Tsunami and Environmental Pollution Hazards: A Note for the Restoration Process - Post-Tsunami Hazard: Reconstruction and Restoration - page 270

Fig. 17.9 Debris storage sites in lowlands along the coastline ( a ) shredded; ( b ) mixed; ( c ) wooden
and ( d ) composite (partially submerged). Miyagi Prefecture
important in areas along the coastline where toxic “hot spots” have been created.
Studies by Komai et al. ( 2013 ) on evaluation risk assessment undertaken in certain
areas of northern Miyagi and Iwate Prefectures showed that toxic substances
(mainly arsenic and lead) present in tsunami deposits pose a relatively high level of
risk requiring appropriate management before being stored or utilized.
Primary and secondary debris collecting sites (Fig. 17.9 ) can be considered as
toxic hot-spot sources of pollution as they lack ground lining. Moreover, shredders
and crushers in direct contact with the soil as well as howling trucks continuously
transporting debris from and through collecting sites are responsible for spreading
large amounts of dust and other contaminated particles in large areas.
Furthermore, as sea salt must be washed off of debris prior to incineration in
order to improve performance and reduce dioxin production, the practice increases
soil salinity; salt accumulates mainly in the cortex of wooden deposits, taking up to
80 cm of cumulative rainfall to remove almost 97-99 % of the salt (Nakanishi 2011 ).
It is important to highlight the fact that soil salination in tsunami-hit areas is
mainly due to its inundation of seawater rather than from salinated debris; this is
particularly conspicuous in certain areas along the Sendai plains in Miyagi where
deposited sea salt has been found to be as far as 15 cm below the tsunami-deposited
sediment (Chagué-Goff et al. 2012a ).
As soil types vary along Miyagi's coastline, i.e. Fluvic, Brown (Cambisols)
and Fulvic Andosols as well as Korosuko (Andosols), Red Yellow and Regosol
(Soil Science 2014 ; Yagi 2012 ; Kanno et al. 2010 ), the likelihood of pollutants
seeping deep into the soil also varies. The possibility of pollutants contaminating