scholarly journals Lignin phenols in sediment cores and its indications of degradation and organic carbon sources of the Yantan Reservoir, China

2021 ◽  
Author(s):  
Xin Lin ◽  
Li Gao ◽  
Jiaqi Huang ◽  
Jun Fan ◽  
Ming Yang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Spatial Heterogeneity ◽  
Early Stage ◽  
Sediment Cores ◽  
Carbon Isotopic Composition ◽  
Woody Tissue ◽  
Lignin Phenols ◽  
Organic Carbon Burial ◽  
Temporal And Spatial ◽  
Inlet Zone

Abstract Three sediment cores collected from the Yantan Reservoir, located in the Pearl River, southwest China, were analyzed for lignin phenols, elemental and stable carbon isotopic composition to investigate the variation patterns, vegetation sources, degradation stage, and relative proportions of terrestrial sedimentary organic carbon (OC). Significant temporal and spatial heterogeneity in terrestrial OC burial was indicated by the changes of lignin contents at different depths in different sampling sites: the inlet zone, the central reservoir zone in front of dam and the reservoir bay. The interception impact of upstream dam, the influence of artificial regulation, as well as the role of interzonal recharge made the terrestrial OC burial remains complex in the reservoir. The oxidized lignin signatures showed spatial heterogeneity suggesting active oxidative degradation and demethylation/demethoxy degradation of sedimentary lignin during deposition, especially in the inlet zone. An angiosperm herbaceous tissue and gymnosperm woody tissue contributed the sedimentary lignin. A soil-plankton-plant three-end-member mixing model revealed that soil-derived OC dominated before impoundment and at the early stage of reservoir operation, while the contribution of autochthonous OC began to dominate after gradually aging and eutrophicating of the reservoir. Our study of lignin evolution in reservoir highlights important temporal and spatial reservoir carbon components and their contribution to sedimentary carbon pools, providing new insights into the estimation of organic carbon burial in reservoirs.

scholarly journals CO<sub>2</sub> and CH<sub>4</sub> fluxes are decoupled from organic carbon loss in drying reservoir sediments

2019 ◽  
Author(s):  
Tricia Light ◽  
Núria Catalán ◽  
Santiago Giralt ◽  
Rafael Marcé
Keyword(s):  
Organic Carbon ◽  
Sediment Cores ◽  
Carbon Mineralization ◽  
Organic Carbon Content ◽  
Co2 Efflux ◽  
Carbon Loss ◽  
Organic C ◽  
Reservoir Sediments ◽  
Organic Carbon Burial ◽  
Organic Carbon Mineralization

Abstract. Reservoirs are a prominent feature of the current global hydrological landscape, and their sediments are the site of extensive organic carbon burial. Meanwhile, reservoirs frequently go dry due to drought and/or water management decisions. Nonetheless, the fate of organic carbon buried in reservoir sediments upon drying is largely unknown. Here, we conducted a 45-day-long laboratory incubation of sediment cores collected from a western Mediterranean reservoir to investigate carbon dynamics in drying sediment. Drying sediment cores emitted more CO2 over the course of the incubation than sediment cores incubated with overlaying water (206.7 ± 47.9 vs. 69.2 ± 18.1 mmol CO2 m−2 day−1, mean ± SE). Organic carbon content at the end of the incubation was lower in drying cores, which suggests that this higher CO2 efflux was due to organic carbon mineralization. However, the apparent rate of organic C reduction in the drying sediments (568.6 ± 247.2 mmol CO2 m−2 day−1, mean ± SE) was higher than C emission. Meanwhile, sediment cores collected from a reservoir area that had already been exposed for 2+ years displayed net CO2 influx from the atmosphere to the sediment (−136.0 ± 27.5 mmol CO2 m−2 day−1, mean ± SE) during the incubation period. Sediment mineralogy suggests that this CO2 influx was caused by a relative increase in calcium carbonate chemical weathering. Thus, we found that while organic carbon decomposition in newly dry reservoir sediment causes measurable organic carbon loss and carbon gas emissions to the atmosphere, other processes can offset these emissions on short time frames and compromise the use of carbon emissions as a proxy for organic carbon mineralization in drying sediments.

