Factors controlling the variability and emissions of greenhouse gases (CO2, CH4 and N2O) in three estuaries of the Southern Iberian Atlantic Basin during July 2017

Sierra, A.; Jiménez-López, D.; Ortega, T.; Gómez-Parra, Abelardo; Forja, Jesús M.

doi:10.1016/j.marchem.2020.103867

Cited by 22 publications

(3 citation statements)

References 106 publications

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“…A positive correlation between N 2 O% and CO 2 % in the estuaries implies that the factors that influence the production of these two gases could be common ((Harley et al, 2015). In our study, both N 2 O% and CH 4 % were positively correlated to CO 2 %, suggesting that both the gases were produced via the decomposition of the organic material obtained from advective transport from the intertidal areas adjacent to the estuaries (Sierra et al, 2020). The correlation between N 2 O% and CO 2 % suggests that denitrification occurring in the intertidal sediments may also be of interest in discussing the dynamics of N 2 O for this system (Harley et al, 2015).…”

Section: Spatial Patternsupporting

confidence: 53%

Distribution and Dynamics of Radiatively Active Gas (RAG) Emissions From Major Estuaries of the Sundarbans Mangrove, India

et al. 2022

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The world’s largest mangroves ecosystem, the Sundarbans, being highly productive and a place for extensive organic matter cycling, is considered to be the hotspot for biogeochemical studies in the tropical estuarine environment. Hence, the spatial and temporal dynamics of the biogenic gases (CO2, CH4, and N2O), also known as radiatively active gases, were measured in mangrove-dominated estuaries of the system. In addition to spatial and seasonal observation, three full tidal cycles were observed at one site. Results showed that the air/water gas saturations were widely distributed and highly variable along the stretch. The gas saturations showed varying responses to salinity and tidal fluctuations. This indicated that localized biogeochemical processes may be more influential than simple mixing and dilution processes in controlling the variability of these gases. The surface waters were always supersaturated with CH4 (Up to 13,133%) relative to the atmosphere. However, N2O ranged from 8 to 1,286% and CO2 from 30 to 2075%. N2O fluxes were ∼4.8 times higher in the pre-monsoon than the post-monsoon. CH4 fluxes were ∼3.6 times higher in the pre-monsoon than both the monsoon and the post-monsoon. CO2 fluxes were ∼10 times higher in the monsoon than both the pre-monsoon and the post-monsoon. The seasonality in the gas saturation could be linked more to the availability of substrates than physicochemical parameters. Overall, air/water CH4 fluxes varied maximally (0.4–18.4 μmol m−2 d−1), followed by CO2 fluxes (−0.6–10.9 mmol m−2 d−1), and N2O fluxes varied the least of all (−0.6–5.4 μmol m−2 d−1). Interestingly, CH4 and N2O fluxes were positively correlated to each other (p < 0.05), suggesting organic matter decomposition as the key factor in the production of these two gases. Finally, these water–air CO2, CH4, and N2O flux estimates show that the estuaries are a modest source of CH4 but fluctuate between sources and sinks for CO2 and N2O gases.

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Section: Spatial Patternsupporting

confidence: 53%

Distribution and Dynamics of Radiatively Active Gas (RAG) Emissions From Major Estuaries of the Sundarbans Mangrove, India

et al. 2022

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“…However, other studies have reported higher fluxes of 90-180 µmol m −2 d −1 in an Archipelago of the northern Baltic Sea (Myllykangas et al, 2020), and 126-163 µmol m −2 d −1 in the Belgian North Sea in May (Borges et al, 2019). In southern Spain, an average diffusive methane flux of 101 ± 116 µmol m −2 d −1 was obtained for the estuaries, and 8.0 ± 4.0 µmol m −2 d −1 for the marine area (Sierra et al, 2020).…”

