<figure><img src="image_1.png" /></figure>

HAL
open science

# Strong impacts of biomass burning, nitrogen fertilization, and fine particles on gas-phase hydrogen peroxide (H2O2)

Can Ye, Chaoyang Xue, Pengfei Liu, Chenglong Zhang, Zhuobiao Ma, Yuanyuan Zhang, Chengtang Liu, Junfeng Liu, Keding Lu, Yujing Mu

<figure><img src="image_2.png" /></figure>

## ► To cite this version:

Can Ye, Chaoyang Xue, Pengfei Liu, Chenglong Zhang, Zhuobiao Ma, et al.. Strong impacts of biomass burning, nitrogen fertilization, and fine particles on gas-phase hydrogen peroxide (H2O2). Science of the Total Environment, 2022, 843, pp.156997. 10.1016/j.scitotenv.2022.156997. insu-04046942

HAL Id: insu-04046942

https://insu.hal.science/insu-04046942v1

Submitted on 27 Sep 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_3.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
1 Strong Impacts of Biomass Burning, Nitrogen Fertilization, and Fine

2 Particles on Gas-phase Hydrogen Peroxide (H₂O₂)

3 Can Ye¹,², Chaoyang Xue³*, Pengfei Liu¹,⁴,⁵, Chenglong Zhang¹,⁴,⁵, Zhuobiao Ma¹,⁴,⁵, Yuanyuan

4 Zhang¹,⁴,⁵, Chengtang Liu¹,⁴,⁵, Junfeng Liu¹,⁴,⁵, Keding Lu², Yujing Mu¹,⁴,⁵*.

5 ¹Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China

6 ²State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and

7 Engineering, Peking University, Beijing 100871, China.

8 ³Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), CNRS – Université Orléans – CNES,

9 45071 Orléans Cedex 2, France

10 ⁴Centre for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of

11 Sciences, Xiamen 361021, China

12 ⁵University of Chinese Academy of Sciences, Beijing 100049, China

13

14 Correspondence to: Chaoyang Xue (chaoyang.xue@cnrs-orleans.fr), Yujing Mu (yjmu@rcees.ac.cn)

15 **Abstract.** Gas-phase hydrogen peroxide (H₂O₂) plays an important role in atmospheric chemistry as an indicator of the atmospheric oxidizing capacity. It is also a vital oxidant of sulfur dioxide (SO₂) in the aqueous phase, resulting in the formation of acid precipitation and sulfate aerosol. However, sources of H₂O₂ are not fully understood especially in polluted areas affected by human activities. In this study, we reported some high H₂O₂ cases observed during one summer and two winter campaigns conducted at a polluted rural site in the North China Plain. Our results showed that agricultural fires led to high H₂O₂ concentrations up to 9 ppb, indicating biomass burning events contributed substantially to primary H₂O₂ emission. In addition, elevated H₂O₂ and O₃ concentrations were measured after
22 fertilization as a consequence of the enhanced atmospheric oxidizing capacity by soil HONO emission. Furthermore, 23 H₂O₂ exhibited unexpectedly high concentration under high NOₓ conditions in winter, which are closely related to 24 multiphase reactions in particles involving organic chromophores. Our findings suggest that these special factors 25 (biomass burning, fertilization, and ambient particles), which are not well considered in current models, are significant 26 contributors to H₂O₂ production, thereby affecting the regional atmospheric oxidizing capacity and the global sulfate 27 aerosol formation. 28

29 Key words: H₂O₂, biomass burning, fertilization, particles, organic chromophores 30

31 Highlights

32 ● Biomass burning events led to high H₂O₂ concentrations up to 9 ppb observed.

33 ● H₂O₂ and O₃ were greatly enhanced after fertilization events due to HONO emission by fertilized soil.

34 ● Particle-phase reactions involving organic chromophores contributed to H₂O₂ production.

35 Graphical abstract

<figure><img src="image_4.png" /></figure>
Atmospheric hydrogen peroxide ($H_2O_2$) acts as a temporary reservoir of $HO_x$ ($OH+HO_2$) radicals and hence an indicator of the oxidizing capacity of the atmosphere. Besides, $H_2O_2$ itself is one of the most important oxidants in the atmosphere and can oxidize $SO_2$ in clouds, droplets, and deliquesced particles (Penkett et al., 1979; Calvert and Stockwell, 1983), with the formation of sulfate, an important component of fine particulate matter that impacts air quality, climate, and human health (Grantz et al., 2003; Nel, 2005; Fuzzi et al., 2015). Furthermore, $H_2O_2/HNO_3$ was suggested as a robust indicator to determine whether ozone production is more sensitive to $NO_x$ or VOCs (Sillman, 1995; Sillman et al., 1998). Vermeuel et al. (2019) evaluated the sensitivity of $O_3$ to VOCs and $NO_x$ alongside the Lake Michigan Coastline utilizing the modeled ratio of $H_2O_2$ and $HNO_3$ production rates. Results indicated that the $O_3$ production was strongly VOC-limited in the urban areas and became more $NO_x$-limited as the plume advected North. As $O_3$ pollution is becoming a big concern with increase of $NO_x$ and VOCs emissions (Tan et al., 2018; Yu et al., 2020), $H_2O_2$ has drawn more attention in both urban and rural areas.

