The role of hydrology in annual organic carbon loads and terrestrial organic matter export from a midwestern agricultural watershed

2007 ◽  
Vol 71 (6) ◽  
pp. 1448-1462 ◽  
Author(s):  
Brent J. Dalzell ◽  
Timothy R. Filley ◽  
Jon M. Harbor
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Agricultural Watershed ◽  
Terrestrial Organic Matter

scholarly journals Routing of terrestrial organic matter from the Congo River to the ultimate sink in the abyss: a mass balance approach (André Dumont medallist lecture 2017)

2020 ◽  
Vol 23 (1-2) ◽  
pp. xx-xx
Author(s):  
FRANÇOIS BAUDIN ◽  
CHRISTOPHE RABOUILLE ◽  
BERNARD DENNIELOU
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Submarine Canyon ◽  
Terrestrial Organic Matter ◽  
Sediment Dispersal ◽  
Congo River ◽  
Source To Sink ◽  
Depositional System ◽  
Turbidite System

We address the role of the Congo River sediment dispersal in exporting and trapping organic carbon into deep offshore sediments. Of particular interest is the Congo submarine canyon, which constitutes a permanent link between the terrestrial sediment sources and the marine sink. The Congo River delivers an annual sediment load of ~40 Tg (including 2 Tg of C) that feed a mud-rich turbidite system. Previous estimates of carbon storage capacity in the Congo turbidite system suggest that the terminal lobe complex accounts for ~12% of the surface area of the active turbidite system and accumulates ~18% of the annual input of terrestrial particulate organic carbon exiting the Congo River. In this paper, we extend the approach to the whole active turbidite depositional system by calculating an average burial of terrestrial organic matter in the different environments: canyon, channel, and levees. We estimate that between 33 and 69% of terrestrial carbon exported by the Congo River is ultimately trapped in the different parts of turbidite system and we evaluate their relative efficiency using a source to sink approach. Our carbon budget approach, which consider annual river discharge versus offshore centennial accumulation rates, indicates that about half of the total particulate organic matter delivered yearly by the Congo River watershed escapes the study area or is not correctly estimated by our deep offshore dataset and calculations.

scholarly journals The Role of Organic Matter on Uranium Precipitation in Zoovch Ovoo, Mongolia

Minerals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 310 ◽  
Author(s):  
Dimitrios Rallakis ◽  
Raymond Michels ◽  
Marc Brouand ◽  
Olivier Parize ◽  
Michel Cathelineau
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Late Cretaceous ◽  
Uranium Deposit ◽  
Vitrinite Reflectance ◽  
Driven Systems ◽  
Sem Observation ◽  
Organic Matter Type ◽  
Clay Layers

The Zoovch Ovoo uranium deposit is located in East Gobi Basin in Mongolia. It is hosted in the Sainshand Formation, a Late Cretaceous siliciclastic reservoir, in the lower part of the post-rift infilling of the Mesozoic East Gobi Basin. The Sainshand Formation corresponds to poorly consolidated medium-grained sandy intervals and clay layers deposited in fluvial-lacustrine settings. The uranium deposit is confined within a 60- to 80-m-thick siliciclastic reservoir inside aquifer driven systems, assimilated to roll-fronts. As assessed by vitrinite reflectance (%Rr < 0.4) and molecular geochemistry, the formation has never experienced significant thermal maturation. Detrital organic matter (type III and IV kerogens) is abundant in the Zoovch Ovoo depocenter. In this framework, uranium occurs as: (i) U-rich macerals without any distinguishable U-phase under SEM observation, containing up to 40 wt % U; (ii) U expressed as UO2 at the rims of large (several millimeters) macerals and (iii) U oxides partially to entirely replacing macerals, while preserving the inherited plant texture. Thus, uranium is accumulated gradually in the macerals through an organic carbon–uranium epigenization process, in respect to the maceral’s chemistry and permeability. Most macerals are rich in S and, to a lesser extent, in Fe. Frequently, Fe and S contents do not fit the stoichiometry of pyrite, although pyrite also occurs as small inclusions within the macerals. The organic matter appears thus as a major redox trap for uranium in this kind of geological setting.

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.

