This study examined potential microbial impacts of cyanide contamination in an aquifer\naffected by ferrocyanide disposal from nuclear waste processing at the US Department of Energyâ??s\nHanford Site in south-eastern Washington State (USA). We examined bacterial productivity and\nmicrobial cell density in groundwater (GW) from wells with varying levels of recent and historical\ntotal cyanide concentrations. We used tritiated leucine (3H-Leu) uptake as a proxy for heterotrophic,\naerobic bacterial productivity in the GW, and we measured cell density via nucleic acid staining\nfollowed by epifluorescence microscopy. Bacterial productivity varied widely, both among wells\nthat had high historical and recent total cyanide (...)concentrations and among wells that had\nlow total ....values. Standing microbial biomass varied less, and was generally greater than that\nobserved in a similar study of uranium-contaminated hyporheic-zone groundwater at the Hanford\nSite. Our results showed no correlation between 3H-Leu uptake and recent or historical cyanide\nconcentrations in the wells, consistent with what is known about cyanide toxicity with respect to iron\nspeciation. However, additional sampling of the .... affected groundwater, both in space and time,\nwould be needed to confirm that the... contamination is not affecting the GW biota.
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