陳 林 侯思齊 王煒罡 佟勝睿 裴克梅 葛茂發(fā),*

(1中國科學(xué)院化學(xué)研究所,分子動(dòng)態(tài)與穩(wěn)態(tài)結(jié)構(gòu)國家重點(diǎn)實(shí)驗(yàn)室,北京分子科學(xué)國家實(shí)驗(yàn)室,北京 100190;2浙江理工大學(xué)化學(xué)系,杭州 310018）

1 Introduction

Nitrous acid(HONO）is an important trace gas in tropospheric photochemistry,which plays a significant role in polluted urban atmosphere.1-3Furthermore,it is an important source of the primary oxidant in the atmosphere:the OH radical.

The diurnally averaged contributions to the OH budget of this reaction is up to 34%.1,2,4-9As one of the key species in photochemical cycles,OH radical can react with organic matters in a series of light oxidation process,which can lead to the formation of ozone,acetyl nitrate ester peroxide(PAN）,10and a large number of secondary pollutants and enhance the capacity of atmospheric oxidation.

However,due to the lack of measurements of HONO and its sources and sinks at higher altitudes above Earth′s surface,the overall effect of the proposed HONO sources and the mechanism of HONO formation in the troposphere remain widely unknown.11HONO can be emitted directly by motor vehicles.2Moreover,the gas phase reaction(Reaction 2）is an important source in forming HONO,5and this reaction plays a role mainly during daytime when OH and NO concentrations are high.The most generally accepted heterogeneous reaction source mechanisms mainly include heterogeneous hydrolysis of NO2on different humid surfaces,12and the reduction of NO2on soot particles and surfaces containing organic substrates.The heterogeneous reaction of NO2can occur on many different surfaces including mineral dust,soot,and building surfaces.5-8On the other hand,Su et al.13illustrated that the soil nitrite,which is formed by the biological nitrification and denitrification processes,can be a prominent HONO source.Unfortunately,direct emissions,gas phase formation as well as the heterogeneous reactions mentioned above cannot explain the enhancement of HONO during daytime.Therefore,it is extremely urgent to explore the daytime HONO source mechanism,and more comprehensive field and laboratory studies need to be performed,including direct HONO measurements.To develop fast and advanced instruments with high sensitivity and interference-free is the key task due to the very low daytime HONO concentration.14-16

Several approaches were developed for HONO monitoring in the atmosphere.Differential optical absorption spectroscopy(DOAS）17,18is the most established spectroscopy method.Besides DOAS,the Fourier transform infrared(FTIR）spectroscopy,19the tuneable diode laser spectroscopy,20the incoherent broadband cavity enhanced absorption spectroscopy,21the cavity ring down spectroscopy,22,23and the laser induced fluorescence(LIF）24are also used in HONO measurement.Wet-chemical methods are based on the detection of the nitrite ion after adsorption of HONO onto a solid surface(dry denuder）or water/aqueous solution,for example different types of wetted diffusion denuders that couple with ion chromatography systems,25-27HPLC-technique,28and fluorescence29,30stripping coil and ion chromatography,16and GAC(gas and aerosol collector with ion chromatography(IC））technique,31etc.One of the most successful wet-chemical method techniques is the long path absorption photometer(LOPAP）instrument,13,32-35which uses sulphanilamide in HCl to trap HONO in a short stripping coil.The external sampling module by excluding any inlet tubing can effectively minimize the sampling artifacts,and the interferences are removed by a two-channel instrument concept.

Typical HONO concentrations of Beijing were about 0.03×10-9to 1×10-9mol·mol-1in daytime.36-38Unexpected high daytime HONO levels(3.6×10-9mol·mol-1）were also reported at Beijing by Wu et al.,39While a maximum of 1.2×10-8mol·mol-1was also observed in Guangzhou40-43and 7×10-9mol·mol-1was measured in Shanghai,44which implied a strong unknown daytime HONO source.In this work a home-made LOPAP which uses wet chemical sampling and photometric detection to measure HONO was developed.It was designed to be a cheap,sensitive,compact,and continuously working equipment.In this paper,the principle of the home-made LOPAP is presented,moreover,quantification of probable interferences and field measurement are performed to demonstrate the application and problem of the instrument.

