Universität zu Köln

Kalks, Fabian, Noren, Gabriel, Mueller, Carsten W., Helfrich, Mirjam, Rethemeyer, Janet ORCID: 0000-0001-6698-4186 and Don, Axel (2021). Geogenic organic carbon in terrestrial sediments and its contribution to total soil carbon. Soil, 7 (2). S. 347 - 363. GOTTINGEN: COPERNICUS GESELLSCHAFT MBH. ISSN 2199-398X

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Abstract

Geogenic organic carbon (GOC) from sedimentary rocks is an overlooked fraction in soils that has not yet been quantified but influences the composition, age, and stability of total organic carbon (OC) in soils. In this context, GOC is the OC in bedrock deposited during sedimentation. The contribution of GOC to total soil OC may vary, depending on the type of bedrock. However, no studies have been carried out to investigate the contribution of GOC derived from different terrestrial sedimentary rocks to soil OC contents. In order to fill this knowledge gap, 10m long sediment cores from three sites recovered from Pleistocene loess, Miocene sand, and Triassic Red Sandstone were analysed at 1m depth intervals, and the amount of GOC was calculated based on C-14 measurements. The C-14 ages of bulk sedimentary OC revealed that OC is comprised of both biogenic and geogenic components. The biogenic component relates to OC that entered the sediments from plant sources since soil development started. Assuming an average age for this biogenic component ranging from 1000-4000 years BP (before present), we calculated average amounts of GOC in the sediments starting at 1.5m depth, based on measured C-14 ages. The median amount of GOC in the sediments was then taken, and its proportion of soil mass (g GOC per kg(-1) fine soil) was calculated in the soil profile. All the sediments contained considerable amounts of GOC (median amounts of 0.10 g kg(-1) in Miocene sand, 0.27 g kg(-1) in Pleistocene loess, and 0.17 g kg(-1) in Red Sandstone) compared with subsoil OC contents (between 0.53 and 15.21 g kg(-1)). Long-term incubation experiments revealed that the GOC appeared comparatively stable against biodegradation. Its possible contribution to subsoil OC stocks (0.3-1.5m depth) ranged from 1% to 26% in soil developed in the Miocene sand, from 16% to 21% in the loess soil, and from 6% to 36% at the Red Sandstone site. Thus, GOC with no detectable C-14 content influenced the C-14 ages of subsoil OC and may partly explain the strong increase in C-14 ages observed in many subsoils. This could be particularly important in young soils on terrestrial sediments with comparatively low amounts of OC, where GOC can make a large contribution to total OC stocks.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Kalks, Fabian UNSPECIFIED UNSPECIFIED UNSPECIFIED Noren, Gabriel UNSPECIFIED UNSPECIFIED UNSPECIFIED Mueller, Carsten W. UNSPECIFIED UNSPECIFIED UNSPECIFIED Helfrich, Mirjam UNSPECIFIED UNSPECIFIED UNSPECIFIED Rethemeyer, Janet UNSPECIFIED orcid.org/0000-0001-6698-4186 UNSPECIFIED Don, Axel UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-587116
DOI:	10.5194/soil-7-347-2021
Journal or Publication Title:	Soil
Volume:	7
Number:	2
Page Range:	S. 347 - 363
Date:	2021
Publisher:	COPERNICUS GESELLSCHAFT MBH
Place of Publication:	GOTTINGEN
ISSN:	2199-398X
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language AGRICULTURAL SOILS; MINE SOILS; DEEP; MATTER; C-14; STABILITY; CLIMATE; LOESS; MINERALIZATION; RADIOCARBON Multiple languages Soil Science Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/58711