SEMINAR: Greenhouse Gas Emissions from Small Ponds: From Arctic to Western Australia
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Greenhouse Gas Emissions from Small Ponds: From Arctic to Western Australia : SESE and Oceans Institute Seminar |
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Lakes are now considered as significant greenhouse gas (GHG) conduits to the atmosphere. Small and shallow aquatic systems in particular such as ponds and wetlands can represent large GHG emitters as they generally contain high nutrients and organic carbon and have a small volume to area ratio, which does not allow methane oxidation to mitigate GHG production efficiently. The increasing abundance of small ponds associated to permafrost thawing in arctic regions and of wastewater treatment ponds (WWTP) as the human population grow makes these two systems particularly relevant for GHG studies.
Permafrost soils store half of the global below ground organic carbon stock, which is now being mobilized as peat soils thaw and erode. Part of the mobilized carbon is emitted, stored or transformed by ponds and wetlands before it makes its way to the coastal ocean. Permafrost thaw ponds can last from days to millennia, depending on latitude, local geomorphology, ongoing erosion, precipitation regimes, and plant colonization. They are generally large emitters of GHG, with great variations in CH4 fluxes. For example, on Bylot Island (73°N), fluxes varied from -0.1 to 0.9 gC m-2 d-1 for CO2, and from 0.03 to 76 mgC m-2 d-1 for dissolved CH4 (summer 2005 to 2011; N=150). Moreover, CH4 escaping through ebullition was shown to represent up to 95% of total emissions. In addition to the availability of nutrients and the lability of organic carbon, the thermal stratification, the light availability and the type of microbial communities will largely influence the direction and rate of emissions. These factors are being investigated in the Canadian Arctic and subarctic regions.
On their side, WWTP have plenty of organic carbon and nutrients, and sometimes they have toxic cyanobacterial blooms and irregular sludge settling, potentially lowering their treatment efficiency. Although algal blooms use CO2, it is not clear whether they act as mitigating agents (C sink) if the accumulated biomass represents an organic input to pond sediments where CH4 is anaerobically produced. A preliminary study on WWTP in Quebec and WA indicates that these systems are very large CO2 and CH4 emitters (for CO2, up to 20 gC m-2 d-1 measured in Quebec ponds, and for CH4, up to 310 mgC m-2 d-1 measured in WA ponds, excluding ebullition). Diurnal variations in GHG emissions and CH4 ebullition still need to be closely investigated in these systems. A series of WWTP are presently being sampled in southern WA in close collaboration with A. Ghadouani team and Water Corp.
Speaker(s) |
Prof Isabelle Laurion, INRS-ETE, Quebec, Canada. On Sabbatical at UWA
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Location |
Lecture Theatre 1, G17, Mathematics Building
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Contact |
Lorraine Dorn
<[email protected]>
: 3701
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Start |
Thu, 25 Oct 2012 16:00
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End |
Thu, 25 Oct 2012 17:00
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Submitted by |
Lorraine Dorn <[email protected]>
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Last Updated |
Mon, 22 Oct 2012 13:38
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