Temporal Variations of Methane Flux from Submarine Mud Volcanoes off Southwest Taiwan
Date Issued
2014
Date
2014
Author(s)
Yang, Tsung-Han
Abstract
Submarine mud volcanoes are features that episodically emit gases, fluids, and mud onto the seafloor. Methane is the representative gas transport by mud volcanoes efficiently from deep buried sediment to the water column, and potentially to the atmosphere as a greenhouse gas. Gas plume, dissolve methane concentration, methane flux to the atmosphere changes from time to time. This study was conducted during cruise OR3-1693, OR3-1755, OR3-1756, OR3-1776. To understand the activity of gas emissions of mud volcano, we utilized the 38kz echo sounder to scan back and forth over mud volcanoes and obtained acoustic images of plumes. Water column samples were collected above the venting at the tidal maximum and minimum.
Three gravity cores taken at the mudflow site of G96 show high methane concentration (38,522 μl/l ) at shallow depth of 70 cm, while sulfate concentration drop from background value 30mM to 5mM. Dissolved inorganic carbon( DIC) decrease from 0 ‰ to -30 ‰. δ13C of methane located between -12 and -20‰, indicated that methane are mainly thermalgenic in origin.
By calculating top water methane concentration, bottom water methane concentration with gas diffusion equation and diffusion rate, the results show that at shallow water mud volcanoes and mod volcanoes with larger plumes, methane can be transfer to the atmosphere more sufficiently. Methane flux to the atmosphere of three mud volcanoes: MV10：4.3 μmol/ m2/d, MV1：47.1 μmol/ m2/d, MV12：4.9μmol/ m2/d。
Subjects
台灣西南海域
海底泥火山
甲烷通量
潮汐
時序變化
SDGs
Type
thesis
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