Pollution and noncarcinogenic health risk levels of nitrate and fluoride in groundwater of Ramanathapuram district, Tamil Nadu, India

Abstract

ABSTRACT Pollution level and noncarcinogenic health risks due to fluoride and nitrate in the groundwater samples from Ramanathapuram district during pre-monsoon (September 2016) were calculated. One hundred and fifty-two groundwater samples collected were analysed for various physicochemical parameters such as major cations (Ca2+, Mg2+, Na+, K+) and major anions (CO3 2-, HCO3 −, SO4 2-, Cl−, NO3 −, PO4 3-). The fluoride ion concentrations in the collected samples were measured using the fluoride ion-selective electrode. Noncarcinogenic risks were calculated based on fluoride and nitrate concentrations (fluoride – 0.02–1.00 and nitrate – 0.0–4.9). The calculated risk values exceed the United States Environmental Production Agency (USEPA) recommended value of 1. The habitants from the study area are under the health risk due to fluoride and nitrate. Water quality index (WQI) values of the analysed samples indicate that 52% poor, 14% very poor, and 4% unsuitable for drinking purposes. Piper plot shows that 58% of mixed Ca2+-Mg2+-Cl− and 16% of Na+-Cl− groundwater types are predominant in the study area. Gibbs plot reveals that 91% of the samples have rock-water interaction, and it is a principal process that controls the dissolution of minerals from the subsurface into groundwater. Statistical analysis (correlation analysis, factor analysis) reveals that the natural process (rock-water interaction, leaching of sediments) and anthropogenic activities (domestic sewage, untreated effluents from industries) are the reason for the high fluoride and nitrate concentration in the groundwater. High noncarcinogenic health risk places were marked in spatial distribution maps.