Environmental Processes
Subscriber access provided by FONDREN LIBRARY, RICE UNIVERSITY
Fast photochemistry in wintertime haze: Consequences for pollution mitigation strategies. Keding Lu, Hendrik Fuchs, Andreas Hofzumahaus, Zhaofeng Tan, Haichao Wang, Lin Zhang, Sebastian Schmitt, Franz Rohrer, Birger Bohn, Sebastian Broch, Huabin Dong, Georgios Gkatzelis, Thorsten Hohaus, Frank Holland, Xin Li, Ying Liu, Yuhan Liu, Xuefei Ma, Anna Novelli, Patrick Schlag, Min Shao, Yusheng Wu, Zhijun Wu, Limin Zeng, Min Hu, Astrid Kiendler-Scharr, Andreas Wahner, and Yuanhang Zhang Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.9b02422 • Publication Date (Web): 16 Aug 2019 Downloaded from pubs.acs.org on August 19, 2019
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 23
Environmental Science & Technology
and Pollution Control, College of Environmental Sciences and Engineering, Peking University Wu, Zhijun; Peking University, Zeng, Limin; Peking University, State Joint Key Laboratory of Environmental Simulation and Pollution Control Hu, Min; State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering Kiendler-Scharr, Astrid; Forschungszentrum Julich, Wahner, Andreas; Forschungszentrum Julich, Inst. Chemie und Dynamik der Geosphaere Zhang, Yuanhang; Peking University
ACS Paragon Plus Environment
Environmental Science & Technology
Page 2 of 23
1
Fast photochemistry in wintertime haze: Consequences for pollution
2
mitigation strategies.
3
Keding Lu1*, Hendrik Fuchs2, Andreas Hofzumahaus2, Zhaofeng Tan1,a, Haichao Wang1, Lin
4
Zhang3, Sebastian H. Schmitt2, Franz Rohrer2, Birger Bohn2, Sebastian Broch2, Huabin Dong1,
5
Georgios I. Gkatzelis2, Thorsten Hohaus2, Frank Holland2, Xin Li1, Ying Liu1, Yuhan Liu1, Xuefei
6
Ma1, Anna Novelli2, Patrick Schlag2,b, Min Shao1, Yusheng Wu1,c, Zhijun Wu1, Limin Zeng1, Min
7
Hu1, Astrid Kiendler-Scharr2, Andreas Wahner2, & Yuanhang Zhang1,4,5 *
8
1
9
Environmental Sciences and Engineering, Peking University, Beijing, China.
10
2
11
3
12 13
IEK-8: Troposphere, Forschungszentrum Jülich, Jülich, Germany. Laboratory for Climate and Ocean-Atmosphere Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China.
4 CAS
14 15
State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of
Center for Excellence in Regional Atmospheric Environment, Chinese Academy of Science,
Xiamen, China 5
16
Beijing Innovation Center for Engineering Sciences and Advanced Technology, Peking University, Beijing, China
17
a
18
bnow
at: Institute of Physics, University Sao Paulo, Sao Paulo, Brazil.
19
c now
at: Department of Physics, University of Helsinki, Helsinki, Finland.
now at: IEK-8: Troposphere, Forschungszentrum Jülich, Jülich, Germany.
20
1 ACS Paragon Plus Environment
Page 3 of 23
Environmental Science & Technology
21
ABSTRACT
22
In contrast to summer smog, the contribution of photochemistry to the formation of winter haze in
23
northern mid-to-high latitude is generally assumed to be minor due to reduced solar UV and water
24
vapor concentrations. Our comprehensive observations of atmospheric radicals and relevant
25
parameters during several haze events in winter 2016 Beijing, however, reveal surprisingly high
26
hydroxyl radical (OH) oxidation rates up to 15 ppbv/h which is comparable to the high values
27
reported in summer photochemical smog and is 2-3 times larger than those determined in previous
28
observations during winter in Birmingham1, Tokyo2, and New York3. The active photochemistry
29
facilitates the production of secondary pollutants. It is mainly initiated by the photolysis of nitrous
30
acid, ozonolysis of olefins and maintained by an extremely efficiently radical cycling process
31
driven by nitric oxide (NO). This boosted radical recycling generates fast photochemical ozone
32
production rates that are again comparable to those during summer photochemical smog. The
33
formation of ozone, however, is currently masked by its efficient chemical removal by nitrogen
34
oxides contributing to the high level of wintertime particles. The future emission regulations, such
35
as the reduction of nitrogen oxide emissions, therefore are facing the challenge of reducing haze
36
and avoiding an increase in ozone pollution at the same time. Efficient control strategies to mitigate
37
winter haze in Beijing may require measures similar as implemented to avoid photochemical smog
38
in summer.
39
INTRODUCTION
40
Winter haze formation has been experienced since the industrial revolution when more and more
41
people moved into urban areas especially in the cities at northern hemisphere mid-to-high latitude.
42
Taking Beijing, the capital city of China, for example, the number of winter haze days increased
43
dramatically in the last decade, e.g. the number of winter haze days in 2016 were about 20 days
44
more than experienced 20104. This change, to some extent, is thought to be related to warmer
45
temperature in winter due to global climate change, which leads to meteorological conditions that
46
favors stagnant conditions in this area5, 6. On a local scale, the winter haze is considered to be
47
primarily related to the intensified emissions from coal burning (energy and heating supply), traffic
48
and industry, that can accumulate under stagnant wind conditions (small southerly winds of about
49
1-2 m/s 7) and in a low boundary layer (height ca. 340 m 8). In addition, high moisture (RH up to
2 ACS Paragon Plus Environment
Environmental Science & Technology
Page 4 of 23
50
70-80%7) is experienced caused by the semi-closed terrain9, the warm cover structure in the middle
51
troposphere9, and even the heavy particle pollution itself10.
52
Nevertheless, as the winter haze is actually dominated (>50%) by secondary aerosols11, the
53
chemical reactions that are responsible for the conversion of high concentrations of primary air
54
pollutants to secondary pollutants are then of central interest for understanding winter haze
55
pollution. Due to the generally reduced solar UV and water vapor as well as the enhanced aerosol
56
liquid water, the contribution of the photochemistry is thought to be minor in the haze and the
57
heterogeneous reactions have been proposed to be most important for the formation of haze12, 13.
58
One of the major ingredients for haze, SO2, is emitted by coal burning. The mechanism for its
59
conversion to sulfate in the particles is under discussion and the opinions are quite controversial.
