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.     

CO2 concentrations and delta13C (CO2) values in monthly sets of air samples from downtown Parma and the Parma and Taro river valleys, Emilia-Romagna, Italy

Monthly sets of discrete air samples were collected from September 2004 to June 2005 in the town of Parma, along North-South and East-West runs (8 plus 8 samples), using four-litre Pyrex flasks. The CO2 concentrations and delta13C values were determined on these samples with the aim of evaluating quantitatively the contribution of domestic heating to the winter atmospheric CO2 pollution in downtown Parma by comparing autumn and spring atmospheric values with winter values. After separation of CO2 from the other air gases in the laboratory, the CO2 concentrations were calculated from the intensity of the 12C16O2+ ion beam in the mass spectrometer, after calibration with artificial air samples whose CO2 concentration was very carefully determined by the Monte Cimone Observatory (Sestola, Modena, Italy). The reproducibility of these measurements was of approximately +/-0.4 % and, consequently, the most probable error is not higher than+/-2-3 ppmv and does not affect the magnitude of the gradients between different samples. The standard deviation of delta13C measurements ranges from+/-0.02 to +/-0.04 per thousand (1sigma). The results suggest that the contribution of domestic heating to atmospheric CO2 pollution is almost negligible in the case of ground level atmosphere, where the main CO2 pollution is essentially related to the heavy car traffic. This is probably because of the fact that the gases from the domestic heating systems are discharged tens of metres above ground level at a relatively high temperature so that they rise quickly to the upper atmospheric layers and are then displaced by air masses dynamics. Monthly sets of discrete air samples were also collected from October 2004 to June 2005 along North-South runs from the town of Parma to the Apennine ridge following the Parma and the Taro river valleys (8 samples and 7 samples per set, respectively) and measured using the same technique. The aim of this study was the comparison between the town samples, the plain country samples and the samples collected on the northern slope of the Apennines. The results reveal huge variations of both CO2 concentration and delta13C through space and time, some of which can be reasonably explained whereas others are rather difficult to understand. The sets of values are discussed and various hypotheses are suggested.     

太阳光谱对高分辨吸收光谱反演大气CO2浓度影响的研究

以太阳光为辐射源的近红外波段高分辨率吸收光谱广泛应用于大气参数遥测.以CO2浓度反演为例,研究了太阳光谱分辨率的影响.利用美国AER公司编制的太阳光谱计算程序得到大气上界的理论计算太阳光谱作为辐射源,结合自行编制的高分辨率大气透过率模拟软件HRATS对大气中CO2平均浓度进行模拟反演.数值模拟计算结果表明,太阳光谱的准确度对浓度反演非常重要,特别是在超分辨光谱反演中异常重要,虽然反演浓度的偏差与观测分辨率没有明显的线性变化规律,但有趋势:观测分辨率的降低对太阳光谱分辨率的要求也降低,为了精确反演大气中CO2浓度,因此需要充分利用大气层顶的高分辨太阳辐射光谱数据.     

基于离轴积分腔输出光谱对泰州大气NH3浓度观测与分析

氨(NH₃)是大气中活性氮最主要的还原形式, 是形成二次无机铵盐的重要气态前体物。在中国极度污染的条件下, 这些铵盐可占PM_2.5质量的40%～60%。NH₃污染不仅影响全球的光辐射强度, 而且会加剧大气光化学污染。目前, 城市地区氨气来源仍存在一定争议。为研究泰州地区NH₃污染情况, 并深入了解NH₃的来源。2018年6月6日至15日, 基于离轴积分腔输出光谱技术, 开展了夏季泰州地区大气NH₃浓度的连续观测。其他污染物浓度(如NH₃,NO_x,CO,NH+₄)同步进行测量。观测点位距离交通枢纽300 m, 观测期间NH₃的平均浓度为25.1±4.5 μg·m-3, 相比国内外其他城市, 该地区NH₃污染处于较高水平。白天与夜间NH₃浓度均值无明显差异, 但总体呈现白天降低夜晚升高的趋势。夜间温差大, 大气边界层较为稳定, 是污染物得以累积的原因之一; 晨间NH₃浓度急剧升高, 主要考虑为夜间沉积在水汽中的NH_x(气态NH₃与颗粒态NH+₄)的蒸发所带来。随着光照进一步增强, 环境水汽中NH_x的蒸发逐渐结束, 光化学反应过程逐渐占据主导, NH₃浓度上涨速度缓慢, 逐渐趋于平衡, 并在之后出现迅速下降。在湿度较大的夜间, NH_x的沉积过程更加明显。结合观测期间的气象参数以及与常规污染物的相关性, 讨论了泰州地区的污染物变化趋势及污染水平。结果表明, 大部分日期交通排放对泰州地区NH₃浓度影响较小, 仅6月7日早高峰期NH₃与NO_x,CO相关性较好, R2分别为0.740与0.911, 推测当日交通排放影响较大, 交通源是NH₃的重要局地源。进一步进行了后向轨迹分析, 比较了观测期间不同气团所导致的污染物浓度变化。结合观测结果分析可知, 观测点西北方向工业园区污染排放可能是导致6月10日夜间污染事件的重要原因。     

Diurnal variability of delta13C and delta18O 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.     

