scholarly journals Geogenic organic carbon in terrestrial sediments and its contribution to total soil carbon

SOIL ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 347-362
Author(s):  
Fabian Kalks ◽  
Gabriel Noren ◽  
Carsten W. Mueller ◽  
Mirjam Helfrich ◽  
Janet Rethemeyer ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Sediment Cores ◽  
Sedimentary Rocks ◽  
Loess Soil ◽  
Soil Mass ◽  
Strong Increase ◽  
Large Contribution ◽  
Red Sandstone ◽  
Total Soil ◽  
Terrestrial Sediments

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, 10 m long sediment cores from three sites recovered from Pleistocene loess, Miocene sand, and Triassic Red Sandstone were analysed at 1 m depth intervals, and the amount of GOC was calculated based on 14C measurements. The 14C 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 1.5 m depth, based on measured 14C 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 (0.3–1.5 m 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 14C content influenced the 14C ages of subsoil OC and may partly explain the strong increase in 14C 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.

scholarly journals Geogenic organic carbon in terrestrial sediments and its contribution to total soil carbon

2020 ◽  
Author(s):  
Fabian Kalks ◽  
Gabriel Noren ◽  
Carsten Mueller ◽  
Mirjam Helfrich ◽  
Janet Rethemeyer ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Sediment Cores ◽  
Sedimentary Rocks ◽  
Loess Soil ◽  
Red Sandstone ◽  
Total Soil ◽  
Incubation Experiments ◽  
Terrestrial Sediments ◽  
Plant Sources

Abstract. Geogenic organic carbon (GOC) from sedimentary rocks is an overlooked fraction in soils that has not been quantified yet, influencing the composition, age and stability of total organic carbon (OC) in soils. In this context GOC is referred to as the OC in bedrocks deposited during sedimentation. However, the contribution of GOC to total soil OC varies with the type of bedrock. So far studies investigating the contribution of GOC derived from different terrestrial sedimentary rocks to soil OC contents are missing. In order to fill this gap, we analysed 10 m long sediment cores at three sites recovered from Pleistocene Loess, Miocene Sand and Triassic Red Sandstone and calculated the amount of GOC based on 14C measurements. 14C ages of bulk sedimentary OC revealed that OC represents a mixture of biogenic and geogenic components. Biogenic refers to OC that entered the sediments recently from plant sources. All sediments contain considerable amounts of GOC (median amounts of 0.10 g kg−1 at the Miocene Sand, 0.27 g kg−1 at the Pleistocene Loess and 0.17 at Red Sandstone) in comparison to subsoil OC contents (between 0.53–15.21 g kg−1). Long-term incubation experiments revealed that this GOC seemed to be comparatively stable against biodegradation. Its possible contribution to subsoil OC stocks (0.3–1.5 m depth) is ~ 2.5 % in soil developed in the Miocene Sand, ~ 8 % in the Loess soil and ~ 12 % at the Red Sandstone site. Thus GOC having no detectable 14C contents influences 14C ages of subsoil OC and thus may partly explain the strong 14C ages increase observed in many subsoils. This is particularly important in soils on terrestrial sediments with comparatively low amounts of OC, where GOC can considerably contribute to total OC stocks.

scholarly journals Supplementary material to "Geogenic organic carbon in terrestrial sediments and its contribution to total soil carbon"

2020 ◽  
Author(s):  
Fabian Kalks ◽  
Gabriel Noren ◽  
Carsten Mueller ◽  
Mirjam Helfrich ◽  
Janet Rethemeyer ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Carbon ◽  
Total Soil ◽  
Terrestrial Sediments ◽  
Supplementary Material

scholarly journals Late Quaternary paleoenvironment of the Ross Sea continental shelf, Antarctica

