Estimation of submarine groundwater discharge using radium mass-balance in Mumbai Harbour Bay, Mumbai, India

Abstract

The Mumbai Harbour Bay (MHB), Mumbai, India houses a large number of ports, industrial units and urban settlements thus the groundwater may be highly contaminated. In the present study short lived Ra isotopes (223Ra and 224Ra) input sources (viz. water exchange from Arabian Sea, input from Rivers and wastewater discharge, Diffusion of Ra from bottom sediments and desorption from suspended particles) and pathways of removal (radioactive decay and export during the low tide) were estimated in MHB individually. A mass balance for 223Ra and 224Ra in the bay indicated an imbalance of 53.38% and 71.68% respectively. The imbalance was assigned to contribution from submarine groundwater discharge (SGD) and using the concentration in the shallow groundwater (at 2 m depth) of 223Ra and 224Ra the SGD were estimated. Based on 223Ra and 224Ra, the SGD was estimated and found to be 33.4 × 109 L day−1 and 64.9 × 109 L day−1 respectively.