Geochemical studies in the Godavari estuary, India

Abstract

The dissolved O₂, Fe, dissolved organic carbon (DOC), particulate organic carbon (POC), silica and U isotope measurements in river-estuarine waters of the Godavari and the concentrations of 23 elements in the suspended matter of the waters are reported. The DOC and Fe concentrations are lower compared with those in other estuaries of the world and are below the average value reported for world rivers. Silicon behaves non-conservatively; its depletion which is most likely due to biological activity during the non-monsoon periods of sampling ranges from 25 to 37%. The U isotopes behave conservatively although there is some scatter in the low-chlorinity (≤ 2 gCl 1⁻¹) region. Based on the data collected during non-monsoon seasons, the annual U input from Godavari to the Bay of Bengal is estimated to be ≈ 52 tons, although this has to be considered an approximate value owing to the absence of data during the monsoon period. The suspended matter concentrations, ranging from 4.2 to 7.9 mg l⁻¹, are one to two orders of magnitude lower than those of the main rivers on the west coast of India. Of the elemental concentrations and metal/Su ratios reported, Ag, Ai, Ba, Br, Ca and Zn show a large degree of scatter which has yet to be explained. Others, notably, rare earth elements (REE) show a near-constancy to slightly decreasing trend with increasing chlorinity above the ≈ 2 gCll⁻¹ region.