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Brian Devine

Title:An Optical Fibre Sensor System for the Detection of Atmospheric Gaseous Pollutants in an Urban Environment

Brian Devine with Dr James Walsh

It has become necessary in recent times to monitor the different gaseous pollutants and the concentrations of these pollutants in urban areas. The method known as Differential Optical Absorption Spectroscopy (DOAS) has been widely used to perform measurements of these pollutants. This method requires a moving Transceiver apparatus. The Transceiver can be programmed to direct itself towards several fixed Receiver/Emitters located in different areas up to a few kilometres from the Transceiver. The measurements taken are used to determine the concentrations of gaseous pollutants using an Opto-Analyser system. The DOAS method is very accurate but requires the apparatus to be fixed in position and it can be costly.

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The research in this project involves expanding on earlier work [1] to develop a portable miniaturised fibre-optic spectroscopy system to take readings of the atmosphere in an urban environment. The spectra taken of the atmosphere will be compared to a reference spectrum of ambient sunlight. An Ocean Optics micro-spectrometer and different software are used to produce a system that can perform measurements of the spectra and calculate the concentration using the Beer-Lambert Law:                   

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The Beer-Lambert Law is used to determine the absorption A, using measured values for the light intensity I and a reference intensity Io. Using the value for absorption, the concentration c, can be determined when the values for both path length l, and the absorption coefficient ε are known.

The results will be compared to the measurements taken by a fixed DOAS system. The advantages of a miniaturised fibre-optic system will be its portability, low cost and simplicity.

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This project will be carried out at the Dublin Institute of Technology and the FOCAS Institute in conjunction with the Environmental Protection Agency.

References:

  1. J.A.Morales, J.E.Walsh, J.Treacy, “Detection of atmospheric Nitrogen Dioxide using a miniaturised fibre-optic spectroscopy system and the ambient sunlight”, Spectrochimica Acta Part A 61 2005 2073–2079.

  2. http://cluin.org/programs/21m2/openpath/uv-doas/images/uvdoas_config_mono.gif

Contact Details:

Brian Devine BSc,
Optical Sensing and Metrology Group,
Biomedical and Environmental Sensing Laboratory,
FOCAS Building,
Dublin Institute of Technology,
Kevin Street, Dublin 8,
Ireland.
Tel: -353-1-402-7980
Fax: -353-1-402-4988
Email: brian.devine1@student.dit.ie