首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 484 毫秒
1.
The reaction of CO + OH? in aqueous solution to give formate was studied as a carbon monoxide sink on the primitive earth and in the present ocean. The reaction is first order in OH? and first order in the molar CO concentration. The second order rate constant is given by log k(M?1hr?1) = 15.83?4886/T between 25°C and 60°C. Using the solubility of CO in sea water, and assuming a pH of 8 for a primitive ocean of the present size, the halflife of CO in the atmosphere is calculated to be 12 × 106 yr at 0°C and 5.5 × 104 yr at 25°C.Three other CO sinks would have been important in the primitive atmosphere: CO + H2 → H2CO driven by various energy sources, CO + OH → CO2 + H, and the Fischer-Tropsch reaction of CO + H2 → hydrocarbons, etc. It is concluded that the lifetime of a CO atmosphere would have been very short on the geological time scale although the relative importance of these four CO sinks is difficult to estimate.The CO + OH? reaction to give formate is a very minor CO sink on the earth at the present time.  相似文献   

2.
A. V. Pavlov 《Annales Geophysicae》1994,12(10-11):1085-1090
In this paper we present the results of a study of the effect of vibrationally excited oxygen, O* 2, and nitrogen, N* 2, on the electron density, N e, and the electron temperature, T e, in the D and E regions. The sources of O* 2 are O-atom recombination, the photodissociation of O3, and the reaction of O3 with O at D region altitudes. The first calculations of O* 2(j) number densities, N j , are obtained by solving continuity equations for the models of harmonic and anharmonic oscillator energy levels, j=1-22. It is found that day time values of N j are less than nighttime values. We also show that the photoionization of O* 2 (j\geq11) by L<alpha>-radiation has no influence on the D region N e . In the nighttime D region the photoionization O* 2 (j\geq11) by scattered L <alpha>-radiation can be a new source of O+ 2. We show that the N* 2 and O* 2 de-excitation effect on the electron temperature is small in the E region of the ionosphere and cannot explain experimentally observed higher electron temperatures.  相似文献   

3.
Two Fourier transform spectrometers have been used to investigate the properties of the near-infrared hydroxyl (OH) nightglow emission under high-latitude summertime conditions and any association with noctilucent clouds (NLCs). The measurements were made from Poker Flat Research Range, Alaska (65.1°N, 147.5°W), during August 1986. Simultaneous photographic observations of the northern twilight sky were made from Gulkana, Alaska (62.2°N, 145.5°W), approximately 340 km to the south to establish the presence of NLCs over the spectrometer site. Data exhibiting significant short-term variations in the relative intensity (as much as 50-100%) and rotational temperature (typically 5–15 K) were recorded on six occasions when NLCs were observed. Joint measurements were also obtained on several “cloud-free” nights. No obvious relationship was found linking the mean OH intensity or its variation with the occurrence of NLCs. However, a clear tendency was found for the mean OH temperature to be lower on NLC nights than on cloud-free nights. In particular, a significant fraction of the OH(3-1) band spectra recorded by each instrument (16-57%) exhibited temperatures below \sim154 K on NLC nights compared with <3% on cloud-free nights. This result is qualitatively consistent with current models for ice particle nucleation and growth, but the mean OH temperature on NLC nights (\sim156 K) was significantly higher than would be expected for long-term particle growth in this region. These observations raise questions concerning the expected proximity of the high-latitude, summertime OH layer and the NLC growth region.  相似文献   