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355nm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.     

机载FTIR被动遥测大气痕量气体

介绍了以各种地物为背景的机载傅里叶变换红外光谱法(FTIR)被动遥测大气中痕量气体飞行测量试验,讨论了相应的被动下视遥测技术,复杂背景下大气痕量气体红外特征光谱信息获取方法和浓度反演算法模型,定量分析了飞行试验区域内高度1 000 m以下边界层内大气中痕量气体CO和N₂O的平均浓度。这种遥测量技术和数据分析方法可在不预先测量背景辐射光谱的情况下对大尺度区域内大气痕量气体进行快速、机动遥感遥测,以及突发性大气污染事故的应急监测。     

车载被动DOAS的污染气体柱浓度分布重构方法

大气污染的综合防治需要从不同尺度的区域出发,充分研究区域的环境特点,需要对空气质量有作用的多种因素进行全面系统的分析,获取大气污染物浓度时空分布是了解区域污染特征的重要途径。获取高空间分辨的大气污染物柱浓度分布情况是掌握区域污染程度的重要前提。由大气扩散模型,排放源周边的大气污染物的柱浓度服从高斯分布。将车载被动差分光学吸收光谱（DOAS）获取的对流层污染气体垂直柱浓度空间分布信息结合序贯高斯模拟方法重构了高空间分辨率的区域污染物柱浓度分布及其误差分布。分别选取工业园区（钢铁企业）、城市区域（北京市怀柔城区、北京市通州城区）等典型区块进行走航观测,获取观测路径上的NO₂和HCHO柱浓度,结合地理信息网格化车载观测数据,利用序贯高斯模拟获取了观测区域的NO₂和HCHO柱浓度分布以及污染物柱浓度误差分布,重点分析了该方法在排放特征不同的区域柱浓度分布模拟重构的可行性及重构结果的不确定性。某钢铁企业、怀柔城区、通州城区内污染源依次减少,气态污染物分布的结构复杂性依次降低。由半方差分析结果,某钢铁企业由于NO₂排放源多,污染物柱浓度空间依赖性略弱,城市区域污染物柱浓度表现出强烈的空间相关性,并且整体呈现出了区域污染源越复杂,空间相关性的范围越小的特点。基于立体监测数据获取了观测区域百米空间分辨的污染物垂直柱浓度分布及误差分布,在不依赖下垫面数据、源清单数据或人口分布数据的基础上基于实测数据低成本地获取了重点工业区或城市区域气态污染物的分布细节,同已有的卫星遥感等方法获取污染气体垂直柱浓度分布相比,空间分辨率提高了2～3个数量级,同时通过柱浓度误差分布定量评估了模拟重构的准确性。针对不同排放特征的重点区域大气污染状况,提供了新的准确性可评价的实测手段,该方法对了解区域污染状况、污染控制对策及控制效果的评估具有重要作用。     

Partitioning of atmospheric carbon dioxide over Central Europe: insights from combined measurements of CO2 mixing ratios and their carbon isotope composition

Regular measurements of atmospheric CO (2) mixing ratios and their carbon isotope composition ((13)C/(12)C and (14)C/(12)C ratios) performed between 2005 and 2009 at two sites of contrasting characteristics (Krakow and the remote mountain site Kasprowy Wierch) located in southern Poland were used to derive fossil fuel-related and biogenic contributions to the total CO (2) load measured at both sites. Carbon dioxide present in the atmosphere, not coming from fossil fuel and biogenic sources, was considered 'background' CO (2). In Krakow, the average contribution of fossil fuel CO (2) was approximately 3.4%. The biogenic component was of the same magnitude. Both components revealed a distinct seasonality, with the fossil fuel component reaching maximum values during winter months and the biogenic component shifted in phase by approximately 6 months. The partitioning of the local CO (2) budget for the Kasprowy Wierch site revealed large differences in the derived components: the fossil fuel component was approximately five times lower than that derived for Krakow, whereas the biogenic component was negative in summer, pointing to the importance of photosynthetic sink associated with extensive forests in the neighbourhood of the station. While the presented study has demonstrated the strength of combined measurements of CO (2) mixing ratios and their carbon isotope signature as efficient tools for elucidating the partitioning of local atmospheric CO (2) loads, it also showed the important role of the land cover and the presence of the soil in the footprint of the measurement location, which control the net biogenic surface CO (2) fluxes.     