60
It is now proposed that SO2 is most likely oxidized by heterogeneous reactions on aerosol surfaces
61
or in the bulk of the deliquesced aerosols under neutralized conditions14, 15 while the aerosols are
62
more likely to be acidic16. Nevertheless, the contribution of sulfate to PM2.5 is currently only 10 -
63
20% due to the efficient reduction of SO2 emissions11, 17, 18.
64
The particulate nitrate and organic matters are the dominant portions in fine particles during
65
haze episodes in the recent years. As the particulate nitrate and organic compounds in aerosol are
66
mainly the result of photochemical oxidation of NOx and volatile organic compounds (VOCs), the
67
contribution of photochemistry to the formation of haze needs to be explored. It was reported for
68
the first time that significant high levels of OH radicals were present in the winter urban
69
atmosphere in a winter campaign with measurements of radicals in 2000 in Birmingham1. High
70
OH concentrations in that study give strong indication that photochemical processes can be
71
important for the formation of winter air pollution in mid-to-high latitude in the northern
72
hemisphere where strong emissions take place. Direct HOx measurements were also performed in
73
other mega-cities such as in Tokyo in January and February 20042, and in New York in January
74
and February 20043. In these three winter studies in urban atmosphere, relatively fast OH turnover
75
rates were deduced based on the measurements of OH and modeled or measured total OH
76
reactivity giving values of 5-8 ppbv/h around noon time. These values are lower than values
77
determined in summertime at the same locations1-3. In a study performed at a rural site in Colorado
78
in February 2011, the OH turnover rate was determined to be about 2 ppbv/h around noon time
79
from observed OH concentrations and calculated OH reactivity19, much lower than in the
80
campaigns in the urban environments. In recent studies, active photochemistry was found to be the 3 ACS Paragon Plus Environment
Page 5 of 23
Environmental Science & Technology
81
key for the formation of winter ozone pollution20 and haze21 in Utah due to the efficient
82
photochemistry in a low and stagnant atmospheric boundary layer.
83
Because radical precursors like nitrous acid was found to be abundant in winter in Beijing22,
84
a critical point to understand the winter haze formation mechanism is the determination of the role
85
of the photochemistry. In the present work, measurements were done with a comprehensive suite
86
of instruments available for studying photochemistry. The role of photochemical reactions in the
87
formation of fine particles and ozone in winter haze Beijing is determined.
88
METHODS
89
Field measurement campaign. The field campaign BEST-ONE (Beijing winter finE particulate
90
STudy - Oxidation, Nucleation and light Extinctions) was carried out from January 1st to March
91
5th 2016 on the campus of the University of the Chinese Academy of Sciences at Huairou (Figure
92
S1, 40.42°N, 116.69°E), which is located in a rural environment in the north of Beijing in the
93
North China Plain. The north and west of the site is surrounded by mountains. Without major
94
industry nearby, the area was only occasionally affected by local emissions from coal burning in
95
a village 1 km to the east. A large suite of atmospheric trace gas and radical concentrations, and
96
meteorological parameters were measured 20 m above the ground on top of a building (Table 1).
97
The local meteorological conditions were on average characterized by low temperatures (-3 6
98
oC)
99
haze events.
and low relative humidity, RH (36 18%). However, the RH increased to up to 80% during
100
Experimental. OH and HO2 radical concentrations were measured with a home-built instrument
101
utilizing pulsed laser-induced fluorescence (LIF) at 308 nm11. The instrument samples ambient air
102
by gas expansion into a low-pressure volume. At low pressure, OH is detected directly by LIF,
103
whereas HO2 is first chemically converted to OH by reaction with added NO. The measurements
104
of OH and HO2 are calibrated with a photochemical radical source which produces known radical
105
concentrations by photolysis of water vapour at 185 nm. Total OH reactivity (kOH), which is
106
equivalent to the inverse chemical OH lifetime, was measured by laser-photolysis laser induced
107
fluorescence (LP-LIF). For that purpose, OH radicals are produced in ambient air in a flow tube
108
by flash photolysis of ozone at 266 nm. The following OH decay due to reactions with atmospheric
109
reactants is monitored in real-time by LIF. The total OH reactivity is then obtained as a pseudo
110
first-order rate coefficient from the observed OH decay. In addition to the radical measurements, 4 ACS Paragon Plus Environment
Environmental Science & Technology
Page 6 of 23
111
a large suite of trace gases including O3, CO, NO, NO2, N2O5, HONO, HCHO, VOCs, etc were
112
measured locally near the inlets of the LIF instrument. Photolysis frequencies of O3 and NO2 were
113
determined from solar actinic flux spectra that were measured by spectroradiometry. Aerosol
114
chemical composition (< PM1.0) was measured using an Aerodyne High Resolution Time-of-Flight
115
Aerosol Mass Spectrometer (HR-ToF-AMS; short: AMS). The separation of primary and
116
secondary sources to the measured organic aerosol fraction from AMS was achieved by positive
117
matrix factorization. The ion balance of ammonium, nitrate and sulfate shows that sulfate and
118
nitrate explain the observed amount of ammonia. Further details of measurements of radicals, trace
119
gases and aerosols can be found in the Supporting information.
120
Calculations for the projection of NOx and VOC emission reduction strategies. The projection
121
of emission reduction strategies is achieved by calculating the production rates of particulate
122
nitrate and ozone in a chemical box model, in which VOC and NOx concentrations were varied.
123
The model is based on the Regional Atmospheric Chemical Mechanism version 2 (RACM-2)23
124
with modifications described in previous work24, 25. The model calculations were constrained to
125
chemical conditions as currently found in the haze event in this work using measurements of
126
HONO, NO2, CO, CH4, C2−C12 VOC and water vapor concentrations, as well as measured
127
photolysis frequencies, temperature and pressure. In order to realistically estimate the effect of
128
emission reductions, radical production was adjusted to reproduce formation rates as
129
experimentally found in this campaign.
130 131 132
The photochemical O3 formation rate, P(O3), is calculated from the NO2 production rate due to the reactions of peroxy radicals with NO. P(O3) = kHO2+NO[HO2][NO] + i kRO2i+NO[RO2i][NO]
Eq. 1
133
The rate constant kHO2+NO is taken from NASA JPL Publication 15-1026. For the reaction of RO2
134
with NO, rate constants (kRO2i+NO) and NO2 yields (i) are taken from RACM-2.
135 136
The potential for particulate nitrate formation, P(NO3-), is calculated from the partitioning between the gas and particle phase of HNO3 and the heterogeneous hydrolysis of N2O5.
