By Gabrielle Frances Leung1, Miguel Ricardo Hilario1, Grace Betito1, Paola Angela Bañaga1, Xzann Garry Vincent Topacio1, Zenn Marie Cainglet1,3, Shane Marie Visaga2,3, Imee Delos Reyes1, Angela Monina Magnaye2, Lyndon Mark Olaguera2,3, Julie Mae Dado2, Faye Cruz2, Joel Maquiling3, Maria Obiminda Cambaliza1,3, James Bernard Simpas1,3, Gemma Teresa Narisma2,3
1Air Quality Dynamics Laboratory, Manila Observatory, Philippines
2Regional Climate Systems Laboratory, Manila Observatory, Philippines
3Department of Physics, Ateneo de Manila University, Philippines
Buod Pangkaraniwan (as of 17 January 2020)
Pagkatapos ng pagputok ng Bulkang Taal noong ika-12 ng Enero, naitala sa Kalakhang Maynila ang bahagyang pag-akyat ng lebel ng mga partikulong mapanganib sa kalusugan dahil kaya nilang manatili sa baga. Mas malaki ang karamihan ng abo na umabot sa lupa (ngunit maaari pa ring magdulot ng iritasyon). Mula noong umaga ng ika-13 ng Enero, balik-normal na ang kalidad ng hangin sa Kalakhang Maynila.
Kung sakaling pumutok muli ang Bulkang Taal, minumungkahi ang maayos na pagsuot ng surgical masks, lalo na sa mga bata, matatanda, at mga may hika. Dapat rin mag-ingat sa paglilinis ng natitirang abo upang hindi ito malanghap.
Non-Technical Summary (as of 17 January 2020)
In Metro Manila after the 12 January Taal eruption, we measured only moderately elevated levels of dangerous particles small enough to remain in the lungs. Most volcanic particles that reached the ground were larger (though can still cause irritation). Since the morning of 13 January, air quality has been back to normal in Metro Manila.
In case of future eruptions, use of properly fitting surgical masks is recommended as a precautionary measure, especially for sensitive groups (children, the elderly, and people with respiratory problems). It is also recommended to carefully clean up any remaining ash to minimize future exposure.
Summary (as of 17 January 2020)
- Current conditions at the Manila Observatory, Quezon City are back to normal. Previous 24-hour PM2.5 concentration range at the Manila Observatory (5-27 μg/m3) is within “good” levels based on the United States Environmental Protection Agency (US EPA) hourly PM2.5 standard.
- Pollution levels measured from the Manila Observatory and Barangay Fortune (Marikina City) towards the end of the ashfall event on 12 January 2020 were elevated, reaching “moderate” (US EPA hourly PM2.5 standard) but still significantly lower than pollution levels associated with the 2020 New Year’s Day celebrations.
- Ash particles from the 12 January eruption in Quezon City were too large to get into the lungs, but caution is still advised as physical processes (grinding) may break larger particles into smaller, respirable particles. It is recommended to clean up any remaining ash to minimize future exposure.
Taal volcano in Batangas erupted at around 3:00 p.m. (0700Z) on 12 January 2020. The eruption released plumes of hazardous particles and gases into the atmosphere, which were transported northward by high-altitude winds. Within a few hours, ashfall was reported in many locations in Metro Manila, which is about 42-90km north of Taal. There was widespread public concern regarding the potential health hazards associated with this ashfall. This report intends to clarify some of the effects of the ashfall event on air quality in Metro Manila.
After the eruption, the Manila Observatory deployed AS-Lung portable PM2.5 sensors in select areas in Quezon City, Marikina, and Laguna. These sensors measure the concentrations of airborne particles with a diameter of 2.5 micrometers or less—these are hazardous to human health because they can enter and deposit in the lungs and bloodstream. Measurements were made every 15 seconds.