4.
Apatite distributions and compositions from cumulates from the EPR at Hess Deep, the MAR at the Kane Transform, and the SWIR at ODP Hole 735B were determined to assess the variability at each setting and to evaluate the potential utility of apatite in understanding the evolution of the lower ocean crust. Apatite in cumulates with low P2O5 contents are heterogeneously distributed along linear arrays or in tight clusters suggesting they crystallized from planar or pipe-like channels of evolved liquid. Most of the variation in the apatite composition is in the halogen site. The XApF and XApCl are inversely correlated defining trends at near constant XApOH with EPR XApOH=0.25, MAR XApOH=0.45, and SWIR XApOH=0.65. These trends are defined both by sample averages and by the range of individual analyses in samples with large ranges in their F/Cl ratio. These trends are interpreted to reflect the reequilibration of apatite from variably evolved liquids/fluids that moved through the crystal mush. Comparison of the F–Cl–OH contents of apatite with the F–Cl–OH contents of glasses recovered from the same ridges show approximate correspondence: apatite and glasses from the EPR have the highest halogen contents while apatite and glasses from the MAR and SWIR have more OH. Some of the higher Cl contents in the apatite are interpreted to be produced by degassing of the cumulus pile while others reflect the assimilation of a seawater component. We suggest that systematic analysis of apatite from oceanic cumulates might allow cumulates that crystallized at shallow depths and assimilated seawater-derived components to be distinguished from those that crystallized below the level of seawater interaction.  相似文献   

5.
Enthalpy-composition diagrams (H*-X) calculated from existing temperature-composition (T-X) phase diagrams and thermodynamic data provide a simple and effective means for evaluating the enthalpy-temperature effects of magma mixing. If athermal mixing is assumed, adiabatic mixing lines on H*-X diagrams are straight lines because enthalpy, unlike temperature, is an extensive property of a system. Comparison of binary T-X diagrams with their derivative H*-X diagrams shows that incorrect predictions can be obtained when T-X diagrams are used to analyze mixing problems.An H*-X diagram calculated using experimentally determined phase equilibria for anhydrous basalt-rhyolite mixtures predicts that adiabatic mixing of basalt and rhyolite at their respective liquidus temperatures will result in small amounts of crystallization ( < 2 wt.% ). Because the phase equilibria of hydrous basalt-rhyolite mixtures have not yet been determined, an H*-X diagram for such mixtures cannot be constructed. However, existing hydrous phase equilibria can be used to predict whether adiabatic mixtures of anhydrous basalt and hydrous rhyolite will be super- or subliquidus. Calculations at Ptotal = 200 MPa show that on an H*-X diagram a mixing chord drawn between anhydrous basalt and water-saturated rhyolite at their respective liquidus temperatures lies below the enthalpy values calculated for a Paricutin andesite and Mt. St. Helens dacite at their estimated liquidus temperatures. This indicates that the liquidus for mixtures of anhydrous basalt and water-saturated rhyolite is noticeably convex upward, suggesting that larger amounts of crystallization will occur than in the anhydrous case.  相似文献   

6.
刘新  吴定桂  江和龙  宋娜 《湖泊科学》2020,32(2):440-449
活性氧物种(ROS)参与天然水体系统中的光化学反应、氧化还原反应,是影响水体中有机污染物的迁移、转化、环境归宿及生态效应的重要因素.然而目前对草源型可溶性有机物(DOM)分解过程中ROS的产生过程并不清楚.本文通过室内模拟实验首先构建了室内测定3种ROS(~3CDOM~*、~1O_2、·OH)的方法,进而分析草源植物——苔草(Carex tristachya)残体浸出液中DOM光降解过程中ROS的产生过程.结果表明:ROS累积含量的产生随着DOM的降解逐渐升高在3种自由基含量中,~3CDOM*的产生含量最多,·OH产生含量低于另外2种ROS两个数量级.CDOM含量与~3CDOM~*、~1O2、·OH浓度呈现正相关关系,尤其与~3CDOM~*和~1O_2浓度的显著性水平最高,·OH次之.ROS浓度与水质指标呈现出不同的线性相关关系,与硝态氮浓度呈负相关关系,而与亚硝态氮浓度呈现正相关关系,并且亚硝态氮对ROS浓度影响效果极显著.同时类蛋白荧光峰值强度的衰减与ROS累积含量呈现极显著负相关关系,脱明在DOM的光降解过程中蛋白质小分子的降解是产生ROS很重要的一个部分.综上通过对草源型DOM光降解过程中ROS产生过程的研究,增加了对湖泊生态系统中水生植物产生ROS的过程、迁移、转化、归宿及其作用机制的认识.  相似文献   

