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Of the severe stratospheric ozone depletion events (ODEs) reported over the Arctic, the third and most severe occurred during the spring of 2020; we analyzed the reasons for this event herein. We retrieved the critical indicator ozone vertical column density (VCD) using zenith scattered light differential optical absorption spectroscopy (ZSL-DOAS) located in Ny-Ålesund, Svalbard, Norway. The average ozone VCDs over Ny-Ålesund between March 18 and April 18, 2020, were approximately 274.8 Dobson units (DU), which was only about 64.7 % of that in normal years. The retrieved daily averages of ozone VCDs were compared with satellite observations from Global Ozone Monitoring Experiment 2 (GOME-2), a Brewer spectrophotometer, and a Système d’Analyze par Observation Zénithale (SAOZ) spectrometer at Ny-Ålesund; the resulting Pearson correlation coefficients were relatively high at 0.94, 0.86, and 0.91, with relative deviations of 2.3 %, 3.1 %, and 3.5 %, respectively. Compared with normal years, the 2020 daily peak relative ozone loss was approximately 44.3 %. During the 2020 Arctic spring ODE, the ozone VCDs and potential vorticity (PV) had a negative correlation with their fluctuations, suggesting a clear effect of the polar vortex on stratospheric ozone depletion. To better understand what caused the ozone depletion, we also considered the chemical components of this process in the Arctic winter of 2019/2020 with the specified dynamics version of the Whole Atmosphere Community Climate Model (SD-WACCM). The SD-WACCM model results indicated that both ClO and BrO concentrations peaked in late March, which was a critical factor during the ozone depletion observed in Ny-Ålesund. Chlorine activation was clearly apparent during the Arctic spring of 2020, whereas the partitioning of bromine species was different from that of chlorine. By combining observations with modeling, we provide a reliable basis for further research on global climate change due to polar ozone concentrations and the prediction of severe Arctic ozone depletion in the future.

Ozone vertical column densities (VCDs) were retrieved by Zenith Scattered Light-Differential Optical Absorption Spectroscopy (ZSL-DOAS) from January 2017 to February 2020 over Fildes Peninsula, West Antarctica (62.22°S, 58.96°W). Each year, ozone VCDs started to decline around July with a comparable gradient around 1.4 Dobson Units (DU) per day, then dropped to their lowest levels in September and October, when ozone holes appeared (less than 220 DU). Daily mean values of retrieved ozone VCDs were compared with Ozone Monitoring Instrument (OMI) and Global Ozone Monitoring Experiment 2 (GOME-2) satellite observations and the Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) reanalysis dataset, with correlation coefficients (R2) of 0.86, 0.94, and 0.90, respectively. To better understand the causes of ozone depletion, the retrieved ozone VCDs, temperature, and potential vorticity (PV) at certain altitudes were analyzed. The profiles of ozone and PV were positively correlated during their fluctuations, which indicates that the polar vortex has a strong influence on stratospheric ozone depletion during Antarctic spring. Located at the edge of polar vortex, the observed data will provide a basis for further analysis and prediction of the inter-annual variations of stratospheric ozone in the future.

Environmental trace gas monitoring instrument (EMI) onboard GaoFen-5 was launched in May 2018 and has successfully operated on-orbit for more than a year. EMI contains four grating spectrometers, covering wavelengths in the range 240–710 nm with a spectral resolution of 0.3–0.5 nm, and enables one-day global coverage. For EMI on-orbit calibration, two onboard solar diffusers (SD), one surface reflectance aluminum diffuser, and one quartz volume diffuser (QVD) are used to measure solar spectra. The solar spectra are used to perform accurate spectral and radiometric calibrations. EMI on-orbit spectral calibration contains wavelength calibration and instrument spectral response function (ISRF), both of which are the key quantities in trace gas retrievals based on differential optical absorption spectroscopy (DOAS) analysis. The wavelength calibration is performed using the Fraunhofer lines in the solar spectrum, and the ISRF parameters are obtained by fitting high-resolution and EMI-measured solar spectra. Based on the known solar irradiation and characteristic of SD, SD radiance can be calculated and is used for EMI on-orbit radiometric calibration. The radiometric calibration also determines the absolute Earth reflectance spectra that are used as inputs for atmospheric retrieval algorithms. For EMI on-orbit radiometric monitoring, aluminum diffuser is used as reference SD to monitor QVD degradation. An internal white light source is used to detect pixel performance and monitor radiometric throughput.

