Temporal variations of the atmospheric methane concentration and its isotope ratios observed at Ny-Ålesund

第2回極域科学シンポジウム/第34回気水圏シンポジウム 11月15日（火） 統計数理研究所 3階リフレッシュフロ

Temporal Variations of the Mole Fraction, Carbon, and Hydrogen Isotope Ratios of Atmospheric Methane in the Hudson Bay Lowlands, Canada

We have conducted simultaneous measurements of the mole fraction and carbon and hydrogen isotope ratios (δ13C and δD) of atmospheric methane (CH4) at Churchill (58°44′N, 93°49′W) in the northern part of the Hudson Bay Lowlands (HBL), Canada, since 2007. Compared with the measurements at an Arctic baseline monitoring station, Ny‐Alesund, Svalbard (78°55′N, 11°56′E), CH4 mole fraction is generally higher and δ13C and δD are lower at Churchill due to regional biogenic CH4 emissions. Clear seasonal cycles in the CH4 mole fraction, δ13C, and δD are observable at Churchill, and their seasonal phases in summer are earlier by approximately 2 weeks than those at Ny‐Alesund. Using the one‐box model analysis, the phase difference is ascribed to the different seasonal influence of CH4 emissions from boreal wetlands on the two sites. Short‐term CH4 variations are also observed at Churchill throughout the year. The analysis of the observed isotopic signatures of atmospheric CH4 confirmed that the short‐term CH4 variations are mainly produced by biogenic CH4 released from the HBL wetlands in summer and by fossil fuel CH4 transported over the Arctic in winter. Forward simulations of an atmospheric chemistry‐transport model, with wetland CH4 fluxes prescribed by a process‐based model, show unrealistically high CH4 mole fractions at Churchill in summer, suggesting that CH4 emissions assigned to the HBL wetlands are overestimated. Our best estimate of the HBL CH4 emissions is 2.7 ± 0.3 Tg CH4 yr?1 as an average of 2007-2013, consistent with recent estimations by inverse modeling studies

Regional Methane Emission Estimation Based on Observed Atmospheric Concentrations (2002-2012)

Methane (CH4) plays important roles in atmospheric chemistry and short-term forcing of climate. A clear understanding of atmospheric CH4’s budget of emissions and losses is required to aid sustainable management of Earth’s future environment. We used an atmospheric chemistry-transport model (JAMSTEC’s ACTM) for simulating atmospheric CH4. A global inverse modeling system has been developed for estimating CH4 emissions from 53 land regions for 2002-2012 using measurements at 39 sites. An ensemble of 7 inversions is performed by varying a priori emissions. Global net CH4 emissions varied between 505-509 and 524-545 Tg yr-1 during 2002-2006 and 2008-2012, respectively (ranges based on 7 inversion cases), with a step like increase in 2007 in agreement with atmospheric measurements. The inversion system did not account for interannual variations in OH radicals reacting with CH4 in the atmosphere. Our results suggest that the recent update of the EDGAR inventory (version 4.2FT2010) overestimated the global total emissions by at least 25 Tg yr-1 in 2010. The increase in CH4 emission since 2004 originated in the tropical and southern hemisphere regions, coinciding with an increase in non-dairy cattle stocks by ~10 % from 2002 (with 1056 million heads) to 2012, leading to ~10 Tg yr-1 increase in emissions from enteric fermentation. All 7 ensemble cases robustly estimated the interannual variations in emissions, but poorly constrained the seasonal cycle amplitude or phase consistently for all regions due to the sparse observational network. Forward simulation results using both a priori and a posteriori emissions are compared with independent aircraft measurements for validation. Based on the results of the comparison, we reject the upper limit (545 Tg yr-1) of global total emissions as 14 Tg yr-1 too high during 2008-2012, which allows us to further conclude that the increase in CH4 emissions over the East Asia (mainly China) region was 7-8 Tg yr-1 between the 2002-2006 and 2008-2012 periods, contrary to 1-17 Tg yr-1 in the a priori emissions

Reconstruction of variations of isotopic ratios of atmospheric methane: measurements of firn air /ice core and applications of firn air transport model

第6回極域科学シンポジウム分野横断セッション：[IA] 急変する北極気候システム及びその全球的な影響の総合的解明―GRENE北極気候変動研究事業研究成果報告2015―11月19日（木）　国立極地研究所１階交流アトリウ

Dissecting the genetic control of natural variation in salt tolerance of Arabidopsis thaliana accessions