7.
Electrical conductivity of nineteen samples of the Deccan Traps, collected from the Pawagarh area and two boreholes drilled at Koyna, has been measured in the temperature range from 475 K to about 1100 K. The results indicate the change of the conduction mechanism from impurity to electronic/ionic conduction as the temperature increases. Few samples show the normal behaviour, i.e. the increase of conductivity with temperature, while some samples show an anomalous behaviour between the temperatures 600 and 1000 K. This anomalous behavior may be due to either the dehydration of OH? ions or/and the oxidation of Fe2+ to Fe3+.  相似文献   

8.
The uptake coefficients () for OH radicals on some dry salts of tropospheric interest (NaCl and NH4NO3) have been investigated as a function of temperature using the flow tube technique combined with an EPR spectrometer as a detection method. The temperature dependence of -values measured over the temperature range 245–340 K can be expressed in Arrhenius form: OHNaCl=(1.2±0.7)×10−5exp[(1750±200)/T] and OHNH4NO3=(1.4±0.5)×10−4exp[(1000±100)/T]. These Arrhenius expressions lead to very similar -values (\approx4×10−3) for both salts studied at 300 K. It is shown that the heterogeneous OH sinks on solids aerosol play a very minor role in tropospheric chemistry in comparison with the homogeneous sinks.  相似文献   

9.
Middle atmosphere temperatures have been measured by in situ and by remote sensing instruments for several decades. Extensive temperature measurements by rocket-borne falling spheres (FS) were performed from Andøya Rocket Range in northern Norway from the late 1980s onwards. About 90 rockets were successfully launched within eight measurement campaigns and compiled to an empirical temperature statistic. About half of these measurements were in July and August. Since 1997 the Bonn University Rayleigh/Mie/Raman lidar has been operated at Esrange in northern Sweden during winter as well as during summer. One hundred and eight night mean temperature profiles were obtained for July and August from this data set and have been compared to the FS-statistics. A systematic difference could be observed, i.e. the weekly average temperatures taken from the FS-based empirical temperature statistics are up to 10 K warmer than the temperatures measured by lidar, depending on altitude. In particular comparisons during August show larger differences than comparisons with July data. Temperatures were additionally derived from the Rayleigh-scattered light of the Bonn University Na-resonance lidar which was operated during the 1980s at Andøya. No systematic differences between these measurements and the FS-data were found. Gravity waves, tides, volcanic aerosol, and the solar cycle are not likely to cause the observed differences, since their influence is minimised either by data selection (gravity waves and tides) or by measurement times (volcanic aerosol, solar cycle). Additionally to the temperature difference a change in the gravity wave activity was observed, in particular during summer 2002 and 2006. During these years also noctilucent clouds occurred rather late in the season. The latest unambiguous observation of a noctilucent cloud by the U. Bonn lidar at Esrange was on 24 August 2006. All these observations are indications of a long-term temperature change in the polar summer middle atmosphere as predicted by model calculations. While similar changes have already been observed at middle and low latitudes, temperature trend analyses for the polar atmosphere did not reveal any variation up to now.  相似文献   

10.
Using a modified Brewer bubbler ozone sensor, continuous measurements of the ozone concentration near the ground were made at Poona (18°N, 73°E) for one year 1969–1970. The surface ozone concentration shows a pronounced seasonal variation, with a minimum during the monsoon months and a maximum during the pre-monsoon summer months. There is also a marked diurnal variation in surface ozone concentration which clearly follows the diurnal variation of temperature and is again a maximum during the summer months and a minimum during the monsoon. A secondary maximum in ozone concentration occurs in the forenoon during the winter months, associated with the temperature inversions that occur near the ground in this season.Both ozone and radioactive tracers, such as Cs-137 both in air and in precipitation show variations indicating that they have identical source regions and sinks. The latitudinal anomaly of surface ozone and Cs-137 observed in the low latitudes over India is explained as arising from the reduction in the rate of transfer of these tracers from the stratosphere to the troposphere, as a result of the reversed circulation at the upper levels in this season.From continuous measurements of surface ozone made with three electrochemical sensors exposed at three levels, 0, 15 and 35 m above the ground, the ozone flux has been directly calculated for the first time in the tropics. The ozone flux was calculated using both the rate of decay method used by Kroening and Ney and Regener's profile method. The profile method gives values of the order of 1.71 to 7.04×1011 mol/cm2/sec and that obtained by the rate of decay method is found to be 4.2 to 5.6×1011 mol/cm2/sec and are in good agreement with the flux values reported by other investigators.  相似文献   

