WATER CHEMISTRY OF A TECTONIC LAKE OF ASSAM WITH REFERENCE TO PRIMARY NUTRIENTS

The present investigation was carried out to study the variations of the physicochemical properties and primary nutrient parameters of Chandubi Lake, a tectonic lake. Water quality parameters such as water temperature, dissolved oxygen, free carbon dioxide, pH, total hardness, total alkalinity, total carbon, bicarbonate ion and primary nutrients nitrate, orthophosphate and potassium were estimated. The study revealed low levels of total hardness and total alkalinity which is unique in the present investigation for the state of Assam. The presence of free carbon dioxide was recorded throughout the study period indicating the absence of carbonate alkalinity in all zones of Chandubi Lake. The investigation also revealed that the nutrient input in Chandubi Lake is of autochthonous origin. ANOVA (p = 0.05) revealed that there were significant difference in water quality parameters dissolved oxygen (DO), total carbon dioxide (CO2), total hardness (TH) and primary nutrient orthophosphate among the studied zones. The Pearson correlation (p = 0.05) showed that, water temperature has a negative correlation with DO (r = - 0.72), pH (r = - 0.64), dissolved oxygen (DO) has a negative correlation with free carbon dioxide (FCO2) (r = -0.91) and potassium (K) (r = - 0.86), while having a positive correlation with nitrate (NO3) (r = 0.71) and free carbon dioxide (FCO2) having a negative correlation with pH ( r = - 0.90). The overall water quality condition was found to be excellent, which was evident from WQI (< 25%).