Abstract:
Groundwater quality characterization revealed that the ion concentrations are in the order of HCO ; >C1->S0 24- >NO; (anions) and Na+>Ca2->K+>Mg2 (cations2) in the study area. The Piper classification indicated that most of the groundwater samples collected from the study area are Nat HCO3 type. Results of multivariate analysis (PCA) showed that salinity and nutrients are major contaminants in the study area. As the maximum observed C171-1C0; ratio is limited to 7.37 in the shallow groundwater, the present salinity is due to marine environment of coastal aquifer and present land use practices not from the seawater intrusion. Among nutrients, nitrates are high in groundwater (up to 421 mg/i) in the study area. The comparison between Nitrogen load from septic systems and its average groundwater quality (NO ; , PO 34- , EC and K+) indicated that the shallow groundwater nitrate contamination is influenced by septic system and unsewered conditions in the study area.
RISK-N model results indicated that the % of septic systems NO -N contribution into groundwater is mostly dependent on groundwater table condition and population density. The sensitivity analysis of RISK-N model indicated that intermediate vadose zone thickness, seepage from septic tank-soak pit systems, saturated zone denitrification rate, and average plot size are most influential factors in estimation of NO ; -N from septic systems. Results of the present study can be used effectively in addressing groundwater quality problems and in decision making for better groundwater quality management and public health.
