Heavy metal pollution indices estimation and principal component analysis to evaluate the groundwater quality for drinking purposes in coalfield region, India

Open-cast coal mining significantly influences groundwater chemistry day by day through contaminated leachate from overburden dumps. In order to examine this, the groundwater samples from the Korba Coalfield (KCF) region were collected to assess metal toxicity, locate potential sources, and derive metal indices. The concentrations of 10 heavy metals such as Al, Ba, Cd, Cr, Cu, Fe, Mn, Pb, Ni, and Zn were measured out of which few metals such as Al (5.71%), Mn (14.29%), Ni (11.43%), and Zn (2.86%) at a few sites exceeded the World Health Organization (WHO) and Bureau of Indian Standards (BIS) acceptable limits for drinking water. Thus, different methods such as HPI, HEI and MI were used to interpret the pollution index. The findings show that HPI (97.14%) and HEI (94.29%) values are low to medium, while MI (91.43%) is very pure to slightly affected, indicating groundwater are safe for drinking purposes. Furthermore, the scatter plot shows a moderate correlation between HPI and MI (R² = 0.81), whereas a poor correlation between HEI and MI (R² = 0.52), and between HPI and HEI (R² = 0.41), respectively. In addition, PCA generated four PCs (PC1, PC2, PC3, and PC4) with eigenvalues (> 1) of 2.57, 1.818, 1.326, and 1.206 accounting for 25.70%, 18.18%, 13.26%, and 12.06% of the overall variance. Therefore, around 40% of the metals loaded under PC1 and PC2 have a considerably large positive loading, whereas 20% of the large loadings have a significant negative loading (≥ 0.40), responsible for governing the concentration of metals in the groundwater in the examined area. PC3 and PC4, although large and positive loading by two variables each, were insignificant due to lower variance (13.26% and 12.06%). Overall, this current study demonstrates that the quality of groundwater is adequate for drinking uses, except few locations which have high metal concentrations. The variation in the concentration of heavy metals affects the human being as well as animals and causes a number of diseases.