In this study, we attempted to use PAHs as a
chemical proxy to trace the transport of land-derived materials
caused by the tsunami backwash to better understand
how it may have affected the distribution of sedimentary
deposition throughout the seabed of Khao Lak coastal areas.
By analyzing the compositions of sedimentary PAHs
in combination with application of the multivariate descriptive
statistical techniques, PAHs were proven to be a promising
chemical proxy to indicate the tsunami backwash in the
study area. Their spatial distribution could indicate that the
tsunami backwash plays an important role in transporting anthropogenic
PAHs to the nearby coastal area as far as approximately
25 km from the shoreline. In addition, the results
from diagnostic PAH isomer ratios suggested that road
paving asphalt, originated from heavy erosion by the tsunami
wave in front of Pakarang Cape, was among the identified
sources of PAHs. Principle Component Analysis (PCA) results
provided 2 estimated land-derived sources of PAHs,
which were the road dust and oil burning sources. These
estimated signature sources clearly support our hypothesis
that PAHs were transported from the potential sources on
land and deposited into the near-shore seabed during tsunami
backwash.