FACTORS AFFECTING DEPOSITION AND RESIDUAL CONCENTRATION OF RADIOCESIUM IN SEDIMENT ON BANZU TIDAL FLAT

Abstract

 To investigate the deposition and residual concentration of radiocesium produced as a result of the Fukushima Daiichi Nuclear Power Plant (FDNPP) disaster in a tidal flat, the concentrations of ¹³⁴Cs and ¹³⁷Cs in sediment were measured in Banzu tidal flat, Kisarazu City, Chiba, Japan. The highest radiocesium concentration in sediment, 70 Bq/kg-D.W., was almost the same as the radiocesium concentration recorded in surrounding municipalities in 2011. Since the half-life corrected ratios of ¹³⁴Cs and ¹³⁷Cs were calculated to be from 0.40 to 0.79, it is thus indicated that radiocesium deposited before the FDNPP disaster has remained in the sediment of Banzu tidal flat. Radiocesium concentrations denoted by “derived after FDNPP disaster” and “deposited before FDNPP disaster” were estimated from observational results. The factors affecting the deposition and residual concentration of observational and estimated radiocesium were examined by stepwise multiple regression. Although a different set of factors were indicated by regression analysis for every case, ignition loss was included as a factor in all cases.