Abstract
An attempt has been made to identify the chemical processes that control the hydrochemistry of groundwater in the coastal aquifers of Thiruvallur coastal village of Thiruvallur district, Tamil Nadu, south India. The parameters such as pH, EC, TDS and major ion concentrations of Na, K, Ca, Mg, Cl, HCO3, SO4 and NO3 of the groundwater were analyzed. Abundances of these ions are in the following order Na > Ca > Mg > K and HCO3 > Cl > SO4 > NO3. The dominant water types are in the order of NaCl> mixed CaMgCl > CaHCO3 > CaNaHCO3. Water types (mixed CaHCO3, mixed CaMgCl and NaCl) suggest that the mixing of high salinity water caused from surface contamination sources such as irrigation return flow, domestic wastewater and septic tank effluents with existing water followed by ion exchange reaction processes, silicate weathering and evaporation are responsible for the groundwater chemistry of the study area. The above statement is further supported by Gibbs plot where most of the samples fall within the evaporation zone.
Highlights
Hydrogeological and geochemical studies are the basis for scientific groundwater resource management
An attempt has been made to identify the chemical processes that control the hydrochemistry of groundwater in the coastal aquifers of Thiruvallur coastal village of Thiruvallur district, Tamil Nadu, south India
Water types suggest that the mixing of high salinity water caused from surface contamination sources such as irrigation return flow, domestic wastewater and septic tank effluents with existing water followed by ion exchange reaction processes, silicate weathering and evaporation are responsible for the groundwater chemistry of the study area
Summary
Hydrogeological and geochemical studies are the basis for scientific groundwater resource management. The geochemical properties of the groundwater depend on the chemistry of water in the recharge area as well as on the different geological processes that take place in the subsurface. Groundwater is the most important source for water supply in the coastal regions of Thiruvallur district. The study area is situated in the north of Chennai city The main geological formations occurring in the coast are comprising blocks such as Pulal, Sholavaram, Minjur, upper Gondwana consisting of sand and silts that are. The Cooum River, flowing across the southern part of the district, has its origin in the surplus waters of the Cooum tank in Tiruvallur Taluk and receives the surplus waters of a number of tanks It feeds the Chembarambakkam tank through a channel and drains into the Bay of Bengal. Fourteen groundwater samples were collected in the entire study area during the pre-monsoon of 2012 and postmonsoon period of 2013. The analytical precision for the measurements of ions was determined by calculating the ionic balance error that varied between 5 and 10 % (Domenico and Schwartz 1998)
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