Seawater-leaching Testing for Arsenic and Heavy Metals in Tsunami Deposits Produced by the 2011 off the Pacific Coast of Tohoku Earthquake, Northeastern Japan

Tsunami deposits in Northeastern Japan produced by the 2011 off the Pacific coast of Tohoku Earthquake and tsunami contain relatively high concentrations of arsenic and heavy metals. Because the impacts of tsunamis on the distribution and behavior of arsenic and heavy metals should be considered carefully in surface soils and the underground environment after a major disaster, standards are needed for seawater leaching tests to identify arsenic and heavy metals in tsunami deposits. For that purpose, tsunami deposits from the 2011 off the Pacific coast of Tohoku Earthquake were sampled at Kesen-numa city, Minamisanriku town, Ishinomaki city, and Shiogama city in Miyagi Prefecture, Northeastern Japan. Seventeen inorganic elements including As and heavy metals (Li, Sc, V, Cr, Co, Ni, Cu, Zn, As, Rb, Sr, Mo, Cd, Cs, Ba, Pb, U) were measured in a solution leached from tsunami deposits with pure water, artificial seawater, and natural seawater using inductively coupled plasma-mass spectrometry (ICP-MS) and hydride generation-atomic absorption spectrometry (HG-AAS). In the leachate obtained using pure water, concentrations of As and heavy metals were quantified successfully with the ICP-MS method. Concentrations of V, Cr, Co, Ni, Cu, and Zn did not differ from background levels in artificial seawater and natural seawater. When measuring As in seawater leaching tests, HG-AAS is a useful method for performing high-sensitivity analyses. In particular, HG-AAS is superior to ICP-MS for detecting low As concentrations (less than 30 mu g/l) in a seawater leaching test.