1. CONTRIBUTION OF MOUNT MERAPI VOLCANO EMISSION DURING QUIESCENT STATE TO BACKGROUND SO 2 CONCENTRATION IN D.I. YOGYAKARTA PROVINCE Regina Dhevita Purie and Driejana Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung, Indonesia BAQ, December 2006

2. Background SO 2 emission from Merapi volcano might contribute to SO 2 ambient air concentration in the surrounding area Volcanic emission during quiescent state might have impact to environment, however monitoring to emission and its impacts have not got much attention

3. Objectives To examine the spatial distribution of SO 2 from Mt. Merapi during normal activity within the volcano surrounding area To observe its potential impact to the environment

4. Boundary conditions The point source emission is assumed to be continuous The dispersion prediction is carried out within an area of 13.5 km X 13.5 km surrounding Merapi including Kabupaten Magelang, Kabupaten Boyolali, Kabupaten Klaten in Central Java and Kabupaten Sleman in DI Yogyakarta

5. Methodology Collecting primary data from Volcanology Agency for emission data (Q) and plume rise (∆h) from COSPEC measurement in 2002, wind speed, wind direction and atmospheric stability from the Met Office, and topographical data such as the height of mountain and the altitude of receptor area Modeling based on Gaussian Plume Model for daily average concentration during dry season period (April – September) Ambient air sampling of SO 2 to validate the model Observing the evidence of SO 2 impact to surrounding area of Mt.Merapi

6. Mt. Merapi DIY Magelang Boyolali Klaten Study Area

7. Results and discussion The prevailing winds were from south, southwestern and southeastern directions The daily dispersion patterns are found to be similar Six days (a day in every month) are taken as the examples for the predicted dispersion pattern

8. Kab. Boyolali Kab. Magelang Kab. Klaten DIY April 5 th May 23 th June 7 th Mt. Merapi DateAtm Stb Wind speed (ms -1 ) Plume rise (m) Emission (g.s -1 ) April 5 th A150 1,250.00 May 23 th A196 1,793.98 June 7 th A0.5325 1,932.87 SO 2 unit of concentration: µg.m -3 The dispersion pattern of SO 2

9. DateAtm Stb Wind speed (ms -1 ) Plume rise (m) Emission (g.s -1 ) July 12 th A1.51.5375983.796 August 13 th A2611,041.667 September 15 th A275717.593 Mt. Merapi Unit concentration of SO 2 : µg.m -3 Kab. Boyolali Kab. Magelang Kab. Klaten DIY July 12 th Agst 13 th Sept 15 th The dispersion pattern of SO 2

10. The average concentration of SO 2 from April to September 2002 was 23.09 µg.m -3,with the maximum daily concentration SO 2 of 490.72 µg.m -3 and the minimum daily concentration of 2.77 µg.m -3 The maximum concentrations mostly fall within the distance of 0.6 – 3.4 km from the center of the volcano

11. Receptor points Kab. Boyolali Kab. Klaten Kab. Sleman, DIY Kab. Magelang Mt. Merapi The areas where SO 2 deposition are most likely to happen

12. The damage of plantation, such as cabbage, tobacco, tea, and the root of tobacco plant colourosisNecrosis & colourosis colourosis Visible indication of the SO 2 impacts to plantation

13. 91 70 91 65 91 60 04 35 04 40 Tobacco plantation at Dusun Jerakah (438.138,36; 9.170.352,19; 1291,5) Soil Condision at Dusun Jerakah (438.138,36; 9.170.352,19; 1291,5) The impact SO 2 to soil and tobacco plant

14. Inventory emission from volcano is necessary, not only for the purpose of monitoring the volcanic activity, but also for mitigation of the emission impact The locations of maximum concentration were found to be at the same grid locations, covering an area of about 400 to 800 hectares on the distance of 0.6 – 3.4 km in the north-eastern, northern and western of Mount Merapi. The maximum concentrations of SO 2 were found in Kabupaten Magelang, Kabupaten Boyolali and a little part of Kabupaten Klaten area. According to the land use, these areas can be considered as ecological sensitive area. Conclusions and Recommendation

15. Indications of environmental impact caused by volcanic emission of Merapi have been seen, particularly on plantation and the form of soil. Specific mitigation plans therefore might need to be developed for this area, to reduce the impacts to the minimal.

16. Thank You!