Formation mechanism of continuous extreme haze episodes in the megacity Beijing,China,in January 2013
公务员备考Yiru Yang a ,Xingang Liu a ,⁎,Yu Qu b ,Jingli Wang c ,Junling An b ,Yuanhangi Zhang d ,Fang Zhang e
a
State Key Laboratory of Water Environment Simulation,School of Environment,Beijing Normal University,Beijing 100875,China
b
State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry,Institute of Atmospheric Physics,Chine Academy of Sciences,100029,China c
Institute for Urban Meteorology,China Meteorological Administration,Beijing 100081,China d
State Key Joint Laboratory of Environment Simulation and Pollution Control,College of Environmental Sciences and Engineering,Peking University,Beijing 100871,China e
College of Global Change and Earth System Science,Beijing Normal University,Beijing 100875,China
a r t i c l e i n f o a
b s t r a
c t
Article history:
Received 23June 2014
impress的用法
Received in revid form 3November 2014Accepted 30November 2014
Available online 8December 2014The primary objective of this study is to investigate the formation and evolution mechanism of the regional haze in Beijing by analyzing the process of a vere haze e
pisode that occurredfrom1to 31January 2013.The mass concentration of PM 2.5and its chemical components were simultaneously measured at the Beijing urban atmospheric environmental monitoring station.The haze was characterized by a high frequency,a long duration,a large influential region and an extremely high PM 2.5values (N 500μg/m 3).The primary factors driving the haze formation were stationary atmospheric flows (in both vertical and horizontal directions),while a temperature inversion,a lower planetary boundary layer and a higher RH accelerated the formation of the regional haze.In one incident,the temperature inversion layer occurred at a height of 130m above ground level,which prevented the air pollutants from being disperd vertically.The regional transport of pollutants also played an important role in the formation of the haze.Wind from the south of Beijing incread from 58%in January 2012to 63%in January 2013.Becau the area to the south of Beijing is characterized by high industrial development,the unusual wind
direction favored the regional transport of pollutants and verely exacerbated the haze.SO 42−
,NO 3−and NH 4+
are the three major water-soluble ions that contributed to the formation of the haze.The high variability in Cl −and K +indicated that large quantities of coal combustion and biomass burning occurred during the haze.
©2014Elvier B.V.All rights rerved.
Keywords:Haze episodes
Formation mechanism Chemical characteristics Beijing
1.Introduction
Aerosols negatively affect climate change,human health and atmospheric visibility and have become a major issue in China (Tan et al.,2009a,b;Liu et al.,2012;Duan and Tan,2013;Tao et al.,2014a,b ).In a vertical direction,aerosols scatter (Cahill,1996)and absorb (Jacobson,2001)solar and terrestrial radiation,changing the thermal balance of the troposphere.In a horizontal direction,aerosols scatter and absorb light and
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reduce visibility,which can result in a depressive effect on humans becau of the gray sky color (Hyslop,2009)and can increa traffic hazards in the sky and on the ground (Mukherjee and Viswanathan,2001).Coar particles (i.e.,particulate matter with an aerodynamic diameter greater than 10μm)ttle readily on the ground becau of gravity,while the fine particles remain floating and can easily enter the body through the respiratory system (Peters et al.,1997;Schwartz and Neas,2000).Ultrafine particles (i.e.,particulate matter with an aerodynamic diameter equal to or less than 50nm)are able to penetrate the lungs and circulatory system,producing negative effects on the cardiovas-cular (Bai et al.,2007;Carlsten et al.,2007)and immune systems (Diaz-Sanchez et al.,1999;Kang et al.,2010)and possibly the
author at:Ph.D Associate Professor School of Environ-ment,Beijing Normal University,Beijing,100875.Tel.:+861058804585.
E-mail address:liuxingang@bnu.edu (X.Liu).dx.doi/10.1016/j.atmosres.2014.11.0230169-8095/©2014Elvier B.V.All rights
rerved.
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Atmospheric Rearch
j o u r n a l h o me p a g e :ww w.e l s e v i e r.c o m /l o c a t e /a t m o s
nervous system Furthermore,many studies have demonstrated that fine particles,referred to as PM2.,particulate matter with an aerodynamic diameter equal to or less than2.5μm),that contain high concentrations of toxic and hazard substances are related to morbidity and mortality levels(Miller et al.,2007; Araujo et al.,2008;Brook et al.,2010).Moreover,aerosols have a negative effect on agricultural productivity(Chameides et al., 1999).