Measuring delta13C of atmospheric air with non-dispersive infrared spectroscopy

The potential use of non-dispersive infrared spectroscopy for measuring delta(13)C in air is demonstrated. This technique has already been successfully established for breath test analyses in medical diagnostics, where the CO(2) 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 per thousand (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 per thousand for CO(2) concentrations of about 400 ppm with signal averaging over 60 s.     

原位红外光谱法研究大气颗粒物表面非均相反应

大气污染物之间可能发生协同作用,造成严重的二次污染,产生次生环境问题.本实验通过原位红外光谱分析方法研究气态污染物和碳颗粒物之间的吸附过程,发现大气中CO2和NO极易在颗粒物表面发生吸附;CO2在颗粒物表面达到吸附平衡时间很短,NO的吸附平衡时间较长;CO2和SO2会影响NO在颗粒物表面的吸附,CO2在颗粒物表面的吸附几乎不受NO和SO2的影响.     

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.     

大气CO2卫星遥感中植物叶绿素荧光影响的校正

大气CO₂卫星遥感监测的关键在于高精度,而植物叶绿素荧光存在与大气散射相似的光谱特征,干扰大气散射相关参数的反演结果,从而影响CO₂的反演精度。因植物叶绿素荧光强度微弱且影响特征与大气散射高度相关而难以准确校正。鉴于现有大气CO₂卫星遥感精度不足,以及植物叶绿素荧光对大气CO₂反演存在不可忽视的影响程度和复杂性,设计了O₂-A、1.6和2.06 μm CO₂三个光谱带协同的参数化校正方法。首先通过对大气散射采取基于光子路径长度概率密度函数（PPDF）的参数化建模,降低叶绿素荧光与大气散射参数的光谱相关性;其次,针对叶绿素荧光强度弱,难以准确反演的问题,基于轨道碳观测器（OCO-2）的叶绿素荧光产品构建了5km分辨率的全球叶绿素荧光先验信息库,增强CO₂与叶绿素荧光同步反演中对叶绿素荧光的先验约束,提高叶绿素荧光的反演精度。通过O₂-A、1.6和2.06 μm CO₂三个光谱带的协同同时反演大气散射、叶绿素荧光和大气CO₂,并结合叶绿素荧光丰富的先验信息,能够较准确剥离大气散射和叶绿素荧光而提高大气CO₂的反演精度。选择叶绿素荧光强度明显较高的柱总碳观测网络（TCCON）中的Park Falls（45.945°N,90.273°W）站点开展验证,对该站点近4年每年8月份的温室气体观测卫星（GOSAT）数据进行反演,发现植被叶绿素荧光导致GOSAT XCO₂反演结果系统偏低2×10-6(ppm)左右,通过本文的方法进行校正,反演结果的低估程度有明显改善,最大低估由2.58 ppm降低到1.49 ppm,且离散程度也有一定程度的改善,明显控制了CO₂反演中叶绿素荧光的影响,对于实现1%（~4 ppm）的CO₂反演精度来说,提供了有力支撑。     

基于卫星高光谱遥感的2007年-2017年新疆地区大气NO2时空变化趋势分析

自2013年国务院颁布《大气污染防治行动计划》等大气综合治理政策以来,我国东部地区大气颗粒物等重要污染物得到了有效控制。伴随着我国能源政策的变化,西北地区在加大能源开发力度的同时,大气污染亦呈现加剧趋势,但在之前的研究中未得到重视。卫星遥感的监测手段较地面观测具有不受地域限制,观测时间长,观测污染物种类多等优势。其中,星载紫外-可见高光谱仪OMI自2005年在轨运行,在大气污染的时空变化趋势探测、排放源估计以及模式的同化和验证等科学应用中得到广泛应用。中国科学技术大学的卫星对流层NO₂柱浓度产品,通过对OMI原始测量光谱的二次标定和气体反演算法的关键优化,在与地基观测的结果对比验证中呈现良好的相关性,适合用于我国高气溶胶背景下的大气污染分析。结合中国科学技术大学OMI NO₂数据产品,我国新疆地区大气NO₂污染的时空分布特征得以表征。在2007年-2017年期间,新疆地区的NO₂污染集中分布于北疆,其中“乌鲁木齐-昌吉-石河子”城市群（乌昌石地区）与新疆总体NO₂水平月变化相关性很强（相关性系数r=0.942,p-value<0.01）。新疆NO₂年际变化存在明显阶段性特征,与相关政策以及能源行业排放变化相符：2007年-2010年变化趋势不明显,2014年较2010年总体年平均浓度增长18.5％,其中乌昌石地区增长41.3％;2017年较2014年总体平均浓度下降26.4%,乌昌石地区下降42.8%。乌昌石地区由于石油化工企业,经济开发区等分布密集,成为NO₂污染的聚集区,与乌鲁木齐市,昌吉市NO₂变化具有强相关性（r=0.982,p-value<0.01;r=0.951,p-value<0.01）。受采暖时期排放以及特殊气象条件控制,乌昌石地区NO₂污染峰值为12月,冬季污染尤其显著;在2007年-2016年采暖期间（每年10月-次年4月初）,乌昌石地区NO₂水平有显著上升趋势（显著性水平α=0.01）,在未来大气治理中需要格外关注。     