The Environmental Trace Gases Monitoring Instrument (EMI) is the first Chinese satellite-borne UV–Vis spectrometer aiming to measure the distribution of atmospheric trace gases on a global scale. The EMI instrument onboard the GaoFen-5 satellite was launched on 9 May 2018. In this paper, we present the tropospheric nitrogen dioxide (NO2) vertical column density (VCD) retrieval algorithm dedicated to EMI measurement. We report the first successful retrieval of tropospheric NO2 VCD from the EMI instrument. Our retrieval improved the original EMI NO2 prototype algorithm by modifying the settings of the spectral fit and air mass factor calculations to account for the on-orbit instrumental performance changes. The retrieved EMI NO2 VCDs generally show good spatiotemporal agreement with the satellite-borne Ozone Monitoring Instrument and TROPOspheric Monitoring Instrument (correlation coefficient R of ~0.9, bias, Remote sensing: Tuned-up satellite identifies pollutant hot spots Improvements to a high-resolution spectrometer onboard China’s recently-launched GaoFen-5 (GF-5) satellite can give researchers a new tool to assess atmospheric trace gases. Cheng Liu from the University of Science and Technology of China and his colleagues reported the first successful retrieval of nitrogen dioxide from the GF-5 orbiter thanks to crucial adjustments to calibration algorithms. The satellite’s payload Environmental Trace Gases Monitoring Instrument (EMI) uses visible spectroscopic measurements to detect nitrogen dioxide in the atmosphere, which can be used to identify the spatial distribution of pollution emissions on the Earth. To overcome on-orbit issues including detector saturation, the team has optimized the spectral retrieval settings by spectral precalibration, fitting wavelength adjustment, reference spectrum selection, etc. Comparisons to other satellite and ground measurements revealed the optimization effort yielded reliable results for monitoring pollution levels.

In recent years, surface ozone concentrations have increased in many cities in China. Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) is a powerful technique for retrieving the profiles of tropospheric trace gases, such as NO

Ground-based two-dimensional (2D) Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of nitrogen dioxide (NO2) were collected continuously from June 2015 to May 2016 in Hefei, China. The spatial distribution of NO2 concentrations showed that more air pollution was present in eastern and southeastern direction from the study site, and these areas were located in the center of the city and economic developing zone. The seasonal variations of NO2 concentrations were distinct, and the highest levels were detected in winter, while the lowest levels were detected in summer. The mean concentration of NO2 during the heating season (November–March of the following year) was 6.56 ppbv, while that during the non-heating season (April–October) was 4 ppbv. The highest concentrations of NO2, carbon monoxide (CO), and PM2.5 were all observed during the heating season. The results from the potential source contribution function (PSCF) analysis suggested that NO2 pollution in the summer was caused primarily by long-range transport from the east, while that in winter showed significant local influences. By combining the analyses of meteorological trajectory pressure profiles and aerosol optical depths (AODs), the sources of NO2 during the heating season were found to be mainly local emissions, while those during the non-heating season were mainly from long-range transportation.

The environmental trace gas monitoring instrument (EMI) is a space-borne imaging spectrometer onboard GaoFen-5, which was launched in May 2018, covering wavelengths in the range of 240–710 nm to measure NO2, O3, HCHO, and SO2. An advanced EMI-2 instrument with a higher spatial resolution and sufficient signal-to-noise is currently planned for launch on the GaoFen-5(02) satellite in 2021. The EMI-2 instrument bidirectional scattering distribution function (BSDF) is obtained from the absolute irradiance and radiance calibration on-ground. Based on EMI-2 earth and sun optical paths, the key factors of BSDF parameters are introduced. An NIST-calibrated 1000 W FEL quartz tungsten halogen lamp and a 2D turntable are adopted for the absolute irradiance calibration. A large aperture integrating sphere system is used for the absolute radiance calibration. Based on absolute irradiance and radiance calibration functions, the BSDF parameters are obtained, with accuracy of 4.9% for UV1, 4.3% for UV2, 4.1% for VIS1, and 4.2% for VIS2. The on-ground measurement results show that the reflectance spectrum can be calculated from BSDF parameters. On-orbit application of the EMI-2 instrument BSDF are also discussed.