The rapid economic growth in China since the1980s has resulted in high emissions of atmospheric pollutants that have reduced air quality(Guo et al.,2011).In the1990s,the Chine government spent billions of Yuan to combat environmental pollution,especially during period prior to the2008Olympic Games(Streets et al.,2007;Zhou et al.,2010).While some progress was made(Cheng et al.,2013),the trend of poor air quality continued after2008.Hazes have occurred frequently in China during the last decade(Wang et al.,2006;Kan et al., 2007;Li et al.,2010;Duan et al.,2012;Liu et al.,2012;Xu et al., 2013).A haze is defined as a weather condition in which the horizontal visibility is less than10km and the RH is less than 90%(Wu et al.,2007).Fine aerosol ,PM2.5)play a dominant role in the formation and evolution of haze(Liu et al., 2013).
There are four major areas in China with vere haze pollution:the Jing-Jin-Ji Region,the Yangtze River Delta,the Pearl River Delta(PRD)and the Sichuan Basin(Zhang et al., 2012).The first three regions are rapidly developing economic areas with high pollutant emission levels.Under calm meteo-rological conditions,a haze forms readily.The geography of Sichuan Basin does not favor the diffusion of pollutants and the higher RH in this region,which can favor the formation of hazes(Chen and Xie,2013).The concentration of PM2.5varies asonally,generally remaining at a relatively low value in the summer and autumn and increasing in the winter and spring (Chang et al.,2009).The hig
h PM2.5emissions in the winter and early spring result from the large amounts of coal that are burned to provide heat in northern China(Ma et al.,2011). There is regional variation in the air pollution in China; northern China has a more vere aerosol problem than southern China(Zhang,et al.,2012).This can be attributed to the wide spread heating in northern China in winter and the lower rainfall in this area compared with southern China.In addition,the aerosol problem in eastern China is wor than western China becau of the high levels of industrial and traffic emissions.Particulate pollution is becoming increasingly rious in China(Massie et al.,2004;Ramanathan et al.,2005), illustrating the importance and urgency of reducing the atmospheric pollution.
An unprecedented haze incident occurred in China in January2013.The high frequency,high PM2.5values,extended duration and large area of the haze have rarely been previously reported.The maximum instantaneous PM2.5value was higher than500μg/m3,and over75%of the time,a haze condition was obrved.During the most vere period,northern,southern, eastern and middle China were influenced by the haze.The characteristics and formation mechanisms of the extreme haze events have been reported by many other studies.An atmospheric circulation pattern in the middle troposphere over Eurasia was found to have undergone a long wave adjustment, which provided the meteorological background for haze development(Wang et al.,2014).Northwest winds in high altitude
google docss with dust particles on the top boundary layer met southerly airflows,which not only transport industry pollutants to Beijing but also cau widespread haze pollution when moist air mass exist(Tao et al.,2014d).Aerosol particles in southern air mass were especially rich in inorganic and oxidized organic species,whereas northern air mass contained a large fraction of primary species(Zhang et al.,2014).Becau the O3 concentration was low during the haze,fast conversion from the gas pha of NOx and SO2to the particle pha of NO3−and SO42−indicated the importance of heterogeneous formation of NO3−and SO42−on haze formation(Quan et al.,2014).Stagnant meteorological conditions,coal combustion,condary produc-tion and regional transport are regarded as the four major factors driving the formation and evolution of the hazes(Ji et al.,2014; Sun et al.,2014).However,the characteristics of PM2.5 distribution all over the Beijing region in January2013and the reasons driving this distribution are not provided.Additionally, the influence of planetary boundary layer(PBL)on the PM2.5 concentration and haze formation were not investigated.
2.Experiment
2.1.Experimental site
All measurements were conducted in Beijing,the capital of the People's Republic of China and the national center for politics and culture.The gross domestic product(GDP)of Beijing in2012was0.3trillion dollars with a growth rate of 7.7%(v/xwgb/tjgb/ndgb/201302/ t20130207_243837.htm).The city's population is20million, and its population density at the end of2012was1261people per km2.Beijing's total energy consumption was71.8million tons of standard coal,and there were5.2million cars with a growth rate of3%as of2012(v/ xwgb/tjgb/ndgb/201302/t20130207_243837.htm).High levels of energy consumption and the high economic status have resulted in incread emissions of air pollutants in Beijing.
Field measurements were conducted from1to31January 2013at the urban atmospheric environmental monitoring station(39.96°N,116.36°E)on the campus of Beijing Normal University(BNU),which is located in the northern part of Beijing and is~300m south of the third ring road that acts as one of the main traffic routes in Beijing.The obrvation site was located on the roof of a six-floor building(~20m above ground level).All instruments were installed in an air-conditioned room except for the visibility nsor,which was installed outdoors.
