SO2 FLUX MEASUREMENT BY DOAS DOAS (DIFFERENTIAL OPTICAL ABSORPTION SPECTROSCOPY) AND ITS APPLICATION AT BROMO ERUPTION ON JUNE 2004

Convention Bandung 2004 (CB2004)
The 33rd Annual Convention & Exhibition 2004

Indonesian Association of Geologist
Horizon Hotel, 29-30 Nov, 1 Oct 2004, Bandung

SO2 FLUX MEASUREMENT BY DOAS
DOAS (DIFFERENTIAL OPTICAL
ABSORPTION SPECTROSCOPY) AND ITS
APPLICATION AT BROMO ERUPTION ON
JUNE 2004

Hanik Humaida and Yustinus Sulistyo

BPPTK-Direktorat Volkanologi dan Mitigasi Bencana Geologi

Abstract

SO2 is one of the volcanic gases that can provide information about the state of
volcano activity, Commonly, SO2 flux is measured by COSPEC (Correlation
Spectroscopy). This equipment has several disadvantages; such as heavy, bog
size, expensive and stastic operation only. DOAS (Differential Optical
Absorption Spectroscopy) is anew method for SO2 gas flux monitoring that has
advantages compares to the COSPEC. Recently, this method has been
developed. This DOAS consist of 5 units; namely scan miler, condenser lens,
detector, power supply, and a laptop. Its total wieght is up to 11 kg. For
operation of DOAS using traverse method, it need lens unit, detector and
laptop. The weight is only 2 kg DOAS can be operated as static or traverse
method and can be mounted at anyplace.

Measurement of SO2 flux by DOAS has been done at G. Bromo on 12-15 June
2004, after the 8 June eruption. Location of neasurementis about 2 km from
eruption source using tripod. This angle of measurement ranges between 10o
and 12o width of scan is 45 o. Data was analysed by HINAGATA sofware. The
result showed that 30 minutes before the volcano produced ash, the flux of SO2
increased from normal condition until 135 ton/day.

Abstrak

Gas SO2 merupakan salah satu gas yang dapat memberikan informasi tentang
keadaan aktifitas suatu gunungapi. Pengukuran SO2 fluks biasanya dilakukan
dengan COSPEC (Correlation Spectroscopy). COSPEC mempunyai beberapa
kelemahan antara lain berat ukuran sangat besat, mahal, dan harus
dioperasikan secara statis. DOAS (Differential Optical Absorption
Spectroscopy) merupakan metoda baru yang digunakan untuk monitoring fluks
SO2 yang mempunyai beberapa kelebihan, yang sampai saat ini masih terus
dikembangkan. Alat ini terdiri dari 5 bagian yaitu : scan miler, condenser lens,
detector, power supalai dan note PC. Berat total alat ini sampai 11 kg. Untuk

Geo-Environment & Hazard

78

Convention Bandung 2004 (CB2004)
The 33rd Annual Convention & Exhibition 2004

Indonesian Association of Geologist
Horizon Hotel, 29-30 Nov, 1 Oct 2004, Bandung

metoda lintasan yang diperlukan hanya condenser lens, detector dan note PC,
dengan berat hanya 2 kg. DOAS dapat dioperasikan secara statis maupun
gerak dan dapat ditempatkan dimana saja.

Telah dilakukan pengukuran fluks SO2 di G. Bromo pada tanggal 12-15 juni
2004 setelah erupsi 8 June denga DOAS. Lokasi pengukuran dilakukan pada
jarak 2 klm dari pusat letusan dengan metoda triport, kemiringan DOAS
terhadap Plume 10 o – 12o, lebar scan 45o. Data diolah dengan
sofwerHINAGATA. Hasil pengukuran menunjukkan bahwa kurang/lebih 30
menit sebeluim terjadi letusan abu ada peningkatan fluks gas dari kondisi
normal 20 ton/hari menjadi 135 ton/hari.