Greenhouse gas fluxes from the eutrophic Temmesjoki River and its Estuary in the Liminganlahti Bay (the Baltic Sea)

• Published in: Biogeochemistry 2008-09, Vol.90 (2), p.193-208
• Main Authors: Silvennoinen, Hanna, Liikanen, Anu, Rintala, Jaana, Martikainen, Pertti J
• Format: Article
• Language: English
• Subjects: Agricultural land; Aquatic ecosystems; Biogeosciences; Brackish; Carbon dioxide; Carbon dioxide emissions; Catchment areas; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Ecosystems; Emissions; Engineering and environment geology. Geothermics; Environmental Chemistry; Estuaries; Eutrophication; Exact sciences and technology; Farm buildings; Gases; Geochemistry; Greenhouse gases; Land use; Life Sciences; Marine and continental quaternary; Methane; Nitric oxide; Nitrous oxide; Peatlands; Pollution, environment geology; River water; Rivers; Supersaturation; Surface water; Surficial geology; Upstream; Watersheds; Wind speed
• ISSN: 0168-2563; 1573-515X
• DOI: 10.1007/s10533-008-9244-1

We studied concentrations of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) in the eutrophic Temmesjoki River and Estuary in the Liminganlahti Bay in 2003-2004 and evaluated the atmospheric fluxes of the gases based on measured concentrations, wind speeds and water current velocities. The Temmesjoki River was a source of CO₂, CH₄ and N₂O to the atmosphere, whereas the Liminganlahti Bay was a minor source of CH₄ and a minor source or a sink of CO₂ and N₂O. The results show that the fluxes of greenhouse gases in river ecosystems are highly related to the land use in its catchment areas. The most upstream river site, surrounded by forests and drained peatlands, released significant amounts of CO₂ and CH₄, with average fluxes of 5,400 mg CO₂-C m⁻² d⁻¹ and 66 mg CH₄-C m⁻² d⁻¹, and concentrations of 210 μM and 345 nM, respectively, but N₂O concentrations, at an average of 17 nM, were close to the atmospheric equilibrium concentration. The downstream river sites surrounded by agricultural soils released significant amounts of N₂O (with an average emission of 650 μg N₂O-N m⁻² d⁻¹ and concentration of 22 nM), whereas the CO₂ and CH₄ concentrations were low compared to the upstream site (55 μM and 350 nM). In boreal regions, rivers are partly ice-covered in wintertime (approximately 5 months). A large part of the gases, i.e. 58% of CO₂, 55% of CH₄ and 36% of N₂O emissions, were found to be released during wintertime from unfrozen parts of the river.