We present a novel airborne imaging differential optical absorption spectroscopy (DOAS) instrument: Ultraviolet Visible Hyperspectral Imaging Spectrometer (UVHIS), which is developed for trace gas monitoring and pollution mapping. Within a broad spectral range from 200 to 500 nm, operated in three channels, the spectral resolution of UVHIS is better than 0.5 nm. The optical design of each channel comprises a fore-optics with a field of view (FOV) of 40°, an Offner imaging spectrometer, and a charge-coupled device (CCD) array detector of 1032 × 1072 pixels. A first demonstration flight using UVHIS was undertaken on 23 June 2018, above an approximate 600 km2 area in Feicheng, China, with a spatial resolution of about 25 × 22 m2. Measurements of nadir backscattered solar radiation of channel 3 are used to retrieve vertical column densities (VCDs) of NO2 with a mean fitting error of 2.6 × 1015 molec cm−2. The UVHIS instrument clearly detected several emission plumes transporting from south to north, with a peak value of 3 × 1016 molec cm−2 in the dominant one. UVHIS NO2 vertical columns are well correlated with ground-based mobile DOAS observations, with a correlation coefficient of 0.65 for all co-located measurements, and a slight underestimation for polluted observations. This study demonstrates the capability of UVHIS for NO2 local emission and transmission monitoring.

During polar spring, the presence of reactive bromine in the polar boundary layer is considered to be the main cause of ozone depletion and mercury deposition. However, many uncertainties still remain regarding understanding the mechanisms of the chemical process and source of the bromine. As Arctic sea ice has recently been dramatically reduced, it is critical to investigate the mechanisms using more accurate measurements with higher temporal and spatial resolution. In this study, a typical process of enhanced bromine and depleted ozone in the Ny-Ålesund boundary layer in late April 2015 was observed by applying ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) technique. The results showed that there were bromine monoxide (BrO) slant columns as high as 5.6 × 1014 molec cm−2 above the Kings Bay area on 26 April. Meanwhile, the boundary layer ozone and gaseous elemental mercury (GEM) were synchronously reduced by 85 and 90 %, respectively. Based on the meteorology, sea ice distribution and air mass history, the sea ice in the Kings Bay area, which emerged for only a very short period of time when the enhanced BrO was observed, was considered to be the major source of this bromine enhancement event. The oxidized GEM may be directly deposited onto snow/ice and thereby influence the polar ecosystem.

The Environmental trace gas Monitoring Instrument (EMI) onboard the Chinese high-resolution remote sensing satellite GaoFen-5 is an ultraviolet-visible imaging spectrometer, aiming to quantify the global distribution of tropospheric and stratospheric trace gases and planned to be launched in spring 2018. The preflight calibration phase is essential to characterize the properties and performance of the EMI in order to provide information for data processing and trace gas retrievals. In this paper, we present the first EMI measurement of nitrogen dioxide (NO 2 ) from a gas absorption cell using scattered sunlight as the light source by the differential optical absorption spectroscopy technique. The retrieved NO 2 column densities in the UV and Vis wavelength ranges are consistent with the column density in the gas cell calculated from the NO 2 mixing ratio and the length of the gas cell. Furthermore, the differences of the retrieved NO 2 column densities among the adjoining spatial rows of the detector are less than 3%. This variation is similar to the well-known “stripes-pattern” of the Ozone Monitoring Instrument and is probably caused by remaining systematic effects like a nonperfect description of the individual instrument functions. Finally, the signal-to-noise ratios of EMI in-orbit measurements of NO 2 are estimated on the basis of on-ground scattered sunlight measurements and radiative transfer model simulations. Based on our results, we conclude that the EMI is capable of measuring the global distribution of the NO 2 column with the retrieval precision and accuracy better than 3% for the tested wavelength ranges and viewing angles.

