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Retorted Oil Shale Effects on Soil Microbiological Characteristics¹

ABSTRACT

The effects of retorted oil shale additions on the microbiological characteristics of surface soils were investigated in a laboratory study to evaluate possible effects of mixing of soils and retorted shales which might occur as a part of revegetation programs in areas disturbed by oil shale processing. Soils were mixed with retorted oil shale at 5, 10, and 25% addition levels, and compared with normal soil and retorted shale over a 2.5-mo period, with evaluation of microbiological parameters carried out at 2-week intervals. With retorted shale present at up to 10% by weight, no negative effects on oxygen uptake or on actinomycete and bacterial populations were noted, while significant reductions of nitrogen fixation rates, as measured by acetylene reduction, and of dehydrogenase activity, fungal populations, radioactive glucose mineralization, and ATP concentrations occurred, with nitrogen fixation being most affected by shale material. These studies suggest that nonsymbiotic nitrogen fixation in surface soils may be especially sensitive to the presence of retorted oil shale. It would appear necessary to assure that sufficient surface soil is used to cover retorted oil shales to allow development and functioning of a diverse vegetation-microbiological community in such a way that physical mixing or movement of water-soluble retorted oil shale constituents into this surface soil layer would be minimized.

Key Words: nitrogen fixation • land reclamation • revegetation

¹ This research was supported by the Dep. of Energy under contract no. EY-76-S-02-4018, awarded to Colorado State Univ., Dep. of Range Science.

² Research Associate and Professor of Microbiology, respectively, Dep. of Microbiology, Colorado State Univ., Fort Collins, CO 80523.

Received for publication August 17, 1978.