2 Experimental

2.1 LOPAP instrument

In this work,HONO is measured by a home-made LOPAP instrument,which is similar to recently developed instrument for the detection of HONO.The home-made LOPAP instrument consists of three modules,external sampling module,derivation module,and detection module.The setup of the instrument is shown in Fig.1.

2.1.1 External sampling module

HONO is sampled in a temperature controlled(293 K）doublewall stripping coil by chemical reaction in the stripping solution.The solution R1 contains 0.06 mol·L-1sulfanilamide(98%,Alfa Aesar）in 1 mol·L-1HCl(36%-38%,Alfa Aesar）.32,35HONO is almost completely sampled in R1,because of the rapid chemical conversion of HONO into a diazonium salt at low pH values(Reactions 3 and 4）.The sampling unit is placed directly in the atmosphere,which avoids the formation of HONO in sampling processes by using sampling lines.

Fig.1 Schematic setup of the LOPAP instrument

2.1.2 Derivation module

The solution is pumped by a peristaltic pump into the derivation unit,in which a 0.8 mmol·L-1N-(1-naphthyl）ethylenediaminedihydrochloride(96%,Alfa Aesar）(R2）is injected with the peristaltic pump to form the final azo dye during an appropriate residence time in a mixing volume(Reaction 5）.

2.1.3 Detection module

The azo dye solution was pumped into an absorption cell made in Teflon tubing and then detected with a mini-spectrometer by using a diode array detector(Ocean Optics,SD2000）.The absorption spectra were stored on a computer for later data analysis.

As shown in Fig.1,two stripping coils in series were used in the LOPAP instrument.The first coil(channel 1）took out almost all the HONO by a very fast selective chemical reaction with a small amount of interfering species.The second coil(channel 2）took out only interfering species which have low solubility in the very acidic condition(pH=0）without HONO.By subtracting the calibrated signal of the second channel from the calibrated signal in the first channel a better measure of the true HONO concentration was obtained,which was more accurate than using the signal of the first channel only.This setup minimized the occurrence of possible unknown interferences as observed for a wet effluent diffusion denuder.

2.2 Field measurement

The field measurement was performed from 29 August to 4 September 2013 at Institute of Chemistry,Chinese Academy of Sciences(ICCAS,39°59′22.68″N,116°19′21.58″E）,which is located at Hai Dian District of Beijing,near the North Fourth Ring Road with condensed population and transportation.The LOPAP instrument was installed in the third floor of the ICCAS lab building No.2,and the external sampling module was fixed at the platform outside.

The calibration of the instrument was performed every three days to correct small zero drifts,regular automatic zero measurement of 20 min was corrected every 12 h.Along with the HONO concentration,NO2was measured by NOxanalyzer(42i,Thermo,USA）and relative humidity(RH）was measured by using a humidity probe.

3 Results and discussion

3.1 Calibration

It was observed that the logarithm of the ratio of two intensities taken at different wavelengths in the same spectrum(Irefand Iabs）became a liner measure of the concentration c according to Lambert-Beers Law:

where,Iabswas the intensity taken at the maximum absorption at 550 nm and Irefwas the intensity taken at the point where no azo dye absorption at 650 nm with an absorption path length of approximately 250 and 50 cm.l was the absorption path length,and kλdenoted the absorption coefficient of the azo dye which is 5×104L·mol-1·cm-1at 544 nm.C is constant.

The calibration of the channels was performed with a series of standard nitrite solution in R1 at known amounts diluted by the original 1000 mg·L-1solution,while running under zero air.An example of the calibration of the two channels of the LOPAP instrument with different length optical cells is shown in Fig.2.The controlled gas flow rate during this calibration was 1 L·min-1.The corresponding liquid flow rates of R1 were 0.5 mL·min-1each in the two channels.In the case of these measurements,the calibration of the absorption in the two channels,as shown in Fig.2,can be described by the linear dependencies:

Fig.2 Example of a calibration of the prototype LOPAP instrument with a liquid nitrite

The obtained linear relation of the home-made LOPAP is good.In general,at least one calibration should be performed when changing either the channel of the peristaltic pump or solutions of R1 or R2.

