Impact of urbanization on hydrogeochemistry and trace metal distribution on five major ponds in the holy city of Gaya, India

Abstract

Gaya, a prominent city of Bihar (India) with rich cultural and religious significance has been susceptible to massive urbanization, population growth and pollution which have huge impact on its surface water bodies. The study was conducted on five major ponds of Gaya namely Bisar, Dighi, Vaitarni, Ramsagar and Suryakund. This paper attempts to evaluate their drinking and irrigational water quality status, trace metal contamination in water and sediments (except Suryakund), hydrogeochemical characterization and evolutionary trends and processes involved in the water chemistry. The WQI values (>130) revealed that the ponds are facing heavy pollution load and the water is not fit for drinking purposes; however, irrigational indices indicates that the water of these ponds is suitable for irrigational purposes. The ponds' water and sediments are heavily contaminated with trace metals particularly cobalt (CF and PI >17) and lead (CF>1.4 and PI>5) in sediments. The PCA and HCA were also performed to find the relevant sources, trends and groups in trace metal contamination in their water. The hydrogeochemical profile of surface water (Piper's plot, Durov's diagram, Gibbs diagram and IBE) indicated that they are of mixed water type with most abundant facies being Na–Ca–Mg–Cl, Ca–Na–Mg–Cl and Ca–Na–Mg–Cl–HCO3. SI values showed ponds to be oversaturated with Ca–Mg based minerals and dissolution of halite, magnesite and anhydrite indicating high degree of rock water interaction and reverse cation exchange process dominating the water chemistry. However extensive mixing of pollutants and dissolution has caused the overall geochemical character of water to change. The overall study shows that urbanization may further increase the rate of anthropogenic activities overtime which could enhance trace metal accumulation in the ponds and pose a serious health risk.