2 research outputs found
Development of a portable active long-path differential optical absorption spectroscopy system for volcanic gas measurements
No full textActive 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