1998 ◽  
Vol 27 ◽  
pp. 275-280 ◽  
Author(s):  
Akira Nishimura ◽  
Toru Nakasone ◽  
Chikara Hiramatsu ◽  
Manabu Tanahashi
Keyword(s):  
Organic Carbon ◽  
Marine Environment ◽  
Environmental Changes ◽  
Ross Sea ◽  
Late Quaternary ◽  
Sedimentary Environment ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Accelerator Mass Spectrometer

Based on sedimenlological and micropaleontological work on three sediment cores collected at about 167° Ε in the western Ross Sea, Antarctica, and accelerator mass spectrometer l4C ages of organic carbon, we have reconstructed environmental changes in the area during the late Quaternary. Since 38 ka BP at latest, this area was a marine environment with low productivity. A grounded ice sheet advanced and loaded the sediments before about 30-25 ka BP. After 25 ka BP, the southernmost site (76°46'S) was covered by floating ice (shelf ice), preventing deposition of coarse terrigenous materials and maintaining a supply of diatom tests and organic carbon until 20 ka BP. The northernmost site (74°33'S) was in a marine environment with a moderate productivity influenced by shelf ice/ice sheet after about 20 ka BP. Since about 10 ka BP, a sedimentary environment similar to the present-day one has prevailed over this area.

Clay mineralogy of parent materials derived from uppermost Cretaceous and Tertiary sedimentary rocks in southern Saskatchewan

1993 ◽  
Vol 73 (4) ◽  
pp. 447-457 ◽  
Author(s):  
W. E. Dubbin ◽  
A. R. Mermut ◽  
H. P. W. Rostad
Keyword(s):  
Organic Carbon ◽  
Iron Content ◽  
Sedimentary Rocks ◽  
Clay Mineralogy ◽  
Total Iron ◽  
Total Iron Content ◽  
Parent Materials ◽  
Surface Areas ◽  
General Chemical ◽  
Detailed Chemical

Soils developed from parent materials derived from uppermost Cretaceous and Tertiary sedimentary rocks have been delineated from those which do not contain any of these younger sediments. The present study was initiated to determine the validity of this delineation. Parent materials from six locations in southwestern Saskatchewan were collected to determine their general chemical and physical properties. Clay fractions from each of these six parent materials were then subjected to detailed chemical and mineralogical analyses. The two parent materials containing the greatest amount of post-Bearpaw bedrock sediments (Jones Creek, Scotsguard) were characterized by substantially more organic carbon and less CaCO3. The presence of coal and the absence of carbonates in local bedrocks were considered to be the source of these deviations. In general, fine clays were comprised of 64–69% smectite, 14–21% illite and 10–13% kaolinite and coarse clay contained 32–39% smectite, 25–34% illite and 11–14% kaolinite. An exception was found in two fine clays which had less smectite but 3–6% vermiculite. Total iron content of the fine clays ranged from 7.16 to 8.11% expressed as Fe2O3. However, only a small fraction of this iron was extractable using the CDB technique. There were no substantial differences in surface areas or CECs of the clay fractions. Despite minor differences in the chemistry and mineralogy of these six parent materials, a separation of the soil associations does not appear to be warranted. Key words: Parent materials, uppermost Cretaceous, Tertiary, bedrock, clay mineralogy

Soil organic carbon and nitrogen sequestration and turnover in aggregates under subtropical leucaena–grass pastures

Soil Research ◽  
2018 ◽  
Vol 56 (6) ◽  
pp. 632 ◽  
Author(s):  
Kathryn Conrad ◽  
Ram C. Dalal ◽  
Ryosuke Fujinuma ◽  
Neal W. Menzies
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Aggregates ◽  
Soil Mass ◽  
Δ13c And Δ15n ◽  
Organic C ◽  
Carbon And Nitrogen ◽  
Nitrogen Sequestration ◽  
C And N