Many accessions (ecotypes) of Arabidopsis have been collected. Although few differences exist among their nucleotide sequences, these subtle differences induce large genetic variation in phenotypic traits such as stress tolerance and flowering time. To understand the natural variability in salt tolerance, large-scale soil pot experiments were performed to evaluate salt tolerance among 350 Arabidopsis thaliana accessions. The evaluation revealed a wide variation in the salt tolerance among accessions. Several accessions, including Bu-5, Bur-0, Ll-1, Wl-0, and Zu-0, exhibited marked stress tolerance compared with a salt-sensitive experimental accession, Col-0. The salt-tolerant accessions were also evaluated by agar plate assays. The data obtained by the large-scale assay correlated well with the results of a salt acclimation (SA) assay, in which plants were transferred to high-salinity medium following placement on moderate-salinity medium for 7 d. Genetic analyses indicated that the salt tolerance without SA is a quantitative trait under polygenic control, whereas salt tolerance with SA is regulated by a single gene located on chromosome 5 that is common among the markedly salt-tolerant accessions. These results provide important information for understanding the mechanisms underlying natural variation of salt tolerance in Arabidopsis

Variations of tropospheric methane over Japan during 1988–2010

We present observations of CH4 concentrations from the lower to upper troposphere (LT and UT) over Japan during 1988–2010 based on aircraft measurements from the Tohoku University (TU). The analysis is aided by simulation results using an atmospheric chemistry transport model (i.e. ACTM). Tropospheric CH4 over Japan shows interannual and seasonal variations that are dependent on altitudes, primarily reflecting differences in air mass origins at different altitudes. The long-term trend and interannual variation of CH4 in the LT are consistent with previous reports of measurements at surface baseline stations in the northern hemisphere. However, those in the UT show slightly different features from those in the LT. In the UT, CH4 concentrations show a seasonal maximum in August due to efficient transport of air masses influenced by continental CH4 sources, while LT CH4 reaches its seasonal minimum during summer due to enhanced chemical loss. Vertical profiles of the CH4 concentrations also vary with season, reflecting the seasonal cycles at the respective altitudes. In summer, transport of CH4-rich air from Asian regions elevates UT CH4 levels, forming a uniform vertical profile above the mid-troposphere. On the other hand, CH4 decreases nearly monotonically with altitude in winter–spring. The ACTM simulations with different emission scenarios reproduce general features of the tropospheric CH4 variations over Japan. Tagged tracer simulations using the ACTM indicate substantial contributions of CH4 sources in South Asia and East Asia to the summertime high CH4 values observed in the UT. This suggests that our observations over Japan are highly sensitive to CH4 emission signals particularly from Asia

ナンボク リョウキョクイキ ニオケル タイキチュウ ノ オンシツ コウカ キタイ ト カンレン キタイ ノ ヘンドウ

南北両極域における温室効果気体の変動を明らかにし,それらの放出源・吸収消滅源の変動に関する知見を得るために,南極・昭和基地および北極・スバールバル諸島ニーオルスンにおいて系統的な温室効果気体及び関連気体観測を開始し,現在も継続している.大気中のCO_2 濃度は,両極域共に明瞭な季節変化を伴いながら,化石燃料消費と森林破壊によるCO_2 の放出を反映して約1.9 ppmv yr^ の割合で増加している.CH_4 濃度にも明瞭な季節変化と不規則な経年変化が見られ,両極域において1999年までの濃度増加と2000年以降の濃度停滞,そして2007年には再び濃度増加が観測された.CH_4 の同位体比観測から,CH_4 濃度の季節変化,経年変化の原因に関する情報が得られた.大気中のO_2 濃度(δ(O_2 N_2))は両極域において,季節変化と化石燃料消費に起因する経年的減少を示した.Atmospheric Potential Oxygen(APO)とCO_2 濃度の増加率から見積もられた,陸上生物圏と海洋によるCO_2 吸収量(2001-2009年の平均)はそれぞれ1.1,2.7 GtC yr^ であった.ニーオルスンで観測されたN_2O濃度の季節変化を3次元化学輸送モデルによる計算結果と比較することにより,N_2O濃度の季節変化振幅は,夏季に成層圏起源のN_2O濃度が低い気塊が地表付近まで流入することによって,拡大している可能性が示唆された.昭和基地におけるCO濃度の連続観測と3次元化学輸送モデルを用いた解析により,2003年2-3月と2007年2月に,オーストラリアでの大規模な林野火災によって発生したCOが昭和基地に達していることが示された.昭和基地における地上オゾン濃度連続観測によって,1988-2008年までの間に計40例以上の地上オゾン破壊現象を観測した.To elucidate temporal variations of greenhouse gases and their related gases in the Arctic and Antarctic regions and to investigate their sources and sinks, systematic measurements of atmospheric CO_2, CH_4CO, N_2O, O_2 and tropospheric O_3 concentrations have been carried out at Syowa Station, Antarctica and Ny-Alesund, Svalbard. The CO_2 concentrations at both polar sites have increased at a rate of about 1.9 ppmv yr^, reflecting fossil fuel combustion and land use change. The CH_4 concentrations also showed clear seasonal cycles superimposed on complex secular trends. The increase rate of the CH_4 concentration varied with time. CH_4 increases were observed until 1999, the concentrations remained steady from 2000 to 2006 and then rapid increases were observed in 2007. Stable isotope data of CH_4 revealed causes of the seasonal cycles and the secular variations of the CH_4 concentrations. The O_2 concentrations (δ(O_2 N_2)) at both polar sites showed prominent seasonal cycles and secular decreasing trends. From analyses of the Atmospheric Potential Oxygen (APO) and CO_2 concentrations, the CO_2 uptake rates by the terrestrial biosphere and the ocean were estimated to be 1.1 and 2.7 GtC yr^, respectively. By comparing the N_2O concentrations observed at Ny-Alesund and numerical model results, it was suggested that the observed seasonal N_2O cycle could be enlarged by intrusion of a stratospheric air mass with low N_2O concentration into the troposphere in summer. With an analysis using a three dimensional chemical-transport model and the CO concentration at Syowa Station, sporadic increases of CO concentration observed in February-March, 2003 and February, 2007 were ascribed to CO release by large-scale forest fires in Australia. Surface ozone depletion events were observed more than 40 times at Syowa Station from 1988 to 2007