$$50 \quad HO_2 + HO_2 \rightarrow H_2O_2 \qquad R1$$

$$51 \quad k_{R1}=1.5 \times 10^{-12} \text{ cm}^3 \text{ molecule}^{-1} \text{ s}^{-1} \text{ at } 298 \text{ K}$$

$$52 \quad HO_2 + NO \rightarrow NO_2 + OH \qquad R2$$

$$53 \quad k_{R2}=8.9 \times 10^{-12} \text{ cm}^3 \text{ molecule}^{-1} \text{ s}^{-1} \text{ at } 298 \text{ K}$$

Based on the current understanding, $H_2O_2$ is mainly produced by the self-reaction of two hydroperoxy radicals ($HO_2$) (R1), which are produced from the oxidation of hydrocarbons by OH radicals or the photolysis of formaldehyde. R1 largely depends on ambient $NO_x$ levels. With high $NO_x$ levels, R2 would dominate relative to R1 due to more rapid $HO_2$ consumption through R2. For example, with typical noontime NO concentration of 1 ppb and $HO_2$ concentration of $4 \times 10^7$ molecules cm$^{-3}$ observed or modelled in the winter NCP (Ma et al., 2019; Slater et al., 2020; Xue et al., 2020), $HO_2$ loss rate through R2 ($8.4 \times 10^6$ molecules cm$^{-3}$ s$^{-1}$) is 3 orders of magnitude faster than that of R1 ($2.6 \times 10^3$ molecules cm$^{-3}$ s$^{-1}$). Field measurements also supported that under the condition of NO concentrations exceeding 1
ppb, H₂O₂ production through R1 will be substantially suppressed (Walker et al., 2006; He et al., 2010; Watanabe et al., 2018). Besides the H₂O₂ formation channel through R1, ozonolysis of alkenes also contributes to H₂O₂ production, which could proceed without sunlight (Becker et al., 1990; Hua et al., 2008). The main sinks of H₂O₂ include photolysis, dry deposition, reaction with OH radicals, and reaction with SO₂ in the liquid phase. The typical photolysis rate of H₂O₂ daily maximum value is 6.0×10⁻⁶ s⁻¹ in the northern midlatitude (Stockwell et al., 1997), corresponding to τphoto=46 h (lifetime against photolysis). As for the reaction of H₂O₂ with OH radicals, the rate constant is 1.7×10⁻¹² cm³ molecule⁻¹ s⁻¹ at 298 K (Atkinson et al., 2004), and the temperature influence on the rate constant is small. τH₂O₂ (lifetime with respect to OH reaction) is estimated to be around 32 h if OH concentration is assumed to be 5 × 10⁶ molecule cm⁻³. Assuming the dry deposition velocity of H₂O₂ is about 2 cm s⁻¹ (Liang et al., 2013), the lifetime of H₂O₂ with respect to dry deposition is 7 h with a boundary height of 1 km. Therefore, dry deposition loss was a dominant factor influencing the lifetime of H₂O₂ in the atmosphere.

H₂O₂ formation does not only depend on NOₓ levels, which was discussed earlier but also as a function of many other chemical and physical parameters. First of all, H₂O₂ concentrations are affected by precursors concentrations like VOCs. High VOC to NOₓ ratio leads to more HO₂ production, in favor of the production of H₂O₂ (Lee et al., 2008; Crowley et al., 2018). O₃ and HONO, which are important contributors to OH radicals in the lower troposphere, also have crucial effect on H₂O₂ formation under certain atmospheric conditions. For instance, in a clean environment, OH radicals mainly come from O₃ photolysis followed by the reaction of O(¹D) with water vapor. In polluted areas (like urban sites), HONO appeared to be an important source of OH radicals (Elshorbany et al., 2010; Xue et al., 2020). In addition, since H₂O₂ is very soluble with high Henry's law constant of 1.07×10⁵ M atm⁻¹ at 298 K (Lee et al., 2000; Reeves and Penkett, 2003), H₂O₂ can be readily consumed via reaction with SO₂ in the atmospheric aqueous phase (Penkett et al., 1979; Hoffmann and Edwards, 1975). Hence, high SO₂ concentrations are usually associated with low H₂O₂ concentrations (Watanabe et al., 2016; Guo et al., 2014). Moreover, solar radiation has a significant impact on H₂O₂ concentrations. Model simulations by Kleinman et al. showed that a 60% decrease in solar radiation intensity could lead to a 65% decrease in H₂O₂ concentrations (Kleinman, 1986), which highlights the important role of solar
radiation in the formation of H₂O₂. The absolute humidity is an important factor for H₂O₂ formation as high humidity may lead to an increase in OH radical and hence more H₂O₂ production (Hamilton Jr and Lii, 1977; Fischer et al., 2019). Also, higher temperature promotes the rate of photochemical reactions, resulting in more radical production and hence more H₂O₂ production (Das and Aneja, 1994; Nunnermacker et al., 2008; Zhang et al., 2018). These factors are well understood and all considered in the box model and regional transport models. However, it was reported that H₂O₂ was still underestimated during polluted periods, indicating that some extra factors affecting H₂O₂ concentrations may be neglected (Qin et al., 2018; Ye et al., 2018). Moreover, there is still a gap between modeled and measured sulfate concentrations during haze events, suggesting sulfate formation is not completed in current mechanisms (Wang et al., 2014; Zheng et al., 2015). Hence, it is essential to incorporate all processes related to H₂O₂ formation into regional models for better predictions. However, there is a relatively small body of literature that is concerned with gas-phase H₂O₂ measurements in China (Wang et al., 2016; Qin et al., 2018; Ye et al., 2018; Zhang et al., 2018), especially in the North China Plain (NCP) where it is encountering serious air pollution.

