Development of a portable active long-path differential optical absorption spectroscopy system for volcanic gas measurements

Journal of Sensors and Sensor Systems
By: , and 

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Abstract

Active long-path differential optical absorption spectroscopy (LP-DOAS) has been an effective tool for measuring atmospheric trace gases for several decades. However, instruments were large, heavy and power-inefficient, making their application to remote environments extremely challenging. Recent developments in fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes (UV-LEDS) have now allowed us to design and construct a lightweight, portable, low-power LP-DOAS instrument for use at remote locations and specifically for measuring degassing from active volcanic systems. The LP-DOAS was used to measure sulfur dioxide (SO2) emissions from La Fossa crater, Vulcano, Italy, where column densities of up to 1.2 × 1018 molec cm−2 (~ 500 ppmm) were detected along open paths of up to 400 m in total length. The instrument's SO2 detection limit was determined to be 2 × 1016 molec cm−2 (~ 8 ppmm), thereby making quantitative detection of even trace amounts of SO2 possible. The instrument is capable of measuring other volcanic volatile species as well. Though the spectral evaluation of the recorded data showed that chlorine monoxide (ClO) and carbon disulfide (CS2) were both below the instrument's detection limits during the experiment, the upper limits for the X / SO2 ratio (X = ClO, CS2) could be derived, and yielded 2 × 10−3 and 0.1, respectively. The robust design and versatility of the instrument make it a promising tool for monitoring of volcanic degassing and understanding processes in a range of volcanic systems.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Development of a portable active long-path differential optical absorption spectroscopy system for volcanic gas measurements
Series title Journal of Sensors and Sensor Systems
DOI 10.5194/jsss-3-355-2014
Issue 3
Year Published 2014
Language English
Publisher AMA Verband für Sensorik und Messtechnik
Contributing office(s) Volcano Science Center, Volcano Hazards Program
Description 23 p.
First page 355
Last page 367
Country Italy
City Vulcano
Other Geospatial La Fossa crater
Online Only (Y/N) N
Additional Online Files (Y/N) N