Effect of groundwater pH and ionic strength on strontium sorption in aquifer sediments: Implications for 90Sr mobility at contaminated nuclear sites

► The sorption of 90Sr to sediments representative of the UK Sellafield site is investigated. ► In artificial groundwater based solutions the degree of 90Sr sorption is controlled by pH. ► In a simulant tank liquor solution, sorption is limited by cation competition due to elevated Na+. ► Sr is adsorbed to sediments as weakly bound surface complexes even in experiments aged for 1 year. ► After 1 year most Sr can be extracted with MgCl2, a finding useful to remediation strategies.