Evaluation of mercury and physicochemical parameters in different depths of aquifer water of Thar coalfield, Pakistan

In the current study, mercury (Hg) and physicochemical parameters have been evaluated in aquifer water at different depths of Thar coal field. The water samples were collected from first aquifer (AQ₁), second aquifer (AQ₂), and third aquifer (AQ₃) at three depths, 50-60, 100-120, and 200-250 m, respectively. The results of aquifer water of three depths were interpreted by using different multivariate statistical techniques. Validation of desired method was checked by spiking standard addition method in studied aquifer water samples. The content of Hg in aquifer water samples was measured by cold vapor atomic absorption spectrometer (CV-AAS). These determined values illustrate that the levels of Hg were higher than WHO recommended values for drinking water. All physicochemical parameters were higher than WHO permissible limits for drinking water except pH and SO₄^2- in aquifer water. The positive correlation of Hg with other metals in aquifer water samples of AQ₁, AQ₂, and AQ₃ of Thar coalfield except HCO₃^- was observed which might be caused by geochemical minerals. The interpretation of determined values by the cluster technique point out the variations within the water quality parameter as well as sampling location of studied field. The aquifer water AQ₂ was more contaminated with Hg as compared to AQ₁ and AQ₃; it may be due to leaching of Hg from coal zone. The concentration of Hg in aquifer water obtained from different depths was found in the following decreasing order: AQ₂ < AQ₁ < AQ₃.