137
P(NO3-) = kOH+NO2[OH][NO2] p + [N2O5] 0.25 𝐶N2O5 Sa 𝛾N2O5
138
HNO3 in the gas phase is mainly produced by the reaction of NO2 with OH. The rate
139
constant kOH+NO2 is taken from NASA JPL Publication 15-1026. Other gas-phase reactions such as
Eq. 2
5 ACS Paragon Plus Environment
Page 7 of 23
Environmental Science & Technology
140
HCHO + NO3, HO2 + NO, N2O5 + H2O that can form HNO3 can be neglected for the conditions
141
analyzed here27. The HNO3 uptake into the particle phase was implemented in the model in such
142
a way that the partitioning of HNO3 into the particle phase was 100% (p = 1). This is justified by
143
high partitioning ratio (> 0.96) of NO3- / (HNO3+NO3-) estimated from both the direct
144
measurements of the gaseous HNO3 and NO3- by a wet denuder system, GAC-IC (Table 1) and
145
the calculations from ISORRPIA-II. The NO3- in the particle phase must also be balanced by NH4+
146
ions, which requires that sufficiently high ammonia (NH3) was available. This is supported by the
147
high NH3 concentrations that were observed in the pollution episodes. In addition, high ammonium
148
concentrations in the particle phase were measured by the analysis of the chemical composition of
149
particles in the AMS. The ion balance between ammonium and nitrate and sulfate explains the
150
high ammonium concentrations, so that both, nitrate and sulfate, are full neutralized. For the
151
transfer of gaseous N2O5 into the particle phase an uptake coefficient (𝛾N2O5) of 0.003 was used,
152
derived from an iterative box model method28. The 𝐶N2O5 denotes the mean molecular speed of
153
N2O5 and Sa denotes the total surface area concentrations derived from the SMPS measurement
154
(Table 1).
155
Modelling of regional ozone production. The GEOS-Chem chemical transport model (v11-02;
156
www.geos-chem.org) is used to simulate the spatial and temporal distributions of ozone pollution
157
over North China. The model is driven by the NASA Goddard Earth Observing System (GEOS)
158
GEOS-FP assimilated meteorological data at a horizontal resolution of 0.25° latitude by 0.3125°
159
longitude. The simulation is conducted with the nested-grid GEOS-Chem model that has the native
160
0.25°×0.3125° horizontal resolution over East Asia with 3-hourly boundary conditions archived
161
from a global simulation at 2°×2.5° resolution. The model includes a detailed NOx–Ox–
162
hydrocarbon–aerosol tropospheric chemical mechanism, and accounts for heterogeneous uptake
163
of HO2, NO2, NO3, and N2O5 by aerosol surfaces29. Chinese Anthropogenic emissions are from
164
the Multi-resolution Emission Inventory for China (MEIC, http://www.meicmodel.org) for the
165
year 2015.
166
RESULTS AND DISCUSSION
167
Overview and Concept of Winter Photochemistry. Either the outflow of urban Beijing due to
168
southerly winds conditions or continental background air originating from Siberia due to strong
169
northerly winds were observed at the measurement site (Figure S2 - S5). In total, five haze 6 ACS Paragon Plus Environment
Environmental Science & Technology
Page 8 of 23
170
pollution events were captured with the full suite of measurement parameters. For each case
171
observed, the accumulations of the secondary pollutants were quite similar. The continental air
172
masses from the north flushed the site before the start of a haze event. Both the concentrations of
173
the primary air pollutants and PM2.5 were very small at the beginning. Under stagnant
174
meteorological conditions with slow southerly winds from the Beijing area secondary pollutants
175
increased quickly due to chemical reactions of primary air pollutants from regional emissions.
176
Finally, the haze was flushed away with again strong northerly wind ending the haze event within
177
a few hours. According to the measurement of the aerosol chemical compositions, the dominant
178
components of the fine particles during the haze conditions were nitrate and organics (Figure 1A).
179
Moreover, the co-enhancement of PM2.5 and the photochemistry indicators - peroxy acetyl nitrate
180
(PAN) and the total oxidant (Ox = O3 + NO2 + NOz, NOz = NOy - NOx) were continuously
181
observed (Figure S2). Both measurements strongly indicate that the particle pollution was
182
associated with atmospheric oxidation processes driven by photochemical smog reactions. Since
183
all haze events showed a similar characteristic (Figure 1 and Figure S6 - S9), results of the episode
184
are discussed in the following text when the highest aerosol load of up to 350 µg/m3 (PM2.5) was
185
experienced.
186
Due to the efficient emission control of SO2, the majority of particle mass in Beijing’s haze
187
events consists of organic compounds and nitrate11, 15, 17, 30 also found in the present study (Figure
188
1A and Figure S6A - S9A). Oxidized volatile organic compounds (VOCs) and nitrogen oxides
189
partitioning in the particulate phase are typically the result of photochemical activity. In wintertime,
190
however, solar radiation is weak due to the low sun and additionally due to the strong attenuation
191
by aerosol extinction in the haze event. Therefore, light-driven chemistry is generally assumed to
192
play a minor role in wintertime haze and different oxidation mechanisms in the aerosol aqueous
193
phase have been suggested to be responsible for the sulfate and nitrate observed in particles13-15.
194
In contrast, direct measurements in this study show that there is a surprisingly efficient
195
photochemical conversion of NOx and VOCs to compounds found in aerosol (Figure 2) during
196
Beijing's winter haze despite reduced solar radiation.
197
Fine Particle and the Total Oxidants. Starting on February 29th, the mass concentration of fine
198
particles (PM1) increased from a few g/m3 to up to 250 g/m3 on March 4th with a large fraction
199
of ammonium nitrate (> 50%, Figure 1A). The build-up of the particle mass took place
200
simultaneously with a gradual increase of total oxidants to over 100 ppbv. The total oxidant is the 7 ACS Paragon Plus Environment
Page 9 of 23
Environmental Science & Technology
201
sum of ozone, NO2 and the oxidized nitrogen species in the gas phase (NOz) derived from total
202
reactive nitrogen (NOy) and NOx measurements (Figure 1B), which were eventually formed from
203
emissions of nitric oxide (NO) (Figure 2). The nitrogen compounds included inorganic species like
204
N2O5 and HNO3, as well as organic compounds like PAN and other oxidized nitrogen compounds
205
(Figure S10). In contrast, the concentration of ozone was relatively small (< 40 ppbv), as it was a
206
major oxidant consumed in the production of oxidized nitrogen species (Figure 2). Moreover, an
207
analysis of the simultaneous measurements of PM2.5 and the total oxidants from the regional
208
network by Beijing Municipal Environmental Monitoring Center showed that the buildup of winter
209
haze accompanied by the accumulation of oxidants were also a regional phenomenon (Figure S11).