In order to more accurately predict H₂O₂ concentrations and evaluate its role in the oxidizing capacity of the atmosphere, a comprehensive investigation of factors controlling gaseous H₂O₂ should be conducted. In this study, H₂O₂ and other relevant pollutants were simultaneously measured at a polluted rural site in the NCP in summertime (31 May to 8 July 2017) and wintertime (1 November to 31 December 2017, 1 to 15 December 2018). Time series of H₂O₂ and related parameters in the three field campaigns were shown in Figure S1. In addition to the factors mentioned above, some special factors were also found to profoundly affect atmospheric H₂O₂ concentrations in our study, which might be overlooked by the current understanding. The following will be some cases observed in our field measurements to reveal these special factors.
The measurements were conducted at a rural site (SRE-CAS, 38.66°N, 115.25°E) located in Wangdu County (Liu et al., 2017; Xue et al., 2020), in Hebei province, which is 150 km southwest of Beijing city in the NCP. This site was surrounded by vast areas of farmlands and impacted by coal combustion in winter and agricultural activities such as biomass burning and fertilization in summer. A high-speed way was located 2 km southwest of the site. There are no industries around the sampling site. All instruments were placed into a container with the sampling inlet about 3.4 m above the ground.

A Germany commercial H₂O₂ monitor (AEROLASER AL-2021) based on a wet chemical technique was employed to measure gas-phase H₂O₂. Firstly, soluble peroxides, including H₂O₂ and organic peroxides, were sampled by a stripping coil with a buffered solution. In order to distinguish H₂O₂ and organic peroxides, the stripping solution was divided into two channels. In the first channel, the peroxides in the stripping solution react with p-hydroxyphenyl acetic acid (POPHA) under the catalysis of peroxidase, resulting in the formation of fluorescent dye. After excitation at 326 nm, the fluorescence could be detected at 400-420 nm. In the second channel, before peroxides reaction with POPHA, enzyme catalase was added to selectively destroy H₂O₂. Then H₂O₂ was determined as the difference between the two channels. Liquid calibration was performed every two days. The detection limit of the instrument was <50 ppt. Detailed information can be found in our previous study (Ye et al., 2018).

HONO was measured by a commercial long path absorption photometer instrument (LOPAP, Model-03, QUMA) (Heland et al., 2001). Briefly, ambient air was sampled by using two same stripping coils connected in series. Because HONO is highly soluble, almost all the ambient HONO was absorbed by the absorption solution in the first stripping coil, while possibly interfering species were sampled in the first as well as the second stripping coil. Thus, the signal
difference between the two channels can largely eliminate the possible influence of the interfering species on the HONO measurement. Instrument background was conducted by sampling ultrapure nitrogen twice per day. The instrument has a detection limit of <5 ppt on 5 min average.

NO and NO₂ were measured with a chemiluminescence analyzer (Thermo Environmental Instruments (TEI), Model 42i) equipped with a photolytic converter. Ozone (O₃) was measured by a commercial UV photometric analyzer (TEI Model 49i). SO₂ was measured by a pulsed fluorescence SO₂ analyzer (Model 43i). The analyzers of NOₓ (NO/NO₂), O₃ and SO₂ were regularly calibrated once per week. PM₂.₅ levels were measured by a standard Tapered Element Oscillating Microbalance system (TEOM 1400A, Thermo Scientific). Organic carbon (OC) and elemental carbon (EC) were measured by using an online organic/elemental carbon analyzer (TR20N9, CECEP Talroad Technology Co., Ltd., China). Meteorological measurements (temperature, pressure, wind speed and direction, relative humidity, and solar radiation) were achieved by a potable weather station (Model WXT520, Vaisala, Finland).

## 3 Results and discussion

### 3.1 Influence of biomass burning events on H₂O₂ chemistry

Figure 1 depicts the time series of H₂O₂, PM₂.₅, and some meteorological parameters from 16 to 19 June 2017. H₂O₂ exhibited a typical diurnal pattern with a maximum in the early afternoon and low concentrations during the night and in the morning. For instance, on 16 June, H₂O₂ reached a maximum value of ~2.5 ppb around 15:00 LST (Local Standard Time). However, at 13:00 LST on the following day, H₂O₂ increased remarkably from ~1 to ~9 ppb in two hours. Notably, PM₂.₅ also increased concurrently with H₂O₂ from ~50 to ~300 µg m⁻³.
<figure><img src="image_5.png" /><figcaption>Figure 1: Time series of H₂O₂, PM₂.₅, solar radiation, and wind speed from 16 to 19 June 2017 in the summer campaign. H₂O₂ and PM₂.₅ were shown in minute-average data.</figcaption></figure>

The significantly positive correlation between H₂O₂ and PM₂.₅ from 13:00 to 18:00 during the event (r²=0.97) indicated the same reason for their increases. However, the wind speed was high during the elevation period (~4-6 m s⁻¹), and there wasn't a significant difference in the solar radiation with regard to other days, indicating photochemical reactions alone couldn't explain the sharp increase of H₂O₂ in such a short period. Considering the high wind speed when the high H₂O₂ event was observed, the exceptionally high H₂O₂ might be ascribed to the regional transport of H₂O₂ from the emission source. In addition, the OC (organic carbon) to EC (elemental carbon) ratio at 15:00 LST being higher than 5 (Figure 2) suggested a biomass burning event encountered here (Watson et al., 2001). The well-defined shape and narrow width of the observed H₂O₂ within the plume indicated that the plume had not experienced
significant dispersion and mixing since it was emitted, suggesting that the sampling site is not far from the emission
source.