2.2.Measurements and methods
The PM2.5mass concentration was measured using a tapered element oscillating microbalance(TEOM,RP1405F,USA)at35 sites in Beijing that were monitored by the Beijing Environ-mental Bureau(wwwpm25/city/beijing.html)and the site at BNU in this study.The visibility was measured using a visibility nsor(Belfort6000,USA),which consisted of a transmitter,a receiver and a controller,and had a range of10m to50km(Liu et al.,2013).The wind direction,wind speed, and relative humidity were monitored at the meteorological station(Vaisala,Finland).A ground-bad microwave radio-meter(MP-3000A,USA)was ud to detect the real-time atmospheric temperature and RH profile.The detection cycle of
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Y.Yang et al./Atmospheric Rearch155(2015)192–203
the radiometer was1min with a detection range of0to10km. The size-gregated atmospheric particles were collected using a nano-sampler(Sun et al.,2014)compod of six size stages with nominal aerodynamic diameter cut-offs at10(the inlet), 2.5,1.0,0.5,and0.1μm.Atmospheric particles were collected over a24-h sampling period between8:00am and8:00am(the following day).The ionic components were analyzed using an ion-chromatograph(ICS-2500DIONEX,USA).Anions were analy
zed using a Dionex AS11Column with12mmol/L NaOH eluted at a flow rate of1.0mL/min.Cations were analyzed using a CS-12A Column with a CSRS-I suppressor and were eluted with20mmol/L methane sulfonic acid(MSA)at a flow rate of 1.0mL/min.The detection limits for F−,Cl−,NO3−,SO42−,NH4+, Ca2+,Mg2+,K+and Na+were0.03,0.03,0.01,0.01,0.06,0.05, 0.1,0.1and0.03mg/L,respectively.The instruments ud in this study are listed in Table1.
3.Results and discussion
3.1.Description of the regional haze in2013
Temporal variations in the RH and visibility in January2013 are depicted in Fig.1a.The red and black lines reprent90%RH and10km visibility boundaries,respectively.Most of the data are within their boundary lines,which indicates that a haze occurred for almost the entire month.The only day without haze was2January;a haze period existed for more than77%of the time.
fireflies
26岁的女人There were eight haze process according to the definition of haze.Information about the eight events is listed in Table2.Three types of hazes can be classified according to Fig.1b.The Type1haze,which included Events1,2,4and6, lasted for approximately2–3days,and the PM2.5concentra-tions peaked at150–250μg/m3,which were relatively low compared with the other e
vents.The Type2haze,which included Events5and7,also had a short duration,but the maximum PM2.5concentration exceeded400μg/m3,which is illustrated by a sharp ri and fall in Fig.1b.The Type3haze, which included Events3and8,lasted for5days,and the maximum PM2.5concentration was greater than400μg/m3. The minimum visibilities in Events3and8were less than 100m.An accumulation of pollutants is clearly visible in Events 3and8.Aerosol sampling was conducted during Events3and 8.Other rearchers have also reported similarly high levels of PM2.5concentration(Che et al.,2014).The haze forecast maps for January14,17,27and29,distributed by the Meteorological Administration of China,are prented in Fig.2.The spatial distribution and temporal variation of the haze over China are shown in the maps.The haze on January14affected a large area of ,most of northern China,central China,and a few areas of southern China.The haze diminished by January 17and only covered a few areas of the Hunan and Hubei provinces in eastern China.Though the region influenced by
初一上册英语单词表
Table1
Overview of the instruments ud in this study.
Instrument Parameter Manufacturer model
TEOM PM2.5Thermo.Electron.RP1405F Nano-sampler Chemical components KUJ a
Visibility meter Visibility Belfort6000
Microwave radiometer Temperature/RH profile MP-3000A
Wind speed/temperature/RH nsor Wind speed,temperature,RH Vaisala
GMT220
HMP45
a KUJ:Kanazawa University of Japan.
R
H
knockdown
Visibility
V
i
s
i
b
i
l
i
t
y
P
M2
.
5
(
u
g
/
m
3
)
Date
Fig.1.Time ries of PM2.5,visibility and RH in January2013.
194Y.Yang et al./Atmospheric Rearch155(2015)192–203起伏的意思
the haze expanded in southern China,northern China was not affected by the haze.In general,the area affected by the haze was greatly diminished.The map is consistent with Fig.1a,where the visibility on January 17was high (N 10km for 14h).The haze expanded on January 27and 29,which affected a large area of northern,eastern,central and southern China.The areas are characterized by large population sizes and high economic productivity.
