Large-scale synoptic patterns significantly affect meteorological conditions and air pollution,yet their impacts on the vertical distribution of formaldehyde(HCHO)and nitrogen dioxide(NO_(2))have been little studied.F...Large-scale synoptic patterns significantly affect meteorological conditions and air pollution,yet their impacts on the vertical distribution of formaldehyde(HCHO)and nitrogen dioxide(NO_(2))have been little studied.From 1 June 2020 to 31 December 2021,Multi-AXis-Differential Optical Absorption Spectroscopy(MAX-DOAS)was used to observe NO_(2) and HCHO vertical profiles in three typical environments of Shanghai,China,representing urban,suburban and coastal rural environments,respectively.HCHO level is the highest at suburban site,NO_(2) is the highest at urban site.HCHO is mainly distributed between 0 and 1 kmin altitude,and NO_(2) is concentrated near the ground.The ratio of HCHO to NO_(2) is used to identify ozone formation regimes,ozone sensitivities vary with environmental area,season and altitude.The principal component analysis in the T-mode approach and typhoon“In-Fa”case is applied to analyze the effects of synoptic patterns on HCHO and NO_(2) vertically.HCHO concentrations show a pattern of low-pressure type>uniform-pressure type>high-pressure type at each altitude layer,while NO_(2) concentrations follow the opposite pattern.Meteorological factors(especially radiation,temperature,relative humidity,cloud cover and wind),external transport and initial emissions contribute to the differences in HCHO and NO_(2) levels across synoptic types.The“In-Fa”case shows how this special synoptic pattern elevates HCHO and NO_(2) levels by improving meteorological conditions,boosting biogenic precursors and shifting air mass directions.This study assesses the impacts of synoptic patterns on HCHO and NO_(2) vertical distribution in Shanghai,offering insights into understanding causes of pollution.展开更多
Yangtze River Delta （YRD） area is one of the important economic zones in China. However, this area faces increasing environmental problems. In this study, we use ground-based multi-axis differential optical absorpti...Yangtze River Delta （YRD） area is one of the important economic zones in China. However, this area faces increasing environmental problems. In this study, we use ground-based multi-axis differential optical absorption spectroscopy （MAX-DOAS） network in Eastern China to retrieve variations of NO2, SO2, and formaldehyde （HCHO） in the YRD area. Three cities of YRD （Hefei, Nanjing, and Shanghai） were selected for long-term observations. This paper presents technical performance and characteristics of instruments, their distribution in YRD, and results of vertical column densities （VCDs） and profiles of NO2, SO2, and HCHO. Average diurnal variations of tropospheric NO2 and SO2 in different seasons over the three stations yielded minimum values at noon or in the early afternoon, whereas tropospheric HCHO reached the maximum during midday hours. Slight reduction of the pollutants in weekends occurred in all the three sites. In general trace gas concentrations gradually reduced from Shanghai to Hefei. Tropospheric VCDs of NO2, SO2, and HCHO were compared with those from Ozone Monitoring Instrument （OMI） satellite observations, resulting in R2 of 0.606, 0.5432, and 0.5566, respectively. According to analysis of regional transports of pollutants, pollution process happened in YRO under the north wind with the pollution dissipating in the southeast wind. The feature is significant in exploring transport of tropospheric trace gas pollution in YRD, and provides basis for satellite and model validation.展开更多
