Quality and degree of pollution of groundwater, using PIG from a rural part of Telangana State, India

Abstract

Impacts of geogenic and anthropogenic sources change seriously quality of groundwater. Inferior groundwater quality directly affects the human health, agricultural output and industrial sector. The aim of the present study is to evaluate the groundwater quality for drinking purpose and also to identify the pollutants responsible for variation of chemical quality of groundwater, using pollution index of groundwater (PIG). Groundwater samples collected from a rural part of Telangana State, India, were analyzed for pH, total dissolved solids (TDS), calcium (Ca²⁺), magnesium (Mg²⁺), sodium (Na⁺), potassium (K⁺), bicarbonate (\[ {\text{HCO}}_{3}^{ - } \]), chloride (\[ {\text{Cl}}^{ - } \]), sulfate (\[ {\text{SO}}_{4}^{2 - } \]), nitrate (\[ {\text{NO}}_{3}^{ - } \]) and fluoride (\[ {\text{F}}^{ - } \]). The groundwater is characterized by Na⁺ and \[ {\text{HCO}}_{3}^{ - } \] ions. The values of TDS, Mg²⁺, Na⁺, K⁺, \[ {\text{HCO}}_{3}^{ - } \], \[ {\text{Cl}}^{ - } \], \[ {\text{SO}}_{4}^{2 - } \], \[ {\text{NO}}_{3}^{ - } \] and \[ {\text{F}}^{ - } \] are more than their threshold limits prescribed for drinking purpose in a few groundwater samples. The computed values of PIG varied from 0.69 to 1.37, which classify the 80% of the present study area into the insignificant pollution zone (PIG: < 1.0) caused by geogenic origin associated with rock-weathering, mineral dissolution, ion exchange and evaporation processes, and the rest (20%) into the low pollution zone (PIG: 1.0 to 1.5) due to influence of anthropogenic source (waste waters and agricultural activities) on the groundwater system, which are proved by ANOVA test. The diagrams (Ca²⁺ + Mg²⁺) versus (\[ {\text{HCO}}_{3}^{ - } \] + \[ {\text{SO}}_{4}^{2 - } \]), Na⁺ versus (Ca²⁺ + Mg²⁺), Na⁺ versus \[ {\text{Cl}}^{ - } \], Ca²⁺ versus \[ {\text{SO}}_{4}^{2 - } \] and Ca²⁺ versus Mg²⁺ support the geogenic origin, whereas the diagram TDS with (\[ {\text{NO}}_{3}^{ - } \] + \[ {\text{Cl}}^{ - } \])/\[ {\text{HCO}}_{3}^{ - } \] confirms the impact of anthropogenic activities on the aquifer chemistry, which substantially proved the explanation of PIG. The characterization of geochemical evolution of groundwater, using trilinear diagram, also further supports the assessment of PIG in the variation of groundwater quality. From this study, the TDS, Mg²⁺, Na⁺, \[ {\text{Cl}}^{ - } \], \[ {\text{SO}}_{4}^{2 - } \] and \[ {\text{NO}}_{3}^{ - } \] are considered as indicators in assessing the groundwater pollution sources.