Obidos 2014 - part 2

This data set summarizes the results of ramped oxidation (RPO) analyses of 11 different particulate organic carbon samples collected from the Amazon River main stem (at Óbidos) and the Tapajós River in April and July 2014, and from the Amazon River main stem (at Óbidos), the Solimões River and the Madeira River in June 2005. The samples were collected at various river depths from surface (~0 meters) to 54 meters. Most samples were freeze dried and analyzed untreated, while one sample (from Óbidos in July 2014) was further fumigated in hydrocholoric acid and rinse in Milli-Q water prior to analysis. These different sample dates, locations, depths and treatment types are specified in various headings and text within each file included in this data set. Further information about these samples may be accessed from another open repository Rosengard (2023), Bouchez et al. (2011, 2014) and Rosengard et al. (2024).

All .csv files ending with '_Tg' are thermogram data from 11 different sample analyses, which include released carbon dioxide (variable 'co2_scaled' in units of ppm) over a range of temperatures (variable 'temp' in units of °C). Sample information is included as text within these files. Note that the Madeira River sample analysis experienced a significant instrument error at temperatures above ~450°C; CO2 data above this temperature should be disregarded.

The .csv file titled 'RPO-EaSummary-9analyses' includes the activation energy (kJ/mol) probability density functions derived from 9 out of the 11 sample thermograms, using the "rampedpyrox" data analysis package (https://rampedpyrox.readthedocs.io/en/latest/walkthrough.html) (Hemingway 2016).

Finally, the .csv file titled 'RPO-GasFractionSummary-11analyses' sums data from fractions of CO2 gas released and collected in discrete temperature intervals during 11 different RPO analyses of the samples described above. For each RPO analysis, up to 5 gas samples with unique masses (µg) of carbon were collected and analyzed for δ13C (per mil) and radiocarbon (Fraction modern, Fm) isotope composition. This file includes isotope values "pre" and "post" a blank correction applied by the "rampedpyrox" data analysis package, as well as standard deviations ("std") for each value. In addition, the mean activation energies of biomolecules oxidized within each temperature interval are provided, derived from the "rampedpyrox" package. The % yield for each RPO analysis was computed as the sum of the µg carbon recovered from all gas fractions divided by the known mass of carbon originally allotted to analysis. Note that some gas fractions were "Lost" prior to analysis, as indicated. In such RPO analyses, no blank correction was possible for δ13C values of gas fractions associated with that sample.

References

Bouchez, Julien, F Métivier, M Lupker, Laurence Maurice, M Perez, J Gaillardet, and C France‐Lanord. (2011). Prediction of Depth‐integrated Fluxes of Suspended Sediment in the Amazon River: Particle Aggregation as a Complicating Factor. Hydrological Processes, 25 (5), 778–94.

Bouchez, Julien, Valier Galy, Robert G Hilton, Jérôme Gaillardet, Patricia Moreira-Turcq, Marcela Andrea Pérez, Christian France-Lanord, and Laurence Maurice. 2014. Source, Transport and Fluxes of Amazon River Particulate Organic Carbon: Insights from River Sediment Depth-Profiles, Geochimica et Cosmochimica Acta, 133, 280–98.

Hemingway, J. D. (2016). rampedpyrox: open-source tools for thermoanalytical data analysis. http://pypi.python.org/pypi/rampedpyrox [online; accessed 2024-08-08]

Rosengard, S. (2023). Obidos 2014 - part 1 (2.0). [Data set]. Zenodo. https://doi.org/10.5281/ZENODO.8392815

Rosengard, S. Z., Moura, J. M. S., Spencer, R. G. M., Johnson, C., McNichol, A., Steen, A. D., & Galy, V. (2024). Depth‐partitioning of particulate organic carbon composition in the rising and falling stages of the Amazon River. Geochemistry, Geophysics, Geosystems, 25(6), e2023GC011273.