scholarly journals In situ adsorption of mercury, methylmercury and other elements by iron oxyhydroxides and organic matter in lake sediments

2010 ◽  
Vol 25 (7) ◽  
pp. 984-995 ◽  
Author(s):  
Stéphane Feyte ◽  
André Tessier ◽  
Charles Gobeil ◽  
Daniel Cossa
Keyword(s):  
Organic Matter ◽  
Lake Sediments ◽  
Iron Oxyhydroxides ◽  
In Situ Adsorption

Chemical investigation of lake sediments and their interpretation

1965 ◽  
Vol 161 (984) ◽  
pp. 295-309 ◽  
Keyword(s):  
Organic Matter ◽  
Lake Sediments ◽  
Land Surface ◽  
Drainage Basin ◽  
Drainage System ◽  
Labile Organic Matter ◽  
Glacial Sediments ◽  
Algal Material ◽  
Lake Waters

Before any interpretation of compositional changes in a lake sediment column can be attempted, it is necessary to recognize the sources from which the sediment has been derived. Unlike bogs, whose deposits consist largely of materials synthesized in situ , lakes and particularly those of the Lake District, are greatly influenced by inflow and their sediments may derive material from a drainage basin some twenty or thirty times as large as the area of the lake itself. The glacial lake sediments consist wholly of mineral clay, often laminated, which must have been derived from the drainage basin. The post-Glacial sediments contain some 70 or 80 % of mineral material similarly derived. The remaining 20 to 30% consists of organic matter which may have originated photosynthetically either on the land surface or in the waters of the lake. The organic matter which eventually becomes buried in the sediment must have reached a state of stability towards oxidation since it must have been exposed to oxidizing conditions either in the soil or at the mud surface for many years before its final incorporation in the sediment. There is evidence from observations on Windermere and on Blelham Tarn, that the algal material produced in the lakes is very readily oxidized at the mud surface and that the oxygen consumed from the lake waters is largely used in oxidation of this comparatively labile organic matter. The major part of the organic material remaining in lake sediments is therefore likely to have been derived from stable residues produced in the soils of the drainage system . The sediment may then be regarded as an accumulation of debris derived from the land surface with minor additions from the lake biomass, though these latter additions may make important contributions to the precipitation of some elements of which phosphorus is an example. The information to be obtained from a study of lake sediments is therefore mainly concerned with events affecting the surrounding land surface rather than the lake itself, though conditions existing in the lake in former times may often be inferred from the sedimentary composition.

scholarly journals Traces of sunlight in the organic matter biogeochemistry of two shallow subarctic lakes

2021 ◽  
Author(s):  
Marttiina V. Rantala ◽  
Carsten Meyer-Jacob ◽  
E. Henriikka Kivilä ◽  
Tomi P. Luoto ◽  
Antti. E. K. Ojala ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Lake Sediments ◽  
Lake Water ◽  
Human Impacts ◽  
Global Environmental Change ◽  
Carbon Export ◽  
Subarctic Lakes ◽  
Carbon Regulation ◽  
In Situ Experiments

AbstractGlobal environmental change alters the production, terrestrial export, and photodegradation of organic carbon in northern lakes. Sedimentary biogeochemical records can provide a unique means to understand the nature of these changes over long time scales, where observational data fall short. We deployed in situ experiments on two shallow subarctic lakes with contrasting light regimes; a clear tundra lake and a dark woodland lake, to first investigate the photochemical transformation of carbon and nitrogen elemental (C/N ratio) and isotope (δ13C, δ15N) composition in lake water particulate organic matter (POM) for downcore inferences. We then explored elemental, isotopic, and spectral (inferred lake water total organic carbon [TOC] and sediment chlorophyll a [CHLa]) fingerprints in the lake sediments to trace changes in aquatic production, terrestrial inputs and photodegradation before and after profound human impacts on the global carbon cycle prompted by industrialization. POM pool in both lakes displayed tentative evidence of UV photoreactivity, reflected as increasing δ13C and decreasing C/N values. Through time, the tundra lake sediments traced subtle shifts in primary production, while the woodland lake carried signals of changing terrestrial contributions, indicating shifts in terrestrial carbon export but possibly also photodegradation rates. Under global human impact, both lakes irrespective of their distinct carbon regimes displayed evidence of increased productivity but no conspicuous signs of increased terrestrial influence. Overall, sediment biogeochemistry can integrate a wealth of information on carbon regulation in northern lakes, while our results also point to the importance of considering the entire spectrum of photobiogeochemical fingerprints in sedimentary studies.

scholarly journals Lipid biomarkers in Holocene and glacial sediments from ancient Lake Ohrid (Macedonia, Albania)

2010 ◽  
Vol 7 (11) ◽  
pp. 3473-3489 ◽  
Author(s):  
J. Holtvoeth ◽  
H. Vogel ◽  
B. Wagner ◽  
G. A. Wolff
Keyword(s):  
Organic Matter ◽  
Lipid Biomarkers ◽  
Lake Ohrid ◽  
Labile Organic Matter ◽  
Glacial Sediments ◽  
Plant Matter ◽  
Lipid Biomarker ◽  
First Results ◽  
Near Shore

