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| Titel |
Phenomenon of organic carbon change in natural waters (system "catchment - Lake") of Russian Federation |
| VerfasserIn |
Marina Dinu, Moiseenko Tatyana, Kremleva Tatyana, Natalia Gashkina |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250107025
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| Publikation (Nr.) |
 EGU/EGU2015-6713.pdf |
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| Zusammenfassung |
| In the last two decades in the Russian Federation was found significant increase in the concentration of dissolved organic carbon in many aqueous systems. Most obviously, these changes may be related to global warming. It is known that increasing the temperature dominate during dry periods and increases the concentration of nutrients, primary production increases, leading to an increase of the dissolved organic matter. At the same time, it is known that some of the increase in DOC may be largely due to a decrease of anthropogenic sulfur deposition and increasing organic matter in the soil. \newline
The European Russia (ER) is a region with substantial industrial emissions of sulphur. In the central part of ER are concentrated metallurgical productions. This has resulted in high concentrations of anthropogenic sulphate and an increase in the prevalence of acidification as well as a rise in metal concentrations in the lakes of North Kola. However, over the last 30 years, sulfur emissions in ?ola North have decreased substantially. \newline
The aim of this work was to explain the mechanisms to improve the content of natural organic matter and to assess its role in the processes of acidification and recovery of water quality while reducing the deposition of technogenic acid.\newline
The increasing of organic matter content in lake waters is being also observed for the totality of lakes in the Kola North. This conforms to the data reported by Skjelkvale et al. (2001a) which demonstrates the significant increase of DOC. Some authors explain the increased DOC levels by reduction in strong acid flow and return of water chemistry to its natural parameters of specifying organic matter concentrations in water. \newline
It is known that DOC level has a direct relationship with water color. In analyzing long-term study data with regard to the group of 75 lakes (obtained during 1990-2010) DOC is increased year-over-year, but the color decreased. The following chemical processes developing in water can explain this phenomenon.\newline
The water color is predominantly determined by large molecules of humus acids which molecular weight >1000 Da. Macromolecular organic substances of humus type can be dissociated in water with formation of a free proton, as well as enter into reactions of decomposition (hydrolysis) and disproportionation with formation of low-molecular weight fragments. Its fragments also are dissociated of proton (see the diagram below). Non-organic strong acids supplied from anthropogenic and natural sources may catalyze the above processes. \newline
The diagram of the organic substances destruction of humus origin is given below, where R$_i$ means non-symmetrical fragments of a natural polymer, X$_i$H - functional groups of organic substances of humus origin, and $n$ - number of protons.
\begin{equation*}
\hspace{1.2mm}HX_1-R_1-R_2-X_2H \begin{array}{l} \rightarrow
R_1-X_1H + R_2-X_2H \quad + \quad R{^'}{_1} X_{1^-} + R{^'}{_2} X_{2^-} + nH^+ \\
\\
\rightarrow HX_1-R_1-R_2 X_2^- + ^- X_1R_1-R_2-X_2H +
^- X_1R_1-R_2 X_2^- + nH^+ \\
\end{equation*}
When strong acids get into a water environment humus acids are degraded into fractions. It could be supposed that the organic matter structure undergoes changes in natural waters, as the fraction of high-molecular weight humus acids decrease. As a consequence of interaction between humus substances and protons the humic acids precipitate to form bottom sediments, whereas fulvic acids remain in water. Fulvic acids are characterized by lower molecular weights (from 500 to 2000 Da) and exert an insignificant effect on the water color. \newline
\newline
Skelkvale, B.L., J.L. Stoddard, D.S. Jeffries, K. Torseth, T. Hogasen, J. Bowman, L. Mannio, Monteith, D.T., et al. 2005. Regional scale evidence for improvements in surface water chemistry 1990-2001. Environmental Pollution 137(1): 165-176. \newline
Moiseenko, T., L. Kudrjavzeva, I. Rodyshkin. 2001. The episodic acidification of small streams in the spring flood period of industrial polar region, Russia. Chemosphere 362: 45-50. |
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