Based on observations of urban mass concentration of fine particulate matter smaller than 2.5 μm in diameter (PM2.5), ground meteorological data, vertical measurements of winds, temperature, and relative humidity ...Based on observations of urban mass concentration of fine particulate matter smaller than 2.5 μm in diameter (PM2.5), ground meteorological data, vertical measurements of winds, temperature, and relative humidity (RH), and ECMWF reanalysis data, the major changes in the vertical structures of meteorological factors in the boundary layer (BL) during the heavy aerosol pollution episodes (HPEs) that occurred in winter 2016 in the urban Beijing area were analyzed. The HPEs are divided into two stages: the transport of pollutants under prevailing southerly winds, known as the transport stage (TS), and the PM2.5 explosive growth and pollution accumulation period characterized by a temperature inversion with low winds and high RH in the lower BL, known as the cumulative stage (CS). During the TS, a surface high lies south of Beijing, and pollutants are transported northwards. During the CS, a stable BL forms and is characterized by weak winds, temperature inversion, and moisture accumulation. Stable atmospheric stratifica- tion featured with light/calm winds and accumulated moisture (RH 〉 80%) below 250 m at the beginning of the CS is closely associated with the inversion, which is strengthened by the considerable decrease in near-surface air temperat- ure due to the interaction between aerosols and radiation after the aerosol pollution occurs. A significant increase in the PLAM (Parameter Linking Aerosol Pollution and Meteorological Elements) index is found, which is linearly re- lated to PM mass change. During the first 10 h of the CS, the more stable BL contributes approximately 84% of the explosive growth of PM2.5 mass. Additional accumulated near-surface moisture caused by the ground temperature de- crease, weak turbulent diffusion, low BL height, and inhibited vertical mixing of water vapor is conducive to the sec- ondary aerosol formation through chemical reactions, including liquid phase and heterogeneous reactions, which fur- ther increases the PM2.5 concentration levels. The contribution of these reaction mechanisms to the explosive growth of PM2,5 mass during the early CS and subsequent pollution accumulation requires further investigation.展开更多
SO 2 measurements made in recent years at sites in Beijing and its surrounding areas are performed to study the variations and trends of surface SO 2 at different types of sites in Northern China.The overall average c...SO 2 measurements made in recent years at sites in Beijing and its surrounding areas are performed to study the variations and trends of surface SO 2 at different types of sites in Northern China.The overall average concentrations of SO 2 are (16.8±13.1) ppb,(14.8±9.4) ppb,and (7.5±4.0) ppb at China Meteorological Administration (CMA,Beijing urban area),Gucheng (GCH,relatively polluted rural area,110 km to the southwest of Beijing urban area),and Shangdianzi (SDZ,clean background area,100 km to the northeast of Beijing urban area),respectively.The SO 2 levels in winter (heating season) are 4–6 folds higher than those in summer.There are highly significant correlations among the daily means of SO 2 at different sites,indicating regional characteristics of SO 2 pollution.Diurnal patterns of surface SO 2 at all sites have a common feature with a daytime peak,which is probably caused by the downward mixing and/or the advection transport of SO 2 -richer air over the North China Plain.The concentrations of SO 2 at CMA and GCH show highly significant downward trends (–4.4 ppb/yr for CMA and –2.4 ppb/yr for GCH),while a less significant trend (–0.3 ppb/yr) is identified in the data from SDZ,reflecting the character of SDZ as a regional atmospheric background site in North China.The SO 2 concentrations of all three sites show a significant decrease from period before to after the control measures for the 2008 Olympic Games,suggesting that the SO 2 pollution control has long-term effectiveness and benefits.In the post-Olympics period,the mean concentrations of SO 2 at CMA,GCH,and SDZ are (14.3±11.0) ppb,(12.1±7.7) ppb,and (7.5±4.0) ppb,respectively,with reductions of 26%,36%,and 13%,respectively,compared to the levels before.Detailed analysis shows that the differences of temperature,relative humidity,wind speed,and wind direction were not the dominant factors for the significant differences of SO 2 between the pre-Olympics and post-Olympics periods.By extracting the data being more representative of local or regional characteristics,a reduction of up to 40% for SO 2 in polluted areas and a reduction of 20% for regional SO 2 are obtained for the effect of control measures implemented for the Olympic Games.展开更多
