The ecological impact of mineral exploitation in the Russian Arctic: A field-scale study of polycyclic aromatic hydrocarbons (PAHs) in permafrost-affected soils and lichens of the Yamal-Nenets autonomous region.

Forty soil and lichen samples and sixteen soil horizon samples were collected in the mining and surrounding areas of the Yamal-Nenets autonomous region (Russian Arctic). The positive matrix factorization (PMF) model was used for the source identification of PAHs. The results of the source identification showed that the mining activity was the major source of PAHs in the area, and that the mining influenced the surrounding natural area. The 5+6-ring PAHs were most abundant in the mining area. The lichen/soil (L/S) results showed that 2+3-ring and 4-ring PAHs could be transported by air and accumulated more in lichens than in the soil, while 5+6-ring PAHs accumulated more in the soil. Strong relationships between the quotient of soil/lichen (QSL) and Log KOA and Log PL and between the quotient of lichen/histic horizon soil and KOW were observed. In addition, hydrogeological conditions influenced the downward transport of PAHs. Particularly surprising is the discovery of the high levels of 5 + 6 rings in the permafrost table (the bottom of the active layer). One hypothesis is given that the global climate change may lead to further depth of active layer so that PAHs may migrate to the deeper permafrost. In the impact area of mining activities, the soil inventory for 5+6-ring PAHs was estimated at 0.14 ± 0.017 tons on average.

Organic matter properties of Fennoscandian ecosystems: Potential oxidation of northern environments under future change?

The oxidative ratio (OR) of an ecosystem, which reflects the ratio of O2:CO2 associated with ecosystem gas exchanges, is an important parameter in understanding the sink of CO2 represented by the terrestrial biosphere. There is a growing body of ecosystem-based approaches to understand OR; however, there are still a number of unknowns. This study addressed two gaps in our understanding of the oxidation of the terrestrial biosphere: (1) What is the oxidation state of Arctic ecosystems, and in particular permafrost soils? (2) Will coupled climate and land use change cause the terrestrial organic matter oxidation state to change? The study considered eight locations along a transect from southern Sweden to northern Norway and sampled different organic matter types (soil, litter, trees, and herbaceous vegetation) as well as different soil orders (Inceptisols, Spodosols, Histosols, and Gelisols). The study showed that although there was no difference between soil orders, there was a significant effect due to location with OR increasing from 1.03 at the southernmost location to 1.09 in the northernmost location; this increase is independent of soil order or type of organic matter. The pattern of post hoc differences in the OR with latitude suggests that the increase in OR is correlated with the northern limit of arable agriculture. The study suggests that the combined effects of climate and land use change could lead to a decrease in terrestrial organic matter OR and an increase in its oxidation state.

The soil carbon/nitrogen ratio and moisture affect microbial community structures in alkaline permafrost-affected soils with different vegetation types on the Tibetan plateau.

In the Tibetan permafrost region, vegetation types and soil properties have been affected by permafrost degradation, but little is known about the corresponding patterns of their soil microbial communities. Thus, we analyzed the effects of vegetation types and their covariant soil properties on bacterial and fungal community structure and membership and bacterial community-level physiological patterns. Pyrosequencing and Biolog EcoPlates were used to analyze 19 permafrost-affected soil samples from four principal vegetation types: swamp meadow (SM), meadow (M), steppe (S) and desert steppe (DS). Proteobacteria, Acidobacteria, Bacteroidetes and Actinobacteria dominated bacterial communities and the main fungal phyla were Ascomycota, Basidiomycota and Mucoromycotina. The ratios of Proteobacteria/Acidobacteria decreased in the order: SM>M>S>DS, whereas the Ascomycota/Basidiomycota ratios increased. The distributions of carbon and nitrogen cycling bacterial genera detected were related to soil properties. The bacterial communities in SM/M soils degraded amines/amino acids very rapidly, while polymers were degraded rapidly by S/DS communities. UniFrac analysis of bacterial communities detected differences among vegetation types. The fungal UniFrac community patterns of SM differed from the others. Redundancy analysis showed that the carbon/nitrogen ratio had the main effect on bacteria community structures and their diversity in alkaline soil, whereas soil moisture was mainly responsible for structuring fungal communities. Thus, microbial communities and their functioning are probably affected by soil environmental change in response to permafrost degradation.