For researchers monitoring volcano activity, Ocean Optics spectrometers and accessories are ideal for measuring the emission of sulfur dioxide and other volcanic gases. Our spectrometers are flexible enough for techniques such as differential optical absorption spectroscopy, air- and ground-based remote sensing and irradiance measurements:
- Portability. Our spectrometers are compact and have low power requirements, making it possible to deploy them from a plane or UAV or hand-carry them into volcano zones.
- UV response. We offer multiple spectrometer options for UV, Visible and NIR wavelengths, but the strong UV response of our Maya2000 Pro model in particular is well suited for monitoring UV light that interacts with volcanic gases.
- Flexibility. Fiber optic spectrometers bring the measurement to the sample. Spectrometers couple to probes, sampling optics and telescope adapters for a variety of applications.
Thanks to the generosity our customers have demonstrated by publishing materials via open-access websites, we are able to share links to several papers referencing the use of Ocean Optics spectrometers for monitoring volcanic emissions:
The following white papers are available under a Creative Commons Attribution License.
Example Setup: Absorbance of Atmospheric Gases
Absorbance measurements are used to quantify the concentration of solutions and gases (as described in this setup) that absorb light in a media that transmits light. In this case, the transmitting light is solar radiation.
There are several possible approaches when monitoring atmospheric gases. In this example, we’re using a USB2000+UV-VIS-ES spectrometer preconfigured for the range from 200-850 nm. Optical bench accessories include a detector collection lens for increased throughput. For better response in the UV, one might consider a Maya2000 Pro spectrometer in place of the USB2000+UV-VIS-ES.
A 200 mm core solarization-resistant optical fiber and collection optics complete the setup. Depending on the experiment, suitable optical fiber alternatives include a 400 mm or larger core diameter assembly. The length of the fiber in the example setup is 2 meters, although a shorter length can be used. Also, because solar UV radiation may not be intense enough to warrant the use of solarization-resistant fiber, our high OH UV-Vis fiber is an acceptable alternative.
To complete the sampling setup, you have several collection options from which to select: a Gershun tube, which couples directly to the spectrometer or to the fiber and has interchangeable apertures on the sampling side for adjusting the field of view; a 74-UV or 84-UV-25 collimating lens; a cosine corrector, which also can be attached directly to the spectrometer or to the fiber for collecting signal from 180° field of view; and an MFA-C-MOUNT or C-MOUNT-MIC adapter for coupling to a telescope.
OceanView spectroscopy software completes the system.
Absorbance of Atmospheric Gases – System Components
|USB2000+UV-VIS-ES||This spectrometer is preconfigured for UV-Vis measurements from 200-850 nm in the sample setup. The spectrometer has a 25 µm slit as the entrance aperture, an order-sorting filter and a detector collection lens for increased sensitivity.|
|QP200-2-SR-BX||Solarization-resistant patch cord assembly, 200 µm diameter, 2 meters length, BX jacketing. Larger core diameter fibers in shorter lengths are also acceptable.|
|Collection Optics Options|
|GER-KIT||Optical fixture for controlling field of view comprises a narrow aluminum tube with fiber connector on one side and aperture on the other. Multiple interchangeable aperture assemblies are available.|
|74-UV or 84-UV-25||Collimating lenses for attaching to optical fibers for controlling the field of view of the sampling setup; 74-UV is 5 mm in diameter with 10 mm focal length and 84-UV-25 is 25.4 mm in diameter with 100 mm focal length.|
|CC-3-UV-S||Sampling optic for light collection from 180° field of view; comprises Spectralon® diffusing material in an anodized aluminum fixture.|
|C-MOUNT-MIC or MFA-C-MOUNT||Adapter assembly with internal C-mount threads allows users to couple setups to devices such as telescopes.|
Differential optical absorption spectroscopy (DOAS) is a common methodology for measuring volcanic gases with prominent UV absorption features.
Ocean Optics spectrometers coupled to telescopes were used to monitor nitrogen dioxide emitted during the burning of sugar cane residue.
An Ocean Optics spectrometer measured sulfur dioxide emission from the volcano cones Benbow and Arum, part of Ambrym island in the Republic of Vanuatu.