<figure><img src="image_6.png" /><figcaption>Figure 2: Time series of OC and EC from 16 to 19 June 2017 in the summer campaign.</figcaption></figure>

Given the short lifetime of H₂O₂ in the atmosphere (typically less than one day), we calculated 1-day back trajectory
with the HYSPLIT model (https://www ready.noaa.gov/HYSPLIT.php, last access: 15 April 2022) and found the
sampling site was influenced by the plume coming from the southern areas (Figure 3a). The fire spot data on 16 June
and 17 June showed that south areas were filled with dense fire spots (Figure 3b), indicative of large areas of
agricultural (wheat straw) fires. Large areas of biomass burning in farmland contributed to the primary H₂O₂ emission,
resulting in the high H₂O₂ concentrations measured at the downwind site. Lee et al. (1997) observed H₂O₂
concentrations up to 10 ppb and attributed this to the direct production of H₂O₂ within biomass burning plumes. Some
studies also found an underestimation of modelled H₂O₂ concentration compared with observations during biomass
burning events (Wang et al., 2016; Crowley et al., 2018). H₂O₂ concentrations at our sampling site increased by a
factor of ~5 (from ~2 ppb to ~9 ppb), which is larger than the value (1.2-3.6) observed in biomass burning plumes by a
recent study (Allen et al., 2022). The difference may be explained by the different photochemical age of the air mass
sampled. In addition to primary emission, H₂O₂ concentrations will also increase with the photoaging of the biomass
burning plume as a consequence of abundant precursors contributing to secondary H₂O₂ production (Yokelson et al.,
2009). Moreover, low NOₓ levels at the rural areas are conducive for secondary H₂O₂ production. Unfortunately, we
are unable to distinguish primary emission from secondary production during the plume transport. Our results provided direct field evidence that biomass burning events significantly affect H₂O₂ concentrations, despite the polluted plume was already aged or diluted. The primary and secondary H₂O₂ produced from biomass burning contributes to odd-hydrogen radicals, thereby affecting the oxidizing capacity of the atmosphere. Given that wildfire is increasing globally and agricultural fires can be commonly seen during harvesting seasons worldwide (Andreae et al., 2019; Liu et al., 2015), they are expected to make great contributions to H₂O₂ production. To better evaluate the global consequence of the biomass burning-related H₂O₂ production, the emission factor and the production mechanism need to be critically determined.

<figure><img src="image_7.png" /><figcaption>Figure 3. (a) 24 h-trajectory arriving at SRE-CAS site at 15:00 (UTC+8), 17 July 2017 when the peak H₂O₂ occurred. (b) Fire spots map on 16 and 17 June 2017 UTC time obtained from the FINN biomass burning inventory (Wiedinmyer et al., 2011). The sampling site is represented by a black triangle. Map copyright: GoogleMap.</figcaption></figure>
187 3.2 Influence of nitrogen fertilization on the H₂O₂ chemistry

188 The summer campaign covered the important agricultural activities period like fertilization. The fertilization process
189 for the agricultural fields around our station was conducted on 13 June, 2017. Details about the fertilization event can
190 be found in our recent study, in which HONO emissions from the fertilized fields were discussed and its potential
191 impacts on O₃ and H₂O₂ were preliminarily mentioned (Xue et al., 2021). Figure 4 exhibited the time series of H₂O₂,
192 O₃ and solar radiation before (6-14 June) and after (14-21 June) the fertilization event. H₂O₂ and O₃ showed
193 pronounced diurnal patterns that were similar to those observed for solar radiation. After fertilization, both H₂O₂ and
194 O₃ diurnal peak values evidently increased (Figure 4 and Figure 5).

<figure><img src="image_8.png" /><figcaption>195
196 Figure 4: Time series of H₂O₂, O₃ and solar radiation intensity before (6-14 June) and after (14-21 June) the fertilization. The red line indicates the time when the fertilization event around the site began.
197</figcaption></figure>
To more accurately elaborate on the influence of fertilization events on H₂O₂, the H₂O₂ concentrations on 17 June, which were mainly affected by biomass burning events as discussed in Section 3.1, were not taken into consideration.

