Size distributions of 29 elements in aerosols collected at urban,rural and curbside sites in Beijing were studied.High levels of Mn,Ni,As,Cd and Pb indicate the pollution of toxic heavy metals cannot be neglected in B...Size distributions of 29 elements in aerosols collected at urban,rural and curbside sites in Beijing were studied.High levels of Mn,Ni,As,Cd and Pb indicate the pollution of toxic heavy metals cannot be neglected in Beijing.Principal component analysis (PCA) indicates 4 sources of combustion emission,crust related sources,traffic related sources and volatile species from coal combustion.The elements can be roughly divided into 3 groups by size distribution and enrichment factors method (EFs).Group 1 elements are crust related and mainly found within coarse mode including Al,Mg,Ca,Sc,Ti,Fe,Sr,Zr and Ba;Group 2 elements are fossil fuel related and mostly concentrated in accumulation mode including S,As,Se,Ag,Cd,Tl and Pb;Group 3 elements are multi-source related and show multi-mode distribution including Be,Na,K,Cr,Mn,Co,Ni,Cu,Zn,Ga,Mo,Sn and Sb.The EFs of Be,S,Cr,Co,Ni,Cu,Ga,Se,Mo,Ag,Cd,Sb,Tl and Pb show higher values in winter than in summer indicating sources of coal combustion for heating in winter.The abundance of Cu and Sb in coarse mode is about 2–6 times higher at curbside site than at urban site indicating their traffic sources.Coal burning may be the major source of Pb in Beijing since the phase out of leaded gasoline,as the EFs of Pb are comparable at both urban and curbside sites,and about two times higher in winter than that in summer.展开更多
Water vapor content, instability, and convergence conditions are the key to short-duration heavy rainfall forecasting. It is necessary to understand the large-scale atmospheric environment characteristics of short- du...Water vapor content, instability, and convergence conditions are the key to short-duration heavy rainfall forecasting. It is necessary to understand the large-scale atmospheric environment characteristics of short- duration heavy rainfall by investigating the distribution of physical parameters for different hourly rainfall intensities. The observed hourly rainfall data in China and the NCEP final analysis (FNL) data during 1 May and 30 September from 2002 to 2009 are used. NCEP FNL data are 6-hourly, resulting in sample sizes of 1573370, 355346, and 11401 for three categories of hourly rainfall (P) of no precipitation (P 〈 0.1 mm h-1), ordinary precipitation (0.1≤ P 〈 20 mm h-1), and short-duration heavy rainfall (P ≥ 20.0 mm h-1), respectively, by adopting a temporal matching method. The results show that the total precipitable water (PWAT) is the best parameter indicating the hourly rainfall intensity. A PWAT of 28 mm is necessary for any short-duration heavy rainfall. The possibility of short-duration heavy rainfall occurrence increases with PWAT, and a PWAT of 59 mm is nearly sufficient. The specific humidity is a better indicator than relative humidity. Both 700- and 850-hPa relative humidity greater than 80% could be used to determine whether or not it is going to rain, but could not be used to estimate the rainfall intensity. Temperature and potential pseudo-equivalent temperature are also reasonable indicators of short-duration heavy rainfall. Among the atmospheric instability parameters, the best lifted index (BLI) performs best on the short- duration rainfall discrimination; the next best is the K index (KI). The three rainfall categories are not well recognized by total totals (TT) or the temperature difference between 850 and 500 hPa (DT85). Three- quarters of short-duration heavy rainfall occurred with BLI less than -0.9, while no short-duration heavy rainfall occurred when BLI was greater than 2.6. The minimum threshold of KI was 28.1 for short-durati展开更多
In 2013,China issued the"Action Plan for the Prevention and Control of Air Pollution"("Ten Statements of Atmosphere")and implemented a series of pollution reduction measures from 2013 to 2017.In ke...In 2013,China issued the"Action Plan for the Prevention and Control of Air Pollution"("Ten Statements of Atmosphere")and implemented a series of pollution reduction measures from 2013 to 2017.In key regions of China,the mass concentrations of particulate matter with aerodynamic equivalent diameters less than 2.5μm(PM2.5)have dropped significantly.However,the contributions of meteorological changes to PM2.5 reduction are largely uncertain,which has attracted particular concern from the government and the public.Here,we investigated the impact of large-scale and boundary layer(BL)meteorological conditions on aerosol pollution and estimated the contributions of meteorological changes to PM2.5 reduction based on in-depth analysis and diagnosis of various observed meteorological elements and an integrated pollution-linked meteorological index(PLAM,which is approximately and linearly related to PM mass concentration).In this study,we found that the meteorological conditions worsened in 2014 and 2015 and improved in 2016 and 2017 relative to those in 2013 in key regions in China.In 2017 relative to 2013,only^5%(approximately 13%of the total PM2.5 decline)of the 39.6%reduction in PM2.5 mass concentrations can be attributed to meteorological changes in the Beijing-Tianjin-Hebei(BTH)region,and only^7%(approximately 20%of the total PM2.5 decline)of the 34.3%reduction can be attributable to meteorological changes in the Yangtze River Delta(YRD)region.Overall,the PM2.5 reduction due to meteorological improvement is much lower than the observed PM2.5 reduction in these areas,which indicates that emission reduction during the five-year implementation of the"Ten Statements of Atmosphere"is the dominant factor in the improvement in air quality.The changes in meteorology and climate are conducive to PM2.5 reduction but do not dominate the substantial improvement in air quality.Similar to the above regions,in the Pearl River Delta(PRD)region,the impact of meteorological changes on the annual averaged PM2.5 concentration from 2013 展开更多
基金supported by the special fund of the State Key Joint Laboratory of Environment Simulation and Pollution Control (No. 11K03ESPCT)the National Department Public Benefit Research Foundation (Ministry of Environmental Protection of the People’s Republic of China) (No. 201009001,201109002)
文摘Size distributions of 29 elements in aerosols collected at urban,rural and curbside sites in Beijing were studied.High levels of Mn,Ni,As,Cd and Pb indicate the pollution of toxic heavy metals cannot be neglected in Beijing.Principal component analysis (PCA) indicates 4 sources of combustion emission,crust related sources,traffic related sources and volatile species from coal combustion.The elements can be roughly divided into 3 groups by size distribution and enrichment factors method (EFs).Group 1 elements are crust related and mainly found within coarse mode including Al,Mg,Ca,Sc,Ti,Fe,Sr,Zr and Ba;Group 2 elements are fossil fuel related and mostly concentrated in accumulation mode including S,As,Se,Ag,Cd,Tl and Pb;Group 3 elements are multi-source related and show multi-mode distribution including Be,Na,K,Cr,Mn,Co,Ni,Cu,Zn,Ga,Mo,Sn and Sb.The EFs of Be,S,Cr,Co,Ni,Cu,Ga,Se,Mo,Ag,Cd,Sb,Tl and Pb show higher values in winter than in summer indicating sources of coal combustion for heating in winter.The abundance of Cu and Sb in coarse mode is about 2–6 times higher at curbside site than at urban site indicating their traffic sources.Coal burning may be the major source of Pb in Beijing since the phase out of leaded gasoline,as the EFs of Pb are comparable at both urban and curbside sites,and about two times higher in winter than that in summer.
