Arbuscular mycorrhizas amplify the risk of heavy metal transfer to human food chain from fly ash ameliorated agricultural soils

• Published in: Environmental pollution (1987) Vol. 329; p. 121733
• Main Authors: Goswami, Vikrant, Deepika, Sharma, Diwakar, Swati, Kothamasi, David
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15-07-2023
• Subjects: Agriculture; Arbuscular mycorrhiza; Barley; Coal Ash - analysis; Environmental Pollutants - analysis; Fly ash; Food Chain; Heavy metals; Human food chain; Humans; Lead - analysis; Metals, Heavy - analysis; Mycorrhizae - chemistry; Plant Roots - chemistry; Plants; Rhizophagus irregularis; Soil; Soil Pollutants - analysis; Barley; Fly ash; Arbuscular mycorrhiza; Heavy metals; Human food chain; Rhizophagus irregularis
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2023.121733

Soil contaminants threaten global food security by posing threats to food safety through food chain pollution. Fly ash is a potential agent of soil contamination that contains heavy metals and hazardous pollutants. However, being rich in macro- and micronutrients that have direct beneficial effects on plant growth, fly ash has been recommended as a low-cost soil ameliorant in agriculture in countries of the Global South. Arbuscular mycorrhizal fungi (AMF), ubiquitous in agricultural soils, enhance efficiency of plant nutrient uptake from soils but can equally increase uptake of toxic pollutants from fly ash ameliorated soils to edible crop tissues. We investigated AMF-mediated amplification of nutrient and heavy metal uptake from fly ash amended soils to shoots, roots and grains of barley. We used a microcosm-based experiment to analyse the impacts of fly ash amendments to soil in concentrations of 0 (control), 15, 30 or 50% respectively, on root colonization by AMF Rhizophagus irregularis and AMF-mediated transfer of N, P and heavy metals: Ni, Co, Pb and Cr to barley tissues. These concentrations of fly ash are equivalent to 0, 137, 275 and 458 t ha−1 respectively, in soil. Root AMF colonization correlated negatively with fly ash concentration and was not detected at 50% fly ash amendment. Shoots, roots and grains of mycorrhizal barley grown with 15, 30 and 50% fly ash amendments had significantly higher concentrations of Ni, Co, Pb and Cr compared to the control and their respective non-mycorrhizal counterparts. Presence of heavy metals in barley plants grown with fly ash amended soil and their increased AMF-mediated translocation to edible grains may significantly enhance the volume of heavy metals entering the human food chain. We recommend careful assessment of manipulation of agricultural soils with fly ash as heavy metal accumulation in agricultural soils and human tissues may cause irreversible damage.
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•Fly ash amelioration in soil and mycorrhiza increased yield and biomass of barley.•Fly ash addition to soil increased sensitivity of barley to mycorrhizal colonization.•Mycorrhizal enriching of heavy metals in barley grain amplifies risk of transfer to humans.•50% fly ash concentration in soil inhibited mycorrhizal colonization of barley root.