Summary of Abstract Submission

Abstract Submission No. IO50-05-0018PresentationPoster

DISSOLVED SR AND 87SR/86SR IN THE EAST INDIAN ESTUARIES: INFERENCES TO SUBMARINE GROUNDWATER DISCHARGE

K. Damodararao*1, Sunil K. Singh1, Vinai K. Rai1

1 Physical Research Laboratory, India

ABSTRACT :

Four tropical estuaries namely Hooghly, Godavari, Mahanadi and the Krishna were studied for dissolved and particulate Sr and its isotopic composition (87Sr/86Sr) to investigate its behaviour and its source/sink in these estuaries. The respective river end-members have Sr concentration 0.8, 1.3, 1.4 and 3.1µmol.kg-1 and 87Sr/86Sr 0.7287, 0.7145, 0.7166 and 0.7139. The Sr and 87Sr/86Sr in silicate fraction of particulates of Hooghly estuary range from 49 to 62µg/g & 0.7576 to 0.7666 with random distribution. Sr varies linearly with Salinity indicating conservative mixing between river and seawaters with trivial supply from other source, if any. 87Sr/86Sr vs. 1/Sr plot shows departure of estuarine waters from the theoretical mixing between river and seawater and hence Sr isotope exchange. In absence of any systematic variations of particulate Sr and its 87Sr/86Sr, it can be argue that non-conservative behaviour of 87Sr/86Sr in these estuaries is due to it supply from Submarine Groundwater Discharge. Inverse model estimates SGD flow rates in range of ~0.5 to 77 cm/day in these estuaries with annual Sr flux of 200 to 480 million moles. These estimates based on monsoon data are 5 to 30 times higher compared to non-monsoon reported earlier in the Hooghly and the Godavari estuaries indicating higher flux of SGD during monsoon due to higher hydraulic gradients.