Geochemical Survey of Tsunami Sediments and Transport of Toxic Elements from Offshore Environment: Urgent Investigation for Earthquake March 11, 2011

摘要

We have surveyed tsunami flooding areas from Aomori to Chibaprefecture to identify various kinds of geological and geochemicalevidences occurred by Tsunami disaster. As a result, it was found thattsunami sediments have layering structure of several hits in a couple ofhours. The lands are covered by almost sandy sediments with somelayers of silt and mud or clay minerals, which have relatively highercontent of organic substances and sulfur. Soils and sediments originatedfrom tsunami contain relatively higher concentration of arsenic andlead elements, compared with natural background. This suggests thatthe sediments were transported from offshore marine mud withanaerobic environment. In some cases, risk mitigation will be necessaryfor safe land utilization.