TY - JOUR
T1 - Methane bubble growth and migration in aquatic sediments observed by X-ray muCT
AU - Liu, Liu
AU - De Kock, Tim
AU - Wilkinson, Jeremy
AU - Cnudde, Veerle
AU - Xiao, Shangbin
AU - Buchmann, Christian
AU - Uteau, Daniel
AU - Peth, Stephan
AU - Lorke, Andreas
PY - 2018/1/29
Y1 - 2018/1/29
N2 - Methane bubble formation and transport is an important component of biogeochemical carbon cycling in aquatic sediments. To improve understanding of how sediment mechanical properties influence bubble growth and transport in freshwater sediments, a 20-day laboratory incubation experiment using homogenized natural clay and sand was performed. Methane bubble development at high resolution was characterized by mu CT. Initially, capillary invasion by micro bubbles (textlangle0.1 mm) dominated bubble formation, with continued gas production (4 days for clay; 8 days for sand), large bubbles formed by deforming the surrounding sediment, leading to enhanced of macropore connectivity in both sediments. Growth of large bubbles (textrangle1 mm) was possible in low shear yield strength sediments (textlangle100 Pa), where excess gas pressure was sufficient to displace the sediment. Lower within the sand, higher shear yield strength (textrangle360 Pa) resulted in a predominance of microbubbles where the required capillary entry pressure was low. Enhanced bubble migration, triggered by a controlled reduction in hydrostatic head, was observed throughout the clay column, while in sand mobile bubbles were restricted to the upper 6 cm. The observed macropore network was the dominant path for bubble movement and release in both sediments.
AB - Methane bubble formation and transport is an important component of biogeochemical carbon cycling in aquatic sediments. To improve understanding of how sediment mechanical properties influence bubble growth and transport in freshwater sediments, a 20-day laboratory incubation experiment using homogenized natural clay and sand was performed. Methane bubble development at high resolution was characterized by mu CT. Initially, capillary invasion by micro bubbles (textlangle0.1 mm) dominated bubble formation, with continued gas production (4 days for clay; 8 days for sand), large bubbles formed by deforming the surrounding sediment, leading to enhanced of macropore connectivity in both sediments. Growth of large bubbles (textrangle1 mm) was possible in low shear yield strength sediments (textlangle100 Pa), where excess gas pressure was sufficient to displace the sediment. Lower within the sand, higher shear yield strength (textrangle360 Pa) resulted in a predominance of microbubbles where the required capillary entry pressure was low. Enhanced bubble migration, triggered by a controlled reduction in hydrostatic head, was observed throughout the clay column, while in sand mobile bubbles were restricted to the upper 6 cm. The observed macropore network was the dominant path for bubble movement and release in both sediments.
U2 - 10.1021/acs.est.7b06061
DO - 10.1021/acs.est.7b06061
M3 - Article
SN - 0013-936X
VL - 52
SP - 2007
EP - 2015
JO - Environmental Science & Technology
JF - Environmental Science & Technology
IS - 4
ER -