3.2 Measurement parameter

With an optical path length of 250 cm,gas flow rate 1 L·min-1,liquid flow rate 0.5 mL·min-1,the instrument had a detection limit of 9×10-12mol·mol-1for a response time(the time of the instrument rising to 90%of the full signal）of 5 min.Here,the detection limit was defined as the mixing ratio calculated from three times the standard deviation of the intercept of the calibration curve.The sensitivity of the instrument was limited by gas flow rate and path length.Increasing gas flow rate will lead to HONO collection efficiency decreasing,and increasing path length will lead to intensity reductions.The response time depended on the volume of the absorption tubing and the liquid flow rate.

Table 1 summaries the measurement range,the detection limit,the response time,the precision,and accuracy of the LOPAP instrument.The detection limits were defined as the mixing ratios calculated from three times the standard deviation of the blank signals.32The relative overall uncertainties for each channel were calculated from the sum of the uncertainties of the gas flow rate,the liquid flow rate,and the uncertainty of the slope of the calibration fit.32

3.3 Interference

Particularly wet chemical instruments usually suffer from in-terferences,which make the quantification and correction of the interferences paramount important.Since the instrument was designed with two channels,interferences and all of the HONO were absorbed in channel 1,while only interferences were absorbed in channel 2.Therefore,the differences of the two channels were considered as the interference-free HONO under the assumption of a small uptake of these interferences were taken in the coils.

Table 1 Summary of parameters of the HONO-LOPAP instrument

In this part,interfering compounds were measured without HONO existing,and the interferences were given as the interference signal after the subtraction of channel 2 from channel 1 divided by the concentration of the interfering compounds(=100%×interference signal(subtraction）/ccompound）.32,34All values given in this part correspond to a gas flow rate of 1.0 L·min-1and a liquid flow rate of 0.5 mL·min-1in R1.

It is known that additional HONO was formed on the walls of the polyfluoroalkoxy(PFA）-tube before the gas inlet caused by heterogeneous reactions.In these cases,careful attention was drawn on removing the additional HONO(but not the species themselves）from the gas flow and keeping all tubes as short as possible.In these experiments,a NOxanalyzer(42i,Thermo,USA）,O3analyzer(49i,Thermo,USA）,and SO2-H2S analyzer(450i,Thermo,USA）were used.

3.3.1 NO interference

The pure NO interference was measured with a concentration of 3×10-7mol·mol-1diluted from a calibration gas mixture containing 1.5×10-5mol·mol-1in zero air.No significant interference signal was detected.

3.3.2 NO2interference

The NO2interference was measured with a concentration range from 1.25×10-7to 3×10-7mol·mol-1.The interference signal was about 5×10-12mol·mol-1.The interference after the subtraction of channel 2 from channel 1 was only 0.02%.

3.3.3 O3interference

The ozone interference was tested with pure ozone source of 2×10-7mol·mol-1,which was generated by zero air with a UV light.There was no significant interference signal detected in each channel,which means that the concentration of the ozone interference is below the detection limit.

3.3.4 O3+NO2interference

2×10-7mol·mol-1ozone in combination with 2×10-7mol·mol-1nitrogen dioxide was found to increase the NO2interference per channel.After the subtraction of channel 2 from channel 1,the interference was found to be similar to the pure NO2interference.

3.3.5 O3+HONO interference

The HONO source was generated by the reaction between sodium nitrite and excess dilute sulfuric acid in a coil.The 2×10-7mol·mol-1O3had hardly any influence on the HONO signal.

3.3.6 NO2+SO2interference

In the liquid phase,the reaction between NO2and SO2is an important interference in wet chemical methods.24Since the reaction between NO2and SO2mainly occurs on the wet surface,the interference of them can be minished by reducing pipe length.1×10-7mol·mol-1SO2in combination with 1×10-7mol·mol-1NO2were found no NO2interference signal changes per channel.After the subtraction of channel 2 from channel 1,the interference was found to be similar to the pure NO2interference.

Table 2 summarises interferences of the LOPAP instrument,and it was found that there were interference signals only when NO2existed and the value was 0.02%.

