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 Stable Carbon Isotopic Composition in Annual Rings of a Pine Tree (Pinus Densiflora) from Yeongwol, Korea: Possible Application to Climate Study

Radiocarbon ◽  
2017 ◽  
Vol 59 (2) ◽  
pp. 373-381
Author(s):  
Chi-Hwan Kim ◽  
Jang Hoon Lee ◽  
Jin Kang ◽  
Sujin Song ◽  
Myung-ho Yun ◽  
...  
Keyword(s):  
Tree Rings ◽  
Pinus Densiflora ◽  
Stable Carbon Isotope ◽  
Carbon Isotopic Composition ◽  
Precipitation Data ◽  
Stable Carbon ◽  
Climate Data ◽  
Carbon Isotopic ◽  
Pine Tree ◽  
Paleoclimate Proxy

AbstractStable carbon isotope ratios were measured on the alpha-cellulose in tree rings of a pine tree (Pinus densiflora) from Yeongwol, Korea. We developed an annual-resolution δ13C series (1835–1905) by correcting the measured data for changes in δ13C of air to minimize non-climatic influences. To investigate the climatic signal in the δ13C series, we performed correlation analysis between δ13C and the Cheugugi climate data. The Cheugugi precipitation data were first recorded by King Sejong (1397–1450) of the Joseon Dynasty. However, the longest set of precipitation data available is the one collected in Seoul (1776–1907). Although many studies support the reliability of the Cheugugi data, no previous studies have investigated the potential of the δ13C signal in tree rings as paleoclimate proxy using the Cheugugi data. Recent precipitation trends in Yeongwol are quite similar to that of Seoul, and we found significant correlations between the Cheugugi data and the δ13C series. We suggest further studies to replicate these results and confirm whether comparing δ13C variations in tree rings and Cheugugi data is a useful method of investigating the potential of the δ13C signal as a paleoclimate proxy in or near the Korean peninsula.

scholarly journals Sources and accumulation of organic carbon in the Pearl River Estuary surface sediment as indicated by elemental, stable carbon isotopic, and carbohydrate compositions

2010 ◽  
Vol 7 (2) ◽  
pp. 2889-2926 ◽  
Author(s):  
B. He ◽  
M. Dai ◽  
W. Huang ◽  
Q. Liu ◽  
H. Chen ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Surface Sediments ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Outer Shelf ◽  
Pearl River ◽  
Terrestrial Organic Matter ◽  
The Pearl River Estuary ◽  
The Pearl River

Abstract. Organic matter in surface sediments from the upper reach of the Pearl River Estuary and Lingdingyang Bay, as well as the adjacent northern South China Sea shelf was characterized by a variety of techniques, including elemental (C and N), stable carbon isotopic (δ 13C) composition, as well as molecular-level analyses. Total organic carbon (TOC) content was 1.61±1.20% in the upper reach down to 1.00±0.22% in Lingdingyang Bay and to 0.80±0.10% on the inner shelf and 0.58±0.06% on the outer shelf. δ13C values ranged from −25.11‰ to −21.28‰ across the studied area, with a trend of enrichment seaward. The spatial trend in C/N ratios mirrored that of δ13C, with a substantial decrease in C/N ratio from 10.9±1.3 in the Lingdingyang Bay surface sediments to 6.5±0.09 in the outer shelf surface sediments. Total carbohydrate yields ranged from 22.1 to 26.7 mg (100 mg OC)−1, and typically followed TOC concentrations in the estuarine and shelf sediments, suggesting that the relative abundance of total carbohydrate was fairly constant in TOC. Total neutral sugars as detected by the nine major monosaccharides (lyxose, rhamnose, ribose, arabinose, fucose, xylose, galactose, mannose, and glucose) yielded between 4.0 and 18.6 mg (100 mg OC)−1 in the same sediments, suggesting that a significant amount of carbohydrates were not neutral aldoses. The bulk organic matter properties, isotopic composition and C/N ratios, combined with molecular-level carbohydrate compositions were used to assess the sources and accumulation of terrestrial organic matter in the Pearl River Estuary and the adjacent northern South China Sea shelf. Results showed a mixture of terrestrial riverine organic carbon with in situ phytoplankton organic carbon in the areas studied. Using a two end-member mixing model based on δ13C values and C/N ratios, we estimated that the terrestrial organic carbon contribution to the surface sediment TOC was ca. 57±13% for Lingdingyang Bay, 19±2% for the inner shelf, which decreased further to 4.3±0.5% on the outer shelf. The molecular composition of the carbohydrate in surface sediments also suggested that the inner estuary was rich in terrestrial-derived carbohydrates but that the contribution of terrestrial-derived carbohydrates decreased offshore. Terrestrial organic carbon accumulation flux was estimated as 1.37±0.92×1011 g yr−1 in Lingdingyang Bay, which accounted for 37±25% of the terrestrial organic carbon transported to the Bay. The burial efficiency of terrestrial organic matter was markedly lower than that of suspended particulate substance (~71%) suggesting that the riverine POC undergoes significant degradation and replacement during transportation through the estuary.

