Hydrochemistry of groundwater in North Rajasthan, India: chemical and multivariate analysis

摘要

This paper presents the hydrochemistry of groundwater of the northern districts of Rajasthan, India. Groundwater samples were collected from 50 sampling stations (rural and suburban areas) and analyzed for pH, EC, TDS, TH, NO3-, SO4 (2-), PO43-, Na (+), K (+), Mg2+, Ca (2+), Fe (2+), F(-)and Cl-. The pH varied from 6.54 to 9.51 in groundwater, slightly higher than WHO limit. The majority of sampling sites (80-100%) showed the high EC, TDS, TH and Na (+) contents in groundwater with an average value of 4.46 S/cm, 2856.1, 1774.4 and 426 mg/L, respectively. Na (+)/Cl(-)ratio was >1 in most of the sampling locations, which indicates the releasing of Na+ from silicate weathering. NO3- in groundwater ranged between (0.37 and 51.4 mg/L), and a few sites indicate an anthropogenic contribution of NO3- in groundwater. The F-in groundwater is a major issue in this area, and F-varied from 0.02 to 7.18 mg/L (with an average of 2.08 mg/L). Piper diagram identified Ca-Mg-HCO3 ([80%) and NaK- HCO(3)(-)as the dominant types of water of this area. The strong correlation between Na-Cl and K-Cl, Ca-Mg-SO4 suggests feldspar weathering in groundwater. Six components with a variance of 79% were extracted, which suggests cation exchange, rock-water interaction and anthropogenic activities as major factors affecting groundwater chemistry of this area. Water quality index of study area ranged between 178.58 and 944.8, and groundwater of about 58% of the study site fell under unsuitable for drinking category. The result of SAR analysis indicated the high Na+ content in groundwater (>10% sites), unsuitable for irrigation purposes. Langelier saturation index indicates that >60% sampling sites may have scaling problems due to excess CaCO3 in groundwater. Results suggest complex geological processes and anthropogenic pressure as major causes of deterioration of the overall quality of groundwater in this area.