3.4 Field measurements

As we have seen from Fig.3,the concentration of HONO varied from 0.36×10-9mol·mol-1to 2.90×10-9mol·mol-1,which is similar to the range of concentration measured in Beijing.The concentrations of NO2were in the range of 1×10-8to 7×10-8mol·mol-1.The concentration of HONO had a clear diurnal variation.The maximum concentration of HONO appeared at 4:00 AM,after sunrise HONO concentration typically decreased due to thephotolysis of HONO.Moreover,there was a slight growth around 7:00 to 9:00 AM,which could be associated with the motor vehicle emissions.The main components of motor vehicle direct emission were NOx(NO and NO2）with HONO accounted for 1%of the NOx,and NO2could convert to HONO through the heterogenous reaction on wet surfaces,which will be explained in detail in below.The minimum concentration of HONO appeared after 14:00 to 17:00 PM,while the solar radiation intensity during that time was at high level.The relationship between HONO concentration and solar radiation intensity can be illustrated by Fig.4,when the solar radiation intensity was high,the concentration of HONO was at low level,while at night the situation was opposite.During the daytime,HONO was easily photolyzed under direct sunlight,thus the concentration was low;but during the night,without sunlight,HONO consumption was very slow,the HONO can accumulate until the next day before sunrise and reach maximum concentration.As the decreasing of the solar radiation intensity from 17:00 PM,HONO concentration increased again,which was contributed by traffic emission.

Table 2 Interferences of the LOPAP instrument obtained from laboratory measurements with typical operational conditions using a gas flow rate of 1.0 L·min-1 and a liquid flow rate of 0.5 mL·min-1

Fig.3 Time series of HONO with NO2

Fig.4 Temporal variations of HONO and NO2with the solar radiation

In addition,the ratio of HONO/NOxcan reflect the contribution of HONO concentration from the burning of fossil fuels and motor vehicle exhaust emissions.45Fig.4 shows that the variation trend between HONO concentration and the concentration ratio of HONO/NOxhas some differences,for example,the ratio of HONO/NOxdecreased while the HONO concentration was still at high level at 3:00 AM,and even during the daytime the variation trend was not fitting well.It implies that there were other sources of HONO besides direct emission,especially at night.Moreover,the ratio of HONO/NOxincreased during the traffic peak.

The ratio between HONO concentration from direct emission and total HONO concentration at night can be calculated by the formula below:46

where,HONOemis the concentration from burning of fossil fuels and motor vehicle exhaust emissions,the coefficient 0.0035 is from traffic tunnel field observation by Kirchstetter.46From the data of the night on September 3,the mean value of r at night was 10.6%with the maximum value 18.4%at 18:00 PM,which was consistent with the traffic peak.

As an important precursor of HONO,NO2can influence the generation of HONO.By analyzing the correlation between NO2and HONO at daytime and night,we found that the correlation coefficient(R2）between NO2and HONO was 0.00246 from 6:00 AM to 18:00 PM and 0.203 from 18:00 to 24:00 PM.However,these values were smaller than 0.429 obtained by Li et al.42measured at Pearl River Delta(PRD）,which demonstrates that the HONO source from heterogenous reaction of NO2was smaller.HONO/NO2is used to evaluate the HONO source from heterogenous reaction of NO2,which is little affected by transmission and convection in theory,except when the value of HONO concentration is high.From Fig.4,the ratio of HONO/NO2was varied from 0 to 8%,which was in accordance with 2%-10%obtained by other field measurements.47-50The ratio of HONO/NO2also had a clear diurnal variation,which was much smaller in daytime than that at night.It can be explained that the heterogenous reaction of NO2mainly occurred at night,which makes heterogenous reaction of NO2an important night source of HONO.In Gutzwiller et al.′s study,51the ratio of HONO/NO2in the atmosphere is usually 4%,and in their opinion this ratio could be explained by neither direct emission nor heterogenous reaction of NO2,in other words there must be other sources of HONO which contributed more than sources mentioned above.For example,photolysis reactions on the surface of the wet soot,photolysis of HNO3to generate HONO and NOx,might help to explain the unknown sources.48,49

4 Conclusions

Ahome-made long path absorption photometer(LOPAP）which uses wet chemical sampling and photometric detection to measure nitrous acid(HONO）has been developed and test.This instrument overcomes the known problems with current HONO measurement techniques and is a cheap,sensitive,compact,and continuously working HONO monitor for not only laboratory but also field studies.

