title: Extraction of heavy metals characteristics of the 2011 Tohoku tsunami deposits using multiple classification analysis.
abstract: Tsunami deposits accumulated on the Tohoku coastal area in Japan due to the impact of the Tohoku-oki earthquake. In the study reported in this paper, we applied principal component analysis (PCA) and cluster analysis (CA) to determine the concentrations of heavy metals in tsunami deposits that had been diluted with water or digested using 1 M HCl. The results suggest that the environmental risk is relatively low, evidenced by the following geometric mean concentrations: Pb, 16 mg kg(-1) and 0.003 ml L(-1); As, 1.8 mg kg(-1) and 0.004 ml L(-1); and Cd, 0.17 mg kg(-1) and 0.0001 ml L(-1). CA was performed after outliers were excluded using PCA. The analysis grouped the concentrations of heavy metals for leaching in water and acid. For the acid case, the first cluster contained Ni, Fe, Cd, Cu, Al, Cr, Zn, and Mn; while the second contained Pb, Sb, As, and Mo. For water, the first cluster contained Ni, Fe, Al, and Cr; and the second cluster contained Mo, Sb, As, Cu, Zn, Pb, and Mn. Statistical analysis revealed that the typical toxic elements, As, Pb, and Cd have steady correlations for acid leaching but are relatively sparse for water leaching. Pb and As from the tsunami deposits seemed to reveal a kind of redox elution mechanism using 1 M HCl.
authors.affiliation: Graduate School of Environmental Sciences, Tohoku University, 6-6-20 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan. Electronic address: k-nakamura@mail.kankyo.tohoku.ac.jp.
authors.forename: Kengo
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: Department of Solid Earth Geochemistry, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka 237-0061, Japan.
authors.forename: Tatsu
authors.initials: T
authors.lastname: Kuwatani
authors.affiliation: National Institute of Advanced Industrial Science and Technology, Higashi1-1-1, Tsukuba, Ibaraki 305-8567, Japan.
authors.forename: Yoshishige
authors.initials: Y
authors.lastname: Kawabe
authors.affiliation: Graduate School of Environmental Sciences, Tohoku University, 6-6-20 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Komai
mesh_terms: D016000:Cluster Analysis; D004784:Environmental Monitoring / Q000379:methods*; D019015:Geologic Sediments / Q000737:chemistry*; D007564:Japan; D019216:Metals, Heavy / Q000032:analysis*; D025341:Principal Component Analysis; D057192:Tsunamis
chemical_list: D019216:Metals, Heavy
keywords: Cluster analysis; Heavy metal; Principal component analysis; Tohoku-oki Tsunami deposit