Origin and Alteration of Organic Matter in Hydrate-Bearing Sediments of the Rio Grande Cone, Brazil: Evidence from Biological, Physical, and Chemical Factors

Radiocarbon ◽  
2019 ◽  
Vol 62 (1) ◽  
pp. 197-206 ◽  
Author(s):  
Luiz F Rodrigues ◽  
Kita D Macario ◽  
Roberto M Anjos ◽  
João M M Ketzer ◽  
Anderson J Maraschin ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Sediment Cores ◽  
Stable Carbon Isotope ◽  
Carbon Isotopic Composition ◽  
Rio Grande ◽  
Terrestrial Organic Matter ◽  
Carbon Isotopic ◽  
Pelotas Basin ◽  
Physical And Chemical

ABSTRACTThe Rio Grande Cone is a major fanlike depositional feature in the continental slope of the Pelotas Basin, Southern Brazil. Two representative sediment cores collected in the Cone area were retrieved using a piston core device. In this work, the organic matter (OM) in the sediments was characterized for a continental vs. marine origin using chemical proxies to help constrain the origin of gas in hydrates. The main contribution of OM was from marine organic carbon based on the stable carbon isotope (δ13C-org) and total organic carbon/total nitrogen ratio (TOC:TN) analyses. In addition, the 14C data showed important information about the origin of the OM and we suggest some factors that could modify the original organic matter and therefore mask the “real” 14C ages: (1) biological activity that could modify the carbon isotopic composition of bulk terrestrial organic matter values, (2) the existence of younger sediments from mass wasting deposits unconformably overlying older sediments, and (3) the deep-sediment-sourced methane contribution due to the input of “old” (>50 ka) organic compounds from migrating fluids.

scholarly journals Spatial heterogeneity and environmental predictors of permafrost region soil organic carbon stocks

2021 ◽  
Vol 7 (9) ◽  
pp. eaaz5236 ◽  
Author(s):  
Umakant Mishra ◽  
Gustaf Hugelius ◽  
Eitan Shelef ◽  
Yuanhe Yang ◽  
Jens Strauss ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Spatial Heterogeneity ◽  
Surface Air Temperature ◽  
Spatially Explicit ◽  
Soil Profiles ◽  
Permafrost Region ◽  
Environmental Predictors ◽  
Soil Organic Carbon Stocks ◽  
Soc Stocks

Large stocks of soil organic carbon (SOC) have accumulated in the Northern Hemisphere permafrost region, but their current amounts and future fate remain uncertain. By analyzing dataset combining >2700 soil profiles with environmental variables in a geospatial framework, we generated spatially explicit estimates of permafrost-region SOC stocks, quantified spatial heterogeneity, and identified key environmental predictors. We estimated that 1014−175+194 Pg C are stored in the top 3 m of permafrost region soils. The greatest uncertainties occurred in circumpolar toe-slope positions and in flat areas of the Tibetan region. We found that soil wetness index and elevation are the dominant topographic controllers and surface air temperature (circumpolar region) and precipitation (Tibetan region) are significant climatic controllers of SOC stocks. Our results provide first high-resolution geospatial assessment of permafrost region SOC stocks and their relationships with environmental factors, which are crucial for modeling the response of permafrost affected soils to changing climate.

scholarly journals Past climate variations recorded in needle-like aragonites correlate with organic carbon burial efficiency as revealed by lake sediments in Croatia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ivan Razum ◽  
Petra Bajo ◽  
Dea Brunović ◽  
Nikolina Ilijanić ◽  
Ozren Hasan ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Stable Carbon Isotope ◽  
Climate Variations ◽  
Before Present ◽  
Stable Carbon ◽  
Climate Trends ◽  
Geochemical Proxies ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Burial Efficiency

AbstractThe drivers of organic carbon (OC) burial efficiency are still poorly understood despite their key role in reliable projections of future climate trends. Here, we provide insights on this issue by presenting a paleoclimate time series of sediments, including the OC contents, from Lake Veliko jezero, Croatia. The Sr/Ca ratios of the bulk sediment are mainly derived from the strontium (Sr) and calcium (Ca) concentrations of needle-like aragonite in Core M1-A and used as paleotemperature and paleohydrology indicators. Four major and six minor cold and dry events were detected in the interval from 8.3 to 2.6 calibrated kilo anno before present (cal ka BP). The combined assessment of Sr/Ca ratios, OC content, carbon/nitrogen (C/N) ratios, stable carbon isotope (δ13C) ratios, and modeled geochemical proxies for paleoredox conditions and aeolian input revealed that cold and dry climate states promoted anoxic conditions in the lake, thereby enhancing organic matter preservation and increasing the OC burial efficiency. Our study shows that the projected future increase in temperature might play an important role in the OC burial efficiency of meromictic lakes.

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