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| - Mercury Speciation in Drainage fromthe New Idria Mercury Mine,California
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| - Little is known about the amount and form of mercuryreleased from inoperative mercury mines in the westernUnited States. To address this, we measured mercuryconcentrations and speciation in water impacted by theNew Idria mine. Total unfiltered mercury concentrations(UHgT) in acid mine drainage (AMD) (5.2 to 41 ng/L) werecomparable to concentrations upstream from the mine(4.2 to 13 ng/L). We measured substantially higher UHgTconcentrations (2900 to 12 400 ng/L) in water 1.2 kmdownstream from the AMD input and estimate that thecreek transports a baseline flux of 1.5 kg of Hg/yr from themine site. We hypothesize that tailings are the primarysource of mercury to this creek. We attribute the decreasein UHgT along a downstream transect to Hg(II) scavengingby iron oxyhydroxide particles that precipitate andsettle out of the water. Likewise, dissolved gaseousmercury concentrations decreased with increasing distancefrom the mine (2.8 ng/L at 1.2 km; 0.56 ng/L at 7.5 km).We regard abiotic atmospheric evasion as the primarymechanism driving this loss. The released mercury isbiologically available, evidenced by high (1.1 to 1.7 ng/L)unfiltered monomethylmercury concentrations downstreamfrom the mine. We attribute the relatively uniformdownstream monomethylmercury concentrations to abalance between microbial methylation and demethylation.
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