scholarly journals Spatial distribution and sources of organic carbon in the surface sediment of the Bosten Lake, China

2015 ◽  
Vol 12 (16) ◽  
pp. 13793-13817 ◽  
Author(s):  
Z. T. Yu ◽  
X. J. Wang ◽  
E. L. Zhang ◽  
C. Y. Zhao ◽  
H. Y. Lan
Keyword(s):  
Spatial Distribution ◽  
Organic Carbon ◽  
Energy Levels ◽  
Carbon Isotopic Composition ◽  
Bosten Lake ◽  
Carbon Isotopic ◽  
Complex Processes ◽  
High Kinetic Energy ◽  
Carbon Reservoir ◽  
Kaidu River

Abstract. Lake sediment is an important carbon reservoir. However, little is known on the dynamics and sources of sediment organic carbon in the Bosten Lake. We collected 13 surface (0–2 cm) sediment samples in the Bosten Lake and analyzed total organic carbon (TOC), total nitrogen (TN), stable carbon isotopic composition in TOC (δ13Corg) and grain size. We found a large spatial variability in TOC content (1.8–4.4 %) and δ13Corg value (−26.77 to −23.98 ‰). Using a three end member mixing model with measured TOC : TN ratio and δ13Corg, we estimated that 54–90 % of TOC was from autochthonous sources. Higher TOC content (> 3.7 %) was found in the east and central-north sections and near the mouth of the Kaidu River, which was attributable to allochthonous, autochthonous plus allochthonous, and autochthonous sources, respectively. The lowest TOC content was found in the mid-west section, which might be a result of high kinetic energy levels. Our study indicated that the spatial distribution of sediment TOC in the Bosten Lake was influenced by multiple and complex processes.

scholarly journals Changes in Organic Matter Deposition Can Impact Benthic Marine Meiofauna in Karst Subterranean Estuaries

2021 ◽  
Vol 9 ◽  
Author(s):  
David Brankovits ◽  
Shawna N. Little ◽  
Tyler S. Winkler ◽  
Anne E. Tamalavage ◽  
Luis M. Mejía-Ortíz ◽  
...  
Keyword(s):  
Organic Matter ◽  
Ecosystem Functioning ◽  
Storm Events ◽  
Terrestrial Organic Matter ◽  
Core Sediment ◽  
Carbon Isotopic ◽  
Cozumel Island ◽  
Intense Storm ◽  
Terrestrial Environments ◽  
Subterranean Estuaries

Subsurface mixing of seawater and terrestrial-borne meteoric waters on carbonate landscapes creates karst subterranean estuaries, an area of the coastal aquifer with poorly understood carbon cycling, ecosystem functioning, and impact on submarine groundwater discharge. Caves in karst platforms facilitate water and material exchange between the marine and terrestrial environments, and their internal sedimentation patterns document long-term environmental change. Sediment records from a flooded coastal cave in Cozumel Island (Mexico) document decreasing terrestrial organic matter (OM) deposition within the karst subterranean estuary over the last ∼1,000 years, with older sediment likely exported out of the cave by intense storm events. While stable carbon isotopic values (δ13Corg ranging from −22.5 to −27.1‰) and C:N ratios (ranging from 9.9 to 18.9) indicate that mangrove and other terrestrial detritus surrounding an inland sinkhole are the primarily sedimentary OM supply, an upcore decrease in bulk OM and enrichment of δ13Corg values are observed. These patterns suggest that a reduction in the local mangrove habitat decreased the terrestrial particulate OM input to the cave over time. The benthic foraminiferal community in basal core sediment have higher proportions of infaunal taxa (i.e., Bolivina) and Ammonia, and assemblages shift to increased miliolids and less infaunal taxa at the core-top sediment. The combined results suggest that a decrease in terrestrial OM through time had a concomitant impact on benthic meiofaunal habitats, potentially by impacting dissolved oxygen availability at the microhabitat scale or resource partitioning by foraminifera. The evidence presented here indicates that landscape and watershed level changes can impact ecosystem functioning within adjacent subterranean estuaries.

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