210
Trace gas removal and photochemical ozone productions. The impact of light extinction in the
211
accumulating haze is seen as a strong decline in the solar radiation and concentration of hydroxyl
212
radicals (OH) by a factor of 10 (Figure 1C). OH is the major atmospheric oxidant that controls the
213
chemical removal of atmospheric pollutants (e.g. CO, NO2, VOCs) thereby producing secondary
214
pollutants. The decrease in the OH concentration seems plausible because tropospheric OH is
215
generally formed by photolysis reactions. Therefore, low OH concentrations apparently support
216
the assumption that photochemistry plays a minor role during haze events13-15. However, the OH
217
concentration is also reduced due to an increasing rate of OH destruction by reactive gases that
218
accumulate during the haze event. The corresponding loss rate coefficient for OH, (total OH
219
reactivity, kOH), was directly measured in the campaign. Values increased from 5 s-1 in relative
220
clean air to up to 80 s-1 under highly polluted conditions (Figure 1D). The photochemical activity
221
of OH can be quantified by the product of the measured OH concentration and OH reactivity
222
([OH]kOH) which is equivalent to the oxidation rate of pollutants by reaction with OH.
223
Surprisingly, this rate increased from approximately 5 ppbv/h to 15 ppbv/h during the formation
224
of the haze (Figure 1E). The measured 3-fold increase demonstrates that the photochemical
225
conversion of emitted compounds into secondary pollutants was very active in the winter haze
226
with oxidation rates similar to values observed in summer in the NCP24, 31.
227
The oxidation by OH was so efficient because OH is quickly recycled in the reaction of
228
hydroperoxy (HO2) radicals with abundant NO from anthropogenic emissions. HO2 is either
229
directly produced from the reaction of OH with CO, or is produced in the reaction of NO with
230
organic peroxy radicals (RO2) resulting from the reaction of VOCs with OH. In the haze event,
8 ACS Paragon Plus Environment
Environmental Science & Technology
Page 10 of 23
231
OH recycling amplified the oxidation rate initiated by a weak primary OH production rate (0.6
232
ppbv/h) by a factor of 20 to 40. The amplification factor of the OH turnover rates is calculated as
233
the ratio of the secondary OH production rate due to the reaction of HO2 with NO relative to the
234
primary production rate of OH by ozonolysis of alkenes and photolysis of HONO and ozone. The
235
determined amplification factor (also known as chain length of the HOx cycle) is much longer than
236
found in previous winter campaigns when values varied between 4 to 7 in the urban areas1-3 and
237
were around 2 in a rural site19. The variation of the amplification factor is not proportional to the
238
changes in the VOCs to NOx ratio as seen in the different winter campaigns1-3, 19. The larger
239
amplification factor observed in this campaign compared to other winter studies indicates that the
240
photochemistry was exceptionally efficient in winter Beijing. These findings could not be
241
explained by chemical box models that use measured long-lived species (VOCs, and NOx, etc.) as
242
constraints25. In the global atmosphere, the most important primary source of OH is the reaction
243
of water vapor with excited state oxygen atoms from the UV-B photolysis of ozone32. In this winter
244
campaign, however, OH formation from ozone photolysis played a negligible role (
11 ACS Paragon Plus Environment
Page 13 of 23
Environmental Science & Technology
321
80 ppbv) along the Taihang Mountain south of Beijing and the Yanshan Mountain east of Beijing.
322
The mean photochemical ozone production rates during the haze event were highest in the cities
323
Beijing and Tianjian with values of up to 10 ppbv/h. In the southern part of Hebei, ozone
324
production was elevated (4 to 6 ppbv/h) compared to the north. The photochemistry in this model
325
is mainly driven by the production of radicals by the photolysis of HONO for wintertime
326
conditions. However, the mean photochemical ozone production rates at the measurement site
327
Huairou were a factor of two higher than modeled values likely due to missing radical sources25.
328
The underestimation of the ozone production rates by the model is also reflected in an
329
underestimation of the total oxidant concentration. The GEOS-Chem model indicates that the
330
measurement site is representative for a wide area in the North China Plain suggesting that current
331
chemical transport models do not well represent the fast-photochemical activity for wintertime
332
haze conditions.
333
As announced in the 13th Five-Year Plan, China's national air pollution control strategies
334
aim primarily at reducing emissions of NOx rather than of VOCs. This study demonstrates the
335
potential for an increase of ozone pollution in Beijing during wintertime in the future due to an
336
active photochemistry. The concurrent reduction of emissions of both, nitrogen oxides and organic
337
compounds, would not only improve air quality by reducing particle loads, but also avoid the risk
338
of ozone pollution (Figure 3) in wintertime. In addition, these measures would apply the entire
339
year and therefore reduce summertime ozone smog. As suggested by emission inventories41,42, the
340
most efficient target for regulations of winter air pollution control could be the vehicle emissions
341
which contribute the largest part of the nitrogen oxide and organic compound emissions in China.
342
The missing radical source is of urgent importance to be clarified to enabling the detailed policy
343
projection for the different geographic areas.
344
As a result of a comprehensive field campaign performed in winter in Beijing, we measured
345
unexpectedly fast wintertime ozone production which is comparably high as observed in
346
summertime photochemical smog. This fast production, however, does not lead to high ozone
347
concentrations, because it is chemically converted by nitrogen oxides and taken up by particles
348
enhancing severe wintertime haze events in Beijing. In addition, precursors of radical species
349
responsible for the ozone formation can be formed from heterogeneous chemistry on particle
350
surfaces, so that this reaction scheme is a self-energizing process. Therefore, wintertime haze in 12 ACS Paragon Plus Environment
Environmental Science & Technology
Page 14 of 23
351
Beijing could be regarded as a type of photochemical smog. Control strategy would need to be
352
similar as those applied to avoid summertime ozone pollution.
353 354
ASSOCIATED CONTENT
355
Supporting Information
356
Additional methods and thirteen additional figures (Figures S1 – S13).