A nationwide, multi-center, retrospective study of symptomatic small bowel stricture in patients with Crohn\u27s disease.

BACKGROUND:Small bowel stricture is one of the most common complications in patients with Crohn\u27s disease (CD). Endoscopic balloon dilatation (EBD) is a minimally invasive treatment intended to avoid surgery; however, whether EBD prevents subsequent surgery remains unclear. We aimed to reveal the factors contributing to surgery in patients with small bowel stricture and the factors associated with subsequent surgery after initial EBD.METHODS:Data were retrospectively collected from surgically untreated CD patients who developed symptomatic small bowel stricture after 2008 when the use of balloon-assisted enteroscopy and maintenance therapy with anti-tumor necrosis factor (TNF) became available.RESULTS:A total of 305 cases from 32 tertiary referral centers were enrolled. Cumulative surgery-free survival was 74.0% at 1 year, 54.4% at 5 years, and 44.3% at 10 years. The factors associated with avoiding surgery were non-stricturing, non-penetrating disease at onset, mild severity of symptoms, successful EBD, stricture length < 2 cm, and immunomodulator or anti-TNF added after onset of obstructive symptoms. In 95 cases with successful initial EBD, longer EBD interval was associated with lower risk of surgery. Receiver operating characteristic analysis revealed that an EBD interval of ≤ 446 days predicted subsequent surgery, and the proportion of smokers was significantly high in patients who required frequent dilatation.CONCLUSIONS:In CD patients with symptomatic small bowel stricture, addition of immunomodulator or anti-TNF and smoking cessation may improve the outcome of symptomatic small bowel stricture, by avoiding frequent EBD and subsequent surgery after initial EBD

Organization of Supramolecular Assemblies of Fullerene, Porphyrin and Fluorescein Dye Derivativeson on TiO_2 Nanoparticles for Light Energy Conversion

TiO_2 nanoparticles were modified with a porphyrin derivative, 5-[4-benzoic acid]-10,15,20-tris[3,5-di-tert-butylphenyl]-21H,23H-porphyrin (H_2P-COOH), and fluorescein derivatives, 9-[2-(3-carboxy-9,10-diphenyl)anthryl]-2,7-difluoro-6-hydroxy-3H-xanthen-3-one (DPAX-COOH) and 2′,7′-difluorofluorescein (FL-COOH). The dye-modified TiO_2 nanoparticles were deposited on nanostructured OTE/SnO_2 electrode together with nanoclusters of fullerene (C_) in acetonitrile/toluene (3:1, v/v) using an electrophoretic deposition technique to afford the dye-modified TiO_2 composite electrode denoted as OTE/SnO_2/(dye + C_)_n. The dye-modified TiO_2 composite electrodes have broad as well as high absorbance properties in the visible region, exhibiting the photoactive response under visible light excitation using I_3^-/I^- redox couple. The incident photon to photocurrent efficiency (IPCE) increases in order: OTE/SnO_2/(H_2P)_n ). The IPCE value can be further improved by replacing H_2P-COOH with a fluorescein derivative containing an electron donor moiety: DPAX-COOH (DPA: diphenylanthracene). The maximum IPCE value (42%) is obtained for OTE/SnO_2/(DPAX-COO–TiO_2 + C_)_n under the bias of 0.2 V vs. SCE