Effects of ions in natural water on the 17O NMR chemical shift of water and their relationship to water cluster

Effects of temperature and some aqueous solutions of electrolytes consisting of ions in natural water on the chemical shifts of NMR of water (O-17 NMR) have been measured. Combining the cluster model of liquid water structure and the dependence of delta((OH2)-O-17) on temperature a relationship deduced of delta((OH2)-O-17) to median water cluster size effects of ions on median water cluster and the size are analyzed. The relationships between O-17 NMR and concentration of ions are linear. Cations increase the median water cluster size and anions decrease it. The bigger the radius of ions with equal ionic charge, the stronger the effect of the ion. The extent of the ionic charge effect is much bigger than that of the ionic radius. The order of the effect of cations and anions is Na+ < K+ < Mg2+ < Ca2+ < Al3+ < Fe3+, and OH- < HCO3- < Cl-, and CO32- < SO42-, respectively. (c) 2006 Published by Elsevier B.V.