Aqueous precipitation and deposition-precipitation method were used to prepare CeO2 supports and Au/CeO2 catalysts, respectively. The effect of preparation condition of support on the catalyst activity was investigate...Aqueous precipitation and deposition-precipitation method were used to prepare CeO2 supports and Au/CeO2 catalysts, respectively. The effect of preparation condition of support on the catalyst activity was investigated. The catalytic combustion of HCHO was considered as the probe reaction for comparing the catalyst activity. The BET, X-ray diffraction, X-ray photoelectron spectroscopy （XPS）, and reduction （TPR） were carried out to analyze the influence factor on the catalysts activity. The results showed that the addition of dispersant and use of microwave in the support preparation procedure could be beneficial for enhancing the interaction of supports and gold species and thus improved the catalytic activity. The total conversion temperature for HCHO was 146 ℃ over AC400. With the modification during supports preparation process, the catalytic activity increased with total conversion temperature decreasing to 98 ℃. The results of XPS indicated that Au^0 and Au^＋1 species coexisted in these catalysts and the activity of catalyst correlated with Au^＋1/Au^0 ratio. Temperature-programmed reduction results demonstrated that the reduction peak appeared between 100-170 ℃ with the inducing of gold. The dependence of activity on the reduction peak temperature implied that ionic gold was catalytic activity component for HCHO oxidation.展开更多
Sodium-treated sepiolite(Na Sep)-supported transition metal catalysts(TM/Na Sep;TM = Cu, Fe, Ni, Mn, and Co) were synthesized via a rotary evaporation method. Physicochemical properties of the as-synthesized samples w...Sodium-treated sepiolite(Na Sep)-supported transition metal catalysts(TM/Na Sep;TM = Cu, Fe, Ni, Mn, and Co) were synthesized via a rotary evaporation method. Physicochemical properties of the as-synthesized samples were characterized by means of various techniques, and their catalytic activities for HCHO(0.2%) oxidation were evaluated. Among the samples, Cu/Na Sep exhibited superior performance, and complete HCHO conversion was achieved at 100 ℃(GHSV = 240000 m L/(g·h)). Additionally, the sample retained good catalytic activity during a 42 h stability test. A number of factors, including elevated acidity, the abundance of oxygen species, and favorable low-temperature reducibility, were responsible for the excellent catalytic activity of Cu/Na Sep. According to the results of the in-situ DRIFTS characterization, the HCHO oxidation mechanism was as follows:(i) HCHO was rapidly decomposed into dioxymethylene(DOM) species on the Cu/Na Sep surface;(ii) DOM was then immediately converted to formate species;(iii) the resultant formate species were further oxidized to carbonates;(iv) the carbonate species were eventually converted to CO2 and H2O.展开更多
基金supported by the National Key Research and Development Program of China(No.2023YFC3705301)the National Natural Science Foundation of China(Nos.22176037,42075097,22376030,42375089,and 21976031).
文摘Large-scale synoptic patterns significantly affect meteorological conditions and air pollution,yet their impacts on the vertical distribution of formaldehyde(HCHO)and nitrogen dioxide(NO_(2))have been little studied.From 1 June 2020 to 31 December 2021,Multi-AXis-Differential Optical Absorption Spectroscopy(MAX-DOAS)was used to observe NO_(2) and HCHO vertical profiles in three typical environments of Shanghai,China,representing urban,suburban and coastal rural environments,respectively.HCHO level is the highest at suburban site,NO_(2) is the highest at urban site.HCHO is mainly distributed between 0 and 1 kmin altitude,and NO_(2) is concentrated near the ground.The ratio of HCHO to NO_(2) is used to identify ozone formation regimes,ozone sensitivities vary with environmental area,season and altitude.The principal component analysis in the T-mode approach and typhoon“In-Fa”case is applied to analyze the effects of synoptic patterns on HCHO and NO_(2) vertically.HCHO concentrations show a pattern of low-pressure type>uniform-pressure type>high-pressure type at each altitude layer,while NO_(2) concentrations follow the opposite pattern.Meteorological factors(especially radiation,temperature,relative humidity,cloud cover and wind),external transport and initial emissions contribute to the differences in HCHO and NO_(2) levels across synoptic types.The“In-Fa”case shows how this special synoptic pattern elevates HCHO and NO_(2) levels by improving meteorological conditions,boosting biogenic precursors and shifting air mass directions.This study assesses the impacts of synoptic patterns on HCHO and NO_(2) vertical distribution in Shanghai,offering insights into understanding causes of pollution.
