Enhanced methane emissions from oil and gas exploration areas to the atmosphere – The central Bohai Sea

Zhang, Yong; Zhao, Huade; Zhai, Weidong; Zang, Kunpeng; Wu, Juying

doi:10.1016/j.marpolbul.2014.02.002

Cited by 26 publications

(14 citation statements)

References 57 publications

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“…However, the locations of DO-deficit areas detected in this study were similar to the DO-deficient zones previously outlined by Zhao et al (2017) and Wei et al (2019). The atmospheric CH 4 mixing ratio in this study (1.89 ± 0.05 ppmv) is much lower than in our previous results from measurements in the central Bohai Sea in July 2012 (2.07 ppmv, Zhang et al, 2014), probably also due to the dilution effect of the three typhoons, which originated from the adjacent open ocean, i.e., the western North Pacific Ocean. However, this field-measured result is slightly higher than the globally averaged marine surface mean value for August 2018 (1.85 ppmv 2 ).…”

Section: Comparisons With Results In the Literaturesupporting

confidence: 86%

“…Spatiotemporal variations in [CH 4 ] and thereby sea-to-air CH 4 fluxes have been previously investigated by Li et al (2010), Zhang et al (2014), and Zang (2018), showing that the Bohai Sea is usually supersaturated with CH 4 , with moderate sea-to-air CH 4 fluxes from 0.8 to 53.9 µmol m −2 d −1 . However, so far, there have been no studies relating the sea-to-air CH 4 flux to multiple sources in this area, although several earlier studies showed that river discharges and oil-gas leakages contributed to the Bohai Sea CH 4 release (Gu et al, 2011;Zhang et al, 2014).…”

Section: Introductionmentioning

confidence: 84%

“…Ex situ processes usually refer to (1) CH 4 release from the seafloor, including release from sediment due to diagenesis of buried organic matter Sun et al, 2018) and release from other natural geological settings such as submarine hydrocarbon seeps (e.g., Boles et al, 2001;Reeburgh, 2007) and (2) CH 4 addition from river runoffs, which is significant in estuarine areas (e.g., Ye et al, 2016;Sun et al, 2018). In addition, anthropogenic eutrophication (e.g., Naqvi et al, 2010;Borges et al, 2016) and episodic oil-gas leakages (e.g., Zhang et al, 2014;Zhang and Zhai, 2015) can enhance the CH 4 concentration in the overlying water column.…”

Section: Introductionmentioning

confidence: 99%

“…The Bohai Sea is a semi-enclosed shallow-water marginal sea of the northwest Pacific Ocean with seasonal stratification (Huang et al, 1999;Zhao et al, 2017;Zhou et al, 2017) and a summertime dissolved oxygen (DO) deficit in its bottom waters (Zhai et al, 2012(Zhai et al, , 2019Zhao et al, 2017;Wei et al, 2019). Spatiotemporal variations in [CH 4 ] and thereby sea-to-air CH 4 fluxes have been previously investigated by Li et al (2010), Zhang et al (2014), and Zang (2018), showing that the Bohai Sea is usually supersaturated with CH 4 , with moderate sea-to-air CH 4 fluxes from 0.8 to 53.9 µmol m −2 d −1 . However, so far, there have been no studies relating the sea-to-air CH 4 flux to multiple sources in this area, although several earlier studies showed that river discharges and oil-gas leakages contributed to the Bohai Sea CH 4 release (Gu et al, 2011;Zhang et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Exploring Sources and Biogeochemical Dynamics of Dissolved Methane in the Central Bohai Sea in Summer