The averaged concentrations of H₂O₂ and O₃ were a factor of 1.32 and 1.31 higher than the levels observed before the fertilization events (Figure 5), but the solar radiation didn't show a significant change, indicating that fertilization may promote the formation of H₂O₂ and O₃. Previous laboratory studies have reported that fertilized soil could be a source of HONO with the use of nitrogen fertilizer (Su et al., 2011; Donaldson et al., 2014). Our previous work also provided field evidence for soil HONO emission after fertilization at this site (Xue et al., 2019). Therefore, one can expect that HONO concentrations may increase after the fertilization and subsequent HONO photolysis could release more OH radicals compared to the period before fertilization, thereby accelerating the photochemical production of H₂O₂ and O₃. Further analysis confirmed that after fertilization events the enhancements of H₂O₂ and O₃ were consistent with the rising ambient HONO levels (Figure 5). Additionally, the significant increase in H₂O₂ (ΔH₂O₂) and O₃ (ΔO₃) appeared around noontime, coincident with the HONO enhancement (ΔHONO) (Figure 5) and inferred soil HONO emission flux in Xue et al. (2021). It is worth mentioning that Tan et al. (2017) reported high OH concentrations up to 3 ×10⁷ cm⁻³ at the same rural site during a summer campaign in 2014, which was ascribed to local HONO emission from the fertilized agricultural fields (Liu et al., 2019). Therefore, agricultural activities may strongly influence the atmospheric oxidizing capacity and hence the concentrations of H₂O₂, which should be better constrained in atmospheric chemical transport models to assess the impacts of H₂O₂ on regional air quality and global climate.
<figure><img src="image_9.png" /><figcaption>Figure 5: Average concentrations of H₂O₂, HONO and O₃ before (6-14 June) and after (14-21 June) the fertilization in June 2017.</figcaption></figure>

### 3.3 Influence of particles on H₂O₂ chemistry

To investigate H₂O₂ production on clean and polluted days in the wintertime, representative cases were selected based on PM₂.₅ levels. Figure 6 shows H₂O₂ and other related chemical species and meteorological parameters measured during the winter campaign. In winter, the photochemical generation of OH radicals is weak as a consequence of significantly reduced solar radiation intensity, water vapor and ozone concentrations. Thus, the concentrations of secondary oxidants like H₂O₂ levels are typically believed to be low (Xue et al., 2016). On 23 and 24 November 2017 during our field measurements (the clean case in Figure 6), the maximum solar radiation intensity was lower than 500 W m⁻² and O₃ concentrations were less than 30 ppb, indicative of the low photochemical activity compared to summer seasons. The corresponding observed H₂O₂ concentrations were less than 0.35 ppb in the clean case.
<figure><img src="image_10.png" /><figcaption>Figure 6: H₂O₂, NO, PM₂.₅, O₃, solar radiation intensity (Sa), relative humidity (RH) and temperature (T) measured in winter. Left panel: clean case (daily-averaged PM₂.₅ concentrations lower than 75 µg m⁻³) from 23 to 25 November 2017; Right panel: polluted case (daily-averaged PM₂.₅ concentrations higher than 75 µg m⁻³) from 13 to 15 December 2018.</figcaption></figure>

In contrast, during the polluted case, the maximum solar radiation intensity (~300 W m⁻²) and O₃ concentrations (~25 ppb) were lower than that in the clean case, while the maximum H₂O₂ concentrations (> 1.5 ppb) in the polluted case
(Figure 6) were four times higher than that in the clean case. Contrary to our conventional thought, measured H₂O₂ concentrations during the polluted periods were unexpectedly high, which were even similar to summer levels.

It should be noted that the periods when H₂O₂ grew rapidly coincided with high NO levels exceeding several tens ppb (Figure 6). As discussed in the introduction section, the reaction rate of R2 was more than three orders of magnitude higher than R1 under the condition of 1 ppb NO. Therefore, gas-phase recombination of HO₂ radicals couldn't explain the high H₂O₂ levels observed. The peak value of H₂O₂ average diurnal pattern during polluted days (daily-averaged PM₂.₅> 75 µg m⁻³) was evidently higher than that during clean days (daily-averaged PM₂.₅< 75 µg m⁻³), indicating particles promoting H₂O₂ production (Figure S2). Moreover, H₂O₂ exhibited a pronounced diurnal pattern following the track of solar radiation, which implied that H₂O₂ was possibly photochemically produced. Taking all these hints into account, in-particle photochemical reactions are likely to produce the gas-phase H₂O₂. Some other typical cases (two clean and two polluted cases) were also identified and summarized in Table 1. These polluted cases with high H₂O₂ levels were observed in different years and should therefore be representative to reveal the promotion effect of particles on H₂O₂ production.

<table><caption>Table 1. Summary of the clean and polluted cases</caption><thead><tr><th>Case type</th><th>Date</th><th>Average PM<sub>2.5</sub> (µg m<sup>-3</sup>)</th><th>H<sub>2</sub>O<sub>2</sub> maximum increase rate<sup>a</sup> (ppb h<sup>-1</sup>)</th><th>Maximum H<sub>2</sub>O<sub>2</sub> (ppb)</th></tr></thead><tbody><tr><td rowspan="2">Clean</td><td>8 December 2017</td><td>14</td><td>0.05</td><td>0.36</td></tr><tr><td>4 December 2018</td><td>32</td><td>0.04</td><td>0.21</td></tr><tr><td rowspan="2">Polluted</td><td>21 December 2017</td><td>135</td><td>0.266</td><td>1.16</td></tr><tr><td>22 December 2017</td><td>216</td><td>0.267</td><td>1.19</td></tr></tbody></table>

ᵃH₂O₂ increase rate was calculated as (Cₜ+1-Cₜ)/1 h. Cₜ represents the hourly-averaged H₂O₂ concentrations at time t.

