constant ratio of [Na+] to [Cl-] at all five gauging points is consistent with NaCl as the primary source of Na+ in surface waters of the basin (Fig. 7.3D). Road salt, sewage effluent, and atmospheric deposition of sea salt are likely significant sources. Although dissolution of natural halite cannot be ruled out, the lack of identifiable surface deposits in the basin suggests that this source is relatively small. A scatter plot of [Mg2+] to [Ca2+] (Fig. 7.3E) suggests relatively uniform flux ratios of Mg2+ to Ca2+ carbonate weathering in much of the basin. Dissolved Si(OH)4, reported as

[SiO2], however, were similar at all four stations representing large discharges, indicating that, to the first approximation, chemical weathering of silicates was not significantly higher in the Mohawk system compared to the upper Hudson or tidal Hudson tributaries (Fig. 7.3F).

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