Evaluation of interactions between soil and coal fly ash leachates using column percolation tests

Area of Science:

• Environmental Science
• Geochemistry
• Ecotoxicology

Background:

• Fly ash, a byproduct of coal combustion, requires careful disposal to mitigate environmental risks.
• Understanding the leaching behavior and ecotoxicity of different fly ash types is crucial for sustainable waste management.

Purpose of the Study:

• To evaluate the environmental impact of coal fly ash (CFA) and lignite fly ash (LFA) during disposal.
• To investigate the influence of soil infiltration on metal release and ecotoxicity of fly ash leachates.

Main Methods:

• Single column and series column percolation tests were conducted using CFA and LFA.
• Physicochemical analyses and bioassays (using Daphnia magna and Vibrio fischeri) assessed metal release (Ba, Cr, Cu, Mo, Se, Zn) and ecotoxicity.
• Modified NEN 7343 protocol was employed for the fly ash/soil experiments.

Main Results:

• Soil infiltration significantly altered the leaching profiles of both CFA and LFA.
• Dynamic leaching conditions and leachate pH influenced the transport of copper (Cu) and zinc (Zn).
• The release and bioavailability of chromium (Cr), Cu, and Zn were modified during infiltration, with organism response not always correlating with metal concentrations.

Conclusions:

• The disposal and handling of fly ash warrant careful consideration due to altered metal leaching and ecotoxicity upon soil interaction.
• Environmental risks associated with fly ash require further investigation, particularly concerning metal bioavailability and ecotoxicological effects.