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Denitrification-Dependent Anaerobic Oxidation of Methane in Freshwater Sediments of Reservoirs in SE Poland

Szal Dorota, Gruca-Rokosz Renata

Journal of Ecological Engineering

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2019

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Vol. 20, nr 9

218--227

EN

The results presented here concern the anaerobic oxidation of methane (CH4) coupled with denitrification (i.e. a process abbreviated to DAMO) in the freshwater sediments of dam reservoirs located in Rzeszów, Maziarnia and Nielisz, SE Poland. The DAMO rate was determined experimentally by adding a 13CH4 isotope marker and NO3as an electron acceptor. The sediments were collected once, in autumn (September), with incubation of the 0–5, 5–10 and 10–15 cm layers then carried out at 10°C, as the temperature corresponding to the in situ conditions at the given time of the year. The DAMO rates were set against the results for the anaerobic oxidation of methane (AOM), which were obtained by incubation of reservoir sediments with the 13CH4 isotope marker alone. The DAMO rates noted were of 0.03–0.69 nmol∙g-1∙h-1 for Rzeszów Reservoir; 0.04–0.47 nmol∙g-1∙h-1 for Maziarnia Reservoir and 0.19–1.04 nmol∙g-1∙h-1 for Nielisz Reservoir. Overall, it was typical for the DAMO rates to be about twice as high as the rates of AOM with no electron acceptor added. The addition of NO3did not accelerate the methane oxidation significantly in any of the sediment layers from Maziarnia Reservoir, while the effects in Rzeszów Reservoir sediments were confined to the 10–15 cm layer. While the DAMO rates were progressively higher in the deeper layers of sediment from Maziarnia Reservoir, the trend was the reverse (downward) with depth at the Rzeszów and Nielisz sites. The results indicate that the process abbreviated as DAMO takes place in dam reservoirs and is related, not only to the presence of NO3-, but also to the sediment parameters.

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Heavy metal contamination in sediments of Rzeszów Reservoir (Poland)

Szal Dorota, Gruca-Rokosz Renata

Czasopismo Inżynierii Lądowej, Środowiska i Architektury / Journal of Civil Engineering, Environment and Architecture

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2019

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z. 66, nr 3

17--24

EN

Sediments of Rzeszów Reservoir were characterized by a higher content of zinc compared to other heavy metals (Cu, Cr, Ni and Cd). The strongest correlations between pairs of heavy metals were Cr-Ni, Ni-Zn, Cu-Ni and Cr-Zn, while there was also a clear relationship between the total chromium and nickel content and the pH value, as well as the percentage of organic matter in the sediments (Cr, Zn, Cu, Ni). The content of chromium and copper occurred at levels exceeding the geochemical background, and the sediments could be classified as of purity class 2 (according to the PIG criterion) or class 3 (according to the Müller’s classification). Ecotoxicological criteria indicate that levels of chromium, nickel and cadmium could affect aquatic life. However, the heavy metals differ in mobility and bioavailability. The highest percentage of ion exchangeable fraction was recorded for nickel, and the lowest for chromium. This means that sediments have a greater ability to release nickel into the water column, as a result of which they are a secondary source of pollution for the aquatic ecosystem.

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Anaerobic oxidation of methane in freshwater ecosystems

Szal Dorota, Gruca-Rokosz Renata

Czasopismo Inżynierii Lądowej, Środowiska i Architektury / Journal of Civil Engineering, Environment and Architecture

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2019

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z. 66, nr 1

17--26

EN

Anaerobic oxidation of methane (AOM) is a biochemical process that plays an important role in aquatic ecosystems, as it significantly reduces the emission of methane (CH4 ) to the atmosphere. Under anaerobic conditions, CH4 can be oxidized with electron acceptors, such as sulphates (SO42-), nitrates (NO3-) or nitrites (NO2-), iron (Fe3+), manganese (Mn4+) and humic substances. The anaerobic oxidation of methane is mainly regulated by anaerobic methanotrophic archaea (ANME) and sulphate reducing bacteria. The AOM process is crucial to understand the CH4 cycle and anticipate future emissions of the gas from water reservoirs. The process is widely described in marine environments, however very little is known about its occurrence and importance in freshwater systems. There is a great demand for this kind of the research, especially in ecosystems exposed to long-term anaerobic conditions, which may be in degraded reservoirs.