The instrument includes two channels in external sampling module.By subtracting the signal of second channel from the first channel the occurrence of possible unknown interferences can be minimized.The instrument has a detection limit of 9×10-12mol·mol-1and an accuracy of 10%at 5 min response time,with a good linear relation.In addition,the probable interferences from NO,NO2,O3,NO2+O3,NO2+SO2,O3+HONO were tested.It was found that there was interference signal only when NO2existed and the value was 0.02%.With the instrument,six days′field observations were performed in Institute of Chemistry,Chinese Academy of Sciences,Beijing,from 29 August to 4 September,2013.The diurnal variation of concentration of HONO and the correlation between HONO concentration and solar radiation intensity,concentrations of NOxand NO2were obtained.Results from the ratio of HONO/NO2indicated unknown sources except heterogenous reaction of NO2.Furthermore,the LOPAP device can be transformed to detect other trace gases such as NO252and O353as well.

(1）Harris,G.W.;Carter,W.P.L.;Winer,A.M.;Pitts,J.N.;Platt,U.;Perner,D.Environ.Sci.Technol.1982,16,414.doi:10.1021/es00101a009

(2）Calvert,J.G.;Yarwood,G.;Dunker,A.M.Res.Chem.Intermed.1994,20,463.doi:10.1163/156856794X00423

(3）Zhu,C.Z.;Zhang,R.X.;Fang,H.J.;Zhao,Q.X.;Hou,H.Q.Acta Phys.-Chim.Sin.2005,21,367.[朱承駐,張仁熙,房豪杰,趙慶祥,侯惠奇.物理化學(xué)學(xué)報(bào),2005,21,367.]doi:10.3866/PKU.WHXB20050405

(4）Harrison,R.M.;Peak,J.D.;Collins,G.M.J.Geophys.Res.1996,101,14429.doi:10.1029/96JD00341

(5）Alicke,B.;Geyer,A.;Hofzumahaus,A.;Holland,F.;Konrad,S.;Patz,H.W.;Schafer,J.;Stutz,J.;Volz-Thomas,A.;Platt,U.J.Geophys.Res.2003,108,PHO 3-1

(6）Zhou,X.L.;Civerolo,K.;Dai,H.P.;Huang,G.;Schwab,J.;Demerjian,K.J.Geophys.Res.2002,107,ACH 13-1.

(7）Aumont,B.;Chervier,F.;Laval,S.Atmos.Environ.2003,37,487.doi:10.1016/S1352-2310(02）00920-2

(8）Acker,K.;Moller,D.;Auel,R.;Wieprecht,W.;Kalass,D.Atmos.Res.2005,74,507.doi:10.1016/j.atmosres.2004.04.009

(9）Kleffmann,J.;Gavriloaiei,T.;Hofzumahaus,A.;Holland,F.;Koppmann,R.;Rupp,L.;Schlosser,E.;Siese,M.;Wahner,A.Geophys.Res.Lett.2005,32.doi:10.1029/2005GL022524.

(10）Kleffmann,J.ChemPhysChem 2007,8,1137.

(11）Li,X.;Rohrer,F.;Hofzumahaus,A.;Brauers,T.;Haseler,R.;Bohn,B.;Broch,S.;Fuchs,H.;Gomm,S.;Holland,F.;Jager,J.;Kaiser,J.;Keutsch,F.,N.;Lohse,I.;Lu,K.D.;Tillmann,R.;Wegener,R.;Wolfe,G.M.;Mentel,T.F.;Kiendler-Scharr,A.;Wahner,A.Science 2014,344,292.doi:10.1126/science.1248999

(12）Finlayson-Pitts,B.J.;Wingen,L.M.;Sumner,A.L.;Syomin,D.;Ramazan,K.A.Phys.Chem.Chem.Phys.2003,5,223.doi:10.1039/b208564j

(13）Su,H.;Cheng,Y.;Oswald,R.;Behrendt,T.;Trebs,I.;Meixner,F.X.;Andreae,M.O.;Cheng,P.;Zhang,Y.;Poeschl,U.Science 2011,333,1616.doi:10.1126/science.1207687

(14）Spataro,F.;Ianniello,A.;Esposito,G.;Allegrini,I.;Zhu,T.;Hu,M.Sci.Total.Environ.2013,447,210.doi:10.1016/j.scitotenv.2012.12.065

(15）Li,L.;Zhang,H.;Ye,G.A.J.Radioanal.Nucl.Chem.2013,295,325.doi:10.1007/s10967-012-1833-8

(16）Cheng,P.;Cheng,Y.;Lu,K.;Su,H.;Yang,Q.;Zou,Y.;Zhao,Y.;Dong,H.;Zeng,L.;Zhang,Y.J.Environ.Sci-China 2013,25,895.doi:10.1016/S1001-0742(12）60251-4

