ῒΐ 臕 /* 膋 (,**/) 臕 0 膭 /01ῌ/1. 臰 腍腊腋腑腃腐腀腆腋腁腂腅腈腎腌腀腄腇腉腏 臂 膽膯 腇 腂臸臚膟膵 腇 腅,**/ 臥 . 膞 ,, 臤膹自腀 ,**/ 臥 ++ 膞 +. 臤膹ῌ腆 Remote FT-IR Measurements of Volcanic Gas Chemistry in the Plume of Asama Volcano Toshiya MORI ῍ and Kenji NOTSU ῍ Remote FT-IR measurements for volcanic gas chemistry were carried out twice before and four times after the ,**. Asama eruptions. In these measurements, solar infrared light scattered by higher clouds or plumes was used as a light source for the FT-IR absorption measurements. We have successfully detected - volcanic gas components, SO,, HCl and HF, in the observed spectra. The HCl/SO, ratios observed after the onset of the ,**. Asama eruptions were between *.+1 and *.,*, which are probably reflecting the ratios not influenced by any hydrothermal interactions. In contrast, the HCl/SO, ratios before the eruptions were slightly lower than those after the eruptions. The slight increase in the ratio from pre-eruptive to post-eruptive periods suggests that the hydrothermal or groundwater impact to the volcanic gas emitting system was small even three years before the eruptions. The observed HF/HCl ratios before the eruptions and in March ,**/ were about *.+, whereas the ratios were higher, over *.+3, during the high activity period from mid-September to October ,**.. During the continuous ash emitting eruptions on September +0, ,**., exceptionally low HF/HCl ratio of *.*- was observed. The HF column amount on this day was probably under detection limit, possibly due to HF depletion caused by adsorption on dense ash in the plume. Key words : FT-IR, volcanic gas, remote measurement, Asama volcano +ῌ ῐ῎ῑ῏ 臬臅腣膄膱腰腲臆臭腮膀至腨腪臢膴腢臎臛腖腫腒腟腮 臷臜腟腔腝腀 腵腃腸腯臱膌膙臇膅臭膨臲膷膝 腅腺膧腀 FT-IR 腟膦腥腆 腍膾腦腝臺腊腩腬腙腣腤腀 臋膎膄膱腞腉 腪腀 腒腣腟腎腤 SO, 腣 + 臆臭腚腐腣臎臛腞腉腛腙 (Notsu et al., +33-)腁 +33* 臥腄+33/ 臥腣腽臊臫膢膉腣臮 膄膴腢腀 臹膏腴腃腷腣膬膁臩臶腮臇膅膨膤腟腔腝腀 腴腃 腷腌腩臲膼腓腬腫膄膱腰腲腣膀膇臎臛腮膫腊腀 SO, 腟 HCl 腣 , 臆臭腣膒膺腲腶腱腳腹臎臛腢腤腕腦腝臆膩腔 腙 (Mori et al., +33-) 腣腮臦臈腪腢腀 臑腏腣膄膱腞 FT- IR 腮膲臺腔腙膄膱腰腲膂膈臌臆腣膀膇臎臛腍膫腭腬腫 腨腋腢腡腛腙腁 SO, 腟 HCl 腚腐腞腡腏腀 SiF. (Francis et al., +330), CO 腅膿臸腂臐腀 +331腆腀 CO,, COS (Mori and Notsu, +331), HF (Love et al., +332 ; Francis et al., +332), H,O (Burton et al., ,***) 腣膮膝 2 膸῍腣膄膱腰腲臆臭 腣臎臛腍 FT-IR 腮臺腊腝膫腭腬腫腨腋腢腡腛腙腁 腗腣 膧腣 FT-IR 腮臺腊腙膄膱腰腲膍臎腣臃臝腤臘腔腏腀 膥 膰腞腤腀 FT-IR 腮臺腊腙膀膇臎臛腢腨腛腝膄膱腰腲腣膂 膈臌臆腣膜膴臱膂腮膻臭腢膑῏腍腞腎腫腨腋腢腡腛腝腎 腙 腅Horrocks et al., +333 ; 膿臸腂臐腀 +333 ; Du#ell et al., ,**- ; Allard et al., ,**/腆腁 FT-IR 腮臺腊腙膄膱腰腲膀膇 膍臎腣臎臛至致腢腜腊腝腤 Oppenheimer et al. (+332) 腢 臀腔腊腁 FT-IR 腮臺腊腙膄膱腰腲腣膀膇臎臛腞腤腀 臎臛臷臨腟 腡腫膄膱腰腲 腅臮膐腧臮腾腆 臆臭腢腨腫臇膅膨腣膒膺腮 臎臛腖腫腁 腗腣腙腦腢腤膍臎臍臗腞腉腫 FT-IR 腌腩膡 腝腀 臷臨膄膱腰腲腣膧至腢臇膅膨膤腍臧臻腢腡腫腁 膍臎 腢膲臺腞腎腫臇膅膨膤腟腔腝腤腀 臮膐臖臓腣膬膁臖臩 (Mori et al., +33/)腀 臮膼臙膧腣臹膏腴腃腷臩臶 (Mori et al., +33-)腀 臄膪臇膅膨膤 (Francis et al., +33/) 腧臒臼膨 (Francis et al., +332 ; Love et al., +332) 腍膔腑腩腬腫腁 膲 臺腞腎腫膨膤腤腀 腗腬腘腬腣膄膱腣膊臡腀 臮腾腀 臖膚腀 臣῎腣臁膖腡腠腢臔腎腏腻臏腖腫腣腞腀 膍臎腢臠腙腛腝 腇 腈++-ῌ**-- 臟膕臞臯膕膘臵膗 1ῌ-ῌ+ 臟膕臔膈臔膈腼ῌ膈膛膠膓膃臖膆膂膈膶膣膳臉 Laboratory for Earthquake Chemistry, Graduate School of Science, The University of Tokyo, 1ῌ-ῌ+ Hongo, Bunkyo-ku, Tokyo ++-ῌ**--, Japan. Corresponding author : Toshiya Mori e-mail : [email protected]
