Abstract
Abstract. Photo-optical systems are common in marine sciences and have been extensively used in coastal and deep-sea research. However, due to technical limitations in the past photo images had to be processed manually or semi-automatically. Recent advances in technology have rapidly improved image recording, storage and processing capabilities which are used in a new concept of automated in situ gas quantification by photo-optical detection. The design for an in situ high-speed image acquisition and automated data processing system is reported ("Bubblemeter"). New strategies have been followed with regards to back-light illumination, bubble extraction, automated image processing and data management. This paper presents the design of the novel method, its validation procedures and calibration experiments. The system will be positioned and recovered from the sea floor using a remotely operated vehicle (ROV). It is able to measure bubble flux rates up to 10 L/min with a maximum error of 33% for worst case conditions. The Bubblemeter has been successfully deployed at a water depth of 1023 m at the Makran accretionary prism offshore Pakistan during a research expedition with R/V Meteor in November 2007.
Highlights
The observation of bubbles in fluids is of primary importance for many physical, medical and chemical engineering processes
Recent advances in technology have rapidly improved image recording, storage and processing capabilities which are used in a new concept of automated in situ gas quantification by photo-optical detection
The key objective for this new design is to be able to monitor bubble seeps for an extended period of time. This can be achieved, for example, by optically imaging gas bubbles while they rise through the volume of observation
Summary
The observation of bubbles in fluids is of primary importance for many physical, medical and chemical engineering processes. There are only a few locations in the world where the bubble flux has been quantified by order-of-magnitude estimations at deep-sea depths, these are Hakon Mosby mud volcano (1250 m) (Sauter et al, 2006), at Hydrate Ridge (580 to 780 m) (Torres et al, 2002), in the Gulf of Mexico (525 to 550 m) (Leifer and MacDonald, 2003), and at Vodyanitskii Mud Volcano (2070 m) (Sahling et al, 2009) At those locations, single seep vents were observed with in situ flux rates ranging between approximately 0.1 and 5 L/min. The key objective for this new design is to be able to monitor bubble seeps for an extended period of time This can be achieved, for example, by optically imaging gas bubbles while they rise through the volume of observation. We report on the first two stages of development
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