Size Does Matter: Importance of Large Bubbles and Small-Scale Hot Spots for Methane Transport

DelSontro, Tonya; Mcginnis, Daniel Frank; Wehrli, Bernhard; Ostrovsky, Ilia

doi:10.1021/es5054286

Cited by 108 publications

(110 citation statements)

References 45 publications

Supporting

Mentioning

104

Contrasting

Unclassified

Order By: Relevance

“…The high rates of methane ebullition from Guntersville compared to CH 4 ebullition at the other reservoirs (Table 3) also support such possibility, because the funnel samplers integrated bubble-emissions over~24-h periods. Based on recent evidence of high within-reservoir spatial variability in ebullition [44], we suggest that an intensive seasonal and diel sampling effort of GHG emissions with increased spatial coverage at Guntersville would be very informative on processes related to CH 4 and CO 2 ebullitive emissions from hydropower reservoirs.…”

Section: Discussionmentioning

confidence: 90%

CO2 is Dominant Greenhouse Gas Emitted from Six Hydropower Reservoirs in Southeastern United States during Peak Summer Emissions

Bevelhimer

Stewart

Fortner

et al. 2016

Water

View full text Add to dashboard Cite

During August-September 2012, we sampled six hydropower reservoirs in southeastern United States for CO 2 and CH 4 emissions via three pathways: diffusive emissions from water surface; ebullition in the water column; and losses from dam tailwaters during power generation. Estimates of average areal emission rates of CO 2 attributable to the six reservoirs (i.e., reservoir plus tailwater emissions) ranged from 994 to 2760 mg¨m´2¨day´1, which is low to moderate compared to CO 2 emissions rates reported for tropical hydropower reservoirs and boreal ponds and lakes, and similar to rates reported for other temperate reservoirs. Similar average rates for CH 4 were also relatively low, ranging from 6 to 187 mg¨m´2¨day´1. On a whole-reservoir basis, estimates of total emissions of CO 2 ranged 10-fold, from 42,740 kg per day for Fontana to 501,151 kg per day for Guntersville, and total emissions of CH 4 ranged over 30-fold, from 251 kg per day for Fontana to 9153 kg per day for Allatoona. Emissions through the tailwater pathway varied among reservoirs, comprising from 19% to 65% of total CO 2 emissions and 0% to 84% of CH 4 emissions, depending on the reservoir. Emission rates were significantly correlated with several reservoir morphological and water quality characteristics, including metrics related to vertical stratification (e.g., minimum water column temperature and maximum dissolved oxygen) and reservoir productivity (e.g., water transparency and chlorophyll a concentration).

show abstract

Section: Discussionmentioning

confidence: 90%

CO2 is Dominant Greenhouse Gas Emitted from Six Hydropower Reservoirs in Southeastern United States during Peak Summer Emissions

Bevelhimer

Stewart

Fortner

et al. 2016

Water

View full text Add to dashboard Cite

show abstract

“…8). DelSontro et al (2015) also reported a strong positive correlation between ebullition flux and bubble volume in open water and found that the largest 10 % of the bubbles observed in Lake Wohlen, Switzerland, accounted for 65 % of the CH 4 transport. According to the authors, large bubbles are disproportionately important because they contain exponentially more CH 4 with increasing diameter, rise faster, and have less time and a relatively smaller surface area to dissolve or exchange CH 4 with the surroundings (DelSontro et al, 2015).…”