In this paper, we present ship-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of tropospheric trace gases' distribution along the Yangtze River during winter 2015. The measurements were performed along the Yangtze River between Shanghai and Wuhan, covering major industrial areas in eastern China. Tropospheric vertical column densities (VCDs) of nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), and formaldehyde (HCHO) were retrieved using the air mass factor calculated by the radiative transfer model. Enhanced tropospheric NO 2 and SO 2 VCDs were detected over downwind areas of industrial zones over the Yangtze River. In addition, spatial distributions of atmospheric pollutants are strongly affected by meteorological conditions; i.e., positive correlations were found between concentration of pollutants and wind speed over these areas, indicating strong influence of transportation of pollutants from high-emission upwind areas along the Yangtze River. Comparison of tropospheric NO 2 VCDs between ship-based MAX-DOAS and Ozone Monitoring Instrument (OMI) satellite observations shows good agreement with each other, with a Pearson correlation coefficient ( R ) of 0.82. In this study, the NO 2 ∕ SO 2 ratio was used to estimate the relative contributions of industrial sources and vehicle emissions to ambient NO 2 levels. Analysis results of the NO 2 ∕ SO 2 ratio show a higher contribution of industrial NO 2 emissions in Jiangsu Province, while NO 2 levels in Jiangxi and Hubei provinces are mainly related to vehicle emissions. These results indicate that different pollution control strategies should be applied in different provinces. In addition, multiple linear regression analysis of ambient carbon monoxide (CO) and odd oxygen (O x ) indicated that the primary emission and secondary formation of HCHO contribute 54.4 ± 3.7 % and 39.3 ± 4.3 % to the ambient HCHO, respectively. The largest contribution from primary emissions in winter suggested that photochemically induced secondary formation of HCHO is reduced due to lower solar irradiance in winter. Our findings provide an improved understanding of major pollution sources along the eastern part of the Yangtze River which are useful for designing specific air pollution control policies.

The variations of atmospheric compositions (ACs) can change the atmospheric interactions with other parts of the ecosystem, and it also affects the energy budget of the Earth. Satellite remote sensing plays a crucial role in monitoring AC by providing a matchless global perspective with consistency over long periods. Although China started space exploration missions in the early 1970s, the situation of lacking operational AC satellite missions was turned around until the launch of FY-3A in 2008. In the following decade, more Chinese pathfinder AC satellite missions were putting into operation, and then lead to a boom in related researches on air quality, trace gases and greenhouse gases (GHG) measurements. In particular, moderate resolution imageries of polar mission FY-3 series are used to monitor air quality, and recent comparable imagery onboard geostationary mission FY-4A could provide similar air pollution observation with higher temporal resolution of up to five minutes. Nadir spectrographs onboard FY-3 series and the latest pathfinder mission GF-5 aims to monitor various trace gases. Moreover, hyper-spectrometers onboard GF-5 and another pathfinder mission TanSat are devoted to mapping the global distribution of GHG, as a supplement to operational mission FY-3D. Besides the progress in the space-borne part, the in-situ calibration and validation have achieved fruitfully since the late 1990s, gaining insight into the consistency between the satellite and in-situ observations over China. Applications and studies based on Chinese satellite missions are still growing since it has only been a few years after their launch. Furthermore, the newly planned missions for monitoring AC with active remote sensing instruments are also illustrated, such as lidar, which will be able to improve the accuracy of space-borne observations.

As the development of megacities, combined air pollution has been of increasing concern in China, which is composed by primary pollution, such as Nitrogen dioxide (NO2), and the followed secondary pollution under certain meteorology circumstances and high concentration of precursors, such as tropospheric ozone, formaldehyde (HCHO) and fine particles. During PRIDE-GBA 2018 Campaign (Particles, Radicals, Intermediates from oxiDation of primary Emissions in Great Bay Area), we performed the high resolution vertical observations of pollution gases and aerosol, which are significant but scarce indexes in studying the mechanisms of tropospheric pollution, using remote sensing techniques. NO2 and HCHO column densities and vertical profiles are reconstructed from data of multi-axis differential optical absorption spectroscopy (MAX-DOAS). Tropospheric ozone profile and aerosol extinction are retrieved by the differential absorption light detection and ranging (LIDAR) system. In order to verifying the accuracy, we evaluated the consistency and reliability of MAX-DOAS and LIDAR measurements. The results showed reasonable agreement with in-situ and off-line observations at Canton Tower. A typical combined pollution process from Sep 29 to Oct 10 was analyzed in detail. More than 200 μg/m3 tropospheric ozone in this case was considered from the anthropogenic sources, including industry, power plant, residential and transportation. The high emission from local industry and polluted air transport from northeast brought the main precursors of this pollution process. The photochemical formation of tropospheric ozone was turned into a VOC-limited regime on polluted days.

