Appraisal on water chemistry of Manakudy estuary, south west coast, India

The sources of toxic trace elements from the rivers to be debouched into the sea through estuaries are either weathered naturally from the soils and rocks or introduced anthropogenicaly from point or non-point sources, in labile form or in particulate form. The chemistry and ecology of an estuarine system are entirely different from the fluvial as well as the marine system. To gain a better understanding of the geochemical behavior of physicochemical parameters, major ions and trace elements and to examine variations in associated chemical fluxes, 20 water samples were collected throughout the Manakudy estuary and analyzed during pre and post monsoon season. The major ion sequence of abundance is followed as Na > Mg > K > Ca > NO3 > SiO4 > P > NO2 with respect to the mean values during both monsoons. Among the trace metals, the mean concentration of Fe, Zn, Mn, and Pb are 4128, 42, 36, & 5.18 mu g/l in premonsoon and 2064, 31,37, 25, & 6.17 mu g/l in postmonsoon is found as high when compared to Cu, Cr, Cd and Co. To precisely identify the toxicity level of trace metals in water, the contamination factor (CF) and potential ecological risk index (PERI) were computed. Cu recorded as highly contaminating metal in estuarine water followed Zn based on CF values. The PERI values show moderate to high risk in premonsoon and moderate to significantly high risk in postmonsoon water. The physico-chemical parameters, major ions and trace elements are interrelated components of water quality properties which controls the estuarine water ecosystem. So that the enrichment and overloading of these components are by the geogenic and anthropogenic processes that adversely affects the species diversity, metabolism and the population of habitats. It is recommended for strategic management plans must be implemented to control the overloading of pollutants in Manakudy estuarine water.