Arbuscular mycorrhizal fungi and exogenous glutathione mitigate coal fly ash (CFA)-induced phytotoxicity in CFA-contaminated soil

Abstract

Coal fly ash (CFA) makes a bulk of the coal combustion wastes generated from coal-fired power plants. There are several environmental mishaps due to coal ash spills around the world and in the United States. Management of CFA-polluted sites has proven inefficient resulting in soil infiltration, leaching, and phytotoxicity. This study assessed the mitigation strategies for CFA-induced phytotoxicity using biological [arbuscular mycorrhizal fungi (AMF)] and chemical [exogenous glutathione (GSH)] agents. Indices of phytotoxicity include seed germination, plant morphometrics, lipid peroxidation and genomic double-stranded DNA (dsDNA) in switchgrass plant (Panicum virgatum). Experiments include laboratory screening (0, 5, 10, 15 and 20% w/w CFA/soil) and greenhouse pot study (0, 7.5 and 15% w/w CFA/soil) culturing switchgrass plant in Armour silt loam soil co-applied with AMF (Rhizophagus clarus) and GSH. Experiments showed that CFA exposure caused a concentration-dependent increase in seed germination. 10% CFA increased seedling growth while 15 and 20% CFA decreased seedling growth and induced leaf chlorosis. Furthermore, CFA (7.5 and 15%) in the 90-d pot study significantly (p < 0.05) impaired plant growth, induced lipid peroxidation and reduced genomic dsDNA. However, the incorporation of AMF or GSH enhanced seed germination, plant growth, and/or genomic dsDNA, reduced lipid peroxidation and prevented leaf chlorosis in CFA-exposed switchgrass plant. This study demonstrates that AMF and GSH have the potential to mitigate CFA-induced phytotoxicity. These biological and chemical strategies could be further harnessed for efficient utilization of switchgrass plant in the phytoremediation of CFA contaminated soil environment while simultaneously limiting CFA-induced phytotoxicity.