The formation and fate of chlorinated organic substances in temperate and boreal forest soils |
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Authors: | Nicholas Clarke Květoslava Fuksová Milan Gryndler Zora Lachmanová Hans-Holger Liste Jana Rohlenová Reiner Schroll Peter Schröder Miroslav Matucha |
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Institution: | 1. Norwegian Forest and Landscape Institute, P.O. Box 115, 1431, ?s, Norway 2. First Faculty of Medicine, Charles University, Katerinská 32, 121 08, Prague, Czech Republic 3. Institute of Microbiology, Czech Academy of Sciences, Vídeňská 1083, 142 20, Prague, Czech Republic 4. Forestry and Game Management Research Institute, Jílovi?tě Strnady 136, 156 04, Prague, Czech Republic 5. Centre for Cultivated Crops, Julius Kühn-Institute (JKI) Federal Research, K?nigin-Luise-Strasse 19, 14195, Berlin, Germany 6. Institute of Experimental Botany, Czech Academy of Sciences, Vídeňská 1083, 142 20, Prague 4, Czech Republic 7. Institute of Soil Ecology, Helmholtz Center Munich, German Research Center for Environmental Health (GmbH), Ingolst?dter Landstr. 1, 85764, Neuherberg, Germany 8. Department of Microbe–Plant Interactions, German Research Center for Environmental Health (GmbH), Ingolst?dter Landstr. 1, 85764, Neuherberg, Germany
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Abstract: | Background, aim and scope Chlorine is an abundant element, commonly occurring in nature either as chloride ions or as chlorinated organic compounds
(OCls). Chlorinated organic substances were long considered purely anthropogenic products; however, they are, in addition,
a commonly occurring and important part of natural ecosystems. Formation of OCls may affect the degradation of soil organic
matter (SOM) and thus the carbon cycle with implications for the ability of forest soils to sequester carbon, whilst the occurrence
of potentially toxic OCls in groundwater aquifers is of concern with regard to water quality. It is thus important to understand
the biogeochemical cycle of chlorine, both inorganic and organic, to get information about the relevant processes in the forest
ecosystem and the effects on these from human activities, including forestry practices. A survey is given of processes in
the soil of temperate and boreal forests, predominantly in Europe, including the participation of chlorine, and gaps in knowledge
and the need for further work are discussed.
Results Chlorine is present as chloride ion and/or OCls in all compartments of temperate and boreal forest ecosystems. It contributes
to the degradation of SOM, thus also affecting carbon sequestration in the forest soil. The most important source of chloride
to coastal forest ecosystems is sea salt deposition, and volcanoes and coal burning can also be important sources. Locally,
de-icing salt can be an important chloride input near major roads. In addition, anthropogenic sources of OCls are manifold.
However, results also indicate the formation of chlorinated organics by microorganisms as an important source, together with
natural abiotic formation. In fact, the soil pool of OCls seems to be a result of the balance between chlorination and degradation
processes. Ecologically, organochlorines may function as antibiotics, signal substances and energy equivalents, in descending
order of significance. Forest management practices can affect the chlorine cycle, although little is at present known about
how.
Discussion The present data on the apparently considerable size of the pool of OCls indicate its importance for the functioning of the
forest soil system and its stability, but factors controlling their formation, degradation and transport are not clearly understood.
It would be useful to estimate the significance and rates of key processes to be able to judge the importance of OCls in SOM
and litter degradation. Effects of forest management processes affecting SOM and chloride deposition are likely to affect
OCls as well. Further standardisation and harmonisation of sampling and analytical procedures is necessary.
Conclusions and perspectives More work is necessary in order to understand and, if necessary, develop strategies for mitigating the environmental impact
of OCls in temperate and boreal forest soils. This includes both intensified research, especially to understand the key processes
of formation and degradation of chlorinated compounds, and monitoring of the substances in question in forest ecosystems.
It is also important to understand the effect of various forest management techniques on OCls, as management can be used to
produce desired effects. |
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Keywords: | Carbon cycle Chlorination Chlorine biogeochemistry Forest management Forest soil Microbial soil processes Organochlorines Soil organic matter (SOM) Temperate and boreal forests |
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