基金supported by the National Natural Science Foundation of China (No: 41530644)the Monitoring and Assessment of Regional Air Quality in China using space Observations, Project Of Long-term sino-5 european co-Operation (MarcoPolo), FP7 (No: 606953)
文摘Yangtze River Delta （YRD） area is one of the important economic zones in China. However, this area faces increasing environmental problems. In this study, we use ground-based multi-axis differential optical absorption spectroscopy （MAX-DOAS） network in Eastern China to retrieve variations of NO2, SO2, and formaldehyde （HCHO） in the YRD area. Three cities of YRD （Hefei, Nanjing, and Shanghai） were selected for long-term observations. This paper presents technical performance and characteristics of instruments, their distribution in YRD, and results of vertical column densities （VCDs） and profiles of NO2, SO2, and HCHO. Average diurnal variations of tropospheric NO2 and SO2 in different seasons over the three stations yielded minimum values at noon or in the early afternoon, whereas tropospheric HCHO reached the maximum during midday hours. Slight reduction of the pollutants in weekends occurred in all the three sites. In general trace gas concentrations gradually reduced from Shanghai to Hefei. Tropospheric VCDs of NO2, SO2, and HCHO were compared with those from Ozone Monitoring Instrument （OMI） satellite observations, resulting in R2 of 0.606, 0.5432, and 0.5566, respectively. According to analysis of regional transports of pollutants, pollution process happened in YRO under the north wind with the pollution dissipating in the southeast wind. The feature is significant in exploring transport of tropospheric trace gas pollution in YRD, and provides basis for satellite and model validation.
基金the National Natural Science Foundation of China (20563003)Natural Science Foundation of Inner Mongolia (200508010203)
文摘Aqueous precipitation and deposition-precipitation method were used to prepare CeO2 supports and Au/CeO2 catalysts, respectively. The effect of preparation condition of support on the catalyst activity was investigated. The catalytic combustion of HCHO was considered as the probe reaction for comparing the catalyst activity. The BET, X-ray diffraction, X-ray photoelectron spectroscopy （XPS）, and reduction （TPR） were carried out to analyze the influence factor on the catalysts activity. The results showed that the addition of dispersant and use of microwave in the support preparation procedure could be beneficial for enhancing the interaction of supports and gold species and thus improved the catalytic activity. The total conversion temperature for HCHO was 146 ℃ over AC400. With the modification during supports preparation process, the catalytic activity increased with total conversion temperature decreasing to 98 ℃. The results of XPS indicated that Au^0 and Au^＋1 species coexisted in these catalysts and the activity of catalyst correlated with Au^＋1/Au^0 ratio. Temperature-programmed reduction results demonstrated that the reduction peak appeared between 100-170 ℃ with the inducing of gold. The dependence of activity on the reduction peak temperature implied that ionic gold was catalytic activity component for HCHO oxidation.
文摘Sodium-treated sepiolite(Na Sep)-supported transition metal catalysts(TM/Na Sep;TM = Cu, Fe, Ni, Mn, and Co) were synthesized via a rotary evaporation method. Physicochemical properties of the as-synthesized samples were characterized by means of various techniques, and their catalytic activities for HCHO(0.2%) oxidation were evaluated. Among the samples, Cu/Na Sep exhibited superior performance, and complete HCHO conversion was achieved at 100 ℃(GHSV = 240000 m L/(g·h)). Additionally, the sample retained good catalytic activity during a 42 h stability test. A number of factors, including elevated acidity, the abundance of oxygen species, and favorable low-temperature reducibility, were responsible for the excellent catalytic activity of Cu/Na Sep. According to the results of the in-situ DRIFTS characterization, the HCHO oxidation mechanism was as follows:(i) HCHO was rapidly decomposed into dioxymethylene(DOM) species on the Cu/Na Sep surface;(ii) DOM was then immediately converted to formate species;(iii) the resultant formate species were further oxidized to carbonates;(iv) the carbonate species were eventually converted to CO2 and H2O.
