Identification of the geochemical processes in groundwater by factor analysis in hard rock aquifers of Madurai District, South India

A study was carried out in the Madurai district of Tamil Nadu, India to identify the hydrogeochemical processes using factor analysis as a predictive tool. It also focuses on characterizing the samples of these factors with respect to standard geochemical plots. In order to obtain a synoptic view of the statistics and the geochemical processes, a total of 53 groundwater samples are collected representing the entire district. The major ions were analyzed; the order of ion dominance are Ca2+ > Na+ > Mg2+ > K+ = Cl− > HCO− 3 > H4SiO− 4 > NO− 3 > SO2− 4 > P3− 4. The samples are classified according to three factors. Factor 1 shows strong positive loadings of Cl−, Ca2+, Mg2+, and NO− 3 with 36.98 % of the total variance (TV); factor 2 accounts for 13.72 % of TV with high loadings of Na+, K+, and HCO− 3; and factor 3 shows strong positive loadings of PO3− 4 and SO2− 4 with TV of 13.1 %. In the Piper plot, few samples fall in the mix region as evidenced by the mixing proportion of two samples using AQUACHEM software. The results suggest that different hydrogeochemical processes, like weathering, ion exchange processes, and anthropogenic activities (like sewage infiltration and agriculture), has predominant impact in the study area. Thus, the study highlights the factor analysis technique as a predictive and effective tool for groundwater evolution

Spatial and temporal variations of radon concentrations in groundwater of hard rock aquifers in Madurai district, India

Radon (222Rn) and other radionuclides in groundwater can lead to health problems if present in higher concentrations. A study was carried out in Madurai district of Tamilnadu by collecting groundwater samples for four different seasons and aims to identify the regions with higher 222Rn concentration along with their spatial and seasonal variations. 222Rn has been compared with field parameters, log pCO2, major ions and uranium to detect the factors responsible for the higher concentration in groundwater. The weathering process induces the release of higher uranium ions from the granitic terrain from the rock matrix which enhances the 222Rn levels in groundwater

A multivariate statistical approach to identify the spatio-temporal variation of geochemical process in a hard rock aquifer

A study has been carried out in crystalline hard rock aquifers of Madurai district, Tamil Nadu, to identify the spatial and temporal variations and to understand sources responsible for hydrogeochemical processes in the region. Totally, 216 samples were collected for four seasons [premonsoon (PRM), southwest monsoon (SWM), northeast monsoon (NWM), and postmonsoon (POM)]. The Na and K ions are attributed from weathering of feldspars in charnockite and fissile hornblende gneiss. The results also indicate that monsoon leaches the U ions in the groundwater and later it is reflected in the 222Rn levels also. The statistical relationship on the temporal data reflects the fact that Ca, Mg, Na, Cl, HCO3, and SO4 form the spinal species, which are the chief ions playing the significant role in the geochemistry of the region. The factor loadings of the temporal data reveal the fact that the predominant factor is anthropogenic process and followed by natural weathering and U dissolution. The spatial analysis of the temporal data reveals that weathering is prominent in the NW part and that of distribution of U and 222Rn along the NE part of the study area. This is also reflected in the cluster analysis, and it is understood that lithology, land use pattern, lineaments, and groundwater flow direction determine the spatial variation of these ions with respect to season

Hydrogeochemical Studies in and Around Kaveripakkam Block, Vellore District, Tamil Nadu

The region like Vellore has a higher density of population to be supported with water. Nearly greater than 50% of the day to day need of people in this Arakonam Taluk including domestic, industrial, agricultural and partly drinking purpose is made by the groundwater resources only. A study on hydrogeochemistry is done to understand the utilization of groundwater for various purposes. A total of 12 groundwater samples were from various parts of Kaveripakkam Block were collected and Physico-chemical parameters [pH, Electrical Conductivity (EC) and Total Dissolved Solid (TDS)], ions (Na, K, Cl, HCO3,Ca, Mg, SO4, PO4, H4SiO4) were analyzed to understand the suitability of groundwater for consumption, cultivation and household purpose and also to identify the hydrogeochemical processes.The Piper trilinear diagram and USSL diagram were also plotted which indicates CaHCO3 facies and shows high salinity hazard. Quality of groundwater has been measured to ensure its suitability for consumption and irrigation, based on WHO standards, US Salinity Laboratory (USSL), Sodium Absorption Ratio (SAR), Residual Sodium Carbonate (RSC), and Na%. The study implies that most of the groundwater samples are suitable for irrigation and drinking purposes. The study also identified that hydrogeochemistry of the region is mainly influenced by weathering processes

A study on variation in dissolved silica concentration in groundwater of hard rock aquifers in Southeast coast of India

Ground water of hard rock aquifers due to its lesser permeability results in the increased residence time, which leads to the higher concentration of ions. Hence in order to understand the hydro-geochemistry of the groundwater of a hard rock aquifer in India, 23 groundwater samples were collected from different locations of the study area and subjected to analysis of major cations and anions. The results of silica showed different range of concentration and was plotted in different groups. In order to understand the reason for this variation, different techniques like Thermodynamics, Statistics and GIS were adopted and it was inferred that the concentration was mainly governed by lithology and land use pattern of the study area

Occurrence of the radionuclides in groundwater of crystalline hard rock regions of central Tamil Nadu, India

A study was conducted to understand the occurrence of the radionuclides in groundwater of crystalline hard rock region. Samples were collected to analyze major cations, anions, U, 222 Rn and stable isotopes of oxygen, hydrogen. It was inferred that few samples have U and 222 Rn concentrations higher than the permissible limit of drinking water standard. High degree of weathering of granitic rocks and long contact time of groundwater with the aquifer matrix could be the reason for enhanced U and 222 Rn levels in groundwater. The association of U with SO4 also proves that there exists anthropogenic influence in groundwater composition

A study on the impact of weathering in groundwater chemistry of a hard rock aquifer

Hydrogeochemistry of groundwater in hard rock terrain are mainly governed by lithology and land use practices. A study area near Madurai region of central Tamil Nadu was selected with various litho-units and a hard rock sedimentary contact with an unconformity. Land use practices in these regions are also varied with lithology. The study was conducted by collecting 54 groundwater samples spatially covering the major litho-units. Collected samples were analyzed for electrical conductivity, pH, total dissolved solids (TDS), temperature, Ca, Mg, Na, K, Cl, HCO3, NO3, H4SiO4, PO4, and SO4. The results of the samples analyzed found to vary spatially. Dominance of ion shows that the alkalies are predominant and HCO3 is the dominant anion. Piper facies show that the samples are alkali-carbonate type indicating the predominance of weathering. Most of the parameters exceed the drinking water permissible limit. Standard plots and statistical analysis also indicate weathering as the major process governing the hydrogeochemistry of the groundwater in the region. Relative mobility of cations indicates that the rate of liberation of alkalies from the lithology is more prominent