Conclusions
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, which
have affected the near-shore portions of the seabed in the
Khao Lak coastal zones.
The PAHs spatial distribution could indicate the distance
at which the land-derived materials were transported offshore as a result of the tsunami backwash. The prominent feature
of surface sediments exported from the Pakarang Cape could
be observed. This evidence indicates that the tsunami backwash
plays an important role in transporting anthropogenic
PAHs to the nearby coastal area as far as approximately 25
kilometers from the shoreline. In addition, the results from
diagnostic PAH isomer ratios suggested that road paving asphalt,
originating from heavy erosion by the tsunami wave in
front of Pakarang Cape, was among the identified sources of
PAHs.
Moreover, 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. However, the temporal distribution is
needed to validate our innovative study in further work.
Acknowledgements. The study was financially supported by the
ThaiGerman Research Cooperation (NRCT-DFG), under the
project Tracing Tsunami Impacts on and offshore in the Andaman
Sea Region, TRIAS, Center of Excellence for Environmental
and Hazardous Waste Management (CE-EHWM) and the 90th
Anniversary of Chulalongkorn University Fund (Ratchadaphiseksomphot
Endowment Fund). The authors would like to thank the
Phuket Marine Biological Center (PMBC) for providing us with
RV CHAKRATONG TONGYAI and to Department of Marine
Science, Faculty of Science, Chulalongkorn University for providing
facility in this study. The authors also gratefully acknowledge
the constructive comments and corrections on the manuscript by
A. Limsakul. The authors gratefully acknowledge the anonymous
reviewers for their valuable comments and suggestions that greatly
improved this work