Silver at an old mining camp, Cobalt, Ontario, Canada

Aueous Ag(I) in different sze f actions, <5 μm, <0.2 μm, and <10 kDa, was analyzed in a low dissolved organic carbon (DOC) and a high DOC environment. The sediment and tailings, contacting the water, were elevated in silver (10–100 mg/kg) from mining. The area is buffered at pH 6 to 8 by carbonate mineral gangue. Aqueous Ag(I) is present at nanogram per liter levels. Significant amounts of Ag are found in the colloidal (0.2 μm to 10 kDa) and are nondetectable (<0.3 ng/L) or a few nanograms per liter in the <10-kDa fraction. Acid-volatile sulfide (AVS) was found in most (oxic) water samples at the nanomolar level. Ag(I) does not accumulate in plants probably due to the strong binding of Ag(I–) with S(II–). One exception occurs for cattails, when the aqueous AVS concentration is less than the colloidal Ag(I) concentration.