Fungal Deterioration of Barrier Concrete used in Nuclear Waste Disposal

Abstract

Fungal biogeochemical activity over a long-term scale may have negative environmental consequences for the management of barrier materials used in nuclear waste disposal. Fungal deterioration of barrier concrete was studied in microcosms simulating a heterogeneous environment with an external source of nutrients for the fungi. Fungi successfully colonized barrier concrete, generally avoiding granite aggregates, and biochemically (by excretion of protons and ligands) and biomechanically deteriorated the concrete. Fungi dissolved the cement matrix leaching structural elements and accumulating them within the fungal biofilm and associated microenvironment. Oxalate-excreting Aspergillus niger formed abundant calcium oxalate crystals on the concrete and encrusting fungal hyphae.

Keywords:

• fungi
• concrete
• biodeterioration
• calcium
• silicon
• oxalate

ACKNOWLEDGMENTS

This study was partly funded by The Ukrainian Ministry of Extreme Situations. The authors gratefully acknowledge the help of Mr. Martin Kierans (Centre for High Resolution Imaging and Processing (CHIPs), College of Life Sciences, University of Dundee, UK) for assistance with scanning electron microscopy. We thank Prof. Nelli Zhdanova for the provision of Cladosporium cladosporioides strain 4 and Dr. Valentina Zakharchenko and Mrs. Lidiya Nakonechnaya for help with fungal identification (Zabolotny Institute of Microbiology and Virology, Kyiv, Ukraine). We are also very grateful to Dr. Laszlo Csetenyi (Concrete Technology Unit, Division of Civil Engineering, University of Dundee) for helpful discussions. SH acknowledges the support of the Scottish Executive Environment and Rural Affairs Department.