Long-term increased lithium exposure in drinking water may be associated with a lower incidence of dementia in a nonlinear way; however, confounding from other factors associated with municipality of residence cannot be excluded.

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In the 12 km 2 catchment area of Syv creek, Denmark, moderate to high concentrations of nitrate (NO3-) occurred in the upper part of the oxidized zone (oxic-I), but dropped within the lower suboxic part (oxic-II), to below the detection limit in the unoxidized zone. Structural Fe 2+ in the clay minerals made up 10 to12% of the Fe in the oxidized zone and increased to approximately 50% in the unoxidized zone. Concurrent with changes in the distribution of structural Fe 2+ the clay mineral constituents changed. Vermiculite was typically found in the oxidized zone whereas chlorite was found in the unoxidized zone only. A conversion of illite and chlorite into vermiculite seems to take place. A significant correlation between NO 3 and the amount of reduced Fe 2 § in the suboxic (oxic-II) zone, indicates that primary structural Fe 2+ in the clay minerals is the reductant in a NO 3 reduction process.