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vol. 19, nr. 1 (2012)
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Effect of light intensity introduced through optical fibres on soil redox status and gases evolution
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Zofia Stępniewska, Ewelina Tokarz
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Katedra Biochemii i Chemii Środowiska, Katolicki Uniwersytet Lubelski Jana Pawła II Al. Kraśnicka 102, 20-718 Lublin |
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vol. 19 (2012), nr. 1,
pp. 171-179
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abstract:
This paper proposes a new solution for improving oxygenation state of anaerobic medium by means of optical fibres. Visible light (400-750 nm) of varying intensity (811-4866 lx) was introduced through optical fibres to an anaerobic medium (Eutric Fluvisol) for 10 days, which could activate phototrophic microorganisms producing oxygen, and indirectly change the redox potential (Eh) and the gas composition formed during the incubation period. Control showed a significant decrease of Eh from the initial level of 320.8 mV to 50.6 mV at the end of incubation. Illumination caused buffering of Eh of tested medium. In these reactors ΔEh was 130.7 mV for 811 lx, 80.7 mV for 4866 lx and the most advantageous combination was 2433 lx where ΔEh was only 30.2 mV. In the illuminated units maximal concentration of oxygen was ~2.5% (811 lx), ~6% (2433 lx) and ~5.1% (4866 lx). The formation of N2 at about 20% for the combination of 2433 lx and 4866 lx, and about 15% for 811 lx was also observed. Respiration activity of phototrophs revealed a high level of CO2 1.3% (811 lx), while the stronger illuminations led to CO2 concentrations of only 0.5% which was connected with intense binding of this gas in the photosynthesis process. Obtained results emphasise the key role of light in anaerobic soil medium. Oxygen produced by the activity of phototrophs may indirectly affect the redox state by Eh buffering and thus prevent anaerobiosis. It also affects gas formation, which may have positive environmental consequences.
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keywords:
optical fibres, anaerobiosis, soil suspension, redox potential, phototrophs
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original in:
English
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