Stabilisation and protection of soil organic carbon (SOC) in macroaggregates and microaggregates represents an important mechanism for the sequestration of SOC. Legume-based grass pastures have the potential to contribute to aggregate formation and stabilisation, thereby leading to SOC sequestration. However, there is limited research on the C and N dynamics of soil organic matter (SOM) fractions in deep-rooted legume leucaena (Leucaena leucocephala)–grass pastures. We assessed the potential of leucaena to sequester carbon (C) and nitrogen (N) in soil aggregates by estimating the origin, quantity and distribution in the soil profile. We utilised a chronosequence (0–40 years) of seasonally grazed leucaena stands (3–6 m rows), which were sampled to a depth of 0.3 m at 0.1-m intervals. The soil was wet-sieved for different aggregate sizes (large macroaggregates, >2000 µm; small macroaggregates, 250–2000 µm; microaggregates, 53–250 µm; and <53 µm), including occluded particulate organic matter (oPOM) within macroaggregates (>250 µm), and then analysed for organic C, N and δ13C and δ15N. Leucaena promoted aggregation, which increased with the age of the leucaena stands, and in particular the formation of large macroaggregates compared with grass in the upper 0.2 m. Macroaggregates contained a greater SOC stock than microaggregates, principally as a function of the soil mass distribution. The oPOM-C and -N concentrations were highest in macroaggregates at all depths. The acid nonhydrolysable C and N distribution (recalcitrant SOM) provided no clear distinction in stabilisation of SOM between pastures. Leucaena- and possibly other legume-based grass pastures have potential to sequester SOC through stabilisation and protection of oPOM within macroaggregates in soil.

scholarly journals Dynamics of organic carbon losses by water erosion after biocrust removal

2014 ◽  
Vol 62 (4) ◽  
pp. 258-268 ◽  
Author(s):  
Yolanda Cantón ◽  
Jose Raúl Román ◽  
Sonia Chamizo ◽  
Emilio Rodríguez-Caballero ◽  
María José Moro
Keyword(s):  
Organic Carbon ◽  
Fine Particles ◽  
Water Erosion ◽  
Strong Increase ◽  
Runoff Water ◽  
Erosion Rates ◽  
Soil Crusts ◽  
C Balance ◽  
Carbon Losses ◽  
Arid And Semiarid

Abstract In arid and semiarid ecosystems, plant interspaces are frequently covered by communities of cyanobacteria, algae, lichens and mosses, known as biocrusts. These crusts often act as runoff sources and are involved in soil stabilization and fertility, as they prevent erosion by water and wind, fix atmospheric C and N and contribute large amounts of C to soil. Their contribution to the C balance as photosynthetically active surfaces in arid and semiarid regions is receiving growing attention. However, very few studies have explicitly evaluated their contribution to organic carbon (OC) lost from runoff and erosion, which is necessary to ascertain the role of biocrusts in the ecosystem C balance. Furthermore, biocrusts are not resilient to physical disturbances, which generally cause the loss of the biocrust and thus, an increase in runoff and erosion, dust emissions, and sediment and nutrient losses. The aim of this study was to find out the influence of biocrusts and their removal on dissolved and sediment organic carbon losses. One-hour extreme rainfall simulations (50 mm h-1) were performed on small plots set up on physical soil crusts and three types of biocrusts, representing a development gradient, and also on plots where these crusts were removed from. Runoff and erosion rates, dissolved organic carbon (DOC) and organic carbon bonded to sediments (SdOC) were measured during the simulated rain. Our results showed different SdOC and DOC for the different biocrusts and also that the presence of biocrusts substantially decreased total organic carbon (TOC) (average 1.80±1.86 g m-2) compared to physical soil crusts (7.83±3.27 g m-2). Within biocrusts, TOC losses decreased as biocrusts developed, and erosion rates were lower. Thus, erosion drove TOC losses while no significant direct relationships were found between TOC losses and runoff. In both physical crusts and biocrusts, DOC and SdOC concentrations were higher during the first minutes after runoff began and decreased over time as nutrient-enriched fine particles were washed away by runoff water. Crust removal caused a strong increase in water erosion and TOC losses. The strongest impacts on TOC losses after crust removal occurred on the lichen plots, due to the increased erosion when they were removed. DOC concentration was higher in biocrust-removed soils than in intact biocrusts, probably because OC is more strongly retained by BSC structures, but easily blown away in soils devoid of them. However, SdOC concentration was higher in intact than removed biocrusts associated with greater OC content in the top crust than in the soil once the crust is scraped off. Consequently, the loss of biocrusts leads to OC impoverishment of nutrient-limited interplant spaces in arid and semiarid areas and the reduction of soil OC heterogeneity, essential for vegetation productivity and functioning of this type of ecosystems.

