A preliminary investigation of lithogenic and anthropogenic influence over fluoride ion chemistry in the groundwater of the southern coastal city, Tamilnadu, India S. Selvam Received: 1 March 2014 /Accepted: 25 January 2015 # Springer International Publishing Switzerland 2015 Abstract A total of 72 groundwater samples were col- lected from open wells and boreholes during pre- and post-monsoon periods in Tuticorin. Samples were ana- lyzed for physicochemical properties, major cations, and anions in the laboratory using the standard methods given by the American Public Health Association. The fluoride concentration was analyzed in the laboratory using Metrohm 861 advanced compact ion chromatog- raphy. The geographic information system-based spatial distribution map of different major elements has been prepared using ArcGIS 9.3. The fluoride concentration ranges between 0.16 mg/l and 4.8 mg/l during pre- monsoon and 0.2–3.2 mg/l during post-monsoon. Alka- line pH, low calcium concentrations, high groundwater temperatures, and semiarid climatic conditions of the study area may cause elevated fluoride concentrations in groundwater, by increasing the solubility of fluoride- bearing formations (fluoride). Linear trend analysis on seasonal and annual basis clearly depicted that fluoride pollution in the study area is increasing significantly. Fluoride concentrations showed positive correlations with those of Na + and HCO 3 - and negative correlations with Ca 2+ and Mg 2+ . The alkaline waters were saturated with calcite in spite of the low Ca 2+ concentrations. Northwestern parts of the study area are inherently enriched with fluorides threatening several ecosystems. The saturation index indicates that dissolution and precipitation contribute fluoride dissolution along with mixing apart from anthropogenic activities. Keywords Tuticorin . Ion chromatography . Anthropogenic . Linear trend analysis . Fluoride minerals . PRM and POM Introduction Groundwater is in demand for domestic, industrial, and agricultural purposes throughout the world as it is wide- ly distributed than surface water. More than 90 % of the coastal population depends on groundwater for their daily needs (Galagan and Vermillion 1957; Fejerskov and Kidd 2007; Selvam et al. 2010). Quality of ground- water is under constant threat due to natural processes as well as anthropogenic activities. Increasing population and rapid urbanization have led to several environmen- tal problems including groundwater pollution (Pradhan 2009; Manap et al. 2012; Selvam and Sivasubramanian 2012; Neshat et al. 2013; Antony Ravindran and Selvam 2014). The presence of different dangerous contami- nants like fluoride, arsenic, nitrate, sulfate, pesticides, and other heavy metals in groundwater has been report- ed from different parts of India (Liu et al. 2005; Mulligan et al. 2001; Mondal et al. 2010). The occur- rence of fluoride in groundwater has attracted attention globally since it has considerable impact on human health. Fluoride occurs naturally in soils and natural water due to chemical weathering of minerals contain- ing this element. Drinking water containing optimal Environ Monit Assess (2015) 187:106 DOI 10.1007/s10661-015-4326-8 S. Selvam (*) Department of Geology, V.O.Chidambaram College, Tuticorin 628008, India e-mail: geoselvam10@gmail.com