Appraisal and comparison of contamination in potable water sources during pre, syn and post monsoon periods in Southwest Lawngtlai district, Mizoram, India

Abstract

The quality of groundwater South-west Lawngtlai district, Mizoram has been assessed in the present work using the samples from ground water sources (WL) in three different seasons as pre-monsoon, monsoon and post-monsoon. The main objective of this study is to investigate the physico-chemical, bacteriological, estimation of heavy metals or trace elements and other cations and anions characteristics used for domestic and household purposes. The main sources of heavy metals/ trace elements along with different parameters in potable water were controlled by the geological composition of the host rock and with other local anthropogenic activities due to increasing urbanization, agricultural runoff containing fertilizers, pesticides, insecticides and industrial effluent. Turbidity has been found exceeding the permissible limits of 5 NTU in some stations. The concentration of Aluminum (Al), Barium (Ba), Gallium (Ga), Iron (Fe), Lithium (Li), Strontium (Sr) and Zinc (Zn) is well within the prescribed limits recommended by BIS and WHO. In all the samples the concentration of Silver (Ag), Cadmium (Cd), Cobalt (Co), Chromium (Cr), Copper (Cu), Molybdenum (Mo) and Nickel (Ni) is found below limit of detection (BLD). The concentration of Arsenic (As), Manganese (Mn) and Lead (Pb) in some stations has been recorded exceeding the permissible limits of 0.05 mg /me, 0.3 mg /me and 0.05 mg /me respectively. especially in the low- lying area of reducing environment such a high concentration of Arsenic in potable may be induced due to the dissolution of rocks, minerals and ores. The occasional high concentration of lead in water sample may be due to gasoline coming out of vehicles as most of the water sources are situated on or near the highway. Most of the value of total coliforms (MPN) has been found exceeding the permissible limits of 10 MPN/100 ml in water sample from all the water sources. The higher value of coliforms in water samples may be attributed to the use of pit latrines, piggeries and poultries, which are predominant in the study area. The total hydrochemistry of the area under study is dominated by alkaline earths and weak acids. Most of the surface, sub-surface and groundwater in the study area can be classified as Ca-Mg-HCO3 facies while in some samples calcium or magnesium is sometimes replaced by sodium. It is highly recommended that the drinking water of the affected areas should be filtered and should be treated chemically or physically for toxic metals.