Geochemical characterization, deciphering groundwater quality using pollution index of groundwater (PIG), water quality index (WQI) and geographical information system (GIS) in hard rock aquifer, South India

Abstract

Fifty groundwater samples were obtained pre and post-monsoon seasons in parts of hard rock terrain in Andhra Pradesh, South India, in order to assess the drinking water quality. PIG values of groundwater samples ranged from 0.95–1.53 and 0.83–1.28 during pre and post-monsoon seasons. PIG values are slightly higher in the pre-monsoon season when compared to the post-monsoon season. In the pre monsoon season, 96% of the groundwater samples showed insignificant pollution class (< 1), 4% of the groundwater samples are low pollution (1–1.5). 82% of the groundwater samples showed insignificant pollution status (< 1), 18% of the groundwater samples fall under the low pollution (1–1.5), is noticed in post-monsoon season, respectively. WQI values of groundwater samples ranged from 108.5–204 mg/L and 112.6–170 mg/L during pre and post-monsoon seasons; its shows that 100% are very poor for drinking purpose. Piper diagram reveals that groundwater is majorly mixed Ca ²⁺-Mg ²⁺-Cl ⁻, Ca ²⁺-Mg ²⁺-Cl ⁻-SO ₄ ²⁻, Na ⁺-K ⁺-Cl ⁻- SO ₄ ²⁻ type in this region. The Gibbs plot indicates that groundwater samples fall within the field of rock dominance. Through applying GIS techniques, the spatial distribution of groundwater quality analysis reveals that most of the groundwater samples do not comply drinking water quality standards and water needs to be prior treatment before consumption.