Hydrochemical characteristic of coastal aquifer from Tuticorin, Tamil Nadu, India.

This article deals with a systematic hydrochemical study carried out in coastal aquifers, Tuticorin, Tamil Nadu, to assess groundwater quality. A total of 29 groundwater samples were collected and analyzed. Results showed that total dissolved solids (TDS), sodium (Na+), magnesium (Mg2+), chloride (Cl-), and sulfate (SO₄²⁻) significantly damaged groundwater systems. The degree of salinization due to seawater mixing in a well or a given area could be indicated by an increase in nearly all major cations and anions. Toxic elements (i.e., Pb and As) were higher than the maximum permissible limits of drinking water. Cross plot of HCO₃⁻/Cl- (molar ratios) versus TDS indicated that about 62% of the analyzed samples were saline. Factor analysis showed that groundwaters, affected by seawater intrusion/industrial activity, were separated from the clusters. An attempt was made to identify the hydrochemical processes that accompany current intrusion of seawater using ionic changes. It was estimated that the mixing rate of seawater intrusion was about 5.81% during April 2007. An index, called 'Seawater Mixing Index' (SMI), was also adopted and its value was SMI>1.18 with EC>3,000 μS/cm about 62% of the sampled waters, were saline. Further, a few trace elements (i.e., Sr, B, and Li) were used as indicators for responding to the change in fresh to saline groundwater environments in coastal aquifers.