Assessment of seasonal variation in hydrochemical composition of groundwater in nangloi block of Delhi state

A study was carried out to assess the seasonal variation in hydrochemical composition of groundwater in Nangloi block of Delhi State during the year 2007–08. The groundwater samples were collected from same tube wells of randomly selected 20 villages in Nangloi block during both pre and post-monsoon seasons (May and October, 2007). Results indicated that quality of groundwater samples in terms of total soluble salts (EC_iw) was in the range of 0.84–7.86 and 0.79–5.75 dS m^−l in pre and post monsoon seasons, respectively. Based on the relative dominance of major cations and anions, the groundwater was classified as Na-Mg-Ca and CI-HCO₃-SO₄ type. Nitrate-nitrogen in groundwater samples during pre and post-monsoon season ranged from 1.5 to 18.8 mg L⁻¹ and 1.5 to 18.4 mg L⁻¹ with mean value of 6.63 and 6.54 mg L⁻¹ and fluoride concentration ranged from 0.24 to 5.12 mg L⁻¹ and 0.20 to 5.99 mg L⁻¹ with mean values of 2.37 and 2.34 mg L⁻¹ respectively.