Potential of Microscopic Fungi Isolated from Mercury Contaminated Soils to Accumulate and Volatilize Mercury(II)

This article evaluates mercury-resistant autochthonous filamentous fungi's role in mercury transformation and mobility with respect to mercury biovolatilization. Aspergillus, Cladosporium, Trichoderma, and Alternaria genera isolated from mercury contaminated and non-contaminated soils were cultivated under static conditions in 8.2-32.7 mg L-1 mercury(II) concentration range to evaluate and compare mercury bioaccumulation, fungal strain resistance, and biovolatilization efficiency. Results indicate the enormous fungal capacity for mercury removal and volatilization, especially by Aspergillus niger and Cladosporium isolates, which volatilized almost 80 % of initial mercury content during 7-day static cultivation in the dark. We presume that the mercury detoxification mechanism changed above our 8.2 mg L-1 initial media concentration with significant domination of mercury volatilization. We suggest that mercury biovolatilization, rather than its deposition or efflux in non-volatile forms, is the major filamentous fungal detoxification mechanism. Our results highlight that the soil filamentous fungi's contribution on mercury biogeochemical cycle may be considered significant, if the conditions for fungal growth are sufficient. Still, when contaminated soil is treated with respect to enhanced fungal growth, biovolatilization may be beneficiary for natural remediation processes applied for mercury contaminated soils.