Stable Carbon and Nitrogen Isotopes in a Peat Profile Are Influenced by Early Stage Diagenesis and Changes in Atmospheric CO(2) and N Deposition.

Tomasz Goslar,Jos T. A. Verhoeven,André F. Lotter,Wolfram M. Kürschner,Alice J. Esmeijer-Liu

doi:10.1007/s11270-011-1001-8

Tomasz Goslar, Jos T. A. Verhoeven + Show 3 more

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https://doi.org/10.1007/s11270-011-1001-8

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Abstract

In this study, we test whether the δ13C and δ15N in a peat profile are, respectively, linked to the recent dilution of atmospheric δ13CO2 caused by increased fossil fuel combustion and changes in atmospheric δ15N deposition. We analysed bulk peat and Sphagnum fuscum branch C and N concentrations and bulk peat, S. fuscum branch and Andromeda polifolia leaf δ13C and δ15N from a 30-cm hummock-like peat profile from an Aapa mire in northern Finland. Statistically significant correlations were found between the dilution of atmospheric δ13CO2 and bulk peat δ13C, as well as between historically increasing wet N deposition and bulk peat δ15N. However, these correlations may be affected by early stage kinetic fractionation during decomposition and possibly other processes. We conclude that bulk peat stable carbon and nitrogen isotope ratios may reflect the dilution of atmospheric δ13CO2 and the changes in δ15N deposition, but probably also reflect the effects of early stage kinetic fractionation during diagenesis. This needs to be taken into account when interpreting palaeodata. There is a need for further studies of δ15N profiles in sufficiently old dated cores from sites with different rates of decomposition: These would facilitate more reliable separation of depositional δ15N from patterns caused by other processes.Electronic supplementary materialThe online version of this article (doi:10.1007/s11270-011-1001-8) contains supplementary material, which is available to authorized users.

Highlights

Increased human activity over the past two centuries has resulted in major environmental changes, including an exponential increase in atmospheric carbon dioxide (CO2) concentration, from 287 to 369 ppm between 1850 and 2000 (Friedli et al 1986; Keeling and Whorf 2005), largely caused by a higher rate of fossil fuel combustion (IPCC 2008)
The bulk peat C content is stable around 458 mg g−1 dry weight through the entire core (Fig. 2a)
The variations in N content result in the opposite pattern in the bulk peat C/N ratio (Fig. 2c)

Summary

Introduction

Increased human activity over the past two centuries has resulted in major environmental changes, including an exponential increase in atmospheric carbon dioxide (CO2) concentration, from 287 to 369 ppm between 1850 and 2000 (Friedli et al 1986; Keeling and Whorf 2005), largely caused by a higher rate of fossil fuel combustion (IPCC 2008) Another major environmental change was the dramatic increase in nitrogen (N) emission and deposition in Europe after approximately 1950 (Bleeker and Erisman 1996; de Ruiter et al 2006; Fowler et al 2004; Freyer et al 1996; Holland et al 1999; Pitcairn et al 1995; Planbureau voor de Leefomgeving 2008; Thomas et al 1988). These have led to an increase in wet deposition of nitrate (NO3−) and ammonium (NH4+), as well as dry deposition of gaseous nitric acid (HNO3), ammonia (NH3), NOx, and particulate NO3− (Asman et al 1998; Erisman et al 1998; Lawrence et al 2000)

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