Trace gas measurements during aircraft flights in the tropopause region over Europe and North Africa

During aircraft flights in May 1981 from Munich (40°N) to north of the Spitsbergen Islands (82°N) and to Monrovia, Liberia (6°N), air samples were obtained in the altitude range of 8 to 11 km and during the ascents and descents near the airports. These samples have been analyzed for the trace gas mixing ratios of CH₄, CO and N₂O. The results of these analyses are presented and discussed.The results provide new evidence of tropospheric-stratospheric exchange events in the vicinity of the subpolar and subtropical tropopause foldings and possibly show a case of transport of CO-enriched air in the upper troposphere above the North Atlantic Ocean.     

Termites and global methane—another assessment

New CH₄ emission data from a number of Northern and Southern Hemispheric, tropical and temperate termites, are reported, which indicate that the annual global CH₄ source due to termites is probably less than 15 Tg. The major uncertainties in this estimate are identified and found to be substantial. Nevertheless, our results suggest that termites probably account for less than 5% of global CH₄ emissions.     

Methoxy formation in the reaction of CH3O2 radicals with NO

Formation of methoxy (CH₃O) radicals in the reaction (1) CH₃O₂+NOCH₃O+NO₂ at 298 K has been observed directly using time resolved LIF. The branching ratio % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqOXdyMaae% 4qaiaabIeadaWgaaWcbaGaae4maaqabaGccaqGpbGaaeiiaiaabIca% ieqacaWF9aGaa8hiaiaa-nbicaWFGaGaeuiLdqKaai4waiaaboeaca% qGibWaaSbaaSqaaiaabodaaeqaaOGaae4taiaac2facaWFVaGaeuiL% dqKaai4waiaaboeacaqGibWaaSbaaSqaaiaabodaaeqaaOGaae4tam% aaBaaaleaacaqGYaaabeaakiaac2facaqGPaaaaa!4E31!\[\phi {\rm{CH}}_{\rm{3}} {\rm{O (}} = -- \Delta [{\rm{CH}}_{\rm{3}} {\rm{O}}]/\Delta [{\rm{CH}}_{\rm{3}} {\rm{O}}_{\rm{2}} ]{\rm{)}}\] has been determined by quantitative cw-UV-laser absorption at 257 nm of CH₃O₂ and CH₃ONO, the product of the consecutive methoxy trapping reaction (2) % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaae4qaiaabI% eadaWgaaWcbaGaae4maaqabaGccaqGpbacbeGaa83kaiaa-bcaieaa% caGFobGaa43taiaa+bcacaGFOaGaa83kaiaa+1eacaGFPaGaa4hiai% abgkziUkaabccacaqGdbGaaeisamaaBaaaleaacaqGZaaabeaakiaa% b+eacaqGGaGaaeOtaiaab+eacaqGGaGaa4hkaiaa-TcacaGFnbGaa4% xkaiaa+5cacaGFGaGaa4hiaiabeA8aMnaaBaaajqwaacqaaiaaboea% caqGibWaaSbaaKazcaiabaGaae4maaqabaqcKfaGaiaab+eaaSqaba% aaaa!55AC!\[{\rm{CH}}_{\rm{3}} {\rm{O}} + NO ( + M) \to {\rm{ CH}}_{\rm{3}} {\rm{O NO }}( + M). \phi _{{\rm{CH}}_{\rm{3}} {\rm{O}}} \] is found to be (1.0±0.2). The rate constant k ₁ is (7±2) 10^-12 cm³/molecule · s in good agreement with previous results.     

The tropospheric distribution of formaldehyde during TROPOZ II

A series of 149 measurements of the HCHO mixing ratio were made between 0 and 10 km altitude and 70° N to 60° S latitude during TROPOZ II. The data show a vertical decrease of the HCHO mixing ratio with altitude at all latitudes and a broad latitudinal maximum in the HCHO mixing ratio between 30° N and 30° S at all altitudes. The measured mixing ratios of HCHO are considerably higher than those expected from CH₄ oxidation alone, but agree broadly with the average latitude by altitude distribution of HCHO derived by a 2D model including emissions of C₁–C₇ hydrocarbons. A number of the regional scale deviations of the measured HCHO distribution from the average modelled one can be explained in terms of the local wind field.     

