Wood-degrading fungal origin of perylene in peatlands of southern Poland: A molecular and statistical approach

Abstract

Perylene is a polycyclic aromatic hydrocarbon (PAH) whose origin remains enigmatic. It has been thought to be derived from hydrocarbons, however much uncertainty remains over whether it is natural or anthropogenic. In this study, a comprehensive study of peat was conducted in the Osobłoga and Kłodnica River Valleys of southern Poland. Here, we show a significant advance in our understanding of the source of perylene using a detailed analysis of macro and minor elements along with its correlation with other PAHs and biogenic compounds. Based on principal component analysis (PCA), a negative correlation between perylene and combustion-derived PAHs was demonstrated, suggesting different origins for these compounds. Diagnostic ratios, such as %Pe/∑PAH and %Pe/∑PAI above 10 %, and a Py/Pe ratio below 9, indicate that the perylene present in these peat samples is of natural origin, formed from terrestrial organic matter. Furthermore, perylene is associated with a dominance of long-chain n-alkanes, which exhibit a strong odd-over-even preference, further supporting its biogenic source. The analysis revealed a weak correlation between total organic carbon (TOC) and perylene content, indicating that perylene concentration does not directly depend on the overall organic carbon content in peat. In contrast, a strong correlation was observed between perylene and wood-type biogenic compounds, specifically periderm (correlation coefficient of 0.2) and wood (correlation coefficient of 0.3). This finding suggests that perylene formation is closely linked to woody biomass. The Conifer Wood Degradation Index (CWDI) was calculated for samples containing conifer wood phytoclasts, providing insights into the degradation processes affecting these components and their relation to perylene formation. Further molecular and statistical studies on Vistulian and Holocene peats in our study also confirm the hypothesis of a natural, specifically fungal, origin of perylene. A comprehensive analysis of peat deposits, combined with advances in molecular and statistical techniques, continues to elucidate on the complex biogeochemical processes that contribute to the presence of perylene in natural environments.