The use of plant-specific pyrolysis products as biomarkers in peat deposits

Abstract

a b s t r a c tPeatlands are archives of environmental change that can be driven by climate and human activity. Proxies for peatland vegetation composition provide records of (local) environmental conditions that can be linked to both autogenic and allogenic factors. Analytical pyrolysis offers a molecular fingerprint of peat, and thereby a suite of environmental proxies. Here we investigate analytical pyrolysis as a method for biomarker analysis. Pyrolysates of 48 peatland plant species were compared, comprising seventeen lichens, three Sphagnum species, four non-Sphagnum mosses, eleven graminoids (Cyperaceae, Juncaceae, Poaceae), five Ericaceae and six species from other families. This resulted in twenty-one potential biomarkers, including new markers for lichens (3-methoxy-5-methylphenol) and graminoids (ferulic acid methyl ester). The potential of the identified biomarkers to reconstruct vegetation composition is discussed according to their depth records in cores from six peatlands from boreal, temperate and tropical biomes. The occurrence of markers for Sphagnum, graminoids and lichens in all six studied peat deposits indicates that they persist in peat of thousands of years old, in different vegetation types and under different conditions. In order to facilitate the quantification of biomarkers from pyrolysates, typically expressed as proportion (%) of the total quantified pyrolysis products, an internal standard (5-aandrostane) was introduced. Depth records of the Sphagnum marker 4-isopropenylphenol from the upper 3 m of a Sphagnum-dominated peat, from samples analysed with and without internal standard showed a strong positive correlation (r 2 ¼ 0.72, P < 0.0005, n ¼ 12). This indicates that application of an internal standard is a reliable method to assess biomarker depth records, which enormously facilitates the use of analytical pyrolysis in biomarker research by avoiding quantification of a high number of products.

Biomarkers and inorganic proxies in the paleoenvironmental reconstruction of mires: The importance of landscape in Las Conchas (Asturias, Northern Spain)

“…Bacteria could therefore be the main source of alkan-2-ones, at least between 312 and 94 cm, as López-Días et al (2013b) inferred for the neighboring Roñanzas mire based on stable carbon isotope measurements of peat n-alkan-2-ones. Furthermore, although the contribution from H. cupressíforme moss to C 19 homolog to peat (Schellekens et al, 2015c) cannot be totally ruled out, in our view this was unlikely to occur as this species was not observed in Las Conchas. Moreover, OM appeared to be dominated by Sphagnum, as inferred from the n-alkane distribution.…”

“…Many taxa of fungi, which also produce alkan-2-ones via an abortive~oxidation sequence (Forney and Markovets, 1971), could be responsible for the predominance of C 19 . Recently, Schellekens et al (2015c) indicated that C 19 was the dominant homologue in the moss Hypnum cupressíforme, suggesting that non-Sphagnum moss could be the source of this compound.…”

Deterioration of the Hanson Logboat: chemical and imaging assessment with removal of polyethylene glycol conserving agent

“…Waterlogged environments often exhibit anaerobic conditions, retarding microbial and fungal decay of wood and enabling wooden objects to survive for thousands of years 14 . It is also noteworthy here that in highly decomposed peat, the presence of lignin reflects enhanced preservation of wood under water-logged conditions 15 . Such conditions do not always prevent deterioration of wood; biological or chemical modification can still occur 16 .…”

Molecular composition of plant parts and sediment organic matter in a Mediterranean seagrass (Posidonia oceanica) mat

“…The only PY-GC-MS product that could not be identified in any plant material but was present in all samples of the core was ferulic acid ME (0.03 ± 0.01%), which might originate from the rhizome (traces detected in milled-wood-lignin extracts; Klap et al 2000) or, alternatively, from graminoid debris (Schellekens et al 2015), which would imply a minor terrestrial source. In addition, a large discrepancy was found between the relatively high proportions of 4-hydroxy-2-methoxycinnamaldehyde in the mat samples (0.2 ± 0.1%) compared to the traces (0.006%) tentatively identified in the root sample.…”