11.
Gravity measurements were made in the Mailaram copper mines, Andhra Pradesh. The observations were distributed between the two shafts situated about 220 m apart and in the three levels up to a maximum depth of 100 m. Assuming a normal free-air gradient, average densities for the three layers were determined as 2.631, 2.604, and 2.823 g cm-3, respectively. Upon incorporating the weighted mean density values from measurements on samples, the free-air gradients were found to be 0.315 mGal m-1 for the second layer (i.e. between the first and second levels) and 0.2978 mGal m-1 for the third layer (i.e. between the second and third levels). The density variation map obtained from the gravity data, the deduced anomalies, the weighted mean density values from measurements on rock samples, and the varying free-air coefficients all suggest correspondence with the concentration of ore lodes.  相似文献   

12.
Information about variations in solar activity and climate on the time intervals from 130 years to four–five last centuries, including results of instrumental measurements (Wolf numbers, actinometry, thermometry) and indirect indicators (ice core acidity, NO 3 ? ion concentration in polar ice, temperature tree-ring reconstructions), has been analyzed for the Northern Hemisphere and its high-latitude part. It has been obtained that the observed relation between secular variations in solar activity and near-Earth temperature resulted from the effect of the corresponding variation in aerosol transparency of the stratosphere on terrestrial climate. It has been also indicated that long-term variations in the aerosol content of the stratosphere can, in turn, be related to secular cycles in atmospheric ionization caused by variations in fluxes of ionizing cosmic particles.  相似文献   

13.
在北京东北方向的兴隆天文台,自主搭建的大气辐射观测仪器对OH夜气辉从2011年12月开始进行观测.利用高分辨率的OH(8-3)带的振转光谱计算了转动温度,并与TIMED/SABER探测的温度进行了比较.观测表明,两年(2012—2013)的OH(8-3)带转动温度平均值为203.0±11.2K,有明显的季节变化,冬季高,夏季低,温差可达60K.与SABER观测温度的季节变化一致.对日平均的转动温度进行年振荡和半年振荡分量的拟合分析表明,年振荡强度(10.8K)远大于半年振荡(2.7K).研究还发现,不同夜晚转动温度变化形态差别很大,既有很强的潮汐控制的波动,又有相对短周期的波动.  相似文献   

14.
40Ar/39Ar step heating of single K-feldspar crystals ( 500 μg) in a furnace with a low argon blank and accurate temperature control provide constraints on the thermal history of the Salton Sea geothermal field, southern California. Estimates of 40Ar loss from detrital K-feldspars, coupled with kinetic information gleaned from laboratory degassing of 39Ar, allow possible thermal histories to be evaluated. Samples from core and cuttings of sandstones from the State 2–14, Landers #1, Dearborn Farms #1, Magmamax #2, Elmore #3 and Sinclair #3 wells have been analyzed for this purpose. No recent 40Ar* loss is recognized in any of the 17 crystals measured, even for samples currently at temperatures greater than 275°C. This observation suggests that the present temperature distributions in these wells have not been maintained for greater than 1000 years. However, aggregates ( 100 mg) of two K-feldspar samples do reveal recent 40Ar* loss from the State 2–14 well, suggesting a time scale of 1000 to 5000 years for near-peak thermal conditions. These estimates of heating duration are broadly consistent with earlier results from thermal modelling, but do not support interpretations that paleotemperatures were once hotter than present.Provenance ages span the Tertiary through Middle Proterozoic but cluster at ages of 25, 70 and 1250 Ma. These age peaks are very common K-feldspar K-Ar ages in detachment terranes of southeastern California and southwestern Arizona, both drained by the Colorado River. This coincidence supports earlier suggestions that the sands of the Salton Trough were derived mainly from the Colorado River.Unrealistically low apparent activation energies (< 20 kcal/mol) for argon transport are observed for several single crystals which yield absurdly low calculated closure temperatures (e.g., -100°C). We infer that this anomalous behaviour results from a combination of the laboratory heating schedule and the distribution of diffusion domain sizes.  相似文献   