scholarly journals The Geochronology and Stratigraphic Evolution of Neogene Sedimentary Rocks in Jackson Hole, Wyoming

1984 ◽  
Vol 8 ◽  
pp. 33-37
Author(s):  
Douglas Burbank
Keyword(s):  
Fission Track ◽  
Sedimentary Rocks ◽  
Magnetic Polarity ◽  
Unique Sequence ◽  
Fluvial Sediments ◽  
Fission Track Dating ◽  
Hole Area ◽  
Terrestrial Sediments ◽  
Jackson Hole ◽  
Stratigraphic Evolution

The Miocene sediments of the Jackson Hole area constitute a unique sequence of terrestrial sediments. While much of the surrounding terrain was undergoing denudation during the Miocene, over 4000 m of volcaniclastic, lacustrine, and fluvial sediments accumulated in the vicinity of Jackson Hole. Recently completed paleontological and palynological studies have served to delineate complex biostratigraphic and climatic histories. The present research project has several goals. Chronologies are being developed for the Miocene sediments through the use of magnetic-polarity stratigraphies and fission-track dating. Sedimentation histories are being studied by combining lithologic data with chronologic information.

Substantial accumulation of mercury in the deepest parts of the ocean and implications for the environmental mercury cycle

2021 ◽  
Vol 118 (51) ◽  
pp. e2102629118
Author(s):  
Maodian Liu ◽  
Wenjie Xiao ◽  
Qianru Zhang ◽  
Shengliu Yuan ◽  
Peter A. Raymond ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Food Webs ◽  
Deep Sea ◽  
Anthropogenic Activities ◽  
Sediment Cores ◽  
Anthropogenic Sources ◽  
Biogeochemical Cycle ◽  
Vertical Profiles ◽  
Surface Ocean ◽  
Increasing Trends

Anthropogenic activities have led to widespread contamination with mercury (Hg), a potent neurotoxin that bioaccumulates through food webs. Recent models estimated that, presently, 200 to 600 t of Hg is sequestered annually in deep-sea sediments, approximately doubling since industrialization. However, most studies did not extend to the hadal zone (6,000- to 11,000-m depth), the deepest ocean realm. Here, we report on measurements of Hg and related parameters in sediment cores from four trench regions (1,560 to 10,840 m), showing that the world’s deepest ocean realm is accumulating Hg at remarkably high rates (depth-integrated minimum–maximum: 24 to 220 μg ⋅ m−2 ⋅ y−1) greater than the global deep-sea average by a factor of up to 400, with most Hg in these trenches being derived from the surface ocean. Furthermore, vertical profiles of Hg concentrations in trench cores show notable increasing trends from pre-1900 [average 51 ± 14 (1σ) ng ⋅ g−1] to post-1950 (81 ± 32 ng ⋅ g−1). This increase cannot be explained by changes in the delivery rate of organic carbon alone but also need increasing Hg delivery from anthropogenic sources. This evidence, along with recent findings on the high abundance of methylmercury in hadal biota [R. Sun et al., Nat. Commun. 11, 3389 (2020); J. D. Blum et al., Proc. Natl. Acad. Sci. U. S. A. 117, 29292–29298 (2020)], leads us to propose that hadal trenches are a large marine sink for Hg and may play an important role in the regulation of the global biogeochemical cycle of Hg.

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