3.2.Formation mechanism of the regional haze
3.2.1.Stationary meteorological conditions
Atmospheric pressure distributions for four reprentative time points are shown in Fig.3.The time points (i.e.,3:00am on the 6th,6:00am on the 17th,0:00on the 19th and 18:00pm on the 26th of January)reprent the Beijing region that was controlled by a spar-isobar pressure,a high-pressure center,an intensive-isobar pressure and a low-pressure center,respectively.The event bega
n at 13:00pm on January 6,when the pollutants started to accumulate.At this time,the Beijing region was controlled by low pressure;the isobars were widely spaced,and the horizontal composition of atmosphere was relatively stagnant.The conditions are unfavorable for the diffusion of pollutants.Similar conditions occurred at 0:00on the 4th,3:00pm on the 16th,12:00on the 20th (time points that were typical of the Type-1period)and 21:00pm on the 12th of January,with the exception that the Beijing region was controlled by a high-pressure system.
Table 2prominent
Information on the hazes in Beijing in January 2013.Event number Duration PM 2.5(Mean ±S.D.)(μg/m 3)Maximum of PM 2.5(μg/m 3)Visibility (Mean ±S.D.)(km)Minimum of visibility (km)13–455±52189 3.239±2.5450.82126–8121±78245
4.384±4.7600.83539–13306±142Over 500 1.060±1.3020.099415–16123±42196 4.239±2.879 1.138517–18166±100469 3.545±4.8930.387620–21108±43175 2.168±1.8750.992722–23331±744450.807±0.7070.1688
25–29
238
±80
456
1.227
±0.950
0.040
Fig.2.Haze forecast maps of China on (a)January 14,(b)January 17,(c)January 27,and (d)January 29.
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Beijing was controlled by a high-pressure center at 6:00am on the 17th,12:00on the 22nd and 12:00on the 27th.At the times,the concentration of PM 2.5incread sharply,reaching over 400μg/m 3in a short time.Likewi,at 18:00on the 26th and 21:00on the 10th,Beijing was controlled by a low-pressure center that also resulted in high PM 2.5concentration.High/low-pressure centers are the typical ca of spar isobars,where the atmosphere gradient is extremely large.Under the control of a high/low-pressure center,the Beijing area had little atmospheric horizontal variation,and the wind speed would be low or there would be no wind.However,there are differences between the two systems.When Beijing was controlled by a high-pressure center,the airflow decread when the RH was low,making it less likely that precipitation would form and remove the pollutants.When controlled by a low-pressure center,Beijing was the center of the surrounding airflow and the pollutan
ts converged in this area.In addition,the rising airflows incread with greater humidity,promoting the condary formation of pollutants and the hygroscopic growth of partic-ulate matter.In contrast,the isobars at 0:00on the 19th were inten,indicating high wind speed and the efficient removal of pollutants.
3.2.2.The low height of the planetary boundary layer
The temporal and height variation in the temperature and RH are illustrated in Fig.4.The data were recorded every 0.1km up to a height of 1km.Relatively low temperatures were recorded from January 1to January 4becau of a strong cold air mass;the average temperature over this period was −7.2°C,while the average temperature for the entire month was −2.6°C.Similar conditions prevailed on January 9,15and 25,when visibility was high and air quality was good.In contrast,relatively high temperatures were recorded at other time periods.Moreover,there were ven cas of temperature inversions,all of which occurred at night.The events are more frequent at night becau there is no solar radiation,and surface radiation becomes an important source of heat ascending to the atmosphere.Temperature inversions result in stagnant synoptic conditions,which are not conducive to air flow,and air pollutants are not easily disperd in a vertical direction.The PBL frequently occurs at the same height (200–300m above ground)as the temperatur
e inversion layer.However,an incident occurred from midnight on January 17to dawn on January 18in which the height of the planetary boundary layer was approximately 130m.At this height,the PBL compresd the pollution in a confined space,restricting the vertical dispersion of the pollutants.As a result,a vere haze (Event 5)happened during this time.Interestingly,even when the lowest PBL occurred between midnight on January 17and dawn on January 18,the PM 2.5concentration was not at its peak.PBL plays an important role in the formation of a haze,but apparently not the only one.Combined with other factors (in other ctions of 3.2),low PBL drove the haze to a more vere situation.
High RH values normally occur at relatively low tempera-tures,which are clearly visible in Fig.4b.However,the RH from January 1to January 4was relatively low,which is illustrated by the blue color in Fig.4b.The combination of cold air,
low
necklace怎么读Fig.3.Pressure distributions at 3:00pm on January 6,6:00pm on January 17,0:00(midnight)on January19and 18:00pm on January 26,reprenting the Beijing region being controlled by a spar-isobar pressure,high-pressure center,intensive-isobar pressure and low-pressure center,respectively.
196Y.Yang et al./Atmospheric Rearch 155(2015)192–203
