Hydrogeochemical characteristics and risk evaluation of potential toxic elements in groundwater from Shanmughanadhi, Tamilnadu, India.

Hydrogeochemical and Health Risk Assessments of trace elements are integral to groundwater resource assessment, utilization, and human health. Investigation of groundwater chemistry and trace elemental impact on local inhabitants were attempted in Shanmuganadhi basin, Tamilnadu, India. About 60 groundwater samples were collected during the pre-monsoon period and analyzed for hydrochemical composition, including major and trace elements (Fe, Cr, Ni, Cu Pb, Mn, and As) to isolate chemical characteristics and human health risk assessment. Groundwater geochemistry is prejudiced by geochemical reactions uniting cation exchange, dissolution and precipitation, adsorption, and anthropogenic contributions. About thirty-two percent of groundwater samples recorded higher F-(>1.5 mg/L) than the prescribed limit suggests sources from rock weathering and silicate dissolution. Nitrates (>45.0 mg/L) suggest sources from agricultural influences. Water types indicate alkalis (Na+ + K+) dominating alkali earth (Ca2+ - Mg2+) and strong acids (Cl- and SO42-) looming weak acid (CO32- and HCO3-) irrespective of water samples. The geochemical stability diagram suggests precipitation of silica, carbonate, and magnesium and dissolution of sulphate minerals along the groundwater flow path. Significant correlation between major ions and trace elements (Pb, Mn, Ni, and Cu) suggests origin from rock weathering, human impacts, and cultivation practices. Non-carcinogenic human risk for trace elements was higher in children compared with adults via ingestion and dermal exposure. The carcinogenic result suggests that Cr in CHK (7.1 × 10-2) and HBG (4.3 × 10-2) have the most excellent chance of cancer risk. The environmental risk category attempted using Comprehensive risk factor (CRI) suggests Pb (3.2-CHK, 2.6-HBG) with potential cancer risk. The comprehensive evaluation index recommends environmental damage between mild to moderate, indicating continuous exposure of traceable elements might result in cancer cause to the inhabitants. The study suggests water quality seems to be prejudiced by various geological and anthropogenic causes and endorses counteractive measures and proper execution of existing laws to protect groundwater resources in the study area.

Chemical weathering and atmospheric carbon dioxide (CO2) consumption in Shanmuganadhi, South India: evidences from groundwater geochemistry.

Chemical weathering in a groundwater basin is a key to understanding global climate change for a long-term scale due to its association with carbon sequestration. The present study aims to characterize and to quantify silicate weathering rate (SWR), carbon dioxide consumption rate and carbonate weathering rate (CWR) in hard rock terrain aided by major ion chemistry. The proposed study area Shanmuganadhi is marked with superior rainfall, oscillating temperature and runoff with litho-units encompassing charnockite and hornblende-biotite gneiss. Groundwater samples (n = 60) were collected from diverse locations and analysed for major chemical constituents. Groundwater geochemistry seems to be influenced by geochemical reactions combining dissolution and precipitation of solids, cation exchange and adsorption along with minor contribution from anthropogenic activities. The SWR calculated for charnockite and hornblende-biotite gneiss was 3.07 tons km-2 year-1 and 5.12 tons km-2 year-1, respectively. The calculated CWR of charnockite and hornblende-biotite gneiss was 0.079 tons km-2 year-1 and 0.74 tons km-2 year-1, respectively. The calculated CO2 consumption rates via silicate weathering were 1.4 × 103 mol km-2 year-1 for charnockite and 5.8 × 103 mol km-2 year-1 for hornblende-biotite gneiss. Lithology, climate and relief were the key factors isolated to control weathering and CO2 consumption rates.