Distribution of 226Ra– 210Pb– 210Po in marine biota and surface sediments of the Red Sea, Sudan

Abstract

Activity concentration levels and ratios of 226Ra, 210Pb and 210Po are presented in multicellular marine algae, molluscs, coral as well as in surface marine sediments collected from the shallower waters of the fringing reefs area extending towards north and south (Flamingo bay) of PortSudan harbour, Sudan. The analyses were performed adopting alpha-spectrometry, liquid scintillation and Cerenkov counting techniques. Surface sediments from this coastal region are poor in their radioactivity content in contrast to similar data reported from different coastal areas around the globe. There is surface enrichment of 210Pb and 210Po with respect to their progenitor 226Ra as it is evident from the activity ratios of 210Pb/ 226Ra (3.03 ± 1.79) and 210Po/ 226Ra (2.23 ± 1.56). Among marine plants and animals investigated, the green algae species, Halimeda, and coral species, Favites, show substantial concentration of radium at 8.2 Bq/kg and 21.9 Bq/kg dry weight, respectively. Similarly, the highest concentration of 210Po was met in Favites at 38.7 Bq/kg followed by brown algae, Cystoseria sp., at 32.6 Bq/kg. There is no variation seen among algal species for 210Pb uptake, however, converse to radium and polonium, Favites (coral) was found to contain the minimum concentration of lead (3.88 Bq/kg). In most species there is preferential accumulation of polonium over its parent radium as indicated by 210Po: 226Ra activity ratio with Cystoseria (brown algae) showing the highest value at 8.81. On the other hand, 210Po: 210Pb activity concentration ratio revealed that coral species Favites (9.97) and the brown algae Sargassum (1.85) have a greater tendency to accumulate 210Po over 210Pb, while in the rest of species; this ratio is less than unity.