Impact of Weathering and Revegetation on Pedological Characteristics and Pollutant Dispersion Control at Coal Fly Ash Disposal Sites

Abstract

Fly ash (FA) as a product of coal combustion in thermal power plants is a hazardous material that is deposited in the immediate vicinity of power plants due to its low rate of utilisation. As a result, fertile agricultural land turns into fly-ash dumps, which disperse fine ash particles around the environment, and toxic materials and salts are leached into groundwater. Revegetating fly ash dumps has proven to be the best way to stabilise the ash both physically and chemically. However, the establishment of vegetation cover at such sites is severely hampered by the unfavourable physical and chemical properties of the unweathered ash, which contains high amounts of potentially toxic elements (PTEs). This chapter provides an overview and dis-cusses the most important issues related to the establishment of vegetation cover at FA disposal sites and the role of plants in stabilising pollutants and mitigating their negative effects as well as their role in soil formation processes. Natural vegetation plays an essential role due to its tolerance to numerous stress conditions caused by pollu-tion and its ability to accumulate PTEs. It has been established that the use of natural plants by means of auxiliary restoration of vegetation cover with the support of appropriate agro-nomic practices (integrated biotechnological approach) can effectively help control the spread of PTEs and support the phytoremedi-ation of this type of environment. The over-view has revealed that ash weathering and the development of vegetation have positive effects on the physical and chemical charac-teristics of wet FAs. Positive changes were manifested in the morphology and texture of ash, a decrease in alkalinity and salinity, the development of horizon A due to the accu-mulation of organic matter and an increase in organic carbon, nitrogen, phosphorus and adsorption capacity. These changes were most pronounced in the upper layer of the FA and are important indicators of the onset of soil formation processes. It is concluded that these processes and the time elapsed after the revegetation are the main driving factors. They are extremely important for the success-ful ecological reclamation of fly ash disposal sites and long-term environmental protection.