In this paper, we present ship-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of tropospheric trace gases distribution along Yangtze River during winter 2015. The measurements were performed along Yangtze River between Shanghai and Wuhan covering major industrial areas in eastern China. Tropospheric vertical column densities (VCDs) of nitrogen dioxide (NO2), sulfur dioxide (SO2), and formaldehyde (HCHO) were retrieved using air mass factor calculated by radiative transfer model. Enhanced tropospheric NO2 and SO2 VCDs were detected over downwind areas of industrial zones over Yangtze River. In addition, spatial distributions of atmospheric pollutants are strongly affected by meteorological conditions, i.e., positive correlations were found between concentration of pollutants and wind speed over these areas indicating strong influence of transportation of pollutants from high-emission upwind areas along Yangtze River. Comparison of tropospheric NO2 VCDs between ship-based MAX-DOAS and OMI satellite observations shows good agreement with each other with Pearson correlation coefficient (R) of 0.82. In this study, NO2/SO2 ratio was used to estimate the relative contributions of industrial sources and vehicle emissions to ambient NO2 levels. Analysis results of NO2/SO2 ratio shows that higher contribution of industrial NO2 emissions in Jiangsu province, while NO2 levels in Jiangxi and Hubei provinces are mainly related to vehicle emissions. These results indicate that different pollution control strategies should be applied in different provinces. In addition, multiple linear regression analysis of ambient carbon monoxide (CO) and odd oxygen (Ox) indicated that the primary emission and secondary formation of HCHO contribute 54.4 ± 3.7 % and 39.3 ± 4.3 % to the ambient HCHO, respectively. The largest contribution from primary emissions in winter suggested that photochemically induced secondary formation of HCHO is reduced due to lower solar irradiance in winter. Our findings provide an improved understanding of major pollution sources along the eastern part of Yangtze River which are useful for designing specific air pollution control policies.

The active differential optical absorption spectroscopy (DOAS) is developed to measure the optical parameters of atmospheric particles, combining two light paths. With the extinction coefficient, the number size distribution from 0.1μm to 1.25μ m was retrieved by a step function.

Bromine monoxide is a reactive halogen species which has crucial impact on the chemistry of the tropospheric polar boundary layer. During polar spring, BrO enhancement can be detected in both northern and southern Polar Regions, while the boundary layer ozone depletion events occur. A considerable challenge for understanding enhanced BrO and the associated ODEs is the difficulty of real-time observations. In this study, a typical process of enhanced bromine and depleted ozone in late April, 2015 at Ny-Ålesund boundary layer was observed using ground-based Multi Axis-Differential Optical Absorption Spectroscopy (MAX-DOAS) technique. The results showed that there were as high as 8 × 1014 molecular cm−2 BrO slant columns above the Kings Bay area in 26 April. Considering meteorology, sea ice distribution and air mass history, the floating sea ice in the Kings Bay area was considered as the major source of this bromine enhancement event. During this period, the boundary layer ozone and gaseous elemental mercury (GEM) was synchronously reduced by 85 % and 90 % separately. The kinetic calculation showed that the ozone loss rate is 10.3 ppbv h−1, which is extremely high compared to other area. The GEM loss rate is about 0.25 ng m−3 h−1. The oxidized GEM may directly deposit to snow/ice and thereby influence the polar ecosystem.

