A centennial record of anthropogenic impacts and extreme weather events in southwestern Taiwan: Evidence from sedimentary molecular markers in coastal margin

Highlights: • Historical reconstruction of human and natural disturbances in SW Taiwan. • Comparative analysis of PAHs and lignin to evaluate sources/processes. • Distinct timing of PAH maxima between western Pacific, Europe and North America. • Consistently low (Ad/Al)_v suggests quick transport of TOM by mountainous rivers. • Both PAHs and lignin point to turbidite flows driven by typhoon floods. - Abstract: A 100-year history of human and natural disturbances in southwestern Taiwan was reconstructed using a suite of molecular markers in four dated sediment cores from the upper slope region off the Gaoping River mouth. Trends in polycyclic aromatic hydrocarbons (PAHs) tracked Taiwan's industrialization/urbanization starting in the 1970s, and the enactment of environmental regulatory policies thereafter. The predominant pyrogenic sources include vehicular, smelter, and coal combustion but spatial differences are observed among sub-regions of the shelf. Profiles of lignin oxidation products (LOPs) point to a significant increase in terrestrial organic matter inputs driven by land development after the 1970s. Low lignin diagenetic signature ratios [(Ad/Al)_v] in all sediments suggest quick transport of fresh plant material from land to sea via mountainous rivers. Shifts in PAHs, LOPs, and radionuclides in recent sediments reveal the deposition of turbidites resulting from typhoon-induced floods. Multiproxy analysis illustrates the interplay between anthropogenic activities and natural processes