Abstract. Organic matter preserved in Lake Ohrid sediments originates from aquatic and terrestrial sources. Its variable composition reflects climate-controlled changes in the lake basin's hydrology and related organic matter export, i.e. changes in primary productivity, terrestrial plant matter input and soil erosion. Here, we present first results from lipid biomarker investigations of Lake Ohrid sediments from two near-shore settings: site Lz1120 near the southern shore, with low-lying lands nearby and probably influenced by river discharge, and site Co1202 which is close to the steep eastern slopes. Variable proportions of terrestrial n-alkanoic acids and n-alkanols as well as compositional changes of ω-hydroxy acids document differences in soil organic matter supply between the sites and during different climate stages (glacial, Holocene, 8.2 ka cooling event). Changes in the vegetation cover are suggested by changes in the dominant chain length of terrestrial n-alkanols. Effective microbial degradation of labile organic matter and in situ contribution of organic matter derived from the microbes themselves are both evident in the sediments. We found evidence for anoxic conditions within the photic zone by detecting epicholestanol and tetrahymanol from sulphur-oxidising phototrophic bacteria and bacterivorous ciliates and for the influence of a settled human community from the occurrence of coprostanol, a biomarker for human and animal faeces (pigs, sheep, goats), in an early Holocene sample. This study illustrates the potential of lipid biomarkers for future environmental reconstructions using one of Europe's oldest continental climate archives, Lake Ohrid.

scholarly journals Separation and 14C Dating of Pure Pollen from Lake Sediments: Nanofossil AMS Dating

Radiocarbon ◽  
1992 ◽  
Vol 34 (3) ◽  
pp. 557-560 ◽  
Author(s):  
Austin Long ◽  
Owen K. Davis ◽  
Jeanne de Lanois
Keyword(s):  
Organic Matter ◽  
Lake Sediments ◽  
Mono Lake ◽  
Bulk Sediment ◽  
Clean Room ◽  
14C Dating ◽  
Ams Dating

We have developed and tested a practical device for manually separating pollen from pollen concentrates in sufficient quantity for AMS 14C dating. It is a combination of standard, commercially available equipment handled in a clean room by an individual trained to recognize pollen. A typical example requires about 15–20 h of hand-picking under the microscope. We show the usefulness of this procedure with results on a mid-Holocene segment from a core from Mono Lake. Sediments from this hardwater lake contain pollen and finely disseminated organic matter, but no macrofossils. The pollen dated ca. 1000 yr younger than the bulk sediment. The sediment “date” is most likely affected by incorporation of limestone-derived carbon, and is erroneously old.

scholarly journals Sediment community responses to marine vs. terrigenous organic matter in a submarine canyon

2013 ◽  
Vol 10 (1) ◽  
pp. 67-80 ◽  
Author(s):  
W. R. Hunter ◽  
A. Jamieson ◽  
V. A. I. Huvenne ◽  
U. Witte
Keyword(s):  
Organic Matter ◽  
Feeding Activity ◽  
N Uptake ◽  
Bacterial Biomass ◽  
Submarine Canyon ◽  
Stable Isotope Labelling ◽  
C And N ◽  
13C Label ◽  
Experimental Treatments

Abstract. The Whittard Canyon is a branching submarine canyon on the Celtic continental margin, which may act as a conduit for sediment and organic matter (OM) transport from the European continental slope to the abyssal sea floor. In situ stable-isotope labelling experiments were conducted in the eastern and western branches of the Whittard Canyon, testing short-term (3–7 days) responses of sediment communities to deposition of nitrogen-rich marine (Thalassiosira weissflogii) and nitrogen-poor terrigenous (Triticum aestivum) phytodetritus. 13C and 15N labels were traced into faunal biomass and bulk sediments, and the 13C label traced into bacterial polar lipid fatty acids (PLFAs). Isotopic labels penetrated to 5 cm sediment depth, with no differences between stations or experimental treatments (substrate or time). Macrofaunal assemblage structure differed between the eastern and western canyon branches. Following deposition of marine phytodetritus, no changes in macrofaunal feeding activity were observed between the eastern and western branches, with little change between 3 and 7 days. Macrofaunal C and N uptake was substantially lower following deposition of terrigenous phytodetritus with feeding activity governed by a strong N demand. Bacterial C uptake was greatest in the western branch of the Whittard Canyon, but feeding activity decreased between 3 and 7 days. Bacterial processing of marine and terrigenous OM were similar to the macrofauna in surficial (0–1 cm) sediments. However, in deeper sediments bacteria utilised greater proportions of terrigenous OM. Bacterial biomass decreased following phytodetritus deposition and was negatively correlated to macrofaunal feeding activity. Consequently, this study suggests that macrofaunal–bacterial interactions influence benthic C cycling in the Whittard Canyon, resulting in differential fates for marine and terrigenous OM.

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