ELECTRON MICROSCOPY INVESTIGATIONS OF AN ARTIFICIAL SOIL AGGREGATE USED IN BOTANICAL AND AGRICULTURAL EXPERIMENTS

As urbanization increases globally, food production will need to be more efficient and spatially intense requiring the use of special aggregates to act as soils. Ideally these aggregates should be well characterized and reusable or have a persistent lifetime to support food production. An artificial aggregate that is widely used in botanical and agricultural research was studied to better understand the mineralogy and texture of the material to better support urban agriculture and food production research. Currently this aggregate type lacks detailed mineralogical characterization, including data from scanning electron microscopy and transmission electron microscopy, despite that this media has been used for decades by tradition. The extent and nature of variation of the media with respect to mineralogy and texture is not well known. Scanning electron microscopy and transmission electron microscopy can provide detailed information regarding the size, shape, and distribution of macropores, mesopores and nanopores as well as provide constraints on the nature and distribution of mineral and organic particles. Transmission electron microscopy was done using grain mounts of crushed suspensions and utilized a JEOL 2100 200 kV instrument. Scanning electron microscopy was done using carbon coated samples and a Zeiss VP 35 instrument. Phyllosilicates, amorphous silica as well as silicate and oxide minerals occur. Ongoing analysis includes detailed interpretation of images, electron diffraction and complex energy dispersive spectroscopy data. Anticipated Powder X-ray diffraction data will constraint the nature of illite, vermiculite, chlorite and expandable clay minerals as well as confirm identification made by electron microscopy. This investigation provides new constraints for detailed cation exchange, nutrient, washing, heat treatment and biological treatment of the artificial aggregate which may be explored for aggregate recycling or reuse in urban agriculture.