Estimation of apparent water age and mixing process of water in the creek ecosystem of Mumbai Harbour Bay

Abstract

Short-lived Ra isotopes (224Ra and 223Ra) were used to estimate the apparent water age and mixing process, in the creek ecosystem of Mumbai Harbour Bay. The apparent water age was estimated using the Radium Age Model and the Radium Balance Approach. The apparent water age for three different sampling trips in the creek varies from 3.65 ± 1.22 to 4.51 ± 1.51 days using the Radium age model. Whereas using the Radium Balance Approach in the creek, the apparent water age was estimated to be 6.51 ± 1.67 days. Similar apparent water age from both approaches was found for the creek ecosystem under steady state. The longitudinal variation of the 224Ra and 223Ra activity ratio from the middle of the creek indicated net water mass movement towards the open sea. The flushing rate of the creek water towards the open sea was estimated to be 6.67 ± 0.89 km day−1. The horizontal mixing coefficient (Kh) of the creek water was estimated to be 800 ± 107 m2s−1 indicating rapid dispersion of the tracer.