programado sin incluir el tramo difusor. Esta nota técnica que describe una serie de simulaciones de diluciones de vertido, asociadas a diferentes situaciones del emisario durante su reparación, permitió demostrar a la administración la utilidad de un tramo difusor. El éxito de este estudio de simulaciones fue la claridad en la presentación de los resultados, de manera que resultó evidente a la administración los beneficios del tramo difusor respecto al incremento de tiempo y de presupuesto en la obra. Para obtener este resultado se requiere un conocimiento profundo de los particulares de la obra marítima y de la teoría académica aplicada, y además es necesario un contacto directo y continuo con los responsables de la administración. Estas dos notas técnicas (Parte I y Parte II) muestran una vía por la cual, a nuestro juicio, se deberían mover las Universidades y Centros de Investigación, para aumentar su utilidad directa en la sociedad.
<p>Carbon dioxide (CO<sub>2</sub>) is a colourless and odourless gas. It is non-flammable, chemically non-reactive and 1.5 times as heavy as air; therefore, may accumulate at low elevations. CO<sub>2</sub> is a toxic gas at high concentration, as well as an asphyxiant gas (due to reduction in oxygen). Irritation of the eyes, nose and throat occurs only at high concentrations. Since the Tajogaite eruption ended on December 13, 2021, high concentrations of CO<sub>2</sub> up to 20% (200.000 ppmv) have been observed inside of buildings of the neighborhoods of La Bombilla and Puerto Naos (La Palma, Canary Islands), which are located about 5 km distance from the Tajogaite eruption vent. Anomalous concentrations of CO<sub>2</sub> are manily detected in the ground-floor and basement of the buildings in Puerto Naos, and the distribution of relatively high CO<sub>2</sub> concentrations &#160;is not homogeneous or uniform throughout the Puerto Naos area (Hern&#225;ndez P.A. et al, 2022).</p><p>The purpose of this study was to use the Tunable Laser Diode (TDL) absorption spectroscopy method to monitor the indoor CO<sub>2</sub> concentration of the ground-floor of one of the buildings of Puerto Naos. A CO<sub>2</sub>-TDL was installed on 9 January 2022 and continues measuring the CO<sub>2</sub> concentration along an optical path of about 6 meters. During the period January-March 2022, daily averages of CO<sub>2</sub> concentrations from fifteen-minute data ranged from 5000 to 25000 ppmv reaching values up to 40000 ppmv (4%). Over time, a clear decreasing trend of the indoor CO<sub>2</sub> concentration has been observed at this observation site and the daily CO<sub>2</sub> averages from fifteen-minute data during the last 3 months (October-December 2022) ranged from 1000 to 2500 ppmv. This clear decreasing trend over time has not been observed at other observation sites where the concentration of CO<sub>2</sub> inside buildings is being monitored. This observation indicates the complexity of the problem and the need to install a dense network of sensors to monitor CO<sub>2</sub> for civil protection purposes.</p><p>&#160;</p><p>Hern&#225;ndez, P. A., Padr&#243;n, E., Meli&#225;n, G. V., P&#233;rez, N. M., Padilla, G., Asensio-Ramos, M., Di Nardo, D., Barrancos, J., Pacheco, J. M., and Smit, M.: Gas hazard assessment at Puerto Naos and La Bombilla inhabited areas, Cumbre Vieja volcano, La Palma, Canary Islands, EGU General Assembly 2022, Vienna, Austria, 23&#8211;27 May 2022, EGU22-7705, https://doi.org/10.5194/egusphere-egu22-7705, 2022.</p>
<p>Carbon dioxide (CO<sub>2</sub>) is colorless, odorless and also heavier than air, which means it can accumulate at low elevations. At high concentrations, CO<sub>2</sub> can be hazardous and can cause asphyxiation by reducing the amount of oxygen available to breathe. In high concentrations, it can also irritate the eyes, nose, and throat. During the post-eruptive phase of Tajogaite eruption, high concentrations of air CO<sub>2</sub>, up to 20% (200,000 ppmv), have been detected both outdoor and indoor of buildings at La Bombilla and Puerto Naos, which are located about 5 km from the eruption vent. Hazardous CO<sub>2</sub> concentrations were detected not only in the basements, but also on the ground floors and even inside of some upper floors buildings in Puerto Naos. In the case of La Bombilla, relatively high CO<sub>2</sub> concentrations were just observed on the ground floors. The spatial distribution of these hazardous indoor CO2 concentrations is not uniform throughout both populated areas (Hern&#225;ndez et al, 2022).</p> <p>In order to study and assess this volcanic hazard, in both evacuated neighborhoods, an instrumental network for air CO<sub>2</sub> monitoring has been established by INVOLCAN in collaboration with the DGSE-GOBCAN and the Universities of the Azores (Portugal) and D&#252;sseldorf Applied Sciences (Germany). The first CO<sub>2</sub> monitoring station was installed on 9 January 2022 and by the time being this network consists of 35 air CO<sub>2</sub> monitoring stations with different full scale (2 of 100%, 22 of 20%, 7 of 5% and 4 of 4%). In the case of La Bombilla the air CO<sub>2</sub> monitoring network consists of 10 different stations monitoring the indoor (7) and outdoor (3) CO<sub>2</sub> concentrations, respectively. The other 25 stations are located in Puerto Naos to monitor the indoor (21) and outdoor (4) ambient air CO<sub>2</sub> concentrations.</p> <p>Observed outdoor CO<sub>2</sub> maximum and mean daily average concentrations > 5% (> 50,000 ppmv) and 0.9% (9,000 ppmv), respectively, have been recorded at Puerto Naos. However, indoor CO<sub>2</sub> monitoring at Puerto Naos have reached maximum and mean daily average concentrations about 20% (200,000 ppmv) and 12% (120,000 ppmv), respectively. In the case of La Bombilla, outdoor CO<sub>2</sub> measurements have reached maximum and mean daily average concentrations > 5% (> 50,000 ppmv) and about 2% (20,000 ppmv). Stations to monitor the indoor air CO<sub>2</sub> concentrations at La Bombilla were just installed (December 2022) and by the time being are recording maximum and mean CO<sub>2</sub> concentrations about 6% (60,000 ppmv) and 1.9% (19,000 ppmv), respectively. Most of the air CO<sub>2</sub> monitoring stations, both outdoor and indoor, shows that the daily averages of CO<sub>2</sub> concentrations from fifteen-minute data during the night are usually higher than during the day.</p> <p>To mitigate the observed hazardous CO<sub>2</sub> concentrations some remediation techniques have been suggested, such as the installation of an indoor air CO<sub>2</sub> monitoring network with a larger number of stations and an automatic alert system for air CO<sub>2</sub> concentration inside residences with forced air ventilation systems.</p> <p>Hern&#225;ndez P. A. et al., EGU General Assembly 2022, Vienna, Austria, 23&#8211;27 May 2022, EGU22-7705, https://doi.org/10.5194/egusphere-egu22-7705, 2022.</p>
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