Association of 241Am and 137Cs in finer size-fractioned saltmarsh sediments from north-west England, UK and potential health risk to coastal population

Abstract

ABSTRACT This study provides an in-depth analysis of the relationship between radionuclide and particle size-class abundance through an investigation of radionuclide distribution in finer sediments within surface core samples collected from two contaminated upper saltmarsh areas of the Dee estuary and Biggar marsh in north-west England. The particle size fractionation (PSF) analysis was carried out following gravitational settling and pipette method to separate all samples into six size-fractioned groups ranging from 63 to <2 µm (very coarse silt to clay), and radioactivity analysis was performed using a well-type High Purity Germanium (HPGe) detector. The highest 241Am and 137Cs activities in PSF samples were found to be 291 ± 5 and 2071 ± 16 Bq kg−1, respectively, for the Dee estuary saltmarsh and 3832 ± 14 and 4840 ± 23 Bq kg−1, respectively, for Biggar saltmarsh and found in the clay fractions for both sites. Correlation of radioactivity concentration data of three size groups ranging from 63 to <2 µm (very coarse silt to clay) confirms a strong and increasing association of radioactivity with fine particles from coarse to fine clay-size particles. Also, examination of textural and radionuclide data of all bulk core and size-fractioned samples revealed that upper saltmarshes are made up of both contaminated and uncontaminated sediments. Furthermore, the annual outdoor external effective dose range for all short core data (0.001–0.11 mSv y−1) and for PSF sample data (0.001–0.08 mSv y−1) reveal that some values exceed the world average value of 0.07 mSv y−1as reported in UNSCEAR [43], for outdoor, which are non-negligible. Thus, the total annual external effective dose associated with existing contaminated saltmarsh sediments represents a possible health risk to saltmarsh users and coastal populations living nearby these saltmarshes.