PM2.5 concentrations elevated during ashfall but still far below New Years’ 2020 levels
The PM2.5 concentrations at one of these sites, a residential area in Barangay (Brgy.) Fortune, Marikina City, is shown in Figure 1. After the Taal eruption at 3:00 p.m. on 12 Jan 2020, PM2.5 concentrations at Brgy. Fortune in Marikina City began to increase at around 4:00 p.m. and peaked around 7:00 p.m (~86 μg/m3; moderate), before returning to pre-eruption levels by midnight. This is consistent with footage from the All Sky camera located at the Manila Observatory shown in Figure 2. The ash cloud rapidly darkened the sky from 4:00 to 4:40 p.m. (coinciding with the initial increase shown in PM2.5 concentrations in Figure 1), and ash began to fall at around 6:30 p.m. As the larger volcanic ash plume particles descend, they may exhibit coagulation then decoagulation, i.e., larger particles break down to smaller pieces leading to a distribution of varied particle sizes. This mechanism is a plausible explanation for the observed increase in PM2.5 (Figure 1) as well as the observed deposited larger particles shown in Figure 2 (and later in Figure 5).
The PM2.5 concentrations from the day of the Taal emission event are shown alongside typical conditions in the same location (green line in Figure 1). Though there were noticeably higher particulate concentrations in the evening of 12 Jan, pollution levels remained “moderate” according to the US EPA hourly PM2.5 standard, which means that such pollution levels are only of concern to particularly sensitive groups (e.g. children, the elderly, and people with pre-existing respiratory problems) or people who are constantly exposed to the pollution (Table 1, Appendix). For comparison, peak hourly PM2.5 concentrations were much higher during the 2020 New Year’s Day fireworks celebrations (more than twice as high at the maximum).
Conditions returned to normal levels within 12 hours after the ashfall event
Figure 3 compares the PM2.5 concentrations on the evening of the ashfall event (Jan 12) and the following morning after ashfall (Jan 13). Note that sampled concentrations were taken as the plume began to dissipate over Metro Manila (peak conditions were higher from 6:00-9:00 p.m., as shown in Figure 1). Conditions returned to normal by the morning of 13 January 2020, with PM2.5 concentrations at the Manila Observatory and in Brgy. Fortune, Marikina both within the US EPA standard for “good” air quality (Table 1, Appendix).
Although Brgy. Fortune is located further away from Taal Volcano than the Manila Observatory, it showed higher PM2.5 concentrations during the same time period. From 9:00 p.m. – 12:00 a.m. on 12 Jan 2020, Brgy. Fortune had an average PM2.5 concentration of 45 μg/m3, and Manila Observatory had an average of 28 μg/m3.
Metro Manila conditions back to normal, Taal emissions transported to West PH Sea
As of current conditions (9:00 a.m., 17 Jan) at the Manila Observatory, hourly-average PM2.5 concentrations for the past 24 hours range between 5 μg/m3 and 27 μg/m3. This range is within “good” levels of the US EPA standard (Table 1, Appendix).
Phivolcs reported “short-lived dark gray ash plumes 500 meters and 800 meters high at 6:17 and 6:21 AM today” as of 16 Jan. Figure 4 shows that ash plumes from a smaller eruption on the morning of 16 Jan transported ash to West Philippine Sea. This supports the observed PM2.5 concentrations in Metro Manila returning to normal.
Ash particles too large to get into lungs, but caution is advised
Based on remote-sensing data from the Manila Observatory, the majority of the ash from the Taal volcano remained aloft at high altitudes (over 12km) above Metro Manila (see Part I of this report here) from around 4:00 p.m. to at least until 9:00 p.m. After that time, the HSRL signal is blocked by low-level clouds, though the ash plume was still visible in the footage from the All Sky camera. Only the largest particles were heavy enough to be pulled down to the ground by gravity, evident in the High Spectral Resolution Lidar (HSRL) images. HSRL data showed that the ashfall was relatively larger in size and irregular in shape, which are typical characteristics of volcanic ash and is supported by actual observations of the ash in Metro Manila as shown in Figure 5. The rest of the particles, which were aloft, continued to be swept by the fast high-altitude winds, and were transported even further northwards offshore.
