Date of Graduation

1996

Document Type

Dissertation/Thesis

Abstract

Fly ash, a "waste" product from coal fired power plants, may show great potential for use as a topsoil substitute in revegetating extremely adverse minesites such as abandoned mine land (AML) and coal refuse due to improvements in chemical and physical properties. In the period 1989 to 1991, two separate studies examined the effects of fly ash used as a topsoil substitute on the physical properties of minesoils in northcentral West Virginia. One study, involving fly ash from three different power plant sources, examined effects on physical properties three years after plot establishment. The other study, which involved fly ash/wood waste applications on two sites with different slopes, examined erodibility and physical property changes over a three-year time period. Overall, results of the research showed fly ash to be superior to minesoil for most of the physical properties which affect plant growth Bulk density was much lower in fly ash than in minesoil. Likewise, total porosity was higher in fly ash. Incorporation of organic matter (sawdust) into fly ash resulted in even lower bulk density and higher total porosity than in pure fly ash. Fly ash had a higher proportion of pores in the mesopore (.0002-.03 mm) range and a lower proportion in the micropore ({dollar}<{dollar}0.0002 mm) range. As a result, water retention difference was two to three times higher in fly ash than in minesoil. Infiltration rate and saturated hydraulic conductivity were much lower in pure fly ash than in minesoil, but with incorporation of organic matter (sawdust) into the fly ash layer, this was reversed. The results also show that fly ash has some shortcomings. One is its initial lack of aggregation. This along with low particle density and silty texture made fly ash inherently more susceptable to erosion than minesoil. Initial erosion values were up to five times higher with fly ash than with minesoil. Use of mulching material was shown to effectively reduce fly ash erodibility by one-half. Fly ash erodibility was further reduced by establishment of vegetative ground cover. In conclusion, fly ash, when used as a topsoil substitute, has a number of advantages over conventional methods in land reclamation including greatly increased water holding capacity, greater total porosity, medium soil texture, and lower bulk density. All of these are very important factors affecting plant growth. Although fly ash can improve these physical properties, it also will require more careful planning and management practices due to its erosion potential.

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