2020

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To clarify the sources and biogeochemical dynamics of dissolved methane (CH 4 ) in shallow-water coastal oceans, we investigated the concentrations, sea-to-air fluxes, and net cycling rate of CH 4 in the central Bohai Sea in summer 2018. During the survey, both summertime stratification and dissolved oxygen (DO) deficit were observed. In the surface layer, CH 4 concentration ([CH 4 ]) ranged from 3.08 to 10.27 nmol kg −1 . The average sea-to-air flux was estimated at 6.46 ± 3.32 µmol m −2 d −1 , indicating that the Bohai Sea serves as a source of atmospheric CH 4 . In the bottom layer, [CH 4 ] ranged from 4.29 to 31.04 nmol kg −1 . The downward increase in [CH 4 ] within the water column indicated substantial sources of CH 4 in the seafloor. Based on the complex relationship between the saturation ratio of CH 4 and DO, three types of CH 4 release from the seafloor were identified, including diagenesis of buried organic matter, natural leakage from geological settings, and anthropogenic release from offshore oil/gas development. The saturation ratios of CH 4 in bottom waters were positively correlated with the degree of stratification of the water column. Using a two-layer box model, sedimentary CH 4 release rates at two oxygen-deficient stations were estimated to be 56.0-60.8 µmol m −2 d −1 , which was much higher than the sea-to-air fluxes. The modeling results also indicated that the majority of seafloor released CH 4 (>90%) was consumed in the water column of this shallow-water coastal sea. This is the first comprehensive study on CH 4 cycling in the Bohai Sea. This work shows the indicative role of DO in identifying multiple CH 4 sources and highlights the dominance of water stratification and microbial consumption in local CH 4 dynamics. KEY POINTS -Dissolved CH 4 exhibited complex relations with oxygen in the Bohai Sea. -Three types of CH 4 sources from seafloor were identified. -Stratification hampered the upward transport of dissolved CH 4 . -Strengths of CH 4 cycling terms are quantified.

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Section: Comparisons With Results In the Literaturesupporting

confidence: 86%

Section: Introductionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Exploring Sources and Biogeochemical Dynamics of Dissolved Methane in the Central Bohai Sea in Summer

2020

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“…However, the mechanisms governing the fate of methane and other hydrocarbons into the water column are still under debate, and their probability to reach the atmosphere seems to be site-dependent [57][58][59][60][61][62][63][64]. Accordingly, although difficult, quantifying the contribution of oceanic methane to the global atmospheric budget is crucial, and this necessarily requires knowledge of local methane fluxes from submarine seeps as input.…”

Section: Introductionmentioning

confidence: 99%

Gas Seepage along the Edge of the Aquitaine Shelf (France): Origin and Local Fluxes

et al. 2017

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During the scientific expedition GAZCOGNE2 at the Bay of Biscay nine gas seeps were sampled for the first time and their flux was measured using an in situ pressure-preservation sampler (PEGAZ, © IFREMER). Overall, three sites were investigated to determine the nature and the origin of the gases bubbling at the seafloor and forming acoustic plumes into the water column, as this was the question raised from the first geologic study of the area. This has guided our study and accordingly corresponds to the main purpose of the present article. Thus, the molecular and isotopic ( D and 13 C) analyses revealed that the gas seeps were primarily composed of methane. Both methane and ethane are of microbial origin, and the former has been generated by microbial reduction of carbon dioxide. Heavier hydrocarbons accounted for less than 0.06% mol of the total amount. Despite the microbial origin of methane, the samples exhibit subtle differences with respect to the 13 C CH 4 values, which varied between −72.7 and −66.1‰. It has been suggested that such a discrepancy was predominantly governed by the occurrence of anaerobic methane oxidation. The PEGAZ sampler also enabled us to estimate the local gas fluxes from the sampled streams. The resulting values are extremely heterogeneous between seeps, ranging from 35 to 368 mLn⋅min −1 . Assuming a steady discharge, the mean calculated methane emission for the nine seeps is of 38 kmol⋅yr −1 . Considering the extent of the seep area, this very local estimate suggests that the Aquitaine Shelf is a very appropriate place to study methane discharge and its fate on continental shelves.

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Increasing temperature and sulfate enhances the efficiency of methane abatement in an anaerobic oxidation of methane bioreactor (AOMB) system

Liang,

Feng,

Chen

et al. 2024

Applied Energy

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Enhanced methane emissions from oil and gas exploration areas to the atmosphere – The central Bohai Sea

Cited by 26 publications

References 57 publications

Exploring Sources and Biogeochemical Dynamics of Dissolved Methane in the Central Bohai Sea in Summer

Exploring Sources and Biogeochemical Dynamics of Dissolved Methane in the Central Bohai Sea in Summer

Gas Seepage along the Edge of the Aquitaine Shelf (France): Origin and Local Fluxes

Increasing temperature and sulfate enhances the efficiency of methane abatement in an anaerobic oxidation of methane bioreactor (AOMB) system

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