357
AUTHOR INFORMATION
358
Corresponding Authors
359
E-mail:
[email protected] 360
E-mail:
[email protected] 361 362
ACKNOWLEDGMENTS
363
We thank the BEST-ONE campaign team, especially the local host - Prof. Dr. Y. X. Zhang, and
364
Mr. P. Huo for their technical help and full support at the field site. Discussions with Miss. L. Mao,
365
Mr. X. R. Chen and Dr. M. J. Tang are also appreciated. This work was supported by the National
366
Natural Science Foundation of China (Grants No. 91544225, 21522701, 21190052, 41375124),
367
the National Science and Technology Support Program of China (No. 2014BAC21B01), the
368
Strategic Priority Research Program of the Chinese Academy of Sciences (Grants No.
369
XDB05010500).
13 ACS Paragon Plus Environment
Page 15 of 23
Environmental Science & Technology
370 371
Figure 1. Atmospheric measurements during the haze event measured in Huairou (north of
372
Beijing) starting from clean air. Aerosol (PM1) chemical composition (A), ozone and nitrogen
373
oxide species resulting from ozone oxidation of NO emissions (NO2, higher gaseous oxidation
374
products NOz, particulate nitrate NO3-) (B), OH concentrations and solar UV-A intensity
375
represented as NO2 photolysis frequency (jNO2) (C), partitioning of the total OH reactivity (kOH) to
376
contribution from CO, NOX and organics (D), OH removal rate (kOH[OH]) (E), ozone production
377
rate (P(O3)) from the reaction of HO2 with NO that is equivalent to the OH recycling rate (F). The
378
total ozone production will be approximately twice a high due to the additional production from
379
the reaction of NO with RO2 whose concentration is typically as high as that of HO2 for high NO
380
concentrations. Grey shaded areas indicate nighttime. 14 ACS Paragon Plus Environment
Environmental Science & Technology
Page 16 of 23
Figure 2. Photochemical pathways mediating the transformation of emitted volatile organic compounds (VOC) and nitric oxide (NO) to particulate matter (PM). OH radicals produced by the photolysis of nitrous acid (HONO) and ozonolysis of alkenes react with VOCs and initiate the formation of oxygenated VOCs that contribute to the formation of organic aerosol (OA). NO2 is formed from the oxidation of NO in the reaction of ozone with peroxy radicals (HO2, RO2). During the day, NO2 reacts with OH to nitric acid (HNO3), which is efficiently converted into particulate nitrate (NO3-) with the participation of ammonia (NH3). Ozone produced by NO2 photolysis during the day is consumed by nightly oxidation of NO2 to N2O5, which adds to nitrate formation in the particle phase. 381
15 ACS Paragon Plus Environment
Page 17 of 23
Environmental Science & Technology
382 383
Figure 3. Projection of the impact of emission reductions for NOx and VOCs on the
384
photochemical production rates of the secondary pollutants for the conditions of the haze
385
event. (A) The daily integrated photochemical production rates of particulate nitrate, P(NO3-), (B)
386
the daily integrated production rates of ozone, P(O3).
16 ACS Paragon Plus Environment
Environmental Science & Technology
Page 18 of 23
387 388
Figure 4. Chemical transport model results for daytime averaged total concentrations of
389
ozone and oxidized nitrogen compounds (NO2 and NOz) (A) and the photochemical ozone
390
production rate (B) during the haze event (3rd and 4th March). The colored circles denote the
391
corresponding experimentally determined values at the Huairou site. The experimentally
392
determined ozone production rate is assumed to be twice as large as calculated from measured
393
HO2 and NO concentrations to account for ozone production from organic peroxy radicals which
394
concentration can be assumed to be similar as that of HO2.
395
17 ACS Paragon Plus Environment
Page 19 of 23
Environmental Science & Technology
396
Table 1. Overview of parameters of instruments for the detection of gas phase trace gas
397
concentrations, particle properties and physical parameters used for the analysis in this study. Species
Time resolution
Limit of Detection
Method
Accuracy (1 )
OH
30 s
0.8×106 cm-3
LIF
± 14%
HO2
30 s
0.2×108 cm-3
LIF
± 17%
kOH
90 s
0.3 s-1
LP – LIF
± 5-20%±0.7 s-1
N2O5
60 s
2 pptv
CEAS
± 19%
HONO
300 s
10 pptv
LOPAP
± 20%
HNO3
0.5 h
65 pptv
GAC
± 30%
HCHO
120 s
25 pptv
Hantzsch
± 5%
PAN
300 s
50 pptv
GC-ECD
± 10%
NH3
0.5 h
30 pptv
GAC
± 30%
O3
60 s
0.5 ppbv
UV
± 10%
CO
60 s
40 ppbv
NDIR
± 10%
SO2
60 s
0.1 ppbv
UV-F
± 10%
NO
60 s
50 pptv
CL
± 10%
NO2
60 s
50 pptv
Photolytic Conv. + CL
± 10%
NOy
60 s
50 pptv
Mo Conv. + CL
± 1%
VOCs
1h
5-70 pptv
GC-MS/FID
± 10-15%
Aerosol surface concentrations
300 s
--
SMPS, APS
± 30%
PM2.5
60 s
0.1 μg/m3
TEOM
± 10%
PM1.0 component
300 s
0.005-0.424 μg/m3
HR-ToF-AMS
± 30%
NO3- of PM2.5
0.5 h
0.034 μg/m3
GAC
± 10%
J-values
60 s
--
SR
± 10%
