Chemical Changes of Minerals Trapped in the Lichen Trapelia involutai Implication for Lichen Effect on Mobility of Uranium and Toxic Metals

Abstract

To elucidate development of minerals trapped in a lichen, we examined the lichen Trapelia involuta growing directly on secondary uranyl minerals and U-enriched Fe oxide and hydroxide minerals. Sericite and other minerals in the underlying rock are trapped in the lichen T. involuta during its biological growth and chemically changed by lichen activities. The presence of chemically changed sericite accompanied by an Fe-bearing mineral in the lichen suggests thatdissolution of sericite is promoted mainly by polysaccharides excreted by the lichen. Oxalic acid or lichen acids absent in the medulla may not play an important role in the dissolution. Our results suggest that lichens on metal-rich rock surface affect the mobility of uranium and other toxic metals through dissolution followed by trap of minerals from the underlying rock. © 2014 Atomic Energy Society of Japan.