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Scientific reports 11(1), 8947 (2021). doi:10.1038/s41598-021-88199-3, Published by Macmillan Publishers Limited, part of Springer Nature, [London]

Due to the high population density and sensitive infrastructures, coastal areas are highly vulnerable to various geohazards such as tsunamis. The impact of tsunamis is traceable in sedimentary archives providing an important tool for reconstructing these events. Here, geochemical and physical evidence of the resulting inundations have been discussed over the last years with increasing interest on identifying and using highly specific tsumanite indicators. To investigate a broader range of potential organic indicators, a multi-tiered geochemical analysis has been applied on tsunami deposit from Japan and Hawaii in this study with the aim to detect and quantify a more comprehensive set of suitable marker compounds. Both areas of investigation differed especially in terms of population and anthropogenic influence. The analyzed fractions of organic matter covered not only the low molecular weight compounds of the extractable and hydrolysable fraction (a part of the non-extractable fraction), but also the macromolecular matter. Three consecutive analytical approaches including extraction, alkaline hydrolysis and pyrolysis have been applied on the sedimentary organic matter to study their potential to contrast between tsunami and non-tsunami layers. The analyses of compound ratios as well as individual concentration profiles in tsunami and non-tsunami layers revealed two parameters, the TARFA (terrigenous to aquatic ratio of fatty acids) and the C29/C27 sterol ratio, which exhibit a high potential to act as tsunamite indicators. Further parameters (TARALK - terrigenous to aquatic ratio of n-alkanes, concentration profiles of long-chain n-aldehydes) showed a minor potential but are worth to be considered in organic geochemical analyses of tsunami affected sediment archives in the future.

While it is well recognized that the frequency and intensity of flood events are increasing worldwide, the environmental, economic, and societal consequences of remobilization and distribution of pollutants during flood events are not widely recognized. Loss of life, damage to infrastructure, and monetary cleanup costs associated with floods are important direct effects. However, there is a lack of attention towards the indirect effects of pollutants that are remobilized and redistributed during such catastrophic flood events, particularly considering the known toxic effects of substances present in flood-prone areas. The global examination of floods caused by a range of extreme events (e.g., heavy rainfall, tsunamis, extra- and tropical storms) and subsequent distribution of sediment-bound pollutants are needed to improve interdisciplinary investigations. Such examinations will aid in the remediation and management action plans necessary to tackle issues of environmental pollution from flooding. River basin-wide and coastal lowland action plans need to balance the opposing goals of flood retention, catchment conservation, and economical use of water.

s & presentations / EGU General Assembly 2020 European Geoscience Union General Assembly, EGU 2020, online, 4 May 2020 - 8 May 2020; G��ttingen : Copernicus Gesellschaft mbH EGU2020-8218, 1 Seite (2020). doi:10.5194/egusphere-egu2020-8218, Published by Copernicus Gesellschaft mbH, G��ttingen