(17）Platt,U.;Perner,D.;Patz,H.W.J.Geophys.Res.1979,84,6329.doi:10.1029/JC084iC10p06329

(18）Kurtenbach,R.;Becker,K.H.;Gomes,J.A.G.;Kleffmann,J.;Lorzer,J.C.;Spittler,M.;Wiesen,P.;Ackermann,R.;Geyer,A.;Platt,U.Atmos.Environ.2001,35,3385.doi:10.1016/S1352-2310(01）00138-8

(19）Ndour,M.;D′Anna,B.;George,C.;Ka,O.;Balkanski,Y.;Kleffmann,J.;Stemmler,K.;Ammann,M.Geophys.Res.Lett.2008,35,L05812.doi:10.1029/2007GL032006

(20）Schiller,C.L.;Locquiao,S.;Johnson,T.J.;Harris,G.W.J.Atmos.Chem.2001,40,275.doi:10.1023/A:1012264601306

(21）Gherman,T.;Venables,D.S.;Vaughan,S.;Orphal,J.;Ruth,A.A.Environ.Sci.Technol.2008,42,890.doi:10.1021/es0716913

(22）Wang,L.M.;Zhang,J.S.Environ.Sci.Technol.2000,34,4221.doi:10.1021/es0011055

(23）Zhang,J.S.;Wang,L.M.Abstr.Am.Chem.Soc.2000,219,U276.

(24）Liao,W.;Hecobian,A.;Mastromarino,J.;Tan,D.Atmos.Environ.2006,40,17.doi:10.1016/j.atmosenv.2005.07.001

(25）Simon,P.K.;Dasgupta,P.K.Environ.Sci.Technol.1995,29,1534.doi:10.1021/es00006a015

(26）Spindler,G.;Hesper,J.;Bruggemann,E.;Dubois,R.;Muller,T.;Herrmann,H.Atmos.Environ.2003,37,2643.doi:10.1016/S1352-2310(03）00209-7

(27）Acker,K.;Febo,A.;Trick,S.;Perrino,C.;Bruno,P.;Wiesen,P.;Moller,D.;Wieprecht,W.;Auel,R.;Giusto,M.;Geyer,A.;Platt,U.;Allegrini,I.Atmos.Environ.2006,40,3123.doi:10.1016/j.atmosenv.2006.01.028

(28）Beine,H.;Colussi,A.J.;Amoroso,A.;Esposito,G.;Montagnoli,M.;Hoffmann,M.R.Environmental Research Letters 2008,3,045005.doi:10.1088/1748-9326/3/4/045005

(29）Huang,G.;Zhou,X.L.;Deng,G.H.;Qiao,H.C.;Civerolo,K.Atmos.Environ.2002,36,2225.doi:10.1016/S1352-2310(02）00170-X

(30）Takenaka,N.;Terada,H.;Oro,Y.;Hiroi,M.;Yoshikawa,H.;Okitsu,K.;Bandow,H.Analyst 2004,129,1130.doi:10.1039/b407726a

(31）Dong,H.B.;Zeng,L.M.;Hu,M.;Wu,Y.S.;Zhang,Y.H.;Slanina,J.;Zheng,M.;Wang,Z.F.;Jansen,R.Atmos.Chem.Phys.2012,12,10519.doi:10.5194/acp-12-10519-2012

(32）Heland,J.;Kleffmann,J.;Kurtenbach,R.;Wiesen,P.Environ.Sci.Technol.2001,35,3207.doi:10.1021/es000303t

(33）Villena,G.;Kleffmann,J.;Kurtenbach,R.;Wiesen,P.;Lissi,E.;Rubio,M.A.;Croxatto,G.;Rappenglueck,B.Atmos.Environ.2011,45,3867.doi:10.1016/j.atmosenv.2011.01.073

(34）Kleffmann,J.;Heland,J.;Kurtenbach,R.;Lorzer,J.;Wiesen,P.Environ.Sci.Pollut.Res.2002,48.

