“…45 In these ponds with corroding spent fuel radiolytic effects will also contribute, these again can transform Pu oxidation states directly or indirectly through formation of H 2 O 2 and other species. 46 Another possibility is suggested as pH values are quite low in all these samples compared to pond pHs, implying that CO 2 absorption has occurred after sampling and before analysis (Table 1). All these analyses, therefore, are on 'aged' samples and whether this ageing has affected the Pu oxidation state distribution compared to pond conditions is uncertain.…”