Previous studies have reported the photochemical production of H₂O₂ free of NO suppression effect in the atmospheric aqueous phase like in clouds and fog water (Faust et al., 1993; Anastasio et al., 1994; Zuo and Hoigné, 1993; Anastasio et al., 1997). The observation is also consistent to our recent chamber and flow tube studies which revealed
that photochemical aging of particles involving organic chromophores could produce gas-phase H₂O₂ (Ye et al., 2021; Liu et al., 2021). Organic chromophores have long been identified as important contributors to the aqueous photo-production of H₂O₂ (Faust et al., 1993; Anastasio et al., 1997; Arellanes et al., 2006; Fang et al., 2019). The filter sample analysis showed that particles at our sampling site in winter contained a significant concentration of light-absorbing chromophores (Wang et al., 2020). Considering the photoactivity and abundance of organic chromophores in particles (Poschl and Shiraiwa, 2015; Herrmann et al., 2015), particles may have a crucial effect on the photochemical production of gas-phase H₂O₂. In winter, especially under the conditions of high NO presence, this multiphase reaction channel for H₂O₂ formation, which is less sensitive to NO concentration, may play a more important role than the classical self-reaction of HO₂ radicals, thereby contributing to more sulfate formation. The enhanced photochemical release of H₂O₂ and subsequent oxidation of SO₂ could also shed light on the discrepancy between observed and modeled sulfate concentrations during polluted periods.

A recent study found evident O₂⁻ and sulfate production on Beijing urban PM₂.₅ filter samples under simulated UV radiation (Zhang et al., 2020). This study also indicated that H₂O₂ might be produced in the aging process of PM₂.₅ and subsequent H₂O₂-oxidation leads to the formation of sulfate, which is in agreement with our findings based on field measurements. Further work is needed to fully understand this unique H₂O₂-production pathway and assess its impacts on the global H₂O₂ abundance and sulfate budget.

## 4 Conclusions and implications

Several field campaigns with measurements on atmospheric H₂O₂ and related parameters were conducted in the rural NCP during different seasons. It allows a determination of special factors (biomass burning, fertilization, and ambient particles) influencing gas-phase H₂O₂ concentrations in this region. First, biomass burning plumes with high H₂O₂ concentrations up to 9 ppb were observed during a summer campaign. The measured H₂O₂ rapidly increased from 1 ppb to 9 ppb in two hours. Such a high H₂O₂ level and rapid increase can't be solely explained by photochemical production. Along with the analysis of back-trajectory and fire spots data, high H₂O₂ level was mainly attributed to
primary emission by large areas of biomass burning event. Second, a significant H₂O₂ increase was observed after the agricultural nitrogen fertilization event in the summer. We found concurrent elevation of HONO levels compared to that before the fertilization events. The enhanced HONO levels, caused by the soil HONO emission from the fertilized agricultural fields, promoted the atmospheric oxidizing capacity and accelerated the production of secondary oxidants like H₂O₂ and O₃. Third, high H₂O₂ concentrations exceeding 1.5 ppb, were observed under the presence of several tens ppb NO during pollution episodes in the winter campaigns. Under such high NO conditions, the traditional gas-phase channel for H₂O₂ formation would be greatly suppressed so that it was far to explained the measured H₂O₂. High H₂O₂ cases were typically accompanied by high PM₂.₅ levels, suggesting the potential role of particles in H₂O₂ production. Analogous to the aqueous H₂O₂ production in the atmospheric aqueous phase like clouds by organic chromophores, high H₂O₂ during winter polluted periods might be produced by chromophores in the particle phase considering the prevalence of chromophores in particles at this site.

Very limited measurements on atmospheric H₂O₂ in China, especially in polluted regions, are currently available despite its important role in the atmospheric oxidizing capacity and sulfate aerosol formation. This study provides a unique dataset (one summer and two winter campaigns) of H₂O₂ measurements in the NCP, which will benefit the assessment of model performance in the prediction of H₂O₂ concentrations and its potential regional and global impacts. Our results also highlight the important roles of the special factors (biomass burning, fertilization, and ambient particles) in enhancing the concentrations of gas-phase H₂O₂. The enhanced H₂O₂ production influenced by these special factors will contribute to the oxidizing capacity of the atmosphere and hence more sulfate aerosol formation, which has a crucial effect on air quality and direct forcing of the earth's climate. Additionally, particle-bound H₂O₂ will further produce OH radical by photolysis and Fenton reaction, which will contribute to the aerosol aging and oxidizing organics within particles. Furthermore, reactive oxygen species (e.g., H₂O₂, OH, O₂⁻) are at least partly responsible for the particle-related adverse health effect. The in-particle production of H₂O₂ may constitute a public risk to human health. However, these special factors influencing H₂O₂ concentrations are not well considered in model estimates of H₂O₂ and may limit the accurate prediction of the H₂O₂ budget in the atmosphere and its associated
climate and health effects. Hence, further research on the factors in controlling H₂O₂ concentrations and model improvements in H₂O₂ simulations are greatly warranted.

302

*Data availability.* Observation data are available at https://zenodo.org/record/4456345#.YAp7DzMufX8

*Competing interests.* The authors declare that they have no conflict of interest.

*Acknowledgements.* This work was supported by the National Natural Science Foundation of China (Nos. 41727805, 41975164, 91544211, 22076202, 21976190, 41905109, 21876186), the China Postdoctoral Foundation (No.2021M700214), the PIVOTS project provided by the Region Centre -Val de Loire (ARD 2020 program and CPER 2015 - 2020), and the Labex VOLTAIRE project (ANR-10-LABX-100-01). The authors thank Miss Wuqi Shen for the help with Graphical Abstract plotting.