15.
Millstone Hill ionospheric storm time measurements of the electron density and temperature during the ionospheric storms (15-16 June 1965; 29–30 September 1969 and 17–18 August 1970) are compared with model results. The model of the Earth’s ionosphere and plasmasphere includes interhemispheric coupling, the H+, O+(4S), O+(2D), O+(2P), NO+, O+2 and N+2 ions, electrons, photoelectrons, the electron and ion temperature, vibrationally excited N2 and the components of thermospheric wind.In order to model the electron temperature at the time of the 16 June 1965 negative storm, the heating rate of the electron gas by photoelectrons in the energy balance equation was multiplied by the factors 5–30 at he altitude above 700 km for the period 4.50-12.00 LT, 16 June 1965. The [O]/[N2] MSIS-86 decrease and vibrationally excited N2 effects are enough to account for the electron density depressions at Millstone Hill during the three storms. The factor of 2 (for 27–30 September 1969 magnetic storm) and the & actor 2.7 (for 16–18 August 1970 magnetic storm) reduction in the daytime peak density due to enhanced vibrationally excited N2 is brought about by the increase in the O++N2 rate factor.  相似文献   

16.
Spectra of the O2(a1g) airglow emission band at 1.27 µm have been recorded during twilight at Maynooth (53.2°N, 6.4°W) using a Fourier transform spectrometer. Synthetic spectra have been generated for comparison with the recorded data by assuming a particular temperature at the emitting altitude, and modelling the absorption of each line in the band as it propagates downward through the atmosphere. The temperature used in generating the synthetic spectra was varied until an optimum fit was obtained between the recorded and synthetic data; this temperature was then attributed to the altitude of the emitting layer. Temperatures derived using this technique for 91 twilight periods over an 18-month period exhibit a strong seasonal behaviour with a maximum in winter and minimum in summer. Results from this study are compared with temperatures calculated from the OH(3, 1) Meinel band recorded simultaneously. In winter OH temperatures exceed O2 values by about 10 K, whereas the opposite situation pertains in summer; this result is interpreted in terms of a possible change in the altitude of the mesopause as a function of season. Estimates of the twilight O2(0, 0) total band intensity indicate that its intensity is lower and that its decay is more rapid in summer than in winter, in agreement with earlier observations.  相似文献   

17.
The paper presents the results of a photometric study of the hydroxyl bands (7–2) and (8–3) in the night airglow spectrum at Mt. Abu in the winter and spring of 1966–1972. The observed nocturnal variation differs from the variation expected from the theoretical studies of Hesstvedt, Hunt, Shimazaki and others. Instead of a gradual fall in intensity after sunset to shortly before sunrise, a peak in intensity is found at a time which changes from month to month and roughly coincides with the transit times of the X-ray star TAU (XR-1)-Crab Nebula. Anexplanation of the observed phenomenon is offered in terms of the increased energy output into the D and E regions of the atmospheres, increased eddy diffusion, and production, of additional O(3P) and O3 in the region 80–95 km. O3 reacting with H gives rise to OH*.  相似文献   

