The selection, integration, and evaluation of a payload for chemical plume detection on an autonomous underwater vehicle

Pennell, Vanessa (2003) The selection, integration, and evaluation of a payload for chemical plume detection on an autonomous underwater vehicle. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (5MB)

Abstract

The oil and gas industry is growing off the East Coast of Canada, and as a result the discharges associated with production continue to grow. Mandates are in place to ensure that these activities proceed in an environmentally acceptable manner. Policies are being introduced worldwide that are leading to zero-discharge or the use of complex risk assessment processes to determine the environmental impacts of these discharges. Little real data exists about the environmental effects of these discharges, and new and innovative methods for data collection need to be considered. One possibility is to use autonomous underwater vehicles (AUV) for environmental monitoring, which is explored in this thesis. -- The steps associated with choosing and implementing an environmental payload on an AUV are discussed in this thesis. It was determined that sample collection methods were not appropriate for use on an AUV, but that in-situ sensors were useful for collecting environmental data. Sea-trials were performed in Burrard Inlet, British Columbia between February 4 and February 6, 2002. The AUV used for this project was the ARCS vehicle, supplied by International Submarine Engineering in British Columbia. The payload for this mission used two in-situ instruments, which were supplied by Applied Microsystems Ltd. The first was an underwater mass spectrometer called the "In-Spectr". It is capable of measuring dissolved gases and volatile organic chemicals to atomic masses of up to 200 atomic mass units. It was used in a continuous mode of sampling that indicated the presence or absence of a chemical. The second instrument measured conductivity, temperature, and depth (CTD) and was called the "Micro-CTD". These instruments were user-friendly and easily integrated into the ARCS vehicle. -- The trials were successful in demonstrating the use of an underwater mass spectrometer on an AUV. It was shown that the payload could be used to detect chemical plumes, which might be considered a viable option for environmental monitoring offshore. A chemical tracer, dimethyl sulphide (DMS), was pumped into the water at a maximum rate of 9 L/h, as stipulated by the BC Ministry of Water, Land and Air Protection. The mass spectrometer successfully detected the location of the DMS in the water ±13.5 m. The CTD was used to complement this data. Temperatures in the Inlet were relatively constant, with variations within one degree Celsius. Salinity increased with depth. The fresher water on the surface could be attributed to the larger volumes of precipitation during the winter months in that geographic region. -- The mass spectrometer was highly sensitive to power interruptions, which forced the instrument to shutdown. It was recommended that a back-up power system be provided. It was also recommended that the internal clocks on all instruments be synchronized before the sea-trials to simplify data analysis.

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