GRADIENT MEASUREMENTS OF METHANE FLUX IN LIN''''AN RICE PADDIES

From July to September of 1990,CH_4 flux measurements were made in Lin'an rice paddies using gradient profiletechniques.Some characteristics of the turbulence structure under the stable conditions have been verified in the surfacelayer according to the in situ measurements.The semi-empirical turbulent parameters β_m,β_h and β_c and their changeswith the stability parameter Ri are given.Observed results indicate that CH_4 flux in the rice-paddy is mainly decided bythe methnogenesis and the process of CH4 transport from internal soils to the atmosphere,and that the CH_4 verticaltransfer is depressed in the stable surface layer.The CH_4 flux shows that its obvious diurnal changes,and the meanCH_4 flux are higher in nighttime and lower in daytime,and the peaks appear at about 2000 BST at night and 0300 BSTin the early morning,respectively.The mean value of CH_4 flux is about 4.18±2.3 mg/m~2 h.     

GRADIENT MEASUREMENTS OF METHANE FLUX IN LIN’AN RICE PADDIES*

From July to September of 1990,CH₄ flux measurements were made in Lin'an rice paddies using gradient profile techniques.Some characteristics of the turbulence structure under the stable conditions have been verified in the surface layer according to the in situ measurements.The semi-empirical turbulent parameters β_m,β_h and β_c and their changes with the stability parameter Ri are given.Observed results indicate that CH₄ flux in the rice-paddy is mainly decided by the methnogenesis and the process of CH₄ transport from internal soils to the atmosphere,and that the CH₄ vertical transfer is depressed in the stable surface layer.The CH₄ flux shows that its obvious diurnal changes,and the mean CH₄ flux are higher in nighttime and lower in daytime,and the peaks appear at about 2000 BST at night and 0300 BST in the early morning,respectively.The mean value of CH₄ flux is about 4.18±2.3 mg/m² h.     

天然气中甲烷和CO2的二元同位素特征

不同成因的天然气由于形成温度不同，往往会有不同的稳定同位素特征。但是，由于经常不能同时获得天然气以及它的生成母体的同位素成分，很难用单独的C或H同位素成分来确定它的形成温度。在形成天然气时，不同的温度会形成不同的二元同位素的浓度，温度越低，二元同位素的比例越大，因此只需要知道天然气本身的二元同位素的浓度，就可以确定形成温度，从而避免了需要知道天然气生成母体的同位素成分这一难题。本文利用高级量子化学计算，预测了不同温度下天然气中甲烷和CO2气体的二元同位索（Clumped isotope）的特征，提供用于天然气成因分析的新方法。     

新疆煤层气资源赋存特征及开发潜力分析

通过对新疆主要煤田的煤炭资源分布特征，煤变质特征及构造特征分析，探讨新疆的煤层气资源赋存特征，对新疆主要煤田煤层气资源的勘探开发潜力进行初步评价，新疆的煤层气基本属于少生中储型，虽然单位含气量较低，但煤炭资源非常丰富，且相对集中，煤气具有较大的勘探开发潜力。     

大气中一氧化碳浓度变化的模拟研究

应用全球二维大气化学模式,模拟了CO、CH4和OH自由基等成分自工业革命到2020年的长期变化.模拟的全球CO平均体积分数在1840年、1991年和2020年分别为27×10-6、76×10-6和105×10-6.从1840到1991年,OH自由基数浓度从7.17×105个分子/cm3下降到5.79×105个分子/cm3,降低了19%.模拟的CH4长期变化与冰芯资料相符.模拟的20世纪80年代CO体积分数年增长率为1.03%～1.06%.大气中CO在20世纪90年代前是增长的,而到90年代初观测到CO体积分数突然下降.应用二维大气化学模式对此原因进行了模拟研究,结果表明,CO排放源的减少是CO体积分数下降的主要因子,平流层臭氧减少是另一个重要因子.尽管CO排放源的减少对大气CH4增长率的变化有较大影响,而CH4排放源减少对CO体积分数变化却几乎没有影响.