Technical Comment: No biochemical evidence for enhanced UV-B radiation at the End Permian Mass Extinction

R code and supporting data for the Technical Comment related to the paper by Liu et al. (2023, https://www.science.org/doi/10.1126/sciadv.abo6102).

Unzip the data_directory to get the sub-fossil Pinus pollen FTIR spectra (from Muthreich 2021). A transcribed version of the sample depth table (SI5 from Liu et al. (2023) is also provided to allow for matching of samples and depths in the FTIR spectra.

Go to Liu et al. (2023) and download the data files from the supplementary materials, and move these to the same data directory.

Go to Brużdziak 2019 (Supporting Information 2) and save as an .xlsx file in the data directory to obtain the water vapour spectra.

The Renv lock file is also provided.

Information about sample collection from Muthreich 2021

The FTIR microspectroscopy transmittance spectra were measured using a Hyperion 3000 iinfrared microscope coupled to the Vertex 70 FTIR spectrometer (both Bruker Optik, Germany), equipped with a globar mid-IR source, a liquid nitrogen-cooled mercury cadmium telluride 128 x 128 focal plane array detector system, x15 objective, and a computercontrolled x/y/z stage. The samples were deposited onto a 1 mm thick and 25 mm diameter IR transparent ZnSe window. The spectra were recorded with a total of 64 scans in the 3845–900 cm^-1 spectral range, with a spectral resolution of 8 cm-1, digital spacing of 3.8522 cm^-1, 2x2 binning, and Blackman-Harris 3-term apodization function. Background spectra were recorded by measuring a sample-free area of ZnSe microscope slide. The OPUS software (Bruker Optik GmbH, Germany) was used for data acquisition and instrument control. The Pinus pollen grains were extracted from a sediment core from Dalmutladdo, Northern Norway (see Bjune et al. 2004 https://doi.org/10.1111/j.1502-3885.2004.tb01142.x) at 20 cm depth following density separation using sodium polytungstate and then washed three times in water before being prepared for microscopy.

References:

P. Brużdziak, Vapor correction of FTIR spectra–a simple automatic least squares approach. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 223, 117373 (2019).

F. Muthreich, New methods in palaeopalynology: Classification of pollen through pollen chemistry (University of Bergen, 2021; https://bora.uib.no/bora-xmlui/bitstream/handle/11250/2825563/drthesis_2021_muthreich.pdf?sequence=2&isAllowed=y).

F. Liu, H. Peng, J. E. A. Marshall, B. H. Lomax, B. Bomfleur, M. S. Kent, W. T. Fraser, P. E. Jardine, Dying in the sun: Direct evidence for elevated UV-b radiation at the end-permian mass extinction. Science Advances. 9, eabo6102 (2023).