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| Titel |
The ecohydrological biotechnology (SBFS) for reduction of dioxin-induced toxicity in Asella lake, Ethiopia |
| VerfasserIn |
M. Urbaniak, Y. Zerihun Negussie, M. Zalewski |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250071636
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| Zusammenfassung |
| The transfer of dioxins along river continuum is a well know process which indicated
permanent increase of their content in the river sediments. Despite this, there is still lack of
empirical data highlighting the role of lakes and reservoirs in dioxins transfer along river
continuum. Using the ecohydrology as a framework for water problem solving, the reduction
of dioxins bioaccumulation in aquatic food chain should be based on two steps: 1) a
reduction of dioxins emission to the water ecosystems and 2) an understanding
of the role that the factors determining dioxins accumulation, transportation and
transformation in the river and lake/reservoir system play for implementation of
ecohydrological biotechnologies and system solutions. From limnological perspective
lakes and reservoirs are considered as traps for organic and mineral sediments and
bounded with them nutrients and other polluting substances. As effect of long term
ecological succession the amount of sedimented matter, nutrients and loads and
concentrations of pollutants usually increases. Such situation was observed in Asella lake,
located in the Arsi zone of the Oromia region about 175 kilometers from Addis
Ababa, Ethiopia. As the results of above processes the high concentration of dioxin
concentrations in the sediments was observed, inducing decline in the water resources
use.
During this study the spatial pattern of dioxins concentration and toxicity (measured as
WHO TEQ concentration) in the sediments of Asella river and lake taken before (in 2009)
and after (in 2010) construction of Sequentional BioFiltering System (SBFS) were compared.
The determination of dioxin concentrations were followed according to US EPA 1613 and
1668 Methods.
Among the samples collected in the 2009 year, the contamination of lake sediments
amounted for 127.65 ng kg-1 dry weight (d.w.), whereas concentration of dioxins in samples
taken at the lake outflow decreased to the value of 26.65 ng kg-1 d.w. The WHO-TEQ
concentrations also showed declining tendency along the river-lake system with the highest
value in the inflow (2.32 ng TEQ kg-1 d.w.), middle in the lake (1.09 ng TEQ kg-1 d.w.) and
the lowest at the lake outflow (0.55 ng TEQ kg-1 d.w.). Samples collected after one year of
SBFS implementation showed 70% reduction of sediment toxicity in the lake indicating
positive role of such ecohydrological solution on the quality of lake ecosystem and in
consequence on the human health.
The obtained data indicate that the reduction of dioxins contamination in the upper part of
the river by construction of the SBFS is fundamental to the improvement of the quality of the
lake and lower part of the river. Implementation of such system reduced the input of dioxins
to the lake through sedimentation and possibly due to acceleration of photo- and
biodegradation processes and in consequence improve the quality of the whole river-lake
system.
The study was financed by the Ministry of Foreign Affairs of the Republic of Poland
within the Polish Aid Programme 2011 project no 23/2011 and 62/2012: “Implementation of
Ecohydrology – a transdisciplinary science for integrated water management and sustainable
development in Ethiopia”. |
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