Estimations of 137Cs activity concentrations using marine parameters issued from MODIS and Copernicus Marine Environment Monitoring Services (CMEMS) data in Souda Bay (Crete, Greece) for the period 2011–2019

Cesium-137, as the main fission product, is of special interest in the marine environment because of its solubility, which results to very low sinking time. Nevertheless, the conservative form of the main percentage of ¹³⁷Cs introduced in the marine environment (70%) makes ¹³⁷Cs to be included in the salinity of sea water. Based on this property, in this study, we examine potential relations between ¹³⁷Cs activity concentrations and marine parameters issued from Earth Observation (EO) data products in the Southern Aegean Sea, in order to investigate the possibility of ¹³⁷Cs to be recorded by satellite data. In particular, measurements of physical and biological marine parameters issued from the Copernicus Marine Environment Monitoring Service (CMEMS) database and MODIS ocean products are retrieved for the dates of ¹³⁷Cs field measurements. Single and multiple regression analyses are performed between the marine parameters and ¹³⁷Cs activity concentration measurements for three distinctive time periods (total, cold, and warm period). The best results are obtained from multiple regressions, one for each time period (r² > 0.70). The models show that during cold period, ¹³⁷Cs activity concentrations are highly correlated to both chlorophyll and nutrients (phosphates) while during warm and the total period, they seem to be mainly correlated to the photosynthetic available incident solar radiation on the sea surface. For each period, we propose a multiparameter model linear in its parameters. Although the results of this study must be considered preliminary due to the limited size of the datasets, for the first time, we show that estimations of ¹³⁷Cs activity concentrations from EO measurements and CMEMS environmental models are feasible, and they can be used as a marine radiological assessment tool for a closed Mediterranean bay such as Souda Bay in Greece.