USE OF DISSOLVED ORGANIC MATTER BY MICROORGANISMS: FORMATION OF WATER QUALITY IN A POND OF A HIGH TROPHIC LEVEL

Fisheries ◽  
2020 ◽  
Vol 2020 (5) ◽  
pp. 25-29
Author(s):  
Anatoliy Sadchikov ◽  
Sergey Ostroumov
Keyword(s):  
Water Quality ◽  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Trophic Level ◽  
Aquatic Ecosystem ◽  
High Trophic Level ◽  
Bacterioplankton Community ◽  
Algae And Bacteria

The role of algae and bacteria in the consumption and mineralization of dissolved organic matter (DOM) in a highly trophic aquatic ecosystem was studied. The phytoplankton and bacterioplankton community consumed 60% of added DOM in August and 56% of DOM in September. Of the uptaken DOM, a significant amount of organic carbon was mineralized. In August 42.7% and in September 29% of organic carbon (of the consumed organic matter) were used for respiration.

scholarly journals Revisiting the disappearance of terrestrial dissolved organic matter in the ocean: a <i>δ</i><sup>13</sup>C study

2014 ◽  
Vol 11 (13) ◽  
pp. 3707-3719 ◽  
Author(s):  
K. Lalonde ◽  
A. V. Vähätalo ◽  
Y. Gélinas
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Solar Radiation ◽  
World Ocean ◽  
Photochemical Reactions ◽  
Global Ocean ◽  
Terrestrial Organic Matter ◽  
The World ◽  
Radiation Induced ◽  
Simulated Solar Radiation

Abstract. Organic carbon (OC) depleted in 13C is a widely used tracer for terrestrial organic matter (OM) in aquatic systems. Photochemical reactions can, however, change δ13C of dissolved organic carbon (DOC) when chromophoric, aromatic-rich terrestrial OC is selectively mineralized. We assessed the robustness of the δ13C signature of DOC (δ13CDOC) as a tracer for terrestrial OM by estimating its change during the photobleaching of chromophoric DOM (CDOM) from 10 large rivers. These rivers cumulatively account for approximately one-third of the world's freshwater discharge to the global ocean. Photobleaching of CDOM by simulated solar radiation was associated with the photochemical mineralization of 16 to 43% of the DOC and, by preferentially removing compounds depleted in 13C, caused a 1 to 2.9‰ enrichment in δ13C in the residual DOC. Such solar-radiation-induced photochemical isotopic shift could bias the calculations of terrestrial OM discharge in coastal oceans towards the marine end-member. Shifts in terrestrial δ13CDOC should be taken into account when constraining the terrestrial end-member in global calculation of terrestrially derived DOM in the world ocean.

The role of hydrologic regimes on dissolved organic carbon composition in an agricultural watershed

2008 ◽  
Vol 72 (21) ◽  
pp. 5266-5277 ◽  
Author(s):  
Peter J. Hernes ◽  
Robert G.M. Spencer ◽  
Rachael Y. Dyda ◽  
Brian A. Pellerin ◽  
Philip A.M. Bachand ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Agricultural Watershed ◽  
Hydrologic Regimes ◽  
Carbon Composition

scholarly journals Stream Macroinvertebrates and Carbon Cycling in Tangled Food Webs

Ecosystems ◽  
2021 ◽  
Author(s):  
Benoît O. L. Demars ◽  
Joanna L. Kemp ◽  
Baptiste Marteau ◽  
Nikolai Friberg ◽  
Barry Thornton
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Food Web ◽  
Food Webs ◽  
Carbon Sources ◽  
Terrestrial Ecosystems ◽  
Terrestrial Organic Matter ◽  
Before And After ◽  
Reference Stream ◽  
Induced Changes

AbstractThe annual global loss of organic carbon from terrestrial ecosystems into rivers is similar to the organic carbon stored in soils each year. Dissolved organic matter (DOM) flows through the food web to macroinvertebrates, but little is known about the effect of DOM increase on stream food webs and how much macroinvertebrates may contribute to the regulation of carbon fluxes in rivers. Using a before and after control impact (BACI) experimental design, we increased by 12% (+ 0.52 mg C L−1) the concentration of DOM in a stream for three weeks by adding sucrose, with a distinctive δ13C signature, to simulate a pulse of natural DOM supply from soils. We partitioned the diet of macroinvertebrates from carbon sources according to the green pathway (autotrophs) and detrital pathways (bacteria and terrestrial organic matter). Our flow food web approach based on C fluxes, with bacteria as a key node, showed the dominant contribution of the detrital pathways for macroinvertebrates in the reference stream. DOM addition induced changes in the diets of individual taxa, but did not have any strong effects on the relative overall contribution of the detrital pathways versus the green pathway. Autotrophic uptake of CO2 respired by bacteria was much larger than bacterial C flux to invertebrates (that is, the classic microbial loop) and allowed a significant fraction of natural allochthonous organic carbon to make its way to macroinvertebrates via autotrophs fixing CO2 respired by bacteria. Overall macroinvertebrates did not regulate directly to any great extent the flux of stream DOM towards downstream ecosystems.

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