Na-呋喃荷移络合物弱相互作用的密度泛函理论研究

在B3LYP／6－311＋G*水平上,对Na-呋喃体系可能存在的弱相互作用复合物进行了全自由度能量梯度优化,发现了Na-呋喃体系存在两个能量极小结构A、B,其中,结构A是Na原子的3s^1电子直接和呋喃杂环体系中的所有重原子的共轭大π 体系 相互偶合,形成一个具有Cs对称性的金属有机复合物;而结构B为Na 原子的3s^1电子主要通过杂原子O和杂环上原有的五中心六电子大π体系形成一个新的平面六中心七电子大π体系,具有C2V对称 性。结果B较结构 A 稳定3.40kJ/mol。结构A中的Na-O键长为0.38nm,&lt;COC为106.9&#176;,由于金属Na对呋喃杂环的作用使整个分子平面变形,C1、C2、C3、C4在同一个平面内,而05则稍微翘离平面且05原子距离由C1、C2、C3、C4 组成的平面的垂直距离约为0.035nm.结构B中Na-O键长为0.26nm,＜COC为106.8&#176;。金属Na原子和杂环中所有的原子在同一个平面内。并在MP2和B3LYP水平下,用3－311＋G＊基组精确计算了最稳定结构B的结合能为△E＝4.5-5.1kJ/mol.     

近红外光谱技术在天然草地植被管理中的应用

植被是监测草地健康和生产力的主要依据,其变化是草地生态系统退化和恢复状况的最直接体现。及时掌握草地植被的变化信息是防止草地退化、实现草地生态系统可持续发展的首要条件。近红外光谱技术以其简便、快捷等优越性广泛应用于不同领域,在草地资源管理中有巨大的应用潜力和前景。文章介绍了近红外光谱技术的原理、特点及其在草地植被物种组成、草地植物茎叶比、凋落物及牧草品质测定等方面的应用特点,综合阐述了近红外光谱技术在草地植被管理中的应用现状,并对其应用前景进行了展望。     

Differential optical absorption spectroscopy measurement of CO2 using a nanosecond white light continuum

We built a differential optical absorption spectroscopy system to measure near-surface CO2 absorption in the atmosphere using a nanosecond white light continuum. The white light laser can cover wavelengths ranging from 420 to 2400 nm, where the CO2 and H2O absorption lines are located. At an optical path length of 568 m, it was possible to evaluate atmospheric CO2 concentration from absorption bands of CO2 and H2O in the vicinity of 2000 nm detected by broadband white light simultaneously.     

大气二氧化碳反演中系统误差的分析与校正

二氧化碳（CO2）高精度反演中易受多种因素的影响,其中一部分是系统误差,如温度廓线、压力廓线、水汽以及大气分层等精度不足所带来的影响,仅利用CO2吸收带的光谱信息很难克服由此带来的误差。这种系统误差的波长依赖性小,可以考虑其他波段进行校正。模拟研究表明,上述系统误差对CO2反演的影响经O2校正后有较大程度地减小。利用大兴安岭地区的温室气体观测卫星（GOSAT）观测数据进行CO2反演,采用氧气（O2）A吸收带校正上述系统误差,结果显示反演精度得到明显提高。     

Measurement of tropospheric CO2 and aerosol extinction profiles with Raman lidar

A prototype Raman lidar was designed for monitoring tropospheric CO2 profile and other scientific investigatious.The third harmonic of Nd:YAG laser (354.7-nm wavelength) was used as stimulated light source to provide nighttime measurements.Filter with high rejection ratio performance was used to extract CO2 Raman signals from Rayleigh-Mie scattering signals effectively.To improve the real time monitoring function,a two-channel signal collection system was designed to collect CO2 and N2 Raman scattering signals simultaneously. The N2 Raman scattering signals were used to retrieve aerosol extinction coefficient.Typical features of CO2 concentration profile and aerosol extinction coefficient in Herei were presented.The mixing ratio of atmospheric CO2 in Hefei can reach about 360-400 ppmv.     

SO2在吸收池内的稳定性研究

在室温条条件下,以Xe灯为光源,利用SO2的紫外吸收光谱,研究了SO2的浓度随时间连续变化规律。实验中考虑了温度和充垫气体N2对SO2的浓度变化的影响。实验结果表明：SO2的浓度基本上是随时间线性变化的;同时,SO2的浓度变化率与光照时间有关。