Isotope composition of Zelkova serrata leaves as an indicator of atmospheric pollution in Japan

In spite of increasing concern regarding the effects of greenhouse gases, atmospheric CO2 concentration continues to increase, with current levels now as high as 370 ppm. This elevated CO2 concentration influences not only atmospheric characteristics, but also ground vegetation: leaf structure, chemical composition and carbon-isotope composition are all affected. It was with this in mind that we investigated the viability of coupling an isotopic and a botanical approach to determine leaf interaction in relation to atmospheric pollution levels. Results show that, among the botanical indexes considered, the most reliable proxy of atmospheric CO2 levels would appear to be leaf mass per area (LMA), which increases with pollution. Our study also shows that LMA determination coupled with carbon-isotope compositions is a sensitive tracer of the local pollution-level variations.     

Atmospheric modelling using FASCOD to identify CO2 absorption bands and their suitability analysis in variable concentrations for remote sensing applications

Recent climate studies have proven that both temperature and CO₂ content of the earth's atmosphere followed a regular 100,000-year cycle of change and that they are closely correlated. Moreover, the observed increase of CO₂ in the atmosphere exceeds the predicted values extrapolated from historical data. Other than industrialization and rapid urbanization, geo-natural hazards such as leakage from hydrocarbon reservoirs and spontaneous combustion of coal contribute a considerable amount of CO₂ to the atmosphere. Several researchers have studied the possibilities and reliabilities of atmospheric CO₂ retrieval by the point-based method (nearly accurate but much localized) and globally (wider observation but many uncertainties). Radiative transfer codes, such as FASCOD (Fast Atmospheric Signature Code) with the HITRAN (High-Resolution Transmission) spectral database can simulate atmospheric transmission and path radiance with customized gas composition (CO₂, water vapour, CO, etc.) and concentration in order to understand the phenomena in a specific wavelength region. In the present study, a number of atmospheric models were constructed with different CO₂ concentrations (ppmv) with a combination of water vapour and other atmospheric gases such as CO, CH₄, N₂O, SO₂, etc., to find out the interference patterns of these gases over CO₂ absorption bands. The transmission features of these gas combinations were analysed by partial least-squares regression models. These models show that the most suitable CO₂ absorption bands are located around 2 μm, such as 1.998 and 2.001 μm. The spectral information derived from different concentrations of CO₂ can be fitted in multivariate models to predict the CO₂ concentration from spectral information in a controlled environment. Furthermore, the present study explores the sensitivity of some available remote sensing sensors in variable CO₂ concentrations for use in real world.     

Combustibles,fuels and their combustion products: A view through carbon isotopes

Stable (i.e. non-radioactive) carbon-isotope composition (δ¹³C) in fuels has been extensively used as an indicator of the processes leading to the generation of their parent crude-oil. With the example of those used in Paris (France), this preliminary study isotopically characterizes fuels and combustibles, as well as the isotopic relations existing with their combustion by-products, i.e. gases (CO₂) and particles (bulk carbon). Results show that δ¹³C in fuels is clearly related to their physical state, with natural gas being strongly depleted in ¹³C while coal yields the highest δ¹³C, and liquid fuels display intermediate values. This relation is also valid for combustion gases, although δ¹³C values of combustion particles form a homogeneous range within which no clear distinction is observed. Combustion processes are accompanied by carbon-isotope fractionation (noted Δ¹³C) resulting from the combustion being incomplete. Carbon-isotope fractionation is strictly negative (Δ¹³C = ?1.3‰) during the formation of combustion gases, but generally positive in particle formation even if values close to zero are observed. Using simple mixing equations for describing the closed system formed by fuel, CO₂ and carbonaceous particles, we discuss the carbon budget for spark-ignition (unleaded gasoline) and diesel engines. Stable carbon isotopes corroborate the already-proved superior efficiency of diesel combustion mode compared with spark ignition, as carbon is preferentially transformed into CO₂.     

Photoacoustic analysis of CO2 content in annual tree rings

We have used laser photoacoustic gas analysis to study the CO₂ content sorbed by the capillary porous system of annual rings in cross-sectional disks of some conifers. The measurement results showed that in most cases, the CO₂ content in gas samples extracted by the vacuum method from annual rings in the disks is higher than the CO₂ content in atmospheric air. In the disks, we observe an annual trend in the CO₂ concentration, correlating in a number of cases with a rise in atmospheric CO₂. The annual trend in the average value of the CO₂ concentration change sign from positive to negative. We hypothesize that the observed pattern for the annual distribution of CO₂ in the disks is connected with a rise in atmospheric CO₂ and a change in the concentration gradient between stem and atmospheric CO₂. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 477–480, May–June, 2009.     