18.
Presently available data on the reaction of SO2 with OH radicals (OH + SO2 + \(M\xrightarrow[{k_1 }]{}\) HSO3 +M) are critically reviewed in light of recent stratospheric sulfur budget calculations. These calculations impose that the net oxidation ratek of SO2 within the stratosphere should fall within the range 10?7≤k≤10?9, if the SO2 oxidation model for the stratospheric sulfate layer is assumed to be correct. The effective reaction rate constantk 1 * =k 1[M] at the stratospheric temperature is estimated as $$k_1^* = \frac{{(8.2 \pm 2.2) \times 10^{ - 13} \times [M]}}{{(0.79 \mp 0.34) \times 10^{ - 13} + [M]}}cm^3 /molecules sec$$ where [M] refers to the total number density (molecules/cm3). Using the above limiting values ofk 1 * , and the estimated OH density concentrations, the net oxidation rate is calculated as 3.6×10?7≤k≤1.3×10?8 at 17 km altitude. This indicates that the upper limit of thesek values exceeds the tolerable range imposed by the model by a factor of about four. Obviously the uncertainty of thek 1 * values and of the OH concentrations in the stratosphere is still too large to make definite conclusions on the validity of the SO2 model.  相似文献   

19.
Recently obtained data on oxygen diffusion in feldspars, quartz, and hornblende permit the prediction of the apparent18O16O temperatures that would be measured in a rock that consisted only of those three minerals, and cooled slowly from high temperature. The computed temperatures would be based on the differences in the18O16O ratios between coexisting pairs of minerals. The present calculation takes into account the diffusion rates for oxygen as a function of temperature, the cooling rate of the rock, the mineral grain sizes, and the mode of the rock. For mineral grains 1 mm in radius, and a cooling rate of 10°C/m.y., the minimum difference in apparent temperature between quartz-feldspar and feldspar-hornblende pairs will be 115°C, despite the assumption of a normal, uneventful, slow cooling history to room temperature. Further, the apparent quartz-hornblende temperature will range over 30°C (590–620°C) depending on the mode of the rock. For a cooling rate of 1000°C/m.y., the apparent difference in temperature can be as much as 400°C. Consequently, consistency in temperatures obtained by oxygen isotope analysis should not be expected in most high-grade metamorphic rocks or igneous rocks which are cooled slowly. Departures from the pattern of temperatures obtained in this model would imply a very rapid quench from high temperature, or a complex history for the rock. For some minerals, including hornblende, the relation between temperature and the equilibrium fractionation of oxygen isotopes between coexisting phases has been derived from observed relations in natural specimens. The choice of the specimens used for such calibrations needs to be re-evaluated in light of these findings. This may result in a change in the equilibrium equation constants.An example from the literature, the San Jose tonalite, Baja California, Mexico, was modelled and yieldsδ18O concentrations in the minerals that correspond closely with the measured values. This suggests that the model used is appropriate, that the rock has had a simple thermal history, and that it cooled at 100–200°C/m.y. over the temperature range 800–500°C. The set of paleotemperatures obtained for a rock will, in general, yield neither the mineral closure temperatures nor the formation or crystallization temperatures. On the other hand, the cooling rate of the rock may be derived from the data. This, in turn, may have important tectonic implications with regard to denudation and uplift rates.  相似文献   

20.
湖泊水体的对流混合是最基本的物理过程,其能显著影响湖泊生态系统温室气体等循环,但浅水湖泊水体对流混合的研究鲜有报道.本研究基于太湖(面积2400 km2,平均水深1.9 m)中尺度通量网的原位、高频、连续和多点的观测数据,分析该大型浅水湖泊水体对流混合速率w*的时空特征.结果表明太湖水体w*的均值为2.49 mm/s,因太湖的风速、水温和辐射等物理参数无空间变化,w*也无明显的空间变化.但是研究表明w*呈现显著的昼夜变化和季节变化,且昼夜变化幅度强于季节变化.总体上夜间w*是白天的4倍多,冬季w*(均值1.79 mm/s)明显低于春季(均值2.42 mm/s)、夏季(均值2.91 mm/s)和秋季(均值2.82 mm/s).太湖w*主要受风速和能量收支影响,白天风速是主要驱动因子,夜晚能量收支是主要驱动因子.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号