We conducted long-term network observations using standardized Multi-Axis Differential optical absorption spectroscopy (MAX-DOAS) instruments in Russia and ASia (MADRAS) from 2007 onwards and made the first synthetic data analysis. At seven locations (Cape Hedo, Fukue and Yokosuka in Japan, Hefei in China, Gwangju in Korea, and Tomsk and Zvenigorod in Russia) with different levels of pollution, we obtained 80 927 retrievals of tropospheric NO2 vertical column density (TropoNO2VCD) and aerosol optical depth (AOD). In the technique, the optimal estimation of the TropoNO2VCD and its profile was performed using aerosol information derived from O4 absorbances simultaneously observed at 460–490 nm. This large data set was used to analyze NO2 climatology systematically, including temporal variations from the seasonal to the diurnal scale. The results were compared with Ozone Monitoring Instrument (OMI) satellite observations and global model simulations. Two NO2 retrievals of OMI satellite data (NASA ver. 2.1 and Dutch OMI NO2 (DOMINO) ver. 2.0) generally showed close correlations with those derived from MAX-DOAS observations, but had low biases of up to ~50%. The bias was distinct when NO2 was abundantly present near the surface and when the AOD was high, suggesting a possibility of incomplete accounting of NO2 near the surface under relatively high aerosol conditions for the satellite observations. Except for constant biases, the satellite observations showed nearly perfect seasonal agreement with MAX-DOAS observations, suggesting that the analysis of seasonal features of the satellite data were robust. Weekend reduction in the TropoNO2VCD found at Yokosuka and Gwangju was absent at Hefei, implying that the major sources had different weekly variation patterns. While the TropoNO2VCD generally decreased during the midday hours, it increased exceptionally at urban/suburban locations (Yokosuka, Gwangju, and Hefei) during winter. A global chemical transport model, MIROC-ESM-CHEM (Model for Interdisciplinary Research on Climate–Earth System Model–Chemistry), was validated for the first time with respect to background NO2 column densities during summer at Cape Hedo and Fukue in the clean marine atmosphere.

Daily patterns of air pollutants are important to improve measurement retrievals and to model the regimes of local air quality. In this study, the daily patterns of SO2 and NO2 as well as their association with visibility and meteorological conditions in a suburban area of Xiamen are investigated. To achieve this goal, continuous field measurements were collected with a Differential Optical Absorption Spectroscopy (DOAS) system in 2011. The K-means clustering is used to classify the daily variation cycles of these measurements associated with different visibility and meteorological conditions such as temperature, relative humidity, wind speed and direction. The Davies-Bouldin index strategy is used to determine the optimal number of clusters. The regime of each cluster associated with visibility and meteorological conditions was then explored and compared. The comparative analyses show that both the maximum hourly average concentrations and the maximum daily average concentrations of SO2 and NO2 occurred in spring. Only 0.04 percent and 3.19 percent of the days with SO2 and NO2, respectively, did not comply with the latest national ambient air quality standards of China (GB 3095-2012). Moreover, the clustering results highlighted three representative patterns of daily SO2 concentrations and four representative patterns of daily NO2 concentrations. Both similarities and differences were presented among these clusters. The consistent changes in aerosol concentration with the changes in the measurements of NO2 and SO2 in each cluster provided supplemental evidence for the presence of the daily patterns of SO2 and NO2.

In this paper, we present an optimized analysis algorithm for non-dispersive infrared (NDIR) to in situ monitor stack emissions. The proposed algorithm simultaneously compensates for nonlinear absorption and cross interference among different gases. We present a mathematical derivation for the measurement error caused by variations in interference coefficients when nonlinear absorption occurs. The proposed algorithm is derived from a classical one and uses interference functions to quantify cross interference. The interference functions vary proportionally with the nonlinear absorption. Thus, interference coefficients among different gases can be modeled by the interference functions whether gases are characterized by linear or nonlinear absorption. In this study, the simultaneous analysis of two components (CO2 and CO) serves as an example for the validation of the proposed algorithm. The interference functions in this case can be obtained by least-squares fitting with third-order polynomials. Experiments show that the results of cross interference correction are improved significantly by utilizing the fitted interference functions when nonlinear absorptions occur. The dynamic measurement ranges of CO2 and CO are improved by about a factor of 1.8 and 3.5, respectively. A commercial analyzer with high accuracy was used to validate the CO and CO2 measurements derived from the NDIR analyzer prototype in which the new algorithm was embedded. The comparison of the two analyzers show that the prototype works well both within the linear and nonlinear ranges.