合肥上空大气二氧化碳Raman激光雷达探测研究

Raman激光雷达是用于大气成分探测与特性研究的有效工具.介绍了中科院安徽光学精密机械研究所自行研制的一台用于测量低对流层大气CO₂时空分布的Raman激光雷达系统,并进行了一系列观测实验和对比分析.系统选用波长355 nm的紫外激光作为光源,利用光子计数卡双通道采集大气中N₂和CO₂的Raman后向散射信号与Li-7500型H₂O/CO₂分析仪进行对比标定,通过反演获得了大气CO₂水平与垂直方向时空分布廓线,并且获得了合肥地区大气边界层CO₂的夜变化趋势.结果表明,大气CO₂在空间的分布相对均匀,Raman激光雷达与CO₂分析仪变化趋势一致性较好,能够对大气CO₂时空分布进行有效、连续的观测.     

CO2 dial for monitoring atmospheric pollutants at the University of Calabria

Summary In this report we introduce the infrared lidar-dial apparatus developed at the University of Calabria. It has been carried out as a tool in the investigation of both the atmospheric pollution of trace gases and other atmospheric parameters as water vapour. The general scheme of the station is described, as well as the performances of the home-made CO₂ laser sources. Finally preliminary measurements of average concentration of ozone and water vapour over a range of about 3 km are presented and discussed in the report.     

Diurnal variability of δ13C and δ18O of atmospheric CO2 in the urban atmosphere of Kraków,Poland

This article presents the results of measurements of the isotopic composition and concentration of atmospheric carbon dioxide, performed on air samples from Kraków (Southern Poland) in different seasons of the year. A simple isotope mass balance model has been applied to determine the contributions of different sources of CO₂ to the urban atmosphere of Kraków city: the latitudinal/regional background, biospheric contributions and anthropogenic emissions. The calculations show that during the summer and early autumn the dominant contribution to local CO₂ peaks is the biosphere, making up to 20% of atmospheric CO₂ during the nocturnal temperature inversion in the lower troposphere. During early spring and winter, anthropogenic emissions are the main local source.     

Optical parametric oscillator-based photoacoustic detection of CO2 at 4.23 μm allows real-time monitoring of the respiration of small insects

A continuous wave, single frequency and continuously tunable optical parametric oscillator is used in combination with photoacoustic spectroscopy to detect trace emissions of CO₂ from insects under atmospheric conditions. The optical parametric oscillator (OPO) contains a periodically poled lithium niobate crystal and is tunable over the 3.9 to 4.8 μm infrared wavelength region. With the strong rotational-vibrational absorption band of CO₂ at 4.23 μm, it is possible to detect CO₂ down to 7 parts per billion volume using 20 mW of the OPO beam. This detection sensitivity was achieved by adding 4% of SF₆ gas to the atmospheric gas mixture to overcome the slow vibrational relaxation of the excited CO₂ levels. The usefulness of this system is demonstrated by real-time measuring of the fluctuations of the CO₂ concentration in the breath of a single ant (Lasius niger) and individual fruit flies (Drosophila melanogaster). PACS 42.65.Yj; 82.80.Kq; 42.62.Fi     

Simulation of operation of multiwave remote gas-analyzer based on NH3-laser

Numerical analysis of a multiwave path gas-analyzer, based on a NH₃-laser pumped by CO₂-laser radiation, is performed for model detection of concentrations of a series of molecular species such as NH₃, HCN, phosgene, NHO₃, CO₂, and H₂O. The potentialities of the gas analyzer and uncertainty of the gas concentration detection were estimated for a 4 km horizontal atmospheric path. The estimation took into account the absorption of laser radiation by the atmospheric aerosol and molecular gases under study and distortion of the laser beam due to atmospheric turbulence.     

探测大气中CO2的Raman激光雷达

基于大气激光后向散射光谱，研究和设计了探测大气CO₂浓度的Raman激光雷达,其发射机采用Nd∶YAG激光的三倍频354.7nm作为工作波长,发射的单脉冲能量350mJ,重复频率20Hz；接收机采用了光电倍增管(量子效率25%)和光子计数器(计数速率200MHz),探测CO₂的Raman散射371.66nm(频移1285cm^-1)信号,(1小时累加)近地面2.5km以内信噪比不小于8.采用组合滤光片来抑制强的354.7nm Mie-Rayleigh后向散射和氧气375.4nm Raman后向散射对信号的严重干扰. 比较分别来自大气CO₂和参考气体N₂的Raman后向散射回波,可反演出大气中CO₂的相对浓度. 关键词： 大气光学 激光雷达 Raman散射光谱 参考气体 Mie-Rayleigh散射     

Analysis of influence of atmosphere extinction to Raman lidar monitoring CO2 concentration profile

