Dynamic soil columns simulate Arctic redox biogeochemistry and carbon release during changes in water saturation.

Thawing Arctic permafrost can induce hydrologic change and alter redox conditions, shifting the balance of soil organic matter (SOM) decomposition. There remains uncertainty about how soil saturation and redox transitions impact dissolved and gas phase carbon fluxes, and efforts to link hydrobiogeochemical processes to ecosystem-scale models are limited. This study evaluates SOM decomposition of Arctic tundra soils using column experiments, water chemistry measurements, microbial community analysis, and a PFLOTRAN reactive transport model.

Indexing Permafrost Soil Organic Matter Degradation Using High-Resolution Mass Spectrometry.

Microbial degradation of soil organic matter (SOM) is a key process for terrestrial carbon cycling, although the molecular details of these transformations remain unclear. This study reports the application of ultrahigh resolution mass spectrometry to profile the molecular composition of SOM and its degradation during a simulated warming experiment. A soil sample, collected near Barrow, Alaska, USA, was subjected to a 40-day incubation under anoxic conditions and analyzed before and after the incubation to determine changes of SOM composition.

Stoichiometry and temperature sensitivity of methanogenesis and CO2 production from saturated polygonal tundra in Barrow, Alaska.

Arctic permafrost ecosystems store ~50% of global belowground carbon (C) that is vulnerable to increased microbial degradation with warmer active layer temperatures and thawing of the near surface permafrost. We used anoxic laboratory incubations to estimate anaerobic CO2 production and methanogenesis in active layer (organic and mineral soil horizons) and permafrost samples from center, ridge and trough positions of water-saturated low-centered polygon in Barrow Environmental Observatory, Barrow AK, USA. Methane (CH4 ) and CO2 production rates and concentrations were determined at -2, +4, or +8 °C for 60 day incubation period.

Soils reveal widespread manganese enrichment from industrial inputs.

It is well-known that metals are emitted to the air by human activities and subsequently deposited to the land surface; however, we have not adequately evaluated the geographic extent and ecosystem impacts of industrial metal loading to soils. Here, we demonstrate that atmospheric inputs have widely contaminated soils with Mn in industrialized regions. Soils record elemental fluxes impacting the Earth's surface and can be analyzed to quantify inputs and outputs during pedogenesis.