Nutrient limitation and microbially mediated chemistry: studies using tuff211 inoculum obtained from the Exploratory Studies Facility, Yucca Mountain

摘要

Flow-through bioreactors are used to investigate the relationship between the211u001esupply (and limitation) of major nutrients required by microorganisms (C, N, P, 211u001eS) and effluent chemistry to obtain data that can be useful to develop models of 211u001emicrobially mediated aqueous chemistry. The bioreactors were inoculated with 211u001ecrushed tuff from Yucca Mountain. Six of the 14 bioreactor experiments currently 211u001ein operation have shown growth, which occurred in as few as 5 days and as much as 211u001ea few months after initiation of the experiment. All of the bioreactors 211u001eexhibiting growth contained glucose as a carbon source, but other nutritional 211u001ecomponents varied. Chemical signatures of each bioreactor were compared to each 211u001eother and selected results were compared to computer simulations of the 211u001eequivalent abiotic chemical reactions. At 21 C, the richest medium formulation 211u001eproduced a microbial community that lowered the effluent pH from 6.4 to as low as 211u001e3.9. The same medium formulation at 50 C produced no significant change in pH but 211u001ecaused a significant increase in Cl after a period of 200 days. Variations in 211u001econcentrations of other elements, some of which appear to be periodic (Ca, Mg, 211u001eetc.) also occur. Bioreactors fed with low C, N, P, S media showed growth, but 211u001ehad stabilized at lower cell densities. The room temperature bioreactor in this