Methane in surface waters of Oregon estuaries and rivers1

Abstract

Methane concentrations in surface waters of Oregon rivers and estuaries were measured over a 4‐yr period. Geographic variations in riverine CH4 were observed. Results from undisturbed forest streams indicate that rivers can contain high natural levels of CH4 not attributable to pollution. Lateral diffusion and runoff from saturated forest and fertilized agricultural soils may be important in determining methane levels in rivers. Methane concentrations in well‐flushed estuaries appear to be controlled mainly by mixing between high CH4‐containing river water and low CH4‐containing seawater endmembers. Rivers and estuaries were found to be sources of methane to the atmosphere. Calculated daily fluxes to the atmosphere ranged from 1.2 to 71 mg CH4 m−2 for rivers and from 0.04 to 21 mg CH4 m−2 for estuarine samples.

Seasonal variability of methane in the rivers and lagoons of Ivory Coast (West Africa)

“…This spatial trend is also consistent with the seasonal CH 4 maximum at low discharge in many temperate rivers (Lilley et al 1996;Middelburg et al 2002;Abril et al 2007). CH 4 in rivers originates from the combination of a terrestrial source, dominating at high river discharge when concentrations are lower or similar, and an aquatic source, dominating at low discharge, when concentrations can be much higher (De Angelis and Lilley 1987;Middelburg et al 2002). As suggested by Middelburg et al (2002), river size is not the only important factor to explain differences in CH 4 concentrations across different rivers.…”

“…In estuarine channels, net CH 4 inputs from the sediments to the water column and CH 4 production in the water column are generally low because oxic and suboxic respiration dominate (Abril and Borges 2004). Consequently, CH 4 in estuarine waters originates from two major sources: (1) rivers, which receive CH 4 from soils, groundwater, wetlands and floodplains on the watershed (De Angelis and Lilley 1987;Richey et al 1988) and (2) tidal wetlands and mud flats, which are generally vegetated and enriched in organic matter to support methanogenesis (Bartlett et al 1987;Chanton et al 1989;Kelley et al 1995;Middelburg et al 2002;Abril and Borges 2004). Majors sinks of CH 4 in estuarine channels are the export to the adjacent coastal zone that dominates in the case of estuaries with a high freshwater discharge and a short residence time (Scranton and McShane 1991;Middelburg et al 2002), the emission to the atmosphere and the bacterial oxidation in the water column and sediment.…”

Methanogenic System of a Small Lowland Stream Sitka, Czech Republic

“…If so, surface water is continually saturated by gases produced by hyporheic metabolism, leading to supersaturation of surface water and induced diffusion of these gases out of river water (volatizing). Moreover, the run-off and drainage of adjacent soils can also contribute greatly to the degree of greenhouse gas supersaturation (De Angelis & Lilley 1987, Kroeze & Seitzinger 1998, Worral & Lancaster 2005, Wilcock & Sorrell 2008. For example, CH4 in the estuarine waters may come from microbial production in water, sediment release, riverine input and inputs of methane-rich water from surrounding anoxic environments (Zhang et al 2008b).…”

Ethylene and methane in the upper water column of the subtropical Atlantic

“…offshore oil and gas production in shelf areas (Brooks & Sackett 1973). Advection of methane enriched coastal waters (Scranton & Farrington 1977;De Angelis & Lilley 1987;Cynar & Yayanos 1992) and riverine influence (Jones & Amador 1993) are also relevant processes. For the open ocean, biological in situ production is assumed to cause elevated methane concentrations in the upper water column < 500 m (Lamontagne et al 1973;Scranton & Brewer 1977;Traganza et al 1979;Burke et al 1983;Owens et al 1991).…”