Section: Spatial Pattern Of Ch 4 and Co 2 Fluxesmentioning

confidence: 88%

Summer fluxes of methane and carbon dioxide from a pond and floating mat in a continental Canadian peatland

et al. 2016

View full text Add to dashboard Cite

Abstract. Ponds smaller than 10 000 m2 likely account for about one-third of the global lake perimeter. The release of methane (CH4) and carbon dioxide (CO2) from these ponds is often high and significant on the landscape scale. We measured CO2 and CH4 fluxes in a temperate peatland in southern Ontario, Canada, in summer 2014 along a transect from the open water of a small pond (847 m2) towards the surrounding floating mat (5993 m2) and in a peatland reference area. We used a high-frequency closed chamber technique and distinguished between diffusive and ebullitive CH4 fluxes. CH4 fluxes and CH4 bubble frequency increased from a median of 0.14 (0.00 to 0.43) mmol m−2 h−1 and 4 events m−2 h−1 on the open water to a median of 0.80 (0.20 to 14.97) mmol m−2 h−1 and 168 events m−2 h−1 on the floating mat. The mat was a summer hot spot of CH4 emissions. Fluxes were 1 order of magnitude higher than at an adjacent peatland site. During daytime the pond was a net source of CO2 equivalents to the atmosphere amounting to 0.13 (−0.02 to 1.06) g CO2 equivalents m−2 h−1, whereas the adjacent peatland site acted as a sink of −0.78 (−1.54 to 0.29) g CO2 equivalents m−2 h−1. The photosynthetic CO2 uptake on the floating mat did not counterbalance the high CH4 emissions, which turned the floating mat into a strong net source of 0.21 (−0.11 to 2.12) g CO2 equivalents m−2 h−1. This study highlights the large small-scale variability of CH4 fluxes and CH4 bubble frequency at the peatland–pond interface and the importance of the often large ecotone areas surrounding small ponds as a source of greenhouse gases to the atmosphere.

show abstract

“…Since the Sauter Mean Diameter has been shown to be useful for estimating bubble dissolution rates for an entire bubble size distribution, the potential increase in Sauter Mean Diameter compared to measured data could be taken into consideration in dissolution calculations. For sites such as the one described in DelSontro () where bubbles over 2 mL (1.56 cm equivalent diameter) are found to contribute significantly to total ebullition flux, the sensor could be altered to contain a wider glass funnel stem which may improve large volume estimates. However, a larger funnel stem means fewer rising bubbles would be elongated, potentially reducing sensor accuracy as described under Potential Mechanism #6.…”

Section: Assessmentmentioning

confidence: 99%

An enhanced bubble size sensor for long‐term ebullition studies

Delwiche

Hemond

2017

Limnology & Ocean Methods

View full text Add to dashboard Cite

Methane ebullition from freshwater sediments is a significant source of greenhouse gas to the atmosphere. Methane bubble size determines the fraction of methane that dissolves into the water column instead of entering the atmosphere, but current methods to measure bubble sizes in situ are limited. Previously, we reported the design for a novel optical bubble size sensor capable of measuring methane bubble sizes in situ. Here, we report sensor enhancements to allow for continuous long‐term sensor deployment, uninterrupted data collection under high ebullition flux, and improved bubble volume measurement accuracy. The enhanced design includes a data and power cable running from the sensor to a custom data buoy housing batteries and an SD memory card. Batteries and SD cards are replaced every 2–4 weeks through the data buoy, allowing for continuous, undisturbed sensor deployment. In addition, sensor parameters have been tuned to reduce error from particle intrusion and fluctuations in raw signals that were observed during transit of some bubbles through the sensor. Field data show that on average the sensor measures cumulative bubble volumes equaling approximately 86% of collected gas volumes. We discuss potential mechanisms of remaining error, some of which may be due to zooplankton intrusion, and suggest directions for future sensor enhancements.

show abstract

Size Does Matter: Importance of Large Bubbles and Small-Scale Hot Spots for Methane Transport

Cited by 108 publications

References 45 publications

CO2 is Dominant Greenhouse Gas Emitted from Six Hydropower Reservoirs in Southeastern United States during Peak Summer Emissions

CO2 is Dominant Greenhouse Gas Emitted from Six Hydropower Reservoirs in Southeastern United States during Peak Summer Emissions

Summer fluxes of methane and carbon dioxide from a pond and floating mat in a continental Canadian peatland

An enhanced bubble size sensor for long‐term ebullition studies

Contact Info

Product

Resources

About