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have successfully detected - volcanic gas components, SO,, HCl and HF, in the observed spectra. The HCl/SO, ratios observed after the onset of the ,**. Asama eruptions were between
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Remote FT-IR Measurements of Volcanic Gas Chemistry in the Plume of Asama Volcano
Toshiya MORI�and Kenji NOTSU�
Remote FT-IR measurements for volcanic gas chemistry were carried out twice before and four times after
the ,**. Asama eruptions. In these measurements, solar infrared light scattered by higher clouds or plumes was
used as a light source for the FT-IR absorption measurements. We have successfully detected - volcanic gas
components, SO,, HCl and HF, in the observed spectra. The HCl/SO, ratios observed after the onset of the ,**.Asama eruptions were between *.+1 and *.,*, which are probably reflecting the ratios not influenced by any
hydrothermal interactions. In contrast, the HCl/SO, ratios before the eruptions were slightly lower than those
after the eruptions. The slight increase in the ratio from pre-eruptive to post-eruptive periods suggests that the
hydrothermal or groundwater impact to the volcanic gas emitting system was small even three years before the
eruptions. The observed HF/HCl ratios before the eruptions and in March ,**/ were about *.+, whereas the
ratios were higher, over *.+3, during the high activity period from mid-September to October ,**.. During the
continuous ash emitting eruptions on September +0, ,**., exceptionally low HF/HCl ratio of *.*- was observed.
The HF column amount on this day was probably under detection limit, possibly due to HF depletion caused by
adsorption on dense ash in the plume.
Key words : FT-IR, volcanic gas, remote measurement, Asama volcano
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IR�uE/I����vwx�� g'(BhyH*"z&{RIS SO,,HClPQM{t� SiF. (Francis et
al., +330), CO �|}� +331�� CO,, COS (Mori and
Notsu, +331), HF (Love et al., +332 ; Francis et al., +332),
H,O (Burton et al., ,***)�~= 2����������'(B FT-IR�EF0hyH*"z&{RIS ��?� FT-IR�EFI�����'���J�/t� ��MJ� FT-IR�EFI g'(&"R0�����vwx���%5v���&��BMO*"z&{R0OI �Horrocks et al., +333 ; |}� +333 ; Du#ell et al.,
,**- ; Allard et al., ,**/�S FT-IR�EFI���� g�'�'(!�&�F0J Oppenheimer et al. (+332)&�/FS
FT-IR�EFI����� g'(MJ� '(-�,{*���� �Z��Z�� ��&"*89:�ij�'()*S ��ID&J�'��MN* FT-IRdG�0� -������?!&89:cB��&{*S �'&uEMO*89:c,/0J� Z����_`�a(Mori et al., +33/)� Ze�?�[\]2^ab (Mori et
Francis, P. Cha$n, C., Maciejewski, A. and Oppenheimer,C. (+330) Remote determination of SiF. in volcanic
plumes : a new tool for volcano monitoring. Geophys.
Res. Lett., ,-, ,.3�,/,.Francis, P., Burton, M.R. and Oppenheimer, C. (+332)Remote measurements of volcanic gas compositions by
solar occultation spectroscopy. Nature, -30, /01�/1*.Hirabayashi, J., Ossaka, J. and Ozawa, T. (+32,) Relation-ship between volcanic activity and chemical compositions
of volcanic gases � A case study on the Sakurajima
volcano. Geochem. J., +0, ++�,+.Hirabayashi, J., Ossaka, J. and Ozawa, T. (+320) Geo-chemical study on volcanic gases at Sakurajima volcano,