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Chemical analysis of sediments using X-Ray fluorescence on-board an Autonomous Underwater Vehicle

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Breen, JP (2013) Chemical analysis of sediments using X-Ray fluorescence on-board an Autonomous Underwater Vehicle. PhD thesis, University of Tasmania.

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Abstract

Advances in robotics have led to the development of autonomous platforms
capable of exploring regions that are inaccessible for humans. These
regions range from extra-terrestrial surfaces, such as Mars and Titan, to the
bottom of our oceans. In addition to robotics there have also been advances
in sensor technologies in areas such as power consumption, size, weight, and
communications. The combination of field robotics with novel sensing capabilities
provides exciting science opportunities. Autonomous measurement
of phenomena present in the environment offers an alternative to expensive,
time-consuming manual measurements.
This thesis investigates the novel use of a miniaturised X-Ray Fluorescence
(XRF) spectrometer sensor system as part of the scientific payload on
an Autonomous Underwater Vehicle (AUV). This will allow the automated
in situ semi-quantitative analysis of heavy metal contamination present in
marine sediments. Heavy metal contamination of sediments is particularly
important because of its potential impact on associated ecosystems and human
health.
To achieve this capability the XRF system has been integrated with the
AUV using a custom housing that enables the sensor to be operated safely
underwater. A landing behaviour has been developed for the AUV that enables
the vehicle to land on the seabed, without signicantly disturbing the
sediment layer, and to then remain in a stationary position for the duration
of the measurement. Automated data analysis using genetic algorithms
was performed on the XRF data on-board the vehicle. This would enable
the AUV control system to make informed decisions based on the results of
measurements facilitating adaptive sampling strategies.
A total of 21 in situ measurements have been performed in the Derwent
estuary region, located in south-east Tasmania, Australia. The results show
significantly higher relative heavy metal concentrations in areas of industrial
activity. This demonstrates the developed system can perform in situ measurements that can be used to observe spatial variations in heavy metal
contamination. The resulting data from these measurements can guide further
comprehensive environmental monitoring missions by supporting site
selection or assisting with the remediation of contaminated sediments.
The research contribution presented in this thesis has been the development
of the capability to autonomously and intelligently perform in situ
measurements and data analysis of marine sediments using an AUV equipped
with a miniaturised XRF spectrometer. The next stage of this research will
aim to increase the scientific return of measurement missions by the realtime
inclusion of scientific sensor data in decision-making processes to enable
adaptive sampling.

Item Type: Thesis (PhD)
Keywords: Autonomous Underwater Vehicles (AUVs), X-Ray Flourescence (XRF) Spectroscopy, robotics, marine sediment chemistry
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Date Deposited: 12 Mar 2014 04:29
Last Modified: 15 Sep 2017 01:06
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