Bacterial processes and biogeochemical changes in the water body of kettle holes - mainly driven by autochthonous organic matter?

The aim of the present study is to investigate the sedimentological characteristics of Lake Koronia down to a depth of 3.5m below lake bottom. Sampling operations took advandage of a season that the lake bottom was exposed to subaerial conditions. The sedimentological analysis proved that sediments consist of mud to sandy mud, with 2 phases of very fine sand fractions. The proportion of dry organic matter contained into sediment, appears to be generally small while the rates of moisture and volatiles are relatively high. Furthermore, this study examines the distribution of ostracod populations in the sediments of the lake in relation to depth, grain size and other environmental conditions of this water body. Four ostracod species were identified: Candona neglecta, Darwinula stevensoni, Heterocypris spp. and Limnocythere inopinata. The study of freshwater ostracods provides information for the palaeoecological/palaeoenvironmental conditions during the sedimentation.

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Beyond high frequency monitoring: an optimised automatic sampling

10.5194/egusphere-egu21-1969 ◽

2021 ◽

Author(s):

Jérémy Mougin

Keyword(s):

Organic Matter ◽

Water Body ◽

High Frequency ◽

Passive Samplers ◽

Size Exclusion ◽

Strong Impact ◽

Small Stream ◽

Automatic Sampling ◽

Frequency Monitoring ◽

On Line

Beyond high frequency monitoring&#160;: an optimised automatic samplingMougin J&#233;r&#233;my, Superville Pierre-Jean, Cornard Jean-Paul, Billon Gabriel&#160;In order to improve the representativity of samples when monitoring a water body, efforts have been made these last years to develop new methodologies to replace grab samples. Passive samplers have allowed to have measurement averaged over several days and represented a first step. High frequency monitoring (usually one measure per hour), either in situ or on-line, led to the observations of daily cycles or transitory phenomena that were not suspected beforehand.However, such method is usually difficult to implement for some trace analytes (e.g. trace metals or pesticides) or for some specific analysis (e.g. size exclusion chromatography on natural organic matter). Automatic sampling and analysis in the lab can be a solution, but it becomes very labor intensive as soon as the sampling frequency is high. Luck is also needed as a long sampling period can sometimes lead to very few variations if the water system is stable. In order to optimise the automatic sampling, a new methodology has been developped in this project.A multiparameter probe measuring general parameters (temperature, pH, turbidity, ORP, conductivity, dissolved oxygen and two fluorometers for organic matter) was coupled with an automatic filtering sampler. The data from the probe are processed on-line and an algorithm decides if the geochemical situation in the water body seems new enough to trigger the sampling, based on previously sampled waters. The aim of this device is to collect the right number of samples with the best representativeness of phenomena taking place in the environment.This method will be tested over a year in 2021 in order to monitor the dissolved organic matter in a small stream with both rural and urban contamination. These high-frequency measurements and samplings could make it possible to better define the sources and dynamics of the organic matter that has a strong impact on the quality of watercourses.

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Effect of dissolved organic matter on mercury release from water body

Journal of Environmental Sciences ◽

10.1016/s1001-0742(10)60497-4 ◽

2011 ◽

Vol 23 (6) ◽

pp. 912-917 ◽

Cited By ~ 7

Author(s):

Yutao Zhang ◽

Xi Chen ◽

Yongkui Yang ◽

Dingyong Wang ◽

Xiao Liu

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Water Body ◽

Mercury Release

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Organo-Mineral Interactions Are More Important for Organic Matter Retention in Subsoil Than Topsoil

Soil Systems ◽

10.3390/soilsystems4010004 ◽

2020 ◽

Vol 4 (1) ◽

pp. 4 ◽

Cited By ~ 2

Author(s):

Vincent Poirier ◽

Isabelle Basile-Doelsch ◽

Jérôme Balesdent ◽

Daniel Borschneck ◽

Joann K. Whalen ◽

...