基金Supported by the Meteorological Integration and Application of Key Techniques(CMAGJ2013Z04)China Meteorological Administration Special Public Welfare Research Fund(GYHY201406002 and GYHY201206004)National(Key)Basic Research and Development(973)Program of China(2013CB430106)
文摘Water vapor content, instability, and convergence conditions are the key to short-duration heavy rainfall forecasting. It is necessary to understand the large-scale atmospheric environment characteristics of short- duration heavy rainfall by investigating the distribution of physical parameters for different hourly rainfall intensities. The observed hourly rainfall data in China and the NCEP final analysis (FNL) data during 1 May and 30 September from 2002 to 2009 are used. NCEP FNL data are 6-hourly, resulting in sample sizes of 1573370, 355346, and 11401 for three categories of hourly rainfall (P) of no precipitation (P 〈 0.1 mm h-1), ordinary precipitation (0.1≤ P 〈 20 mm h-1), and short-duration heavy rainfall (P ≥ 20.0 mm h-1), respectively, by adopting a temporal matching method. The results show that the total precipitable water (PWAT) is the best parameter indicating the hourly rainfall intensity. A PWAT of 28 mm is necessary for any short-duration heavy rainfall. The possibility of short-duration heavy rainfall occurrence increases with PWAT, and a PWAT of 59 mm is nearly sufficient. The specific humidity is a better indicator than relative humidity. Both 700- and 850-hPa relative humidity greater than 80% could be used to determine whether or not it is going to rain, but could not be used to estimate the rainfall intensity. Temperature and potential pseudo-equivalent temperature are also reasonable indicators of short-duration heavy rainfall. Among the atmospheric instability parameters, the best lifted index (BLI) performs best on the short- duration rainfall discrimination; the next best is the K index (KI). The three rainfall categories are not well recognized by total totals (TT) or the temperature difference between 850 and 500 hPa (DT85). Three- quarters of short-duration heavy rainfall occurred with BLI less than -0.9, while no short-duration heavy rainfall occurred when BLI was greater than 2.6. The minimum threshold of KI was 28.1 for short-durati
基金supported by the Atmospheric Pollution Control of the Prime Minister Fund (Grant No. DQGG0104)the National Key Project of MOST (Grant No. 2016YFC0203306)
文摘In 2013,China issued the"Action Plan for the Prevention and Control of Air Pollution"("Ten Statements of Atmosphere")and implemented a series of pollution reduction measures from 2013 to 2017.In key regions of China,the mass concentrations of particulate matter with aerodynamic equivalent diameters less than 2.5μm(PM2.5)have dropped significantly.However,the contributions of meteorological changes to PM2.5 reduction are largely uncertain,which has attracted particular concern from the government and the public.Here,we investigated the impact of large-scale and boundary layer(BL)meteorological conditions on aerosol pollution and estimated the contributions of meteorological changes to PM2.5 reduction based on in-depth analysis and diagnosis of various observed meteorological elements and an integrated pollution-linked meteorological index(PLAM,which is approximately and linearly related to PM mass concentration).In this study,we found that the meteorological conditions worsened in 2014 and 2015 and improved in 2016 and 2017 relative to those in 2013 in key regions in China.In 2017 relative to 2013,only^5%(approximately 13%of the total PM2.5 decline)of the 39.6%reduction in PM2.5 mass concentrations can be attributed to meteorological changes in the Beijing-Tianjin-Hebei(BTH)region,and only^7%(approximately 20%of the total PM2.5 decline)of the 34.3%reduction can be attributable to meteorological changes in the Yangtze River Delta(YRD)region.Overall,the PM2.5 reduction due to meteorological improvement is much lower than the observed PM2.5 reduction in these areas,which indicates that emission reduction during the five-year implementation of the"Ten Statements of Atmosphere"is the dominant factor in the improvement in air quality.The changes in meteorology and climate are conducive to PM2.5 reduction but do not dominate the substantial improvement in air quality.Similar to the above regions,in the Pearl River Delta(PRD)region,the impact of meteorological changes on the annual averaged PM2.5 concentration from 2013