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- Leaf wax biomarkers of a high-mountain lake area in western iberia—Implications for environmental reconstructionsPublication . Santos, Ricardo N.; Schefuß, Enno; Cordeiro, Lívia; Oliveira, Dulce; Hernández, Armand; Ramos, Alexandre M.; Rodrigues, TeresaLeaf wax n-alkane biomarkers are widely used to infer past vegetation dynamics and hydroclimate changes. The use of these compounds strongly relies on the characterization of modern plants. However, few studies have explored leaf waxes of modern plants and their application to reconstructing climate and environmental changes in the Iberian Peninsula, a region known for its high vulnerability to climate change. In this study, we characterize the distributions and compound-specific isotopic compositions of the leaf waxes of dominant plants in the vegetation cover, soil, and surface sediment of the Lake Peixao area, a high-mountain glacial lake in Serra da Estrela (central Portugal). Our results show that the modern oro-Mediterranean (subalpine) vegetation of the study area is dominated by C-3 grasses/herbs and shrubs that preferentially produce long-chain leaf waxes (& GE;C-27). The C-31 n-alkane display the overall highest concentration, produced by some grasses and shrubs, but especially Erica sp (heather), which is highlighted as a major source for the total n-alkane pool in the lake sediments. C-29 is the second-most abundant and the most equally produced n-alkane of the vegetation cover; C-25 and C-27 homologs are mainly associated with aquatic-related grasses/herbs, while C-33 and C-35 are particularly linked to cold-drought tolerant Juniperus sp. shrubs. Shrubs show higher but proportional values than grasses/herbs in the isotopic space, suggesting a directly proportional physiological adaptation of the two ecological forms to the prevailing climatic and environmental factors of the study area. C-29 is pointed as the most representative (or less plant-biased) leaf wax n-alkane in the lake sediments. Thus, delta D of C-29 n-alkane is interpreted as a robust terrestrial hydrological indicator (delta D-terr), which signal is believed to be strongly influenced by the mean air temperature and/or precipitation amount. Despite the sparse vegetation and small catchment area, the apparent hydrogen fractionation factor, determined from delta D-terr of the lake surface sediment, is in line with the modeled global mean values for the latitude of the study area. The different molecular and compound-specific signatures of the studied oro-Mediterranean species have the potential to support future interpretations of leaf wax biomarkers in the Iberian Peninsula.
- Sources and distribution of organic matter and polycyclic aromatic hydrocarbons in sediments of the southwestern Portuguese shelfPublication . Mil-Homens, Mário; Gonçalves, Sofia; Cortés, Alejandro; van Drooge, Barend L.; Stigter, Henko de; Grimalt, Joan O.; Cordeiro, Lívia; Santos, Miguel M.; Almeida, C. Marisa R.; Caetano, MiguelTotal organic carbon (Corg), total nitrogen (Ntot), Corg/Ntot, δ13Corg, δ15N, calcium carbonate (CaCO3), and grain size were analyzed in 70 surface samples and 19 short cores from the southwestern Portuguese shelf. Perylene and USEPA-16 PAHs were quantified in a subset of these samples. The findings suggest that organic matter derives from a mix of terrestrial and marine sources, outlined by Corg, Ntot, and isotopic signatures. Perylene combined with δ13Corg was used to identify the main PAH sources in these environments. Diagnostic perylene ratios revealed contributions from natural sources in the Tagus region and contaminated materials from the Sado Dredged Disposal Site, with additional perylene in Sines linked to atmospheric deposition of pyrogenic sources. A significant correlation between perylene and USEPA-16 PAHs indicates natural and anthropogenic inputs from the Tagus. This multiproxy approach—combining USEPA-16ΣPAHs, perylene, and δ13Corg—offers insights for assessing environmental risks and guiding marine environmental management according to the MSFD.