## 5 References

311 Allen, H. M., Crounse, J. D., Kim, M. J., Teng, A. P., Ray, E. A., McKain, K., Sweeney, C., and Wennberg, P. O.: H2O2 and CH3OOH (MHP) in the Remote Atmosphere: 1. Global Distribution and Regional Influences, Journal of Geophysical Research: Atmospheres, 127, e2021JD035701, https://doi.org/10.1029/2021JD035701, 2022.

314 Anastasio, C., Faust, B. C., and Allen, J. M.: Aqueous phase photochemical formation of hydrogen peroxide in authentic cloud waters, Journal of Geophysical Research: Atmospheres, 99, 8231-8248, 1994.

316 Anastasio, C., Faust, B. C., and Rao, C. J.: Aromatic carbonyl compounds as aqueous-phase photochemical sources of hydrogen peroxide in acidic sulfate aerosols, fogs, and clouds. 1. Non-phenolic methoxybenzaldehydes and methoxyacetophenones with reductants (phenols), Environ Sci Technol, 31, 218-232, 1997.

319 Andreae, M. O.: Emission of trace gases and aerosols from biomass burning - an updated assessment, Atmos Chem Phys, 19, 8523-8546, 2019.

321 Arellanes, C., Paulson, S. E., Fine, P. M., and Sioutas, C.: Exceeding of Henry's law by hydrogen peroxide associated with urban aerosols, Environ Sci Technol, 40, 4859-4866, 2006.
323 Atkinson, R., Baulch, D. L., Cox, R. A., Crowley, J. N., Hampson, R. F., Hynes, R. G., Jenkin, M. E., Rossi, M. J., and Troe, J.: Evaluated kinetic and photochemical data for atmospheric chemistry: Volume I - gas phase reactions of O-x, HOx, NOx and SOx species, Atmos Chem Phys, 4, 1461-1738, 2004.

326 Becker, K. H., Brockmann, K. J., and Bechara, J.: Production of hydrogen peroxide in forest air by reaction of ozone with terpenes, Nature, 346, 256-258, 1990.

328 Calvert, J. G., and Stockwell, W. R.: Acid generation in the troposphere by gas-phase chemistry, Environ Sci Technol, 17, 428A-443A, 1983.

330 Crowley, J. N., Pouvesle, N., Phillips, G. J., Axinte, R., Fischer, H., Petäjä, T., Nölscher, A., Williams, J., Hens, K., and Harder, H.: Insights into HOx and ROx chemistry in the boreal forest via measurement of peroxyacetic acid, peroxyacetic nitric anhydride (PAN) and hydrogen peroxide, Atmos Chem Phys, 2018.

333 Das, M., and Aneja, V. P.: Analysis of Gaseous-Hydrogen Peroxide Concentrations in Raleigh, North-Carolina, J Air Waste Manage, 44, 176-180, 1994.

335 Donaldson, M. A., Bish, D. L., and Raff, J. D.: Soil surface acidity plays a determining role in the atmospheric-terrestrial exchange of nitrous acid, P Natl Acad Sci USA, 111, 18472-18477, 2014.

337 Elshorbany, Y. F., Kleffmann, J., Kurtenbach, R., Lissi, E., Rubio, M., Villena, G., Gramsch, E., Rickard, A. R., Pilling, M. J., and Wiesen, P.: Seasonal dependence of the oxidation capacity of the city of Santiago de Chile, Atmos Environ, 44, 5383-5394, 2010.

340 Fang, T., Lakey, P. S. J., Weber, R. J., and Shiraiwa, M.: Oxidative Potential of Particulate Matter and Generation of Reactive Oxygen Species in Epithelial Lining Fluid, Environ Sci Technol, 53, 12784-12792, 2019.

342 Faust, B. C., Anastasio, C., Allen, J. M., and Arakaki, T.: Aqueous-phase photochemical formation of peroxides in authentic cloud and fog waters, Science, 260, 73-75, 1993.

344 Fischer, H., Axinte, R., Bozem, H., Crowley, J. N., Ernest, C., Gilge, S., Hafermann, S., Harder, H., Hens, K., and Janssen, R. H.: Diurnal variability, photochemical production and loss processes of hydrogen peroxide in the boundary layer over Europe, Atmos Chem Phys, 19, 11953-11968, 2019.
347 Fuzzi, S., Baltensperger, U., Carslaw, K., Decesari, S., van Der Gon, H. D., Facchini, M. C., Fowler, D., Koren, I., Langford, B., Lohmann, U., Nemitz, E., Pandis, S., Riipinen, I., Rudich, Y., Schaap, M., Slowik, J. G., Spracklen, D. V., Vignati, E., Wild, M., Williams, M., and Gilardoni, S.: Particulate matter, air quality and climate: lessons learned and future needs, Atmos Chem Phys, 15, 8217-8299, 10.5194/acp-15-8217-2015, 2015.

351 Grantz, D. A., Garner, J. H. B., and Johnson, D. W.: Ecological effects of particulate matter, Environ Int, 29, 213-239, 2003.

