The data package encompasses field data of clastic and organic sediment, river width and flow velocities of six river transects along the Rio Bermejo, Argentina. The laboratory data entails long-chain n-alkanes and d2H and d13C values of organic matter (soil, deposited sediment, suspended sediment (published by Repasch et al., 2020), leaf litter, floating organic matter, and bedload organic matter from the Rio Bermejo catchment. It further contains the bedload organic matter and estimated bedload organic carbon fluxes of six river transects along the Rio Bermejo.
Fluvial transport of organic carbon from the terrestrial biosphere to the oceans is an important term in the global carbon cycle. Traditionally, the long-term burial flux of fluvial particulate organic carbon (POC) is estimated using river suspended sediment flux; however, organic carbon can also travel in river bedload as coarse particulate organic matter (POMBed). Estimates of fluvial POC export to the ocean are highly uncertain because few studies document POMbed sources, flux and evolution during long-distance fluvial transport from uplands to ocean basins. This knowledge gap limits our ability to determine the global terrestrial organic carbon burial flux. In this study we investigate the flux, sources and transformations of POMBed during fluvial transport over a ~1300 km long reach of the Rio Bermejo, Argentina, which has no tributary inputs. To constrain sourcing of POMBed, we analysed the composition and stable hydrogen and carbon isotope ratios (δ2H, δ13C) of plant wax biomarkers from POMBed at six locations along the Rio Bermejo, and compared this to samples of suspended sediment, soil, leaf litter and floating organic debris (POMfloat) from both the lowland and headwater river system. Across all samples, we found no discernible differences in n-alkane average chain length or nC29 δ13C, indicting a common origin for all sampled POMBed.
We define three potential POMBed sources: Coarse organic debris we sampled at distinct elevations in the catchment: floodplain leaf litter, headwater leaf litter, and headwater POMfloat. We aim to understand the mixing range of the widely spread POMBed. We determine the range of a possible POMBed mixing signal of the sources within the geochemical parameters, and in addition, determine potential missing POMBed sources, using a mixing-space model developed by (Smith et al., 2013).
Leaf litter and POMfloat nC29 δ2H values decrease with elevation, making it a useful proxy for POMBed source elevation. Biomarker δ2H values suggest that POMBed is a mix of distally-derived headwater and locally-recruited floodplain sources at all sampling locations. These results indicate that POMBed can be preserved during transport through lowland rivers for hundreds of kilometres. However, the POMBed flux decreases with increasing transport distance, suggesting mechanical comminution of these coarse organic particles, and progressive transfer into the suspended load. Our provisional estimates suggest that the carbon flux from POMBed comprises less than 1 percent of the suspended load POC flux in the Rio Bermejo. While this represents a small portion of the river POC flux, this coarse, high density material likely has a higher probability of deposition and burial in sedimentary basins, potentially allowing it to be more effective in long-term CO2 drawdown relative to fine suspended particles. Because the rate and ratio of POMBed transport versus comminution likely varies across tectonic and climatic settings, additional research is needed to determine the importance of POMBed in the global carbon cycle.
This data publication is supplementary to a study on the climatic controls on leaf wax hydrogen isotopes, by Gaviria-Lugo et al. (2023). The dataset contains hydrogen isotope ratios from leaf wax n-alkanes (δ2Hwax) taken from soils, river sediments and marine surface sediments along a climatic gradient from hyperarid to humid in Chile. In addition, for each sampling site the hydrogen isotope ratios from precipitation (δ2Hpre) from the grids produced by the Online Isotopes in Precipitation Calculator (OIPC) (Bowen and Revenaugh, 2003). Furthermore, for each sampling site we report mean annual data of precipitation, actual evapotranspiration, relative humidity, and soil moisture, all derived from TerraClimate (Abatzoglou et al., 2018). Also provide data of mean annual temperature and the annual average of maximum daily temperature derived from WorldClim (Fick and Hijmans, 2017). As a final climatic parameter, we also derived data of aridity index from the Consultative Group of the International Agricultural Research Consortium for Spatial Information (CGIARCSI) (Trabucco and Zomer, 2022). In addition to climatic variables, for each site we include land cover fractions of trees, shrubs, grasses, crops, and barren land. These land cover fractions were obtained from Collection 2 of the Copernicus Global Land Cover layers (Buchhorn et al., 2020) via Google Earth Engine.
For further comparison here we provide δ2Hwax compiled from 26 publications (see references) that reported both the n-C29 and n-C31 n-alkanes homologues from soils and lake sediments. For each sampling site of the global compilation, we provide δ2Hpre and the same climatic and land cover parameters as for the Chilean data (i.e., precipitation, actual evapotranspiration, relative humidity, soil moisture, aridity index, temperature, fraction of trees, fraction of grasses, etc.), using the same sources.
The data is provided here as one single .xlsx file containing 9 data sheets, but also as 9 individual .csv files, to be accessed using the file format of preference. Additionally, 5 supplementary figures that accompany the publication Gaviria-Lugo et al. (2023) are provided in one single .pdf file. The samples taken for this study were assigned International Geo Sample Numbers (IGSNs), which are included in the provided tables S4, S5 and S6.
Variations in the δ18O signals from lake sediments in the European Alps have been interpreted to reflect past temperature during the Late Glacial–Early Holocene transition due to the strong similarity with δ18O records from Greenland. However, past changes in evaporative enrichment could have played an important role, but were rarely considered yet. Therefore, we analyze δ2H on n-alkanes and δ18O on hemicellulose sugars from Late Glacial sediments (~15 ka cal. BP) from Bichlersee, Bavarian Alps (47.676007 N, 12.122035 E). With this, deuterium excess as a proxy for lake water evaporative enrichment is modelled based on coupling δ2H and δ18O.
The chronology for this dataset is based on 14C-dating of terrestrial macrofossils and charcoal. The dataset contains geochemical data including total organic carbon and calcium carbonate content and the compound-specific stable hydrogen and oxygen composition of n-alkanes and hemicellulose sugars, respectively. Based on this, deuterium excess as a proxy for evaporative enrichment of lake water is calculated after Hepp et al. (2015, doi:10.1016/j.jhydrol.2014.10.012). For additional paleoclimatic information see Prochnow et al. (in submission).
Neben speziellen mineraloelabbauenden Mikroorganismen wurden drei kommerzielle Mischungen und autochtone Organismen auf ihre Faehigkeit zum Oelabbau untersucht (Agrarplatten, Ruehrkolben, Fermenter). Es wurden hochsiedende Mineraloele herangezogen; die zur Herstellung von schwarzen Offsetdruckfarben dienen. Waehrend der Abbau von n-Alkanen sicher nachgewiesen werden konnte, wurden Oele aus der Druckfarbe nicht abgebaut. Da experimentelle Untersuchungen zur Bioverfuegbarkeit Transportphaenomene ausschliessen, ist die Ursache in der Zusammensetzung der Mineraloele zu suchen. Laboruntersuchungen zur Deinkbarkeit mineraloelhaltiger Zeitungsdrucke unter Einsatz von Mikroorganismen zeigen, dass eine Verbesserung des Weissgrades erreichbar ist.
Am Mikroorganismus Pseudomonas aeruginosa wird der Einfluss der Bioverfuegbarkeit auf den Abbau von n-Alkanen untersucht. Es werden gut und schwer abbaubare C14-markierte n-Alkane eingesetzt, wobei der Einfluss der von Pseudomonas produzierten Rhamnolipide (Biotenside) auf Bioverfuegbarkeit, Aufnahme und Metabolismus in die Experimente einbezogen wird.