Mercury is known as a highly toxic metal, which will have a significant health hazard to the human body. To monitor the trace mercury pollution in air, the development of monitoring instruments has been conducted. In this paper the mercury analyzer is developed based on the cold atomic absorption spectrometry theory by exploiting the transverse Zeeman-Effect background correction technology. The experiments have been done to test the performance of the system. At the same time, the same experiments with RA-915 mercury analyzer have been done to compare with the results. First, zero gas was measured for an hour and high concentration mercury sample gas was measured for four days. The results of zero gas shows that the detection limit of the system is 2.19ng/m 3 and the standard deviation is 0.73. The concentration fluctuation is within a tight range of ±1.5ng/m 3 . The results of high concentration sample gas are in good agreement with the results of RA-915, and the correlation coefficient is 0.95. Second, laboratory air was measured for 12 hours. The results compared with RA-915 are in good agreement and have the same variation trend. Additionally, the atmospheric mercury concentration near the non-ferrous metal smelter in Tongling city has been measured by the system and the RA-915. The measurement results from two analyzers have a good linear correlation with correlation coefficient of 0.98 and slope of 1.027. It indicates that the system has accurate background correction ability, low detection limit and is applicable to long-term air mercury on-line monitoring.

A bibliometric approach is used in this study for the assessment of greenhouse gas (GHG) research trends on a global scale. The relevant literature published from 2000 to 2014 in journals of all subject categories of the Science Citation Index Expanded from the Web of Science Core Collection databases has been used. The strings ‘greenhouse gas*’ or ‘green house gas*’ are used for retrieving data. The information of GHG research-related literature is analysed, including the types and languages of literature, characteristics of articles published, source countries/territories of articles, distribution of articles in different subject categories and journals, frequency/number of words in the title of articles and the frequency/number of keywords used. Over the past 15 years, an obvious growth trend is seen in the number of published articles, and countries/territories involved in the study of GHG. The number of the world articles published by the seven most developed industrialized countries (G7) is maximum in the field of GHG research. The G7 countries have played a predominant role in GHG research in the last 15 years. Analysis of the title words, author keywords and keywords plus showed that ‘greenhouse gas emission’ and ‘climate change’ were the keywords with highest frequency during the whole research period. Carbon sequestration and biotechnology have been widely used in reducing the environmental pressure of the greenhouse effect and the dependence on fossil energy.

Continuous data of aerosol optical thickness monitored using differential optical absorption spectroscopy (DOAS) are correlated with the concentration of ground-measured suspended particulate matter (SPM). A high correlation is found between the DOAS and the ground SPM data, making it possible to calculate the mass extinction efficiency of the aerosols in the atmosphere. It is found that the value of mean mass extinction efficiency (MEE) varies over a range of 2.6–13.7 m2 g−1, with smaller and larger values occurring for size distributions dominated by coarse and fine particles, respectively.

[ABSTRACT] We report on air-pollution monitoring campaign in the Kyoto and Chiba area during 2004. With differential optical absorption spectroscopy (DOAS) method, average concentrations of NO2, SO2, O3, H2O and aerosol particles can be measured. For NO2, SO2, O3 and H2O, the DOAS results are found to be consistent with the results of the ground sampling measurements. For aerosol, the optical thickness at 550 nm is correlated with the concentration of ground-measured suspended particulate matter (SPM), leading to a good correlation between the DOAS and SPM data. Also, the mass extinction efficiency (MEE) is analyzed for aerosol particles in the lower troposphere. From Chiba measurements, it is found that the average MEE is about 7.6 m^2g-^1, and the value exhibits a good inverse correlation with the particle size.

The high resolution imaging differential optical absorption spectroscopy (IDOAS) technique is introduced to measure the emissions of air pollutants from power plant plume. The SO2 emission rate of the plume can be estimated combined with wind speed.

We developed one satellite payload based on convex grating IDOAS system which can measure trace gases concentration, such as NO2, SO2 and O3, called Environmental trace gases Monitoring Instrument(EMI). The instrument is a space based spectrometer designed to measure sunlight transmitted, reflected and scattered by the Earth atmosphere or surface. The instrument measures simultaneously and contiguously radiation in the wavelength range from 240 to 710 nm at moderate spectral resolution (0.3 nm - 0.5 nm) in nadir.The main objective of the instrument mission is to improve our knowledge of global atmospheric change and the related global issues of importance to the chemistry and physics of our atmosphere. The primary scientific objective of the isturment is the global measurement of trace gases in the atmospher.

With a novel light-weight and absolutely calibrated ultraviolet (UV) spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands (320-335 nm) using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model (Tracy). The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.