Polycyclic aromatic compounds in plants and peat in the peatlands of the European part of Russian Arctic

AIM: To investigate PAH accumulation in the peat of the swampy hollows in the series of European Arctic tundra sites and to evaluate the effect of PAH composition in the living plants on the peat PAHs in view of their deposition depth and geographic location. METHODS: The samples were analyzed by the reversed phase HPLC in a gradient mode and spectrofluorimetrical detection. The ASE-350 Accelerated Solvent Extractor system was used for complete extraction of PAHs from peat and plants. RESULTS: We determined PAH content in mire plants and peat from three biomes of the European part of the Russian Arctic: forest-tundra, southern tundra, and northern tundra. A correlation analysis allowed us to reveal similarity in the PAH accumulation in plants of the different biomes. A PCA analysis highlighted differences between PAH profiles in different biomes studied. We found significant correlations between the degree of peat decomposition, the share of herbaceous plant residuals in the peat layers, the share of lignin in peat, and the content of 5,6-ring PAHs in peat. The patterns of PAH distribution across the peat layers may be used as a natural model for studying PAH transformation and formation of new PAHs from high molecular weight precursors of plant origin like lignin. There is a correlation between PAHs in the plant peat-formers on the surface and in the peat. Additional PAHs are formed as lignin and other complex organics and are decomposed in the course of peat formation that is associated mostly with herbaceous plant residuals destruction. CONCLUSION: A total PAH accumulation in the peat is revealed to be decreasing and the PAH accumulation peaks—to be smoothed at the boundaries of the seasonally thawing layer and in the permafrost along the latitudinal gradient from south to north. In lower paleological peat horizons, it is explained by a botanical composition and historical period of peat-forming and in the upper peat layers, by a colder climate in the northern areas and changes in the fungal communities that decompose peat organic matter. The PAH composition is similar in terms of the dominant plant species at the peatlands of forest-tundra and northern tundra. We consider the data obtained on the PAH content in the plants to be applicable for other natural peatlands of the tundra and forest-tundra biomes.