Temporal variation of 137Cs and 90Sr transfer factors in Mumbai harbor

Understanding the long-term behaviour of anthropogenic radionuclides in the environment is vital, especially that of long-lived radionuclides as they may get integrated in the human food chain and cause potential exposure in addition. This involves studying their behaviour in different environmental matrices, their persistence, and the rate at which they enter the food chain. 137 Cs and 90 Sr are two such radionuclides introduced into the environment through anthropogenic activities. Radionuclides present in seawater gradually get distributed into the sediment and plants growing in these areas/shores. This absorption can result in their bioaccumulation, transfer to the food chain e.g., to biota in water, to vegetation, to terrestrial herbivores feeding on the vegetation, finally human through various food consumption. Aim of the present study is to understand the temporal behaviour of 137 Cs and 90 Sr in different matrices. Both elements have long half-lives, making it essential to monitor their behavior in the environment. Hence, radiochemical separation and various analytical techniques were employed to determine the activity concentrations. The calculated ratios of the concentration of 137 Cs between seawater and sediment is observed to be in the range of 0.82 ×10 -6 - 4.7 ×10 -6 and of 90 Sr in the range of 0.001 - 0.007 indicating accumulation of 137 Cs and 90 Sr activity in the sediment, with 137 Cs demonstrating a significantly higher affinity for sediment as compared to 90 Sr. Whereas the ratios of activity in vegetation to sediment is observed to be higher for 90 Sr (0.3-0.8) compared to 137 Cs (0.003-0.03). The temporal variation studies spread over ~10 years have indicated that there is no enhancement of 137 Cs and 90 Sr concentration in any of the environmental matrices over the ambient levels prevailing due to global fallout.