Methane and Dissolved Organic Matter in the Ground Ice Samples from Central Yamal: Implications to Biogeochemical Cycling and Greenhouse Gas Emission

Petr B Semenov,Irina D Streletskaya,Sergei A Malyshev,Boris G Vanshtein,Elizaveta V Shatrova,Anfisa A Pismeniuk,Marina O Leibman,Alexander I Kizyakov

doi:10.3390/geosciences10110450

Abstract

Permafrost thawing leads to mobilization of the vast carbon pool into modern biogeochemical cycling through the enhanced release of dissolved organic matter (DOM) and production of greenhouse gases (CO2 and CH4). In this work, we focus on the study of methane and DOM distribution and genesis in the ground ice samples of thermodenudational exposure in the Central Yamal (Russian Arctic). We propose that the liberation of the ice-trapped CH4 and generation of CO2 by DOM mineralization are the earliest factors of atmospheric greenhouse gases emission as a result of permafrost thawing. The observed enormously “light ” isotope signatures of methane (δ13C < −80‰, δD < −390‰) found in the tabular ground ice units significantly divergent in morphology and localization within the exposuremay be related to subzero (cryogenic) carbonate reduction a as significant factor of the local methane enrichment. DOM is mainly formed (>88%) by biochemically refractory humic acids. Distribution of the labile protein-like DOM reflects the specific features of carbon and nitrogen cycles in the tabular ground ice and ice wedge samples. Tabular ground ice units are shown to be a significant source of methane and high quality organic matter as well as dissolved inorganic nitrogen (DIN). Ice wedges express a high variation in DOM composition and lability.

Highlights

The ongoing climate change promotes the processes of cryogenicnature in the permafrost-affected landscapes [1]
Based on the published data, we propose that the liberation of the ground ice-trapped CH4 and generation of CO2 by aerobic respiration of the labile dissolved organic matter (DOM) are the processes providing the immediate emission of greenhouse gas (GHG)
Free gas content varied from 5.4 cm3 /kg (TGI sample #6) to 55.4 cm3 /kg at a mean value of 28.33 cm3 /kg (Table 2), indicating one order variation

Summary

Introduction

The ongoing climate change promotes the processes of cryogenicnature in the permafrost-affected landscapes [1]. The most important issue of the permafrost thawing is the mobilization of the vast carbon pool into modern biogeochemical cycling. Dissolved organic carbon (DOC) is the most mobile fraction of C transported by diffusion or advective fluxes of dissolved organic matter (DOM) species [4,5]. Permafrost-derived DOM contains low molecular weight substrates that have been enzymatically. Geosciences 2020, 10, 450 processed for biological consummation within the soil paleoenvironment before being physically locked by freezing. The accelerated turnover of the DOM-linked carbon pool is proposed to be responsible for a positive feedback loop of climate warming due to amplified greenhouse gas (GHG) generation

Methods

Results

Conclusion