Geochemical and Statistical Analysis of Heavy Metals and Elements in Tsunami Deposits at Coastal Areas of Northeastern Japan

摘要

Huge amount of tsunami deposits remain after the large earthquake andrntsunami occurred on March 11, 2011. This event may bring arnpossibility of environmental pollutions, particularly in the environmentrnof soil and sediments around coastal areas of eastern Japan. Therefore arngeochemical survey and investigation for soil contamination risk wasrncarried out, to make clear the risk level caused by tsunami event and itsrndeposits. Samples of tsunami deposits were analyzed by means ofrnchemical and physical methods to accumulate the database forrnevaluating the environmental risk. Various kinds of tsunami depositsrnwere observed at the coastal areas, some of them are sandy sedimentsrnand others are muddy with much clay components. The result ofrnchemical analysis showed that some portions of deposits contain a littlernhigher content of arsenic and lead, however, almost are similarrncomponent compared with normal subsurface soils. In the analysis ofrnphysical properties of deposits, a series of database was developed forrnparticle distribution, soil and clay components, and content of organicrnmatters. An approach of statistical analysis of elements in tsunamirndeposits was conducted by using an original technic of sparse modeling,rnin which the discrimination between tsunami deposits and normalrnmarine stratums has been investigated.