352 Guo, J., Tilgner, A., Yeung, C., Wang, Z., Louie, P. K. K., Luk, C. W. Y., Xu, Z., Yuan, C., Gao, Y., Poon, S., Herrmann, H., Lee, S., Lam, K. S., and Wang, T.: Atmospheric Peroxides in a Polluted Subtropical Environment: Seasonal Variation, Sources and Sinks, and Importance of Heterogeneous Processes, Environ Sci Technol, 48, 1443-1450, 10.1021/es403229x, 2014.

356 Hamilton Jr, E. J., and Lii, R. R.: The Dependence on H2O and on NH3 of the Kinetics of the self-reaction of HO2 in the gas-phase formation of HO2: H2O and HO2: NH3 complexes, International Journal of Chemical Kinetics, 9, 875-885, 1977.

359 He, S. Z., Chen, Z. M., Zhang, X., Zhao, Y., Huang, D. M., Zhao, J. N., Zhu, T., Hu, M., and Zeng, L. M.: Measurement of atmospheric hydrogen peroxide and organic peroxides in Beijing before and during the 2008 Olympic Games: Chemical and physical factors influencing their concentrations, J Geophys Res-Atmos, 115, Artn D1730710.1029/2009jd013544, 2010.

363 Heland, J., Kleffmann, J., Kurtenbach, R., and Wiesen, P.: A new instrument to measure gaseous nitrous acid (HONO) in the atmosphere, Environ. Sci. Technol., 35, 3207-3212, https://doi.org/10.1021/es000303t, 2001

365 Herrmann, H., Schaefer, T., Tilgner, A., Styler, S. A., Weller, C., Teich, M., and Otto, T.: Tropospheric Aqueous-Phase Chemistry: Kinetics, Mechanisms, and Its Coupling to a Changing Gas Phase, Chem Rev, 115, 4259-4334, 2015.

367 Hoffmann, M., and Edwards, J.: Kinetics of the oxidation of sulfite by hydrogen peroxide in acidic solution, The Journal of Physical Chemistry, 79, 2096-2098, 1975.

369 Hua, W., Chen, Z. M., Jie, C. Y., Kondo, Y., Hofzumahaus, A., Takegawa, N., Chang, C. C., Lu, K. D., Miyazaki, Y., Kita, K., Wang, H. L., Zhang, Y. H., and Hu, M.: Atmospheric hydrogen peroxide and organic hydroperoxides during PRIDE-
371 PRD'06, China: their concentration, formation mechanism and contribution to secondary aerosols, Atmos Chem Phys, 8,
372 6755-6773, DOI 10.5194/acp-8-6755-2008, 2008.

373 Kleinman, L. I.: Photochemical formation of peroxides in the boundary layer, Journal of Geophysical Research: Atmospheres, 91, 10889-10904, 1986.

375 Lee, M., Heikes, B. G., Jacob, D. J., Sachse, G., and Anderson, B.: Hydrogen peroxide, organic hydroperoxide, and formaldehyde as primary pollutants from biomass burning, Journal of Geophysical Research: Atmospheres, 102, 1301-1309, 10.1029/96jd01709, 1997.

378 Lee, M., Kie, J. A., Kim, Y. M., and Lee, G.: Characteristics of atmospheric hydrogen peroxide variations in Seoul megacity during 2002-2004, Sci Total Environ, 393, 299-308, 10.1016/j.scitotenv.2007.11.037, 2008.

380 Lee, M. H., Heikes, B. G., and O'Sullivan, D. W.: Hydrogen peroxide and organic hydroperoxide in the troposphere: A review, Atmos Environ, 34, 3475-3494, DOI 10.1016/S1352-2310(09)00432-X, 2000.

382 Liang, H., Chen, Z. M., Huang, D., Zhao, Y., and Li, Z. Y.: Impacts of aerosols on the chemistry of atmospheric trace gases: a case study of peroxides and HO2 radicals, Atmos Chem Phys, 13, 11259-11276, 10.5194/acp-13-11259-2013, 2013.

384 Liu, M. X., Song, Y., Yao, H., Kang, Y. N., Li, M. M., Huang, X., and Hu, M.: Estimating emissions from agricultural fires in the North China Plain based on MODIS fire radiative power, Atmos Environ, 112, 326-334, 2015.

386 Liu, P. F., Zhang, C. L., Xue, C. Y., Mu, Y. J., Liu, J. F., Zhang, Y. Y., Tian, D., Ye, C., Zhang, H. X., and Guan, J.: The contribution of residential coal combustion to atmospheric PM2.5 in northern China during winter, Atmos Chem Phys, 17, 11503-11520, 10.5194/acp-17-11503-2017, 2017.

389 Liu, P., Ye, C., Zhang, C., He, G., Xue, C., Liu, J., Liu, C., Zhang, Y., Song, Y., Li, X., Wang, X., Chen, J., He, H., Herrmann, H., and Mu, Y.: Photochemical Aging of Atmospheric Fine Particles as a Potential Source for Gas-Phase Hydrogen Peroxide, Environ Sci Technol, 10.1021/acs.est.1c04453, 2021.

392 Liu, Y., Lu, K., Li, X., Dong, H., Tan, Z., Wang, H., Zou, Q., Wu, Y., Zeng, L., Hu, M., Min, K.-E., Kecorius, S., Wiedensohler, A., and Zhang, Y.: A Comprehensive Model Test of the HONO Sources Constrained to Field Measurements at Rural North China Plain, Environ Sci Technol, 53, 3517-3525, 10.1021/acs.est.8b06367, 2019.
Ma, X. F., Tan, