Raw palynomorph FTIR spectra under common extraction chemical treatments (HCl, KOH and acetolysis)
The sub-fossil spore and pollen samples were obtained from a 360 cm peat core (HM20), which was collected using a Russian corer from an ombrotrophic raised bog at Holcroft Moss, NW England (53°26'09.4"N, 2°28'31.4"W, 23 m.a.s.l.). Peat samples were taken at seven depth ranges (42-47 cm, 81-89 cm, 121-129 cm, 161-169 cm, 201-209 cm, 241-249 cm, and 281-289 cm, corresponding to D01 to D07 in this dataset). Before any acid and alkali treatment, all palynomorphs were washed by pyrophosphate (Na4P2O7) and centrifugated in sodium polytungstate (SPT).
For acid and alkali treatments, peat samples were placed in 50 mL centrifuge tubes with either 10% (v/v) hydrochloric acid (HCl) or 10% (w/v) potassium hydroxide (KOH) and placed in the water bath at 90ºC for treatment times of 5, 10, 30, 60, 120, and 210 minutes. For acetolysis, peat samples were firstly dehydrated in glacial acetic acid prior to addition of Erdtman (1960) acetolysis mixture (9 parts acetic anhydride and 1 part concentrated 18.4 M sulphuric acid). Samples were placed in a hot water bath at 90ºC for treatment times of 1, 3, 5,10, 30, 60, and 120 minutes. Immediately on removal from the water bath, the reaction was stopped by topping up the samples with glacial acetic acid. Following all treatments, samples were centrifuged and washed with type-1 deionised water (3 cycles). Different treatment times were chosen to cover a range of typical treatment applications, as well as to extend into much longer than typical treatment times. Control samples received only water washes.
Samples were analysed using a Perkin Elmer Spotlight 400 Fourier Transform Infrared (FTIR) Imaging System equipped with continuum IR microscope (using a Reflachromat 15× objective) and fitted with MCT-A liquid nitrogen-cooled detector. We used transmission mode with an aperture size of 30 μm × 30 μm for Alnus, and 40 μm × 40 μm for Calluna and Sphagnum. Both background and pollen/spore spectra were measured using 16 scans at a resolution of 4 cm-1 in the range between 4000 and 650 cm-1.
