Abstract
The chemical and physical forms of mercury compounds accumulated in the cell wall of the liverwort, Jungermannia vulcanicola Steph. and Scapania undulata (L.) Dum. in an acid (pH 4.2-4.7) stream, Kashiranashigawa Japan were studied employing high-resolution electron microscopy with X-ray microanalysis. The accumulation rates of mercury in both liverworts were studied in the stream by a transplanting technique and by energy-dispersive X-ray fluorescence spectrometry. High-resolution transmission electron microscopy revealed the distribution of single crystalline particles with a diameter of 5-15 nm and polycrystalline particles with a diameter of 10-200 nm in the cell wall of J. vulcanicola and S. undulata. Electron micro-diffraction measurements of the crystals showed the diffraction pattern of mercury sulfide (cubic metacinnabar, HgS, black) which is insoluble in water and nontoxic to organisms. The accumulation rate of mercury from water by both liverworts, obtained by transplanting the shoots from the midstream and downstream site to an upstream site in which mercury levels were about 0.6 microgram/L water, was about 300-1000 microgram/g/month. (Author 's abstract)