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Liikanen, Anu; Huttunen, Jari T.; Murtoniemi, Timo; Tanskanen, Heikki; Väisänen, Tero; Silvola, Jouko; Alm, Jukka; Martikainen, Pertti J.

doi:10.1023/a:1026070209387

Cited by 55 publications

(17 citation statements)

References 26 publications

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“…They also highlight that factors influencing N 2 O production pathways in the benthic environment are still not clearly identified, particularly with regard to the relative importance of nitrification, nitrifier denitrification, and denitrification (Mengis et al, 1996;Liikanen et al, 2003b;Liikanen and Martikainen, 2003;McCrackin and Elser, 2010).…”

Section: V Freymond Et Al: Year-round N 2 O Production By Benthimentioning

confidence: 99%

Year-round N2O production by benthic NOx reduction in a monomictic south-alpine lake

et al. 2013

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Abstract. Nitrous oxide (N 2 O) is a potent greenhouse gas, generated through microbial nitrogen (N) turnover processes, such as nitrification, nitrifier denitrification, and denitrification. Previous studies quantifying natural sources have mainly focused on soils and the ocean, but the potential role of terrestrial water bodies in the global N 2 O budget has been widely neglected. Furthermore, the biogeochemical controls on the production rates and the microbial pathways that produce benthic N 2 O in lakes are essentially unknown. In this study, benthic N 2 O fluxes and the contributions of the microbial pathways that produce N 2 O were assessed using 15 N label flow-through sediment incubations in the eutrophic, monomictic south basin of Lake Lugano in Switzerland. The sediments were a significant source of N 2 O throughout the year, with production rates ranging between 140 and 2605 nmol N 2 O h −1 m −2 , and the highest observed rates coinciding with periods of water column stratification and stably anoxic conditions in the overlying bottom water. Nitrate (NO − 3 ) reduction via denitrification was found to be the major N 2 O production pathway in the sediments under both oxygen-depleted and oxygen-replete conditions in the overlying water, while ammonium oxidation did not contribute significantly to the benthic N 2 O flux. A marked portion (up to 15 %) of the total NO − 3 consumed by denitrification was reduced only to N 2 O, without complete denitrification to N 2 . These fluxes were highest when the bottom water had stabilized to a low-oxygen state, in contrast with the notion that stable anoxia is particularly conducive to complete denitrification without accumulation of N 2 O. This study provides evidence that lake sediments are a significant source of N 2 O to the overlying water and may produce large N 2 O fluxes to the atmosphere during seasonal mixing events.

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Section: V Freymond Et Al: Year-round N 2 O Production By Benthimentioning

confidence: 99%

Year-round N2O production by benthic NOx reduction in a monomictic south-alpine lake

et al. 2013

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“…E-government promotes a better life characterized by representative and participative democracy, transparent, open and collaborative decision making, close relation between government, business and citizens, enhanced service delivery, new infrastructure and info-structure, integrated and seamless government services that cut across departmental boundaries and providing a convenient and timely one-stop service to the citizens, and equity in the provision of government services. 5,6 Put differently, e-government has a possibility of increasing honesty, efficiency and effectiveness, accountability and participatory democracy in the interaction between the government and the citizens.…”

Section: Background and Introductionmentioning

confidence: 99%

The Nature and Accessibility of E-Government in Sub Saharan Africa

Ngulube¹

2007

irie

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Electronic government (e-government) is a phenomenon that is linked to the information society and the advantages associated with it. E-government allows government departments to network and integrate their services using information and communication technologies (ICTs) in order to improve service delivery and enhance the relationship between the government and the public. The major ingredients of e-government are infrastructure, human resources and information. The reality in Sub Saharan Africa (SSA) is that all these ingredients are insufficient. The ICT infrastructure is not widely available to rural populations. In most cases, both government officials and the people who may want to use government services online lack basic skills. Government information is not properly organized as records management systems in many countries are collapsing.

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“…This has obvious consequences for the nutrient (and pollutant) exchange rate within the sediment, and at the sediment–water interface. In previous studies investigating sediment pollutant and nutrient exchange, fluxes measured by chambers often exceeded those calculated from pore water profiles. ,− The authors attributed these enhanced fluxes to methane bubbling. These fluxes can obviously be enhanced when bubbling rates are sufficiently high (e.g., at active seep sites) or in permeable sediments with advective pore water transport.…”

Section: Discussionmentioning

confidence: 92%

“…Enhanced pore water fluxes at the sediment interface as measured by benthic flux chambers has often been attributed to bubble release. ,− Thus, several studies have investigated the effect of bubble migration and release on pore water exchange processes at the sediment–water interface. Klein demonstrated up to 50% increased tracer flux in low-permeability sediments when introducing artificial bubble events, while O’Hara et al were able to show a nearly linear relationship between gas release rates and pore water advection in permeable sediments.…”

Section: Introductionmentioning

confidence: 99%

Effect of Sediment Gas Voids and Ebullition on Benthic Solute Exchange

Flury

Glud

Premke

et al. 2015

Environ. Sci. Technol.

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The presence of free gas in sediments and ebullition events can enhance the pore water transport and solute exchange across the sediment-water interface. However, we experimentally and theoretically document that the presence of free gas in sediments can counteract this enhancement effect. The apparent diffusivities (Da) of Rhodamine WT and bromide in sediments containing 8-18% gas (Da,YE) were suppressed by 7-39% compared to the control (no gas) sediments (Da,C). The measured ratios of Da,YE:Da,C were well within the range of ratios predicted by a theoretical soil model for gas-bearing soils. Whereas gas voids in sediments reduce the Da for soluble species, they represent a shortcut for low-soluble species such as methane and oxygen. Therefore, the presence of even minor amounts of gas can increase the fluxes of low-soluble species (i.e., gases) by several factors, while simultaneously suppressing fluxes of dissolved species.

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Untitled

Cited by 55 publications

References 26 publications

Year-round N<sub>2</sub>O production by benthic NO<sub>x</sub> reduction in a monomictic south-alpine lake

Year-round N<sub>2</sub>O production by benthic NO<sub>x</sub> reduction in a monomictic south-alpine lake

The Nature and Accessibility of E-Government in Sub Saharan Africa

Effect of Sediment Gas Voids and Ebullition on Benthic Solute Exchange

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Untitled

Cited by 55 publications

References 26 publications

Year-round N&lt;sub&gt;2&lt;/sub&gt;O production by benthic NO&lt;sub&gt;x&lt;/sub&gt; reduction in a monomictic south-alpine lake

Year-round N&lt;sub&gt;2&lt;/sub&gt;O production by benthic NO&lt;sub&gt;x&lt;/sub&gt; reduction in a monomictic south-alpine lake

The Nature and Accessibility of E-Government in Sub Saharan Africa

Effect of Sediment Gas Voids and Ebullition on Benthic Solute Exchange

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Product

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Year-round N<sub>2</sub>O production by benthic NO<sub>x</sub> reduction in a monomictic south-alpine lake

Year-round N<sub>2</sub>O production by benthic NO<sub>x</sub> reduction in a monomictic south-alpine lake