Keyword(s):

Organic Matter ◽

Crop Residue ◽

Crop Residues ◽

Clay Content ◽

X Ray Diffraction ◽

Density Fractions ◽

Organic Matter Concentration ◽

Fractionation Procedure ◽

Autochthonous Organic Matter ◽

C And N

Decomposing crop residues contribute to soil organic matter (SOM) accrual; however, the factors driving the fate of carbon (C) and nitrogen (N) in soil fractions are still largely unknown, especially the influence of soil mineralogy and autochthonous organic matter concentration. The objectives of this work were (1) to evaluate the retention of C and N from crop residue in the form of occluded and mineral-associated SOM in topsoil (0–20 cm) and subsoil (30–70 cm) previously incubated for 51 days with 13C-15N-labelled corn residues, and (2) to explore if specific minerals preferentially control the retention of residue-derived C and N in topsoil and subsoil. We used topsoil and subsoil having similar texture and mineralogy as proxies for soils being rich (i.e., topsoil) and poor (i.e., subsoil) in autochthonous organic matter. We performed a sequential density fractionation procedure and measured residue-derived C and N in occluded and mineral-associated SOM fractions, and used X-ray diffraction analysis of soil density fractions to investigate their mineralogy. In accordance with our hypothesis, the retention of C and N from crop residue through organo-mineral interactions was greater in subsoil than topsoil. The same minerals were involved in the retention of residue-derived organic matter in topsoil and subsoil, but the residue-derived organic matter was associated with a denser fraction in the subsoil (i.e., 2.5–2.6 g cm−3) than in the topsoil (i.e., 2.3–2.5 g cm−3). In soils and soil horizons with high clay content and reactive minerals, we find that a low SOM concentration leads to the rapid stabilization of C and N from newly added crop residues.

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Study on the Mechanism of Organic Matter Enrichment in Early Cambrian Marine Shales in the Lower Yangtze Area, South China: An Example Using Well JXY1

Geofluids ◽

10.1155/2020/2460302 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Sihong Cheng ◽

Bin Li ◽

Kun Zhang ◽

Weiwei Liu ◽

Jun Peng ◽

...

Keyword(s):

Organic Matter ◽

Oxygen Isotope ◽

Water Body ◽

Organic Carbon Content ◽

Hydrocarbon Generation ◽

Early Cambrian ◽

Biological Productivity ◽

Carbon And Oxygen Isotope ◽

Lower Yangtze ◽

Hydrothermal Activities

The abundance of organic matter in shales, which has a direct effect on the hydrocarbon generation potential of shales, is an important organic geochemical parameter for evaluating shale gas reservoirs. The total organic carbon content (TOC content) in shale is controlled by the abundance of original sedimentary organic matter. Therefore, it is very important to study the mechanism of organic matter enrichment in shale. In this paper, the Lower Cambrian marine shales from the Lower Yangtze region are selected as the research subject, most of which originate from a typical area well called Well JXY1. The degree of pyritization (DOP) is used to characterize the redox environment of the water body, while the P/Al ratio is used to analyze the biological productivity of paleoseawater. The paleosalinity of seawater is calculated via carbon and oxygen isotope analysis. In addition, the early Cambrian hydrothermal activities were studied by using core description; Si, Al, Fe, and Mn elemental analysis; and oxygen isotope calculations. The results show that during the early Cambrian Wangyinpu sedimentary period, the seawater was an anaerobic water body with H2S, and the oxygen concentration was approximately 0 mL/L. In the middle stages of the Wangyinpu sedimentary period, the water body had the strongest reducibility and the highest biological productivity. Moreover, the paleoocean in this period between the Yangtze plate and the Cathaysian plate was greatly affected by hydrothermal activities, with temperatures ranging from 90°C to 120°C. Active hydrothermal activities promoted high biological productivity and an anaerobic environment, both of which were conducive to the preservation and enrichment of organic matter, resulting in extremely high TOC content in the Wangyinpu shales (from 6.5% to approximately 16%).

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