inhibit calcite
crystal growth in experiments. The purpose of this study is to quantify an
d understand the kinetic effects of hydrophobic organic acids isolated from
the Florida Everglades and a fulvic acid from Lake Fryxell, Antarctica, on
the crystal growth of calcite (CaCO3). Highly reproducible calcite growth
experiments were performed in a sealed reactor at constant pH, temperature,
supersaturation (Omega = 4.5), P-CO2 (10(-3.5)atm), and ionic strength (0.
1 M) with various concentrations of organic acids. Higher plant-derived aqu
atic hydrophobic acids from the Everglades were more effective growth inhib
itors than microbially derived fulvic acid from Lake Fryxell. Organic acid
aromaticity correlated strongly with growth inhibition. Molecular weight an
d heteroatom content correlated well with growth inhibition, whereas carbox
yl content and aliphatic nature did not. Copyright (C) 1999 Elsevier Scienc
e Ltd.