Hydrogeochemical characterization of fluoride rich groundwater of Wailpalli watershed, Nalgonda District, Andhra Pradesh, India

Abstract

The groundwater of Nalgonda district is well known for its very high fluoride content for the past five decades. Many researchers have contributed their scientific knowledge to unravel causes for fluoride enrichment of groundwater. In the present paper, an attempt has been made to relate the high fluoride content in the groundwater to hydrogeochemical characterization of the water in a fracture hard rock terrain--the Wailpally watershed. Groundwater samples collected from all the major geomorphic units in pre- and post-monsoon seasons were analyzed for its major ion constituents such as Ca(2+), Mg(2+), Na(+), K(+), CO3-, HCO3-, Cl(-), SO4(-2), NO3-, and F(-). The groundwaters in the watershed have the average fluoride content of 2.79 mg/l in pre-monsoon and 2.83 mg/l in post-monsoon. Fluoride concentration in groundwater does not show perceptible change neither with time nor in space. The ionic dominance pattern is in the order of Na(+) > Ca(2+) > Mg(2+) > K(-) among cations and HCO3- Cl(-) > SO4(-2) NO3- F(-) among anions in pre-monsoon. In post-monsoon, Mg replaces Ca(2+) and NO3- takes the place of SO4(-2). The Modified Piper diagram reflect that the water belong to Ca(+2)-Mg(+2)-HCO3- to Na(+)-HCO3- facies. Negative chloralkali indices in both the seasons prove that ion exchange between Na(+) and K(+) in aquatic solution took place with Ca(+2) and Mg(+2) of host rock. The interpretation of plots for different major ions and molar ratios suggest that weathering of silicate rocks and water-rock interaction is responsible for major ion chemistry of groundwater in Wailpally watershed. Chemical characteristics and evolution of this fluoride-contaminated groundwater is akin to normal waters of other hard rock terrain; hence, it can be concluded that aquifer material play an important role in the contribution of fluoride in to the accompanying water. High fluoride content in groundwater can be attributed to the continuous water-rock interaction during the process of percolation with fluoride-bearing country rocks under arid, low precipitation, and high evapotranspiration conditions.

Fluoride hazard and assessment of groundwater quality in the semi-arid Upper Panda River basin, Sonbhadra district, Uttar Pradesh, India

“…The relatively high concentration of HCO 3 -across the study area indicates that freshly recharged groundwater is present throughout the aquifer. The ionic dominance pattern for groundwater resembles that of leachable ions from the soils, suggesting a lithogenic origin of minerals in the groundwater (Reddy et al 2010, Raju et al 2011. The range and mean chemical compositions of four major hydrochemical facies are shown in Table 2.…”

“…7). The negative relationship between fluoride and Ca+Mg (Kundu et al 2001, Reddy et al 2010) may be due to prior precipitation of CaCO 3 from water and only limited incorporation of F -in the CaCO 3 structure, so that there is always a net balance of Fin solution. Semi-arid climatic conditions and low rainfall facilitate evapotranspiration, which leads to an increase in alkalinity of soil and groundwater.…”

“…Generally, the quality of groundwater depends on the composition of recharge water, the interaction between the water and the soil, the soilgas, the rock with which it comes into contact in the unsaturated zone, and the residence time and reactions that take place within the aquifer (Fetter 1994, Appelo andPostma 2005). Major ion chemistry analysis of groundwater provides the basis to investigate the weathering reactions in the basin (Jalali 2007, Reddy et al 2010, Raju et al 2011, Raju 2012. By understanding the different geochemical processes that are involved in the evolution of water species, the precise reasons for contamination may be traced, especially in geogenic cases, as the chemical parameters of water indicate the footprints of its chemical contributors and the absorption processes involved in its evolution.…”

“…Groundwater of similar chemical composition or ionic make-up, and within the same watershed or sub-basin, may have different fluoride concentrations. Reddy et al (2010) evaluated the geochemistry of groundwater in Wailpalli watershed, Andhra Pradesh, India, and concluded that aquifer material plays an important role in the contribution of fluoride to the accompanying groundwater. The excess fluoride content in groundwater, its ill effects on human physiology, and its source and origin in the subsurface have attracted the attention of wide spectrum of researchers (e.g.…”

Fluoride in Drinking Water: Health Effects and Remediation

“…In Kurmapalli watershed, rocks are enriched in fluoride from 460 to 1706 mg/kg (Mondal et al 2009). Co-precipitation and/or adsorption of fluoride by calcrete deposits in Wailapalli watershed had resulted in high fluoride in groundwater (Reddy et al 2010).…”