Temperature
60 s
-50°C - 50°C
Met One 083E
±0.1 °C
Pressure
60 s
600 - 1100 hPa
Met One 092
±0.35 hPa
Relative humidity
60 s
0 - 100%
Met One 083E
±2.0%
Wind speed
60 s
0.45 - 60 m/s
Met One 014A
± 0.11 m/s
Wind direction
60 s
0°- 360° m/s)
Met One 024A
±5°
(>0.45
398 18 ACS Paragon Plus Environment
Environmental Science & Technology
Page 20 of 23
399
References
400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442
1. Heard, D. E.; Carpenter, L. J.; Creasey, D. J.; Hopkins, J. R.; Lee, J. D.; Lewis, A. C.; Pilling, M. J.; Seakins, P. W.; Carslaw, N.; Emmerson, K. M., High levels of the hydroxyl radical in the winter urban troposphere. Geophys Res Lett 2004, 31, (18), Artn L18112. 2. Kanaya, Y.; Cao, R. Q.; Akimoto, H.; Fukuda, M.; Komazaki, Y.; Yokouchi, Y.; Koike, M.; Tanimoto, H.; Takegawa, N.; Kondo, Y., Urban photochemistry in central Tokyo: 1. Observed and modeled OH and HO2 radical concentrations during the winter and summer of 2004. Journal of Geophysical Research-Atmospheres 2007, 112, (D21), Artn D21312. 3. Ren, X. R.; Brune, W. H.; Mao, J. Q.; Mitchell, M. J.; Lesher, R. L.; Simpas, J. B.; Metcalf, A. R.; Schwab, J. J.; Cai, C. X.; Li, Y. Q.; Demerjian, K. L.; Felton, H. D.; Boynton, G.; Adams, A.; Perry, J.; He, Y.; Zhou, X. L.; Hou, J., Behavior of OH and HO2 in the winter atmosphere in New York city. Atmos Environ 2006, 40, S252-S263. 4. Mao, L.; Liu, R.; Liao, W.; Wang, X.; Shao, M.; Liu, S. C.; Zhang, Y., An observationbased perspective of winter haze days in four major polluted regions of China. National Science Review 2019, 6, (3), 515- 523. 5. Cai, W. J.; Li, K.; Liao, H.; Wang, H. J.; Wu, L. X., Weather conditions conducive to Beijing severe haze more frequent under climate change. Nat Clim Change 2017, 7, (4), 257262. 6. Zou, Y. F.; Wang, Y. H.; Zhang, Y. Z.; Koo, J. H., Arctic sea ice, Eurasia snow, and extreme winter haze in China. Sci Adv 2017, 3, (3), 1-8. 7. Wu, P.; Ding, Y. H.; Liu, Y. J., Atmospheric circulation and dynamic mechanism for persistent haze events in the Beijing-Tianjin-Hebei region. Advances in Atmospheric Sciences 2017, 34, (4), 429-440. 8. Zhong, J. T.; Zhang, X. Y.; Wang, Y. Q.; Sun, J. Y.; Zhang, Y. M.; Wang, J. Z.; Tan, K. Y.; Shen, X. J.; Che, H. C.; Zhang, L.; Zhang, Z. X.; Qi, X. F.; Zhao, H. R.; Ren, S. X.; Li, Y., Relative Contributions of Boundary-Layer Meteorological Factors to the Explosive Growth of PM2.5 during the Red-Alert Heavy Pollution Episodes in Beijing in December 2016. J Meteorol Res-Prc 2017, 31, (5), 809-819. 9. Zhu, W. H.; Xu, X. D.; Zheng, J.; Yan, P.; Wang, Y. J.; Cai, W. Y., The characteristics of abnormal wintertime pollution events in the Jing-Jin-Ji region and its relationships with meteorological factors. Science of the Total Environment 2018, 626, 887-898. 10. Zhong, J. T.; Zhang, X. Y.; Wang, Y. Q.; Wang, J. Z.; Shen, X. J.; Zhang, H. S.; Wang, T. J.; Xie, Z. Q.; Liu, C.; Zhang, H. D.; Zhao, T. L.; Sun, J. Y.; Fan, S. J.; Gao, Z. Q.; Li, Y. B.; Wang, L. L., The two-way feedback mechanism between unfavorable meteorological conditions and cumulative aerosol pollution in various haze regions of China. Atmos Chem Phys 2019, 19, (5), 3287-3306. 11. Huang, R. J.; Zhang, Y. L.; Bozzetti, C.; Ho, K. F.; Cao, J. J.; Han, Y. M.; Daellenbach, K. R.; Slowik, J. G.; Platt, S. M.; Canonaco, F.; Zotter, P.; Wolf, R.; Pieber, S. M.; Bruns, E. A.; Crippa, M.; Ciarelli, G.; Piazzalunga, A.; Schwikowski, M.; Abbaszade, G.; Schnelle-Kreis, J.; Zimmermann, R.; An, Z. S.; Szidat, S.; Baltensperger, U.; El Haddad, I.; Prevot, A. S. H., High secondary aerosol contribution to particulate pollution during haze events in China. Nature 2014, 514, (7521), 218-222. 12. Zheng, G. J.; Duan, F. K.; Su, H.; Ma, Y. L.; Cheng, Y.; Zheng, B.; Zhang, Q.; Huang, T.; Kimoto, T.; Chang, D.; Poschl, U.; Cheng, Y. F.; He, K. B., Exploring the severe winter haze
19 ACS Paragon Plus Environment
Page 21 of 23
443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487
Environmental Science & Technology
in Beijing: the impact of synoptic weather, regional transport and heterogeneous reactions. Atmos Chem Phys 2015, 15, (6), 2969-2983. 13. Li, L. J.; Hoffmann, M. R.; Colussi, A. J., Role of Nitrogen Dioxide in the Production of Sulfate during Chinese Haze-Aerosol Episodes. Environ Sci Technol 2018, 52, (5), 2686-2693. 14. Cheng, Y. F.; Zheng, G. J.; Wei, C.; Mu, Q.; Zheng, B.; Wang, Z. B.; Gao, M.; Zhang, Q.; He, K. B.; Carmichael, G.; Poschl, U.; Su, H., Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China. Sci Adv 2016, 2, (12),1-11. 