A humidification system was deployed to measure aerosol hygroscopicity at a rural site of the North China Plain during the haze red-alert period 17–22 December 2016. The aerosol scattering coefficients under dry [rel...A humidification system was deployed to measure aerosol hygroscopicity at a rural site of the North China Plain during the haze red-alert period 17–22 December 2016. The aerosol scattering coefficients under dry [relative humidity(RH) 〈 30%] and wet(RH in the range of 40%–85%) conditions were simultaneously measured at wavelengths of450, 550, and 700 nm. It is found that the aerosol scattering coefficient and backscattering coefficient increased by only 29% and 10%, respectively when RH went up from 40% to 80%, while the hemispheric backscatter fraction went down by 14%, implying that the aerosol hygroscopicity represented by the aerosol scattering enhancement factor f(RH) is relatively low and RH exerted little effects on the aerosol light scattering in this case. The scattering enhancement factors do not show significant differences at the three wavelengths, only with an approximate 2% variation, suggesting that the aerosol hygroscopicity is independent of the wavelength. Aerosol hygroscopicity is highly dependent on the aerosol chemical composition. When there is a large mass fraction of inorganics and a small mass fraction of organic matter, f(RH) reaches a high value. The fraction of NO3^- was strongly correlated with the aerosol scattering coefficient at RH = 80%, which suggests that NO3^- played an important role in aerosol hygroscopic growth during the heavy pollution period.展开更多
An extensive field experiment for measurement of physical and chemical properties of aerosols was conducted at an urban site in the Chinese Academy of Meteorological Sciences(CAMS) in Beijing and at a rural site in ...An extensive field experiment for measurement of physical and chemical properties of aerosols was conducted at an urban site in the Chinese Academy of Meteorological Sciences(CAMS) in Beijing and at a rural site in Gucheng(GC), Hebei Province in December 2016. This paper compares the number size distribution of submicron particle matter(PM1, diameter 〈 1 μm) between the two sites. The results show that the mean PM1 number concentration at GC was twice that at CAMS, and the mass concentration was three times the amount at CAMS. It is found that the accumulation mode(100–850 nm) particles constituted the largest fraction of PM1 at GC, which was significantly correlated with the local coal combustion, as confirmed by a significant relationship between the accumulation mode and the absorption coefficient of soot particles. The high PM1 concentration at GC prevented the occurrence of new particle formation(NPF) events, while eight such events were observed at CAMS. During the NPF events, the mass fraction of sulfate increased significantly, indicating that sulfate played an important role in NPF. The contribution of regional transport to PM1 mass concentration was approximately 50% at both sites, same as that of the local emission. However, during the red-alert period when emission control took place, the contribution of regional transport was notably higher.展开更多
Dabaoshan Mine,the largest mine in south China,has been developed since the 1970s.Acid mine drainage (AMD) discharged from the mine has caused severe environmental pollution and human health problems.In this article...Dabaoshan Mine,the largest mine in south China,has been developed since the 1970s.Acid mine drainage (AMD) discharged from the mine has caused severe environmental pollution and human health problems.In this article,chemical characteristics,mineralogy of ocher precipitations and heavy metal attenuation in the AMD are discussed based on physicochemical analysis,mineral analysis,sequential extraction experiments and hydrogeochemistry.The AMD chemical characteristics were determined from the initial water composition,water-rock interactions and dissolved sulfide minerals in the mine tailings.The waters,affected and unaffected by AMD,were Ca-SO4 and Ca-HCO3 types,respectively.The affected water had a low pH,high SO42 and high heavy metal content and oxidation as determined by the Fe^2+ /Fe^3+ couple.Heavy metal and SO4^2- contents of Hengshi River water decreased,while pH increased,downstream.Schwertmannite was the major mineral at the waste dump,while goethite and quartz were dominant at the tailings dam and streambed.Schwertmannite was transformed into goethite at the tailings dam and streambed.The sulfate ions of the secondary minerals changed from bidentate-to monodentate-complexes downstream.Fe-Mn oxide phases of Zn,Cd and Pb in sediments increased downstream.However,organic matter complexes of Cu in sediments increased further away from the tailings.Fe^3+ mineral precipitates and transformations controlled the AMD water chemistry.展开更多
