MICROBIAL EFFECT ON WEATHERING OF APATITE MINERALS FOR PHOSPHORUS

The objective of this study is to isolate and observe microbial effects on the weathered surfaces of apatite. Microbial communities associated with soil environments (containing highly weathered minerals, and depleted in phosphorus) may “preferentially” alter the weathering rate of apatite minerals in comparison to other, non-phosphorus bearing minerals. Phosphorus is a necessary constituent for biological production, and is primarily found as an accessory mineral in many rock types, commonly in the form of fluorapatite [Ca5(PO4)3F]. Those effects are most likely to be exhibited as differences in volume and/or geometry of etch pits on mineral surfaces.

The effects microbes have had on the Earth’s stratigraphic record may be seriously under-estimated and/or mistakenly relegated to other processes. Additionally, understanding the processes by which microbes are able to separate phosphorus from phosphate-rich minerals, and the spatial relationships between microbial biofilms and the geometry of surface etchings, could be instrumental in developing technologies that could utilize microorganisms for bio-processing of phosphatic ores in an environmentally cleaner, faster, more cost efficient manner. Initial range finding experiments were performed, using quartz sand with apatite “seeds”, and packed into reactor cells equipped with a porous base. Reactor cells were then partially submerged in local groundwater, where capillary action kept apatite seeds in contact with groundwater. Initial experiments recorded change in apatite mass at time intervals of two, six, and twelve weeks. 75% of apatite seeds revealed a decrease in mass, while 25% indicates either no change, or an increase in mass. Increases in mass occurred only after six weeks, and amount to <0.37% of original mineral mass. Similar experiments are currently integrating biotic and abiotic controls. Environmental SEM analyses should indicate any relationships between mineral mass and biomass, or between the geometry of etching surfaces and the presence of microbial colonization or biofilms.