Center for Environment and Energy Research and Studies (CEERS)
Abstract
The December 26, 2004 Indian Ocean tsunami was one of the largest in
human history, devastating the coastal wetlands of surrounding
countries. This study present the chemical analyses of tsunamigenic and
pre-tsunami sediments from Hikkaduwa and Hambantota lagoons in southern
Sri Lanka, to assess their geochemical composition, their source, and
subsequent environmental impacts. Principal component analysis of the
tsunami sediments shows that 42% of the total variance is accounted for
calcium oxide and Sr. That is, the tsunami deposits are rich in
biogenic phases derived from shallow marine sediments. High organic
matter contents of the tsunami sediments of up to 80 wt% also support
this interpretation. The association of chlorine (<9.4 wt%), brome
(<170 mg/kg), arsenic (<17 mg/kg), iron (III) oxide (<12.9
wt%) and sulfur (<7.6 wt%) accounts for 33% of the variance,
reflecting higher salinity. This further suggests that the sediments
were mainly derived from a marine environment, rather than from
non-marine sands and/or soils. Immobile element contents and relations
(thorium, scandium and zirconium) suggest that the tsunami sediment
source was mostly felsic in composition, with some mafic component, and
mixed with predominantly shallow marine shelf or slope sediments.
Additional compositional variations in the tsunami sediments in both
lagoons may be associated with variations of wave strength along the
coast and by the morphology of the continental shelf. Lower elemental
abundances in Hambantota lagoon sediments compared to Hikkaduwa
equivalents may thus reflect a greater non-marine component in the
former, and greater shelf sediment component in the latter