Protocols for UV camera volcanic SO2 measurements

Abstract

Ultraviolet camera technology offers considerable promise for enabling 1 Hz timescale acquisitions of volcanic degassing phenomena, providing two orders of magnitude improvements on sampling frequencies from conventionally applied scanning spectrometer systems. This could, for instance enable unprecedented insights into rapid processes, such as strombolian explosions, and non-aliased corroboration with volcano geophysical data. The uptake of this technology has involved disparate methodological approaches, hitherto. As a means of expediting the further proliferation of such systems, we here study these diverse protocols, with the aim of suggesting those we consider optimal. In particular we cover: choice and set up of hardware, calibration for vignetting and for absolute concentrations using quartz SO 2 cells, the retrieval algorithm and whether one or two filters, or indeed cameras, are necessary. This work also involves direct intercomparisons with narrowband observations obtained with a scanning spectrometer system, employing a differential optical absorption spectroscopic evaluation routine, as a means of methodological validation.

UV camera measurements of fumarole field degassing (La Fossa crater, Vulcano Island)

“…In this work we took advantage of the high spatial (0.3 m per pixel) and time resolution (~0.5 Hz) of the UV camera (Kantzas et al, 2010) to propose a new approach for exploring multiple-source SO 2 gas emissions from fumarolic fields. The camera-derived individual fumarole SO 2 fluxes (Figs.…”

“…Then, taking a suitable row of pixels, we calculated the integrated column amount (ICA) across the plume of interest, and multiplied this by the plume speed (derived by the cross-correlation method) to compute the SO 2 flux. For more details about the technique see Kantzas et al (2010). The UV camera approach, in common with DOAS, is a passive remote sensing methodology that measures sunlight scattered in the atmosphere towards the sensor.…”

“…In this study, we follow the protocol for UV camera measurement outlined by Kantzas et al (2010) to image the sulphur dioxide flux distribution of the fumarolic field of La Fossa crater (Vulcano Island, Aeolian Islands), a small (386 m high) pyroclastic cone in a state of degassing unrest since the late 1970s (Chiodini et al, 1995). In particular, we show that the UV camera can be used to derive volcanic SO 2 flux data from individual vents within a fumarolic system, and their relative contribution to the bulk emissions.…”

New Advances in Dial-Lidar-Based Remote Sensing of the Volcanic CO2 Flux

“…Concurrently with our lidar observations, a dual-UV camera system (Kantzas et al, 2010;Tamburello et al, 2012;Burton et al, 2014) was used to monitor the temporal variations of the SO 2 flux and plume transport speed. A fully autonomous system, similar to that used in other recent work (D'Aleo et al, 2016), was mounted on the roof of the laboratory truck and operated every day from 6 am to 4 pm (Local Time).…”

“…Distinct bandpass filters, centerd at either 310 nm (where SO 2 absorbs) or 330 nm (no SO 2 absorption), were mounted on the back on the lenses of the two cameras. Each set of co-acquired images from the two UV cameras was processed using the methodology of Kantzas et al (2010) and integrated into the Vulcamera software (Tamburello et al, 2011(Tamburello et al, , 2012, to calculate an absorbance for each camera pixel. Absorbance was converted into an SO 2 column amount from readings of a co-exposed Ocean optics USB2000+ UV Spectrometer, as outlined in Lübcke et al (2013).…”