Section: Diffusive Methane Fluxmentioning

confidence: 91%

Detailed Patterns of Methane Distribution in the German Bight

et al. 2021

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Although methane is a widely studied greenhouse gas, uncertainties remain with respect to the factors controlling its distribution and diffusive flux into the atmosphere, especially in highly dynamic coastal waters. In the southern North Sea, the Elbe and Weser rivers are two major tributaries contributing to the overall methane budget of the southern German Bight. In June 2019, we continuously measured methane and basic hydrographic parameters at a high temporal and spatial resolution (one measurement per minute every 200–300 m) on a transect between Cuxhaven and Helgoland. These measurements revealed that the overall driver of the coastal methane distribution is the dilution of riverine methane-rich water with methane-poor marine water. For both the Elbe and Weser, we determined an input concentration of 40–50 nmol/L compared to only 5 nmol/L in the marine area. Accordingly, we observed a comparatively steady dilution pattern of methane concentration toward the marine realm. Moreover, small-scale anomalous patterns with unexpectedly higher dissolved methane concentrations were discovered at certain sites and times. These patterns were associated with the highly significant correlations of methane with oxygen or turbidity. However, these local anomalies were not consistent over time (days, months). The calculated diffusive methane flux from the water into the atmosphere revealed local values approximately 3.5 times higher than background values (median of 36 and 128 μmol m–2 d–1). We evaluate that this occurred because of a combination of increasing wind speed and increasing methane concentration at those times and locations. Hence, our results demonstrate that improved temporal and spatial resolution of methane measurements can provide a more accurate estimation and, consequently, a more functional understanding of the temporal and spatial dynamics of the coastal methane flux.

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“…However, the three gases can behave quite differently at the boundary layer because of other non‐diffusion processes such as microbubble entrainment (Beaulieu et al., 2012; McGinnis et al., 2015; Prairie & del Giorgio, 2013; Rosentreter et al., 2017), the effect of surface films and microbial activity in the microlayer (Cunliffe et al., 2013; Frew et al., 2004; Salter et al., 2011; Schmidt & Schneider, 2011), chemical reactions in water (Hoover & Berkshire, 1969; Wanninkhof & Knox, 1996), and/or enzymatic enhancement (Berger & Libby, 1969; Emerson, 1995). Therefore, fluxes of CH 4 and N 2 O in estuaries may be overestimated or underestimated when based on k 600 models intended for CO 2 (Borges et al., 2004; Ferrón et al., 2007; Sierra et al., 2020). A direct comparison in a large river system showed that k 600 values calculated from CH 4 ( k 600 CH4) and N 2 O ( k 600 N 2 O) were statistically indistinguishable but were consistently higher than from CO 2 ( k 600 CO 2 ) (Beaulieu et al., 2012).…”

Section: Introductionmentioning

confidence: 99%

Divergent Gas Transfer Velocities of CO₂, CH₄, and N₂O Over Spatial and Temporal Gradients in a Subtropical Estuary

et al. 2021

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The coastal ocean plays an important role in global carbon (C) and nitrogen (N) budgets coupling biogeochemical cycles between land, ocean, and atmosphere (Bauer et al., 2013;Regnier et al., 2013). Estuaries are dynamic coastal ecosystems that act like a filter along the land-ocean aquatic continuum by not only biogeochemically processing and sequestering C and N originated from upstream rivers and adjacent wetlands, but also by exchanging carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) with the atmosphere (Bange et al., 1996;Borges & Abril, 2011;Cai, 2011). Accurate estimates of local water-air fluxes from estuaries are key to evaluating greenhouse gas emissions at regional and global scales (Chen et al., 2013;Saunois et al., 2020;Tian et al., 2020). Molecular diffusion is considered the predominant pathway of dissolved CO 2 , CH 4, and N 2 O to reach the atmosphere, although there is evidence of other non-diffusion processes

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Factors controlling the variability and emissions of greenhouse gases (CO2, CH4 and N2O) in three estuaries of the Southern Iberian Atlantic Basin during July 2017

Cited by 22 publications

References 106 publications

Distribution and Dynamics of Radiatively Active Gas (RAG) Emissions From Major Estuaries of the Sundarbans Mangrove, India

Distribution and Dynamics of Radiatively Active Gas (RAG) Emissions From Major Estuaries of the Sundarbans Mangrove, India

Detailed Patterns of Methane Distribution in the German Bight

Divergent Gas Transfer Velocities of CO₂, CH₄, and N₂O Over Spatial and Temporal Gradients in a Subtropical Estuary

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Factors controlling the variability and emissions of greenhouse gases (CO2, CH4 and N2O) in three estuaries of the Southern Iberian Atlantic Basin during July 2017

Cited by 22 publications

References 106 publications

Distribution and Dynamics of Radiatively Active Gas (RAG) Emissions From Major Estuaries of the Sundarbans Mangrove, India

Distribution and Dynamics of Radiatively Active Gas (RAG) Emissions From Major Estuaries of the Sundarbans Mangrove, India

Detailed Patterns of Methane Distribution in the German Bight

Divergent Gas Transfer Velocities of CO2, CH4, and N2O Over Spatial and Temporal Gradients in a Subtropical Estuary

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Divergent Gas Transfer Velocities of CO₂, CH₄, and N₂O Over Spatial and Temporal Gradients in a Subtropical Estuary