Equilibrium molecular dynamics simulations have been performed to examine the hydration characteristics of Mg2+ and SO42- ions over a range of salt concentrations in the solution. While the hydration structure of the monatomic cation agrees with previous reports in the literature, the larger and more complex anion exhibits hitherto unreported novel coordination features. These result from its low charge density as well as the charge distribution over the five active sites. While the number of water molecules that hydrate the ions below the hydration limit is almost constant, this number rapidly reduces as the solution becomes saturated and ion-pairs are formed. (C) 2011 Elsevier B. V. All rights reserved.