Partitioning of various uranium forms and quantification of the influencing factors to their behaviors in estuarine sediments

Abstract

Compared with the extensive research on the behaviors of uranium (U), the contribution rates of different influencing factors have been relatively less evaluated. In this study, the biogeochemical behaviors of U in the Yellow River Estuarine Wetland (YREW) were investigated through sequential extraction procedures. The contribution of different influencing factors to U biogeochemical behaviors were quantified by the method of multiple least-squares linear regression. The results indicate that uranium in sediments is predominantly in residual form (U_F5, making up 71 % of the total U) which is inert during biogeochemical processes. The following order of the other four active U forms is: carbonate bounded form (U_F2) > iron/manganese oxides bounded form (U_F3) > organic matter or sulfide bounded form (U_F4) > exchangeable form (U_F1). Compared with the content of the Yellow River suspended particulate matters (SPMs), U_F1 and U_F3 exhibited releasing from the sediment, while U_F2 and U_F4 became enriched in YREW. The results of multiple least-squares linear regression indicate that the biogeochemical behaviors of U are mostly controlled by REDOX (74 %), followed by organic matter (12.9 %), pH (7.7 %), particle size (3.5 %), and salinity (1.9 %).