Amy M. Johnson

Global Biogeography and Quantitative Seasonal Dynamics of Gemmatimonadetes in Soil

ABSTRACT Bacteria belonging to phylum Gemmatimonadetes comprise approximately 2% of soil bacterial communities. However, little is known of their ecology due to a lack of cultured representation. Here we present evidence from biogeographical analyses and seasonal quantification of Gemmatimonadetes in soils, which suggests an adaptation to low soil moisture.

Effect of pH on surface characteristics of switchgrass-derived biochars produced by fast pyrolysis.

Surface properties of switchgrass-derived biochars produced at fast pyrolysis temperatures of 450, 600 and 800 °C were characterized at different solution pHs in order to determine the structural and chemical changes of artificially-weathered biochars when incorporated into soil. As biochars were acidified from pH 7 to 3, crystalline minerals dissolved slowly releasing nutrients; however, residual minerals were still detected in biochars produced at higher pyrolysis temperatures after pH treatment. Moreover, the amount of exchangeable bases and other inorganic compounds released from the biochars increased when pH decreased. As minerals dissolved from the biochars, total surface area and pore volume were found to increase. Surface functional groups and water vapor adsorption capacity at 0.8 P/Po also increased, whereas the potential CEC of biochars decreased due to the replacement of exchangeable sites by hydrogen ion. Therefore, during the aging process, it is predicted that soil-incorporated biochars will slowly release nutrients with changes in surface functionality and porosity, which are expected to enhance water holding capacity of soil and provide a beneficial habitat for microbial colonization.

Geotechnical Characterization of Steep Slopes on Reclaimed Mine Lands in East Tennessee

Over compaction of mine spoil after the Surface Mining Control and Reclamation Act of 1977 has led to reclaimed mine lands which will not grow economically viable native hardwood forests. This has been remedied by using the low compaction grading technique. This construction technique attempts to balance stability which utilizes compaction, and tree growth which needs a looser growing medium. The physical characteristics of reclaimed mine slopes using the low compaction grading technique were studied. Several methods to measure unit weight were examined including using a nuclear density gauge and two different replacement methods similar to the sand cone density test. Also, grain size distributions were calculated for the three areas studied. The in-situ angle of the material and the internal friction angle of the material were measured and used in a simple infinite slope analysis to determine slope stability. It was found that the unit weight reading were highly variable which is mainly due to the variable nature of the material. Also, it was found that there was no correlation between density and depth which suggests that the material had not been heavily compacted. Next, it was found that the low compaction grading technique provides a suitable tree root growth medium due to low unit weights and high void ratios. Lastly, it was found that the infinite slope analysis provided sufficient factor of safety values with an upper bound of 1.9. These values were acceptable because of the low cost and consequences of failure of a surface mine slope.