15. Wang, G. H.; Zhang, R. Y.; Gomez, M. E.; Yang, L. X.; Zamora, M. L.; Hu, M.; Lin, Y.; Peng, J. F.; Guo, S.; Meng, J. J.; Li, J. J.; Cheng, C. L.; Hu, T. F.; Ren, Y. Q.; Wang, Y. S.; Gao, J.; Cao, J. J.; An, Z. S.; Zhou, W. J.; Li, G. H.; Wang, J. Y.; Tian, P. F.; Marrero-Ortiz, W.; Secrest, J.; Du, Z. F.; Zheng, J.; Shang, D. J.; Zeng, L. M.; Shao, M.; Wang, W. G.; Huang, Y.; Wang, Y.; Zhu, Y. J.; Li, Y. X.; Hu, J. X.; Pan, B.; Cai, L.; Cheng, Y. T.; Ji, Y. M.; Zhang, F.; Rosenfeld, D.; Liss, P. S.; Duce, R. A.; Kolb, C. E.; Molina, M. J., Persistent sulfate formation from London Fog to Chinese haze. P Natl Acad Sci USA 2016, 113, (48), 13630-13635. 16. Guo, H. Y.; Weber, R. J.; Nenes, A., High levels of ammonia do not raise fine particle pH sufficiently to yield nitrogen oxide-dominated sulfate production. Sci Rep-Uk 2017, 7, Artn 12109. 17. Guo, S.; Hu, M.; Zamora, M. L.; Peng, J. F.; Shang, D. J.; Zheng, J.; Du, Z. F.; Wu, Z.; Shao, M.; Zeng, L. M.; Molina, M. J.; Zhang, R. Y., Elucidating severe urban haze formation in China. P Natl Acad Sci USA 2014, 111, (49), 17373-17378. 18. Xu, W. Q.; Sun, Y. L.; Wang, Q. Q.; Zhao, J.; Wang, J. F.; Ge, X. L.; Xie, C. H.; Zhou, W.; Du, W.; Li, J.; Fu, P. Q.; Wang, Z. F.; Worsnop, D. R.; Coe, H., Changes in Aerosol Chemistry From 2014 to 2016 in Winter in Beijing: Insights From High-Resolution Aerosol Mass Spectrometry. Journal of Geophysical Research-Atmospheres 2019, 124, (2), 1132-1147. 19. Kim, S.; VandenBoer, T. C.; Young, C. J.; Riedel, T. P.; Thornton, J. A.; Swarthout, B.; Sive, B.; Lerner, B.; Gilman, J. B.; Warneke, C.; Roberts, J. M.; Guenther, A.; Wagner, N. L.; Dube, W. P.; Williams, E.; Brown, S. S., The primary and recycling sources of OH during the NACHTT-2011 campaign: HONO as an important OH primary source in the wintertime. J Geophys Res-Atmos 2014, 119, (11), 6886-6896. 20. Edwards, P. M.; Brown, S. S.; Roberts, J. M.; Ahmadov, R.; Banta, R. M.; deGouw, J. A.; Dube, W. P.; Field, R. A.; Flynn, J. H.; Gilman, J. B.; Graus, M.; Helmig, D.; Koss, A.; Langford, A. O.; Lefer, B. L.; Lerner, B. M.; Li, R.; Li, S. M.; McKeen, S. A.; Murphy, S. M.; Parrish, D. D.; Senff, C. J.; Soltis, J.; Stutz, J.; Sweeney, C.; Thompson, C. R.; Trainer, M. K.; Tsai, C.; Veres, P. R.; Washenfelder, R. A.; Warneke, C.; Wild, R. J.; Young, C. J.; Yuan, B.; Zamora, R., High winter ozone pollution from carbonyl photolysis in an oil and gas basin. Nature 2014, 514, (7522), 351-354. 21. Womack, C. C.; MeDuffie, E. E.; Edwards, P. M.; Bares, R.; de Gouw, J. A.; Docherty, K. S.; Dube, W. P.; Fibiger, D. L.; Franchin, A.; Gilman, J. B.; Goldberger, L.; Lee, B. H.; Lin, J. C.; Lone, R.; Middlebrook, A. M.; Millet, D. B.; Moravek, A.; Murphy, J. G.; Quinn, P. K.; Riedel, T. P.; Roberts, J. M.; Thornton, J. A.; Valin, L. C.; Veres, P. R.; Whitehill, A. R.; Wild, R. J.; Warneke, C.; Yuan, B.; Baasandorj, M.; Brown, S. S., An Odd Oxygen Framework for Wintertime Ammonium Nitrate Aerosol Pollution in Urban Areas: NOx and VOC Control as Mitigation Strategies. Geophysical Research Letters 2019, 46, (9), 4971-4979. 22. Hendrick, F.; Müller, J. F.; Clémer, K.; Wang, P.; De Mazière, M.; Fayt, C.; Gielen, C.; Hermans, C.; Ma, J. Z.; Pinardi, G.; Stavrakou, T.; Vlemmix, T.; Van Roozendael, M., Four
20 ACS Paragon Plus Environment
Environmental Science & Technology
488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532
Page 22 of 23
years of ground-based MAX-DOAS observations of HONO and NO2 in the Beijing area. Atmos. Chem. Phys. 2014, 14, (2), 765-781. 23. Goliff, W. S.; Stockwell, W. R.; Lawson, C. V., The regional atmospheric chemistry mechanism, version 2. Atmos Environ 2013, 68, 174-185. 24. Tan, Z.; Fuchs, H.; Lu, K.; Hofzumahaus, A.; Bohn, B.; Broch, S.; Dong, H.; Gomm, S.; Häseler, R.; He, L.; Holland, F.; Li, X.; Liu, Y.; Lu, S.; Rohrer, F.; Shao, M.; Wang, B.; Wang, M.; Wu, Y.; Zeng, L.; Zhang, Y.; Wahner, A.; Zhang, Y., Radical chemistry at a rural site (Wangdu) in the North China Plain: observation and model calculations of OH, HO2 and RO2 radicals. Atmos. Chem. Phys. 2017, 17, (1), 663-690. 25. Tan, Z. F.; Rohrer, F.; Lu, K. D.; Ma, X. F.; Bohn, B.; Broch, S.; Dong, H. B.; Fuchs, H.; Gkatzelis, G. I.; Hofzumahaus, A.; Holland, F.; Li, X.; Liu, Y.; Liu, Y. H.; Novelli, A.; Shao, M.; Wang, H. C.; Wu, Y. S.; Zeng, L. M.; Hu, M.; Kiendler-Scharr, A.; Wahner, A.; Zhang, Y. H., Wintertime photochemistry in Beijing: observations of ROx radical concentrations in the North China Plain during the BEST-ONE campaign. Atmos Chem Phys 2018, 18, (16), 1239112411. 26. Burkholder, J. B., Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies. 2015, http://jpldataeval.jpl.nasa.gov. 27. Wang, H. C.; Lu, K. D.; Chen, X. R.; Zhu, Q. D.; Chen, Q.; Guo, S.; Jiang, M. Q.; Li, X.; Shang, D. J.; Tan, Z. F.; Wu, Y. S.; Wu, Z. J.; Zou, Q.; Zheng, Y.; Zeng, L. M.; Zhu, T.; Hu, M.; Zhang, Y. H., High N2O5 Concentrations Observed in Urban Beijing: Implications of a Large Nitrate Formation Pathway. Environ Sci Tech Let 2017, 4, (10), 416-420. 