However, it should be noted that even though the particulates affecting Metro Manila were too large to be deposited and remain in the lungs, these particles can still negatively affect human health. PM10 (airborne particles with a diameter of 10 micrometers or less), which includes particles larger than PM2.5, can still cause irritation to the eyes, skin, nose, and lungs, and can still make breathing difficult even if it cannot be deposited in the lungs . Furthermore, these large particles can still be broken up into smaller ones once on the ground through different mixing processes (e.g. by being mechanically crushed by vehicles).The smaller particles can then be resuspended in the air and respired into the lungs .
General public still cautioned to be vigilant
Sensitive people (children, the elderly, people with respiratory illnesses) are encouraged to use properly-fitting surgical masks when outdoors in areas with volcanic ash. Proper care should be taken in cleaning up any remaining volcanic ash to minimize exposure. Taal Volcano is still on alert level 4, which means that future eruptions are still possible within hours to days.
What happened to the ash plume from the 12 Jan eruption?
Although Taal is still releasing smoke plumes as of 17 Jan, these are being ejected to lower altitudes (500 – 800 m) and being transported towards the southwest. This is different from the high altitude northward transport observed after the large initial eruption on 12 Jan that injected the ash plume as high as 14.8km (125hPa).
The evolution of the phreatic eruption can be seen in satellite-based measurements of brightness temperature (Figure 6a, 6b). Brightness temperature is a measure of radiative energy which indicates the presence of clouds, and is typically used to infer cloud top height (including ash clouds). Satellite observations suggest that an ash cloud appeared at 4:00 p.m. on 12 Jan, reached Central Luzon by 7:00 p.m. and moved northward to Northern Luzon by 9:00 p.m. and started to dissipate by 3:00 a.m. the following day (13 Jan). The calculated cloud top height from the same data source  indicates that the plume reached about 15 km and these are the white colored areas over Luzon where the brightness temperature is less than -75 °C. (Note that very low values of brightness temperature, i.e. very cold temperatures, imply very high altitude cloud top heights.) This is consistent with the northward transport of the ash plume by stronger northward winds at higher altitudes (125 hPa, approximately 14.8 km) shown in Figure 7. This means that the ashfall experienced by provinces to the north of Taal volcano is mainly from ash that reached greater than 15 km. Some of the ash transported descended to the surface but most stayed aloft. The larger particles from the ash plume reached the surface because they are heavier as opposed to the lighter and smaller particles that were mostly transported further northward.As previously reported, winds from the south at a height of 14.8 km (125 hPa) corresponds to the northward transport of the ash plume (Figures 6a, 6b, and 8). The shift to winds from the southwest in the early morning of 13 Jan over Northern Luzon also geared the ash plume eastward when it reached Luzon strait. The ash plume continued to dissipate and became indistinguishable from the bands associated with the disturbance at West Pacific (Figure 8).
Table 1. US EPA AQI for hourly PM2.5 concentrations.
We acknowledge the use of AHI data from the Japanese Meteorological Agency (JMA), imagery from the University of Wisconsin Madison Space Science and Engineering Center (SSEC) as part of the NASA CAMP2Ex (Cloud, Aerosol and Monsoon Processes Philippines Experiment) and the Cooperative Institute for Research in the Atmosphere (CIRA), and the NASA Worldview application team as part of the NASA Earth Observing System Data and Information System (EOSDIS). We also acknowledge the University of Wisconsin High Spectral Resolution Lidar (HSRL) and the Naval Research Laboratory (NRL) All-Sky Camera, which are deployed at the Manila Observatory. The AS-Lung personal samplers were provided through the support of the following: Academia Sinica (through Dr. Candice Lung); the Advanced Institute on Disaster Risk Reduction with Systems Approach for Slow-Onset Climate Disasters (AI SOCD), funded by the International Council for Science – Regional Office for Asia and the Pacific (ICSU – ROAP); and the Coastal Cities at Risk in the Philippines (CCARPH) project, funded by the International Development Research Centre (IDRC). Finally, we thank Dr. Jeffrey Reid of NRL for his invaluable comments and input.
The information in this report are provided as a public service. For official updates and warnings, please refer to PHIVOLCS and other government agencies.
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