Lidar （Light detection and ranging） system monitoring of the atmosphere is a novel and powerful technique tool. The Raman lidar is well established today as a leading research tool in the study of numerous important areas in the atmospheric sciences. In this paper, the principle of Raman lidar technique measurement CO2 concentration profile is presented and the errors caused by molecular and aerosol extinction for CO2 concentration profile measurement with Raman lidar are also presented. The standard atmosphere extinction profile and ＇real-time＇ Hefei area extinction profile are used to conduct correction and the corresponding results are yielded. Simulation results with standard atmosphere mode correction indicate that the errors caused by molecule and aerosol extinction should be counted for the reason that they could reach about 8 ppm and 5 ppm respectively. The relative error caused by Hefei area extinction correction could reach about 6%. The errors caused by the two components extinction influence could produce significant changes for CO2 concentration profile and need to be counted in data processing which could improve the measurement accuracies.     

Measurements of carbon dioxide and oxygen concentrations in a diffusion respirator on the basis of track membranes

Concentrations of CO₂ and O₂ in the breathing hose and inside the mask of the diffusion respirator have been measured using an atomic emission spectrometer. The gas exchange system of this respirator efficiently, within 1 min, restores oxygen concentration in the inhaled air from 18.5 vol % to its atmospheric concentration (21 vol %) and carbon dioxide concentration from 2.9 vol % to a stationary concentration of ～0.12 vol %. In the optimal configuration of the respirator, CO₂ concentration inside the mask during breath is 0.23 vol %. The time resolution of the method is 200 ms and the CO₂ detection limit is 0.08 vol %.     

On the reaction mechanism of CO2 reforming of methane over a bed of coal char

CO₂ reforming of methane was studied over a bed of coal char in a fixed bed reactor at temperatures between 1073 and 1223 K and atmospheric pressure with a feed composition of CH₄/CO₂/N₂ in the ratio of 1:1:8. Experimental results showed that the char was an effective catalyst for the production of syngas with a maximum H₂/CO ratio of one. It was also found that high H₂/CO ratios were favoured by low pressures and moderate to high temperatures. These results are supported by thermodynamic calculations. A mechanism of seven overall reactions was studied and three catalytic reactions of CH₄ decomposition, char gasification and the Boudouard reaction was identified as being of major importance. The first reaction produces carbon and H₂, the second consumes carbon, and the third (the Boudouard reaction) converts CO₂ to CO while consuming carbon. Equilibrium calculations and experimental results showed that any water present reacts to form H₂ and carbon oxides in the range of temperatures and pressures studied. Carbon deposition over the char bed is the major cause of deactivation. The rate of carbon formation depends on the kinetic balance between the surface reaction of the adsorbed hydrocarbons with oxygen containing species and the further dissociation of the hydrocarbon.     

Measuring δ13C of atmospheric air with non-dispersive infrared spectroscopy

The potential use of non-dispersive infrared spectroscopy for measuring δ¹³C in air is demonstrated. This technique has already been successfully established for breath test analyses in medical diagnostics, where the CO₂ concentration ranges from 1 to 5 vol.% in the exhaled breath of vertebrates. For breath tests, the sensitivity and accuracy has been improved to reach a standard deviation of 0.2 ‰ (delta-value). Further adjustments were necessary to improve the sensitivity of the instrument at concentration levels typical of atmospheric air. The long-term stability is given by a standard deviation of 0.35 ‰ for CO₂ concentrations of about 400 ppm with signal averaging over 60 s.     

Isotope-selective infrared multiphoton dissociation of CF3Br in a supersonic free jet

The carbon-isotope selectivity in the multiphoton dissociation of CF₃Br is studied in the collisional region of supersonic free jet. The isotopic abundance of¹²C and¹³C in C₂F₆ formed by recombination of the dissociation products is measured with a quadrupole mass spectrometer. An enrichmet factor of 9.4 is obtained for¹²C with the 9R(30)CO₂ laser line while the factor of 6.9 is obtained for¹³C with the 9P(16) line.     

Using a laser-based CO2 carbon isotope analyser to investigate gas transfer in geological media

CO₂ stable carbon isotopes are very attractive in environmental research to investigate both natural and anthropogenic carbon sources. Laser-based CO₂ carbon isotope analysis provides continuous measurement at high temporal resolution and is a promising alternative to isotope ratio mass spectrometry (IRMS). We performed a thorough assessment of a commercially available CO₂ Carbon Isotope Analyser (CCIA DLT-100, Los Gatos Research) that allows in situ measurement of δ ¹³C in CO₂. Using a set of reference gases of known CO₂ concentration and carbon isotopic composition, we evaluated the precision, long-term stability, temperature sensitivity and concentration dependence of the analyser. Despite good precision calculated from Allan variance (5.0 ppm for CO₂ concentration, and 0.05 ‰ for δ ¹³C at 60 s averaging), real performances are altered by two main sources of error: temperature sensitivity and dependence of δ ¹³C on CO₂ concentration. Data processing is required to correct for these errors. Following application of these corrections, we achieve an accuracy of 8.7 ppm for CO₂ concentration and 1.3 ‰ for δ ¹³C, which is worse compared to mass spectrometry performance, but still allowing field applications. With this portable analyser we measured CO₂ flux degassed from rock in an underground tunnel. The obtained carbon isotopic composition agrees with IRMS measurement, and can be used to identify the carbon source.     

