2007 Fiscal Year Final Research Report Summary
A study of atmospheric budget of methyl chloride
| Project/Area Number |
18340179
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geochemistry/Astrochemistry
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| Research Institution | National Institute for Environmental Studies |
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Principal Investigator |
YOKOUCHI Yoko National Institute for Environmental Studies, Environmental Chemistry Division, Section Leader (20125230)
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| Co-Investigator(Kenkyū-buntansha) |
TSUNOGAI Urumu Hokkaido University, Faculty of Science, Associate Professor (50313367)
SAITO Takuya National Institute for Environment Studies, Environmental Chemistry Division, Research Scientist (40414370)
OKUDA Toshinori Hiroshima University, Faculty of Science, Professor (20214059)
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| Project Period (FY) |
2006 – 2007
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| Keywords | methyl chloride / tropical plants / budget / emission / stable isotope |
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| Research Abstract |
Stable carbon isotope ratios of methyl chloride (CH_3C1) emitted from tropical plants were measured using growing in a glasshouse. Using the isotope signatures to an isotopic mass balance calculation, global CH_3C1 emission by tropical plants was estimated to be approximately 1500-3000 Gg yr^<-1>. At a tropical rain forest in Peninsular Malaysia, we conducted a survey of CH_3C1 emitting plants for the 117 species of tropical plants, and 23 species were identified as CH3C1-emitting plants with the mean flux of 5 μg m^<-2> h^<-1>. The estimated fluxes were consistent with the canopy scale fluxes (5〜66μg m^<-2> h^<-1>) measured by the micrometeorological. gradient method at the forest. Emission of CH_3C1 from a subtropical island (Iriomote Island) was estimated to be 2〜26 μg m^<-2> h^<-1> using the enhanced CH_3C1 concentration at downwind sites.
To determine δ^<13>C of CH_3C1 in seawater, we developed an analytical system enabling both extraction of CH_3C1 in seawater on board a research vessel together with NMHCs, and storage within a glass ampoule under CO_2 matrix for several months without changing their δ^<13>C, allowing determination of the δ^<13>C values by using CF-IR MS at a shore-based laboratory. By using the analytical system, we can determine δ^<13>C at precisions<2‰ for CH_3C1 and<1‰ for NMHCs dissolved in 2.2 L seawater. The δ_<13>C determination in coastal seawater reveal distinct differences in the range of variation in the δ^<13>C between alkanes, alkenes, and CH_3C1. While the alkenes exhibited almost uniform δ^<13>C from-26 to-27‰VPDB, both alkanes (-27 to-35‰VPDB) and CH_3C1 (-49±16±VPDB) exhibited more C^<13>-depleted values with greater variations. The δ^<13>C can be a useful tool to study the mechanisms and/or the pathways of their production in seawater.
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