(35）Kleffmann,J.;Lorzer,J.C.;Wiesen,P.;Kern,C.;Trick,S.;Volkamer,R.;Rodenas,M.;Wirtz,K.Atmos.Environ.2006,40,3640.doi:10.1016/j.atmosenv.2006.03.027

(36）An,J.;Zhang,W.;Qu,Y.Atmos.Environ.2009,43,3454.doi:10.1016/j.atmosenv.2009.04.052

(37）Hendrick,F.;Muller,J.F.;Clemer,K.;Wang,P.;De Maziere,M.;Fayt,C.;Gielen,C.;Hermans,C.;Ma,J.Z.;Pinardi,G.;Stavrakou,T.;Vlemmix,T.;Van Roozendael,M.Atmos.Chem.Phys.2014,14,765.doi:10.5194/acp-14-765-2014

(39）Wu,Z.;Hu,M.;Shao,K.;Slanina,J.Chemosphere 2009,76,1028.doi:10.1016/j.chemosphere.2009.04.066

(40）Qin,M.;Xie,P.;Su,H.;Gu,J.;Peng,F.;Li,S.;Zeng,L.;Liu,J.;Liu,W.;Zhang,Y.Atmos.Environ.2009,43,5731.doi:10.1016/j.atmosenv.2009.08.017

(41）Hao,N.;Zhou,B.;Chen,D.;Chen,L.M.J.Environ.Sci-China 2006,18,910.doi:10.1016/S1001-0742(06）60013-2

(42）Li,X.;Brauers,T.;Haeseler,R.;Bohn,B.;Fuchs,H.;Hofzumahaus,A.;Holland,F.;Lou,S.;Lu,K.D.;Rohrer,F.;Hu,M.;Zeng,L.M.;Zhang,Y.H.;Garland,R.M.;Su,H.;Nowak,A.;Wiedensohler,A.;Takegawa,N.;Shao,M.;Wahner,A.Atmos.Chem.Phys.2012,12,1497.doi:10.5194/acp-12-1497-2012

(43）Su,H.;Cheng,Y.F.;Cheng,P.;Zhang,Y.H.;Dong,S.;Zeng,L.M.;Wang,X.;Slanina,J.;Shao,M.;Wiedensohler,A.Atmos.Environ.2008,42,6219.doi:10.1016/j.atmosenv.2008.04.006

(44）Zhang,Y.H.;Su,H.;Zhong,L.J.;Cheng,Y.F.;Zeng,L.M.;Wang,X.S.;Xiang,Y.R.;Wang,J.L.;Gao,D.F.;Shao,M.;Fan,S.J.;Liu,S.C.Atmos.Environ.2008,42,6203.doi:10.1016/j.atmosenv.2008.05.002

(45）Kleffmann,J.;Kurtenbach,R.;Lorzer,J.;Wiesen,P.;Kalthoff,N.;Vogel,B.;Vogel,H.Atmos.Environ.2003,37,2949.doi:10.1016/S1352-2310(03）00242-5

(46）Kirchstetter,T.W.;Harley,R.A.Environ.Sci.Technol.1996,30,2843.doi:10.1021/es960135y

(47）Stutz,J.;Alicke,B.;Ackermann,R.;Geyer,A.;Wang,S.H.;White,A.B.;Williams,E.J.;Spicer,C.W.;Fast,J.D.J.Geophys.Res.2004,109,D03307.doi:10.1029/2003JD004135

(48）Febo,A.;Perrino,C.;Allegrini,I.Atmos.Environ.1996,30,3599.doi:10.1016/1352-2310(96）00069-6

(49）Alicke,B.;Platt,U.;Stutz,J.J.Geophys.Res.2002,107,D22.doi:10.1029/2000JD000075

(50）Zhou,X.;Huang,G.;Civerolo,K.;Roychowdhury,U.;Demerjian,K.L.J.Geophys.Res.2007,112,D08311.doi:10.1029/2006JD007256

(51）Gutzwiller,L.;Arens,F.;Baltensperger,U.;Gaggeler,H.W.;Ammann,M.Environ.Sci.Technol.2002,36,677.doi:10.1021/es015673b

(52）Villena,G.;Bejan,I.;Kurtenbach,R.;Wiesen,P.;Kleffmann,J.Atmos.Meas.Technol.2011,4,1663.doi:10.5194/amt-4-1663-2011

(53）Peters,S.;Bejan,I.;Kurtenbach,R.;Liedtke,S.;Villena,G.;Wiesen,P.;Kleffmann,J.Atmos.Environ.2013,67,112.doi:10.1016/j.atmosenv.2012.10.058