基金Supported by the National Key Project of the Ministry of Science and Technology of China(2016YFC0203306)Basic Scientific Research Project of the Chinese Academy of Meteorological Sciences(2016Z001)
文摘Based on observations of urban mass concentration of fine particulate matter smaller than 2.5 μm in diameter (PM2.5), ground meteorological data, vertical measurements of winds, temperature, and relative humidity (RH), and ECMWF reanalysis data, the major changes in the vertical structures of meteorological factors in the boundary layer (BL) during the heavy aerosol pollution episodes (HPEs) that occurred in winter 2016 in the urban Beijing area were analyzed. The HPEs are divided into two stages: the transport of pollutants under prevailing southerly winds, known as the transport stage (TS), and the PM2.5 explosive growth and pollution accumulation period characterized by a temperature inversion with low winds and high RH in the lower BL, known as the cumulative stage (CS). During the TS, a surface high lies south of Beijing, and pollutants are transported northwards. During the CS, a stable BL forms and is characterized by weak winds, temperature inversion, and moisture accumulation. Stable atmospheric stratifica- tion featured with light/calm winds and accumulated moisture (RH 〉 80%) below 250 m at the beginning of the CS is closely associated with the inversion, which is strengthened by the considerable decrease in near-surface air temperat- ure due to the interaction between aerosols and radiation after the aerosol pollution occurs. A significant increase in the PLAM (Parameter Linking Aerosol Pollution and Meteorological Elements) index is found, which is linearly re- lated to PM mass change. During the first 10 h of the CS, the more stable BL contributes approximately 84% of the explosive growth of PM2.5 mass. Additional accumulated near-surface moisture caused by the ground temperature de- crease, weak turbulent diffusion, low BL height, and inhibited vertical mixing of water vapor is conducive to the sec- ondary aerosol formation through chemical reactions, including liquid phase and heterogeneous reactions, which fur- ther increases the PM2.5 concentration levels. The contribution of these reaction mechanisms to the explosive growth of PM2,5 mass during the early CS and subsequent pollution accumulation requires further investigation.
基金supported by the National Basic Research Program of China (No.2005CB4222002)the National Natural Science Foundation of China (No. 20407001,40775074)+1 种基金the Basic Research Fund of CAMS (No. 2008Z011,2011CX001,2011Z003)the China Meteorological Administration(No. GYHY200706036,GYHY201106050)
文摘SO 2 measurements made in recent years at sites in Beijing and its surrounding areas are performed to study the variations and trends of surface SO 2 at different types of sites in Northern China.The overall average concentrations of SO 2 are (16.8±13.1) ppb,(14.8±9.4) ppb,and (7.5±4.0) ppb at China Meteorological Administration (CMA,Beijing urban area),Gucheng (GCH,relatively polluted rural area,110 km to the southwest of Beijing urban area),and Shangdianzi (SDZ,clean background area,100 km to the northeast of Beijing urban area),respectively.The SO 2 levels in winter (heating season) are 4–6 folds higher than those in summer.There are highly significant correlations among the daily means of SO 2 at different sites,indicating regional characteristics of SO 2 pollution.Diurnal patterns of surface SO 2 at all sites have a common feature with a daytime peak,which is probably caused by the downward mixing and/or the advection transport of SO 2 -richer air over the North China Plain.The concentrations of SO 2 at CMA and GCH show highly significant downward trends (–4.4 ppb/yr for CMA and –2.4 ppb/yr for GCH),while a less significant trend (–0.3 ppb/yr) is identified in the data from SDZ,reflecting the character of SDZ as a regional atmospheric background site in North China.The SO 2 concentrations of all three sites show a significant decrease from period before to after the control measures for the 2008 Olympic Games,suggesting that the SO 2 pollution control has long-term effectiveness and benefits.In the post-Olympics period,the mean concentrations of SO 2 at CMA,GCH,and SDZ are (14.3±11.0) ppb,(12.1±7.7) ppb,and (7.5±4.0) ppb,respectively,with reductions of 26%,36%,and 13%,respectively,compared to the levels before.Detailed analysis shows that the differences of temperature,relative humidity,wind speed,and wind direction were not the dominant factors for the significant differences of SO 2 between the pre-Olympics and post-Olympics periods.By extracting the data being more representative of local or regional characteristics,a reduction of up to 40% for SO 2 in polluted areas and a reduction of 20% for regional SO 2 are obtained for the effect of control measures implemented for the Olympic Games.
