Application of Binary Diagnostic Ratios of Polycyclic Aromatic Hydrocarbons for Identification of Tsunami 2004 Backwash Sediments in Khao Lak, Thailand

Abstract

Identification of Tsunami deposits has long been a controversial issue among geologists. Although there are many identification criteria based on the sedimentary characteristics of unequivocal Tsunami deposits, the concept still remains ambiguous. Apart from relying on some conventional geological, sedimentological, and geoscientific records, geologists need some alternative “proxies” to identify the existence of Tsunami backwash in core sediments. Polycyclic aromatic hydrocarbons (PAHs) are a class of very stable organic molecules, which can usually be presented as complex mixtures of several hundred congeners; one can assume that the “Tsunami backwash deposits” possess different fingerprints of PAHs apart from those of “typical marine sediments.” In this study, three-dimensional plots of PAH binary ratios successfully identify the Tsunami backwash deposits in comparison with those of global marine sediments. The applications of binary ratios of PAHs coupled with HCA are the basis for developing site-specific Tsunami deposit identification criteria that can be applied in paleotsunami deposits investigations.

An application of aromatic compounds as alternative tracers of tsunami backwash deposits

“…All sampling sites were chosen on the basis of the data obtained from above mentioned hydro-acoustic mapping instruments ( Feldens et al., 2009 ). Surface marine deposits were obtained along the Khao Lak coastal area in order to chemically characterize the distributional pattern of 13 PAH congeners namely Phe, An, Fluo, Pyr, B[a]A, Chry, B[b]F, B[k]F, B[e]P, B[a]P, Ind, D[a,h]A, and B[g,h,i]P ( Pongpiachan, 2014 ; Tipmanee et al., 2012 ). In addition, the sediment sampling locations are clearly shown in Figure 1 .…”

“…21). Apart from several concerns associated with the reliability of applying diagnostic binary ratios of PAHs, previous studies have shown some promising results for characterizing tsunami backwash deposits ( Pongpiachan, 2014 ; Tipmanee et al., 2012 ). In this manuscript, eight diagnostic binary ratios namely, Fl/(Fl+Pyr), B[ e ]P/(B[ e ]P+B[ a ]P), B[ b,j,k ]F/B[ g,h,i ]P, Ind/B[ g,h,i ]P, B[ a ]P/B[ e ]P, B[ a ]A/Chry, B[ a ]P/B[ g,h,i ]P and Ind/(Ind+B[ g,h,i ]P), were employed as geochemical tracers to classify their potential origins of sediments collected at the 2004 tsunami affected coastal areas, where sampling positions were clearly described in Table 2 ( Tsapakis and Stephanou, 2005 ; Yunker and Macdonald, 2003 ).…”

“…Some distinctive features of tsunami deposits can be considered as several consequences of the processes of tsunami generation, propagation, and the sedimentary responses ( Dawson and Stewart, 2007 ). In spite of numerous efforts on characterizing sedimentary features of tsunami backwash deposits offshore and historic tsunami onshore by using geophysical records, there were only few studies using geochemical tracers such as water soluble ionic species, heavy metals and polycyclic aromatic hydrocarbons (PAHs) in order to investigate the tsunami evidences ( Goto et al., 2011 ; Irizuki et al., 2019 ; Pongpiachan et al., 2013a , Pongpiachan et al., 2013b , Pongpiachan et al., 2013c , Pongpiachan et al., 2013d , Pongpiachan et al., 2013e ; Pongpiachan, 2014 ; Prasath and Khan, 2008 ; Szczuciński et al., 2005 , 2007 ; Tipmanee et al., 2012 ; Watanabe et al., 2020 ). It was found that the 2011 Tohoku-oki tsunami deposits contained comparatively high contents of water-soluble chloride which can be applied as geochemical tracers for investigating historic tsunami ( Goto et al., 2011 ).…”

“…Some particular concerns with respect to the contaminations of polycyclic aromatic hydrocarbons (PAHs) and other chemical compounds in tsunami-inundated area were subsequently investigated in Phang Nga province, Thailand ( Pongpiachan et al., 2013a , b , c ; Pongpiachan, 2014 ; Prasath and Khan, 2008 ; Tipmanee et al., 2012 ). Twelve PAH congeners (i.e., phenanthrene (Phe), anthracene (An), fluoranthene (Fluo), pyrene (Pyr), benz[a]anthracene (B[a]A), chrysene (Chry), benzo[b]fluoranthene (B[b]F), benzo[k]fluoranthene (B[k]F), benzo[a]pyrene (B[a]P), indeno[1,2,3-cd]pyrene (Ind), dibenz[a,h]anthracene (D[a,h]A), and benzo[g,h,i]perylene (B[g,h]P) were comprehensively characterized in marine deposits at the 26 December 2004 Indian Ocean tsunami affected coastal area ( Pongpiachan et al., 2013a ).…”

Exploring Offshore Sediment Evidence of the 1755 CE Tsunami (Faro, Portugal): Implications for the Study of Outer Shelf Tsunami Deposits

“…Although it might be less likely to have significant sedimentary imprints of tsunamis in deeper offshore areas (i.e., mid to outer shelf) [5], the controversial differentiation between tsunami and storm deposits [11] can be neglected when studying sediments beneath the storm wave base [12]. Relatively few studies have focused on analyzing deeper offshore sedimentary records [2,3,8,[13][14][15][16][17][18][19][20][21][22]] and even fewer have involved possible historical/palaeotsunami deposits in such environments [2][3][4]13,17,[22][23][24][25][26].…”