First Measurements of Gas Flux with a Low-Cost Smartphone Sensor-Based UV Camera on the Volcanoes of Northern Chile

Abstract

<jats:p>UV cameras have been used for over a decade in order to remotely sense SO2 emission rates from active volcanoes, and to thereby enhance our understanding of processes related to active and passive degassing. Whilst SO2 column density retrievals can be more accurate/sophisticated using alternative techniques (e.g., Differential Optical Absorption Spectrometer (DOAS), Correlation Spectrometer (COSPEC)), due to their higher spectral resolutions, UV cameras provide the advantage of high time-resolution emission rates, a much greater spatial resolution, and the ability to simultaneously retrieve plume speeds. Nevertheless, the relatively high costs have limited their uptake to a limited number of research groups and volcanic observatories across the planet. One recent intervention in this regard has been the introduction of the PiCam UV camera, which has considerably lowered instrumental cost. Here we present the first data obtained with the PiCam system from seven persistently degassing volcanoes in northern Chile, demonstrating robust field operation in challenging conditions and over an extended period of time, hence adding credence to the potential of these units for more widespread dissemination to the international volcanic gas measurement community. Small and weak plumes, as well as strongly degassing plumes were measured at distances ranging 0.6–10.8 km from the sources, resulting in a wide range of SO2 emission rates, varying from 3.8 ± 1.8 to 361 ± 31.6 td−1. Our acquired data are discussed with reference to previously reported emission rates from other ground-based remotely sensed techniques at the same volcanoes, in particular considering: resolution of single plume emissions in multi-plume volcanoes, light dilution, plume geometry, seasonal effects, and the applied plume speed measurement methodology. The main internal/external factors that influence positive/negative PiCam measurements include camera shake, light dilution, and the performance of the OpenCV and control points post processing methods. A simple reprocessing method is presented in order to correct the camera shake. Finally, volcanoes were separated into two distinct groups: low and moderate SO2 emission rates systems. These groups correlate positively with their volcanological characteristics, especially with the fluid compositions from fumaroles.</jats:p>

A GIS-based multi-hazard assessment at the San Pedro volcano, Central Andes, northern Chile

“…The volcano is currently being monitored by the Southern Andes Volcanological Observatory (in Spanish: Observatorio Volcanológico de Los Andes del Sur, OVDAS) 1 and monitoring reports are produced monthly (e.g., OVDAS, 2022;Amigo, 2021). Regarding monitoring studies, no deformation was detected during InSAR surveys (Pritchard and Simons, 2004), but there are records of seismic disturbances (Pritchard et al, 2014;OVDAS, 2022), small thermal anomaly hotspots (Jay et al, 2013), and fumarolic degassing (Aguilera et al, 2020). Moreover, a single gas plume has been observed by various authors in the modern western cone throughout the last 50 years (Francis et al, 1974;O'Callaghan and Francis, 1986;Bertin and Amigo, 2019;Aguilera et al, 2020).…”

“…Several types of studies have been carried out on the San Pedro volcano, for example, geological (Francis et al, 1974;O'Callaghan and Francis, 1986;Francis and Wells, 1988;De Silva and Francis, 1991;González-Ferrán, 1995), petrographic (Francis et al, 1974;O'Callaghan and Francis, 1986;Godoy et al, 2017;González-Maurel et al, 2019a;González-Maurel et al, 2020), geochronological (O'Callaghan andFrancis, 1986;Mamani et al, 2008;Godoy et al, 2014Godoy et al, , 2017Delunel et al, 2016;Bertin and Amigo, 2019;González-Maurel et al, 2019b), historical eruption recordings (Casertano, 1963;González-Ferrán, 1995;Petit-Breuilh, 2004;Siebert et al, 2010;Bertin andAmigo, 2015, 2019), regional (Lara et al, 2011;Amigo et al, 2012) and local volcanic hazard assessments (Bertin and Amigo, 2015), emergency crisis plans (ONEMI, 2019), seismic (Pritchard et al, 2014), surface deformation (Pritchard and Simons, 2004;Pritchard et al, 2014), morphometric (Grosse et al, 2014;Aravena et al, 2015), spectral thermal anomalies (Jay et al, 2013), volatile fluxes (Aguilera et al, 2020), and glaciological (Barcaza et al, 2017). In northern Chile, model-based double-hazard assessments have been produced regionally for a series of volcanoes (Amigo et al, 2012).…”

“…We only simulated the climactic phase of the eruptions (following Sandri et al, 2016;Biass et al, 2017), with a chosen eruption duration of 1-6 h for all scenarios. All tephra fallout scenarios assume that a vent will open at the summit crater of the modern western cone San Pedro, as this location has a vent currently emitting a gas plume (Aguilera et al, 2020).…”

Evolution of the magmatic-hydrothermal system at Lastarria volcano (Northern Chile) between 2006 and 2019: Insights from fluid geochemistry

“…Each camera has a bandpass filter with a transmission wavelength on-band and off-band for SO 2 absorption, corresponding to 310 and 330 nm, respectively. The instrument is connected to a laptop via WiFi, with the Picam then controlled through Python 3 code (Aguilera et al, 2020). Prior to each measurement sequence the Picam was calibrated with gas cells with column densities of 100, 467, and 1,989 parts per million by meter (ppm m).…”

“…The sequences were processed using a python-based code in order to determine SO 2 emission rates (Wilkes et al, 2017;Aguilera et al, 2020). Plume velocity was calculated using cross-correlation technique, because the error with this technique is minor, considering the high temporal and spatial resolution of UV camera (McGonigle et al, 2005;Kantzas et al, 2010).…”