Major ion chemistry and quality assessment of the groundwater resources of Nanded tehsil, a part of southeast Deccan Volcanic Province, Maharashtra, India

摘要

Groundwater quality assessment study was undertaken in the Nanded tehsil, District Nanded (the term tehsil is used for an administrative block in case of India) which is the part of southeast Deccan Volcanic Province in Maharashtra, India, with a view to assess the suitability of groundwater resources for the purpose of drinking and irrigation. Fifty (50) representative dug/bore well water samples were collected and analyzed for determining the geochemical variations and quality of groundwater in the study area. By clutching hydrochemical analysis and GIS-based inverse distance weightage (IDW) technique, the spatial variation of groundwater quality was inferred. The physicochemical parameters, viz. pH, EC, TDS, TH, Ca2+, Mg2+, Na+, K+, CO3-, HCO3-, Cl-, NO3-, SO4-, were determined to assess the groundwater quality. As per the World Health Organization (WHO) standards, TDS (60%), TH (98%), Ca (06%), Mg (04%), Na (14%) and Cl (24%) samples exceed the desirable limits but all the groundwater samples are within the permissible limit except EC. The parameters such as EC, TDS, Cl-, Na+, TH, HCO3- and Ca2+ show significant positive correlation with other parameters. The hydrogeochemical analysis suggests that the dominant ions present in groundwater are Cl-, Na+, Ca2+ and HCO3-. The Piper plot shows that the alkaline earth exceeds alkalies and alkali exceeding the alkaline earths in case of 60 and 40% samples, respectively. Strong acids exceed weak acid representing 76% of the total samples and only 24% samples represent weak acid exceeding strong acid. The groundwater from the study area is mostly of Na-Ca-Cl-HCO3, Na-Cl-HCO3, Na-HCO3-Cl, Mg-Ca-Na-Cl-HCO3, Na-Mg-Cl, etc., types in the descending order of dominance. The suitability of groundwater for irrigation was determined on the basis of SAR, RSC, MAR, % Na, KR, TDS, CAI, GR, etc. According to the Cl- classification, 6% of groundwater samples can severely affect the plants. From Kelly's ratio, 19 (38%) samples are found to be unsuitable due to surplus (>1) sodium content. The MAR demonstrates that, 6% samples fall in bad category; however, % Na shows that, 20% are doubtful and only 4% samples are unsuitable for irrigation. The Gibbs diagram represents the rock dominance processes in all the groundwater samples, which are affecting the groundwater quality in the study area. The US salinity diagram reveals that C4S2 zone includes 8% and C4S3 represents 4% of samples (with EC = <2250, 10 18), respectively, which are supposed to be unsuitable for irrigation in the study area.