We investigated the influence of ionic strength on migration behaviors of Sr and Eu in the presence of humic acid (HA). The
breakthrough curve of Sr through a quartz sand column in the presence of HA was identical to that in the absence of HA. Europium
migration in quartz sand was enhanced by the presence of HA at low ionic strength. At high ionic strength, Eu migration in
the presence of HA was hindered compared to that in the absence of HA. Adsorption of europium on quartz sand in the absence
of HA decreases with increased ionic strength.