28. Wagner, N. L.; Riedel, T. P.; Young, C. J.; Bahreini, R.; Brock, C. A.; Dube, W. P.; Kim, S.; Middlebrook, A. M.; Ozturk, F.; Roberts, J. M.; Russo, R.; Sive, B.; Swarthout, R.; Thornton, J. A.; VandenBoer, T. C.; Zhou, Y.; Brown, S. S., N2O5 uptake coefficients and nocturnal NO2 removal rates determined from ambient wintertime measurements. J Geophys Res-Atmos 2013, 118, (16), 9331-9350. 29. Li, K.; Jacob, D. J.; Liao, H.; Shen, L.; Zhang, Q.; Bates, K. H., Anthropogenic drivers of 2013-2017 trends in summer surface ozone in China. P Natl Acad Sci USA 2019, 116, (2), 422427. 30. Zhang, R. Y.; Wang, G. H.; Guo, S.; Zarnora, M. L.; Ying, Q.; Lin, Y.; Wang, W. G.; Hu, M.; Wang, Y., Formation of Urban Fine Particulate Matter. Chem Rev 2015, 115, (10), 3803-3855. 31. Lu, K. D.; Hofzumahaus, A.; Holland, F.; Bohn, B.; Brauers, T.; Fuchs, H.; Hu, M.; Haseler, R.; Kita, K.; Kondo, Y.; Li, X.; Lou, S. R.; Oebel, A.; Shao, M.; Zeng, L. M.; Wahner, A.; Zhu, T.; Zhang, Y. H.; Rohrer, F., Missing OH source in a suburban environment near Beijing: observed and modelled OH and HO2 concentrations in summer 2006. Atmos Chem Phys 2013, 13, (2), 1057-1080. 32. Levy, H., Normal Atmosphere - Large Radical and Formaldehyde Concentrations Predicted. Science 1971, 173, (3992), 141-143. 33. Kanaya, Y.; Cao, R. Q.; Akimoto, H.; Fukuda, M.; Komazaki, Y.; Yokouchi, Y.; Koike, M.; Tanimoto, H.; Takegawa, N.; Kondo, Y., Urban photochemistry in central Tokyo: 1. Observed and modeled OH and HO2 radical concentrations during the winter and summer of 2004. J Geophys Res-Atmos 2007, 112, (D21), Artn D21312. 34. Wu, Z. J.; Wang, Y.; Tan, T. Y.; Zhu, Y. S.; Li, M. R.; Shang, D. J.; Wang, H. C.; Lu, K. D.; Guo, S.; Zeng, L. M.; Zhang, Y. H., Aerosol Liquid Water Driven by Anthropogenic
21 ACS Paragon Plus Environment
Page 23 of 23
533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569
Environmental Science & Technology
Inorganic Salts: Implying Its Key Role in Haze Formation over the North China Plain. Environ Sci Tech Let 2018, 5, (3), 160-166. 35. Sun, J. X.; Liu, L.; Xu, L.; Wang, Y. Y.; Wu, Z. J.; Hu, M.; Shi, Z. B.; Li, Y. J.; Zhang, X. Y.; Chen, J. M.; Li, W. J., Key Role of Nitrate in Phase Transitions of Urban Particles: Implications of Important Reactive Surfaces for Secondary Aerosol Formation. Journal of Geophysical Research-Atmospheres 2018, 123, (2), 1234-1243. 36. Liu, Y. C.; Wu, Z. J.; Wang, Y.; Xiao, Y.; Gu, F. T.; Zheng, J.; Tan, T. Y.; Shang, D. J.; Wu, Y. S.; Zeng, L. M.; Hu, M.; Bateman, A. P.; Martin, S. T., Submicrometer Particles Are in the Liquid State during Heavy Haze Episodes in the Urban Atmosphere of Beijing, China. Environ Sci Tech Let 2017, 4, (10), 427-432. 37. Thornton, J. A.; Kercher, J. P.; Riedel, T. P.; Wagner, N. L.; Cozic, J.; Holloway, J. S.; Dube, W. P.; Wolfe, G. M.; Quinn, P. K.; Middlebrook, A. M.; Alexander, B.; Brown, S. S., A large atomic chlorine source inferred from mid-continental reactive nitrogen chemistry. Nature 2010, 464, (7286), 271-274. 38. Odum, J. R.; Jungkamp, T. P. W.; Griffin, R. J.; Flagan, R. C.; Seinfeld, J. H., The atmospheric aerosol-forming potential of whole gasoline vapor. Science 1997, 276, (5309), 9699. 39. Jimenez, J. L.; Canagaratna, M. R.; Donahue, N. M.; Prevot, A. S. H.; Zhang, Q.; Kroll, J. H.; DeCarlo, P. F.; Allan, J. D.; Coe, H.; Ng, N. L.; Aiken, A. C.; Docherty, K. S.; Ulbrich, I. M.; Grieshop, A. P.; Robinson, A. L.; Duplissy, J.; Smith, J. D.; Wilson, K. R.; Lanz, V. A.; Hueglin, C.; Sun, Y. L.; Tian, J.; Laaksonen, A.; Raatikainen, T.; Rautiainen, J.; Vaattovaara, P.; Ehn, M.; Kulmala, M.; Tomlinson, J. M.; Collins, D. R.; Cubison, M. J.; Dunlea, E. J.; Huffman, J. A.; Onasch, T. B.; Alfarra, M. R.; Williams, P. I.; Bower, K.; Kondo, Y.; Schneider, J.; Drewnick, F.; Borrmann, S.; Weimer, S.; Demerjian, K.; Salcedo, D.; Cottrell, L.; Griffin, R.; Takami, A.; Miyoshi, T.; Hatakeyama, S.; Shimono, A.; Sun, J. Y.; Zhang, Y. M.; Dzepina, K.; Kimmel, J. R.; Sueper, D.; Jayne, J. T.; Herndon, S. C.; Trimborn, A. M.; Williams, L. R.; Wood, E. C.; Middlebrook, A. M.; Kolb, C. E.; Baltensperger, U.; Worsnop, D. R., Evolution of Organic Aerosols in the Atmosphere. Science 2009, 326, (5959), 1525-1529. 40. Ehhalt, D. H., Photooxidation of trace gases in the troposphere. Phys Chem Chem Phys 1999, 1, (24), 5401-5408. 41. Wu, R. R.; Xie, S. D., Spatial Distribution of Ozone Formation in China Derived from Emissions of Speciated Volatile Organic Compounds. Environ Sci Technol 2017, 51, (5), 25742583. 42. Yang, X. F.; Liu, H.; Man, H. Y.; He, K. B., Characterization of road freight transportation and its impact on the national emission inventory in China. Atmos Chem Phys 2015, 15, (4), 2105-2118.
570
22 ACS Paragon Plus Environment
Environmental Science & Technology
ACS Paragon Plus Environment
Page 24 of 23