基金Supported by the National Key Project of Ministry of Science and Technology of China(2016YFC0203305 and 2016YFC0203306)National Natural Science Foundation of China(41475118 and 41675129)Chinese Academy of Meteorological Sciences Basic Research Fund(2017Z011,2016Z001,and 2016Y004)
文摘A humidification system was deployed to measure aerosol hygroscopicity at a rural site of the North China Plain during the haze red-alert period 17–22 December 2016. The aerosol scattering coefficients under dry [relative humidity(RH) 〈 30%] and wet(RH in the range of 40%–85%) conditions were simultaneously measured at wavelengths of450, 550, and 700 nm. It is found that the aerosol scattering coefficient and backscattering coefficient increased by only 29% and 10%, respectively when RH went up from 40% to 80%, while the hemispheric backscatter fraction went down by 14%, implying that the aerosol hygroscopicity represented by the aerosol scattering enhancement factor f(RH) is relatively low and RH exerted little effects on the aerosol light scattering in this case. The scattering enhancement factors do not show significant differences at the three wavelengths, only with an approximate 2% variation, suggesting that the aerosol hygroscopicity is independent of the wavelength. Aerosol hygroscopicity is highly dependent on the aerosol chemical composition. When there is a large mass fraction of inorganics and a small mass fraction of organic matter, f(RH) reaches a high value. The fraction of NO3^- was strongly correlated with the aerosol scattering coefficient at RH = 80%, which suggests that NO3^- played an important role in aerosol hygroscopic growth during the heavy pollution period.
基金Supported by the National Key Project of Ministry of Science and Technology of China(2016YFC0203306 and 2016YFC0203305)Chinese Academy of Meteorological Sciences Basic Research Fund(2017Z011,2016Z001,and 2016Y004)
文摘An extensive field experiment for measurement of physical and chemical properties of aerosols was conducted at an urban site in the Chinese Academy of Meteorological Sciences(CAMS) in Beijing and at a rural site in Gucheng(GC), Hebei Province in December 2016. This paper compares the number size distribution of submicron particle matter(PM1, diameter 〈 1 μm) between the two sites. The results show that the mean PM1 number concentration at GC was twice that at CAMS, and the mass concentration was three times the amount at CAMS. It is found that the accumulation mode(100–850 nm) particles constituted the largest fraction of PM1 at GC, which was significantly correlated with the local coal combustion, as confirmed by a significant relationship between the accumulation mode and the absorption coefficient of soot particles. The high PM1 concentration at GC prevented the occurrence of new particle formation(NPF) events, while eight such events were observed at CAMS. During the NPF events, the mass fraction of sulfate increased significantly, indicating that sulfate played an important role in NPF. The contribution of regional transport to PM1 mass concentration was approximately 50% at both sites, same as that of the local emission. However, during the red-alert period when emission control took place, the contribution of regional transport was notably higher.
基金supported by the Guangdong Provincial Natural Science Foundation (No. 06202438)the Research Funds of the Guangxi Key Laboratory of Environmental Engineering,Protection and Assessment (No.GuiKeNeng 0801Z020)
文摘Dabaoshan Mine,the largest mine in south China,has been developed since the 1970s.Acid mine drainage (AMD) discharged from the mine has caused severe environmental pollution and human health problems.In this article,chemical characteristics,mineralogy of ocher precipitations and heavy metal attenuation in the AMD are discussed based on physicochemical analysis,mineral analysis,sequential extraction experiments and hydrogeochemistry.The AMD chemical characteristics were determined from the initial water composition,water-rock interactions and dissolved sulfide minerals in the mine tailings.The waters,affected and unaffected by AMD,were Ca-SO4 and Ca-HCO3 types,respectively.The affected water had a low pH,high SO42 and high heavy metal content and oxidation as determined by the Fe^2+ /Fe^3+ couple.Heavy metal and SO4^2- contents of Hengshi River water decreased,while pH increased,downstream.Schwertmannite was the major mineral at the waste dump,while goethite and quartz were dominant at the tailings dam and streambed.Schwertmannite was transformed into goethite at the tailings dam and streambed.The sulfate ions of the secondary minerals changed from bidentate-to monodentate-complexes downstream.Fe-Mn oxide phases of Zn,Cd and Pb in sediments increased downstream.However,organic matter complexes of Cu in sediments increased further away from the tailings.Fe^3+ mineral precipitates and transformations controlled the AMD water chemistry.