6–14.7 mM), variable concentrations of Cl− (0.2–6.2 mM) and other major cations, Ca2+ (1.2–4.8 mM), Mg2+ (0.5–2.6 mM), Na+ (0.2–7.3 mM) and K+ (0.01–5.7 mM). The groundwater displayed low concentrations of SO42− (0.0–1.5 mM), PO43−(0–9.7 μM), NH3+ (0–2.8 μM), NO2− (0–0.2 μM) and negligible amounts of nitrate and sulfide below detection limits. A piper plot (Fig.

3) indicates that shallow groundwater of Nawalparasi is Ca-HCO3 dominant. Osimertinib research buy Anions are clearly dominated by HCO3−. Ca2+ dominated cations in the upper and lower region and a localized increase in Na+ was observed in the middle region. Bivariate plots of major ion ratios may help to identify the relative importance of processes such as silicate weathering, carbonate weathering and evaporite dissolution on the concentration of major cations and anions in groundwater (e.g. Mukherjee and Fryar, 2008). The Na normalized Ca versus HCO3− plot [after Gaillardet et al. (1999) and Mukherjee and Fryar (2008)] (Fig. 4a) suggests that the tubewell water samples range from being influenced by silicate weathering to carbonate dissolution. The ratio of Na normalized Mg:Ca [after Gaillardet et al. (1999) and Mukherjee and Fryar (2008)] (Fig. 4b) suggests that the source of Mg is mostly by carbonate dissolution and partly

by silicate weathering. A bivariate plot of Ca + Mg versus HCO3− [after Mukherjee and Fryar (2008)] (Fig. 4c) displays a broader scatter and suggests that the source of HCO3− is mostly carbonate dissolution or organic matter oxidation (Mukherjee and Fryar, 2008). Average (Ca + Mg)/HCO3− of tubewell water samples selleck chemicals llc MTMR9 of the upper region were found to be 0.48, middle region was 0.38 and the lower region was 0.50. The molar ratio of (Na + K) to Cl was greater than 1 for 59 tubewell water samples, which suggests silicate weathering is an important process

(Mukherjee and Fryar, 2008 and Stallard and Edmond, 1983), especially in the middle region. A bivariate plot of (Na + K)/Cl and Si suggests that these cations relative to Cl increase as Si becomes >250 μM (Fig. 4d), which is an indicator of significant silicate weathering (Mukherjee and Fryar, 2008). Si also generally increased along the flow-path of the aquifer (Fig. 5). Aqueous geochemistry is summarized in Table 1 and bivariate plots of AsTot and other species are shown in Fig. 6. The concentration of AsTot in the filtered water samples from tubewells in the upper region ranged from below detection limits (BDL) to 1.7 μM with an average of 0.5 μM. Eighteen groundwater samples exceeded the WHO limit in this region. The aqueous speciation of As is dominated by As(III). The concentration of Fe(aq) varied from BDL to as high as 121.6 μM with mean of 54.9 μM. Fe aqueous speciation is dominated by Fe2+ which varied from 0.0 to 121.6 μM with an average of 59.2 μM. Manganese concentrations are also high and varied from BDL to 45.5 μM with an average of 8.3 μM.