A study of greenhouse gases and air trajectories at Plateau Rosa

Summary The attention paid to changes in atmospheric concentrations of greenhouse gases has recently increased, with particular regard to the relationships between variations of their annual trends and of their shorter-period fluctuations on the one hand, and some geophysical and biological natural processes (like atmospheric transport, volcanic eruptions, ENSO events, seasonal vegetation cycles, and so on) on the other hand. Careful analysis and interpretation of the above relationships, in fact, can often disclose unknown mechanisms acting on modulations of these gases and make it possible for us to better understand the contributions made to them by natural causes, contrasted with anthropogenic ones. This paper presents and discusses the results of a series of CO₂ air concentration data, measured at Plateau Rosa (3480 m a.s.l.—Italian Western Alps) over a period of about four years, and correlated with atmospheric transport processes on synoptic scale. These results have shown the leading role played by some kinds of atmospheric circulation patterns in creating situations of not fully mixed air streams (and, as such, not representative of background conditions) and have also suggested a ?meteorological? selection scheme for CO₂ data to be used in evaluating more reliable annual trends.     

Effect of CO2 gasification reaction on oxy-combustion of pulverized coal char

For oxy-combustion with flue gas recirculation, as is commonly employed, it is recognized that elevated CO₂ levels affect radiant transport, the heat capacity of the gas, and other gas transport properties. A topic of widespread speculation has concerned the effect of the CO₂ gasification reaction with coal char on the char burning rate. To give clarity to the likely impact of this reaction on the oxy-fuel combustion of pulverized coal char, the Surface Kinetics in Porous Particles (SKIPPY) code was employed for a range of potential CO₂ reaction rates for a high-volatile bituminous coal char particle (130 μm diameter) reacting in several O₂ concentration environments. The effects of boundary layer chemistry are also examined in this analysis. Under oxygen-enriched conditions, boundary layer reactions (converting CO to CO₂, with concomitant heat release) are shown to increase the char particle temperature and burning rate, while decreasing the O₂ concentration at the particle surface. The CO₂ gasification reaction acts to reduce the char particle temperature (because of the reaction endothermicity) and thereby reduces the rate of char oxidation. Interestingly, the presence of the CO₂ gasification reaction increases the char conversion rate for combustion at low O₂ concentrations, but decreases char conversion for combustion at high O₂ concentrations. These calculations give new insight into the complexity of the effects from the CO₂ gasification reaction and should help improve the understanding of experimentally measured oxy-fuel char combustion and burnout trends in the literature.     

Breath ammonia detection based on tunable fiber laser photoacoustic spectroscopy

A new detection method for ammonia in high concentration of CO₂ and H₂O is reported, which uses a wavelength modulated photoacoustic spectrometer based on a near-infrared tunable erbium-doped fiber laser in combination with an optical fiber amplifier. The multi-wavelength (1522.44 nm, 1522.94 nm and 1545.05 nm) photoacoustic signal measurement is established to detect multi-spectrum signal in samples. The problem of ammonia detection in high concentration of CO₂ and H₂O is resolved at atmospheric pressure. The minimum detection limit of 16 ppb (signal-to-noise ratio = 1) in simulated breath samples (5.3% CO₂ and 6.2% H₂O (100% relative humidity at 37°C)) is achieved.     

A complete study of CO2 line parameters around 4845 cm for Lidar applications

A diode laser spectrometer was used in the Groupe de Spectrométrie Moléculaire et Atmosphérique of Reims (France) to study CO₂ line intensities, self-broadening coefficients and air-pressure-broadening coefficients near 2.063 μm. The spectral region ranging from 4843 to 4848 cm⁻¹, which is suitable for the measurement of atmospheric carbon dioxide (CO₂) mixing ratios was studied using a new generation-commercial diode laser from Nanoplus. Three lines of the (20°1)_III←(0 0 0) band of CO₂ have been studied. The results of intensity measurements and self-broadening coefficients are compared with previous determinations and available databases. Furthermore, the air-broadening coefficients for these transitions are also reported and analyzed. Finally, these new parameters are used for the measurement of atmospheric CO₂ mixing ratio with the 2 μm heterodyne differential absorption Lidar from the Laboratoire de Météorologie Dynamique at Palaiseau (France). These new parameters demonstrate a dramatic improvement of the retrieved atmospheric CO₂ concentrations.