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

Abstract

We studied concentrations of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) 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 CO 2 , CH 4 and N 2 O to the atmosphere, whereas the Liminganlahti Bay was a minor source of CH 4 and a minor source or a sink of CO 2 and N 2 O. 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 CO 2 and CH 4 , with average fluxes of 5,400 mg CO 2 -C m -2 d -1 and 66 mg CH 4 -C m -2 d -1 , and concentrations of 210 lM and 345 nM, respectively, but N 2 O 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 N 2 O (with an average emission of 650 lg N 2 O-N m -2 d -1 and concentration of 22 nM), whereas the CO 2 and CH 4 concentrations were low compared to the upstream site (55 lM and 350 nM). In boreal regions, rivers are partly icecovered in wintertime (approximately 5 months). A large part of the gases, i.e. 58% of CO 2 , 55% of CH 4 and 36% of N 2 O emissions, were found to be released during wintertime from unfrozen parts of the river.

Nitrous oxide in the Changjiang (Yangtze River) Estuary and its adjacent marine area: Riverine input, sediment release and atmospheric fluxes

“…Concentrations and emissions of N 2 O in estuaries are generally found to be related to the estuarine dissolved inorganic nitrogen (DIN) levels (Seitzinger and Kroeze, 1998;Dong et al, 2004). Mean Silvennoinen et al (2008) DIN concentrations in the Changjiang estuary in this study were 12.5 ± 5.8, 12.6 ± 8.6 and 15.6 ± 8.0 µM for June, August and October 2006, respectively. Although the correlation between N 2 O concentrations and DIN was not obvious at most cruises, N 2 O and DIN data in the Changjiang Estuary fit well in the plot of estuarine N 2 O versus DIN on a global scale (Fig.…”

Air–sea exchanges of CO<sub>2</sub> in the world's coastal seas

“…Coastal waters receive large inputs of terrestrial material, such as suspended sediments and nutrients in solution or in particulate matter, in organic or inorganic forms and through river and groundwater discharge, as well as by exchange with the atmosphere, the sediments and the open ocean. They therefore tend to show greater temporal and spatial variability than open oceans, and are more affected by human activities (Cameron and Pritchard, 1963;Alongi, 1998;Chen and Tsunogai, 1998;Rabouille et al, 2001;Chen, 2002Chen, , 2003Chen, , 2004Slomp and Van Cappellen, 2004;Beusen et al, 2005;Chavez et al, 2007;Doney et al, 2007;Radach and Patsch, 2007;Peng et al, 2008;Seitzinger et al, 2010;Dürr et al, 2011;Jiang et al, 2013). However, unlike the open oceans, in which millions of observations have been made and the air-sea exchanges of CO 2 have been valued using various developed models (such as by Khatiwala et al, 2013;Schuster et al, 2013;Wanninkhof et al, 2013), coastal waters have been relatively poorly examined.…”

Longitudinal discontinuities in riverine greenhouse gas dynamics generated by dams and urban wastewater

“…While agricultural activities, including rice cultivation, animal husbandry, and N fertilization, represent the primary anthropogenic source of CH 4 and N 2 O in anthropogenically impacted river systems (Silvennoinen et al, 2008;Garnier et al, 2013), the relative contribution of wastewater and landfills often increases drastically in urbanized watersheds (Yu et al, 2013;Smith et al, 2017;Wang et al, 2017b). Downstream changes in CH 4 concentrations along the lower reach reflect localized 430 impacts of urban tributary inputs, which caused pulsatile increases in the mainstem CH 4 concentrations and decreases in δ 13 C in CH 4 downstream of the tributary inflow (Fig.…”

“…Measurements of multiple GHGs in highly human-impacted river systems have provided drastically different pictures of the longitudinal and seasonal patterns of GHGs from those observed in large natural rivers (Silvennoinen et al, 2008;Burgos et al, 2015;Crawford et al, 2016;Smith et al, 2017;Wang et al, 2017b). A growing number of dams constructed on rivers worldwide have altered riverine flows of water and materials to the oceans, trapping over 100 billion metric tons of sediment and up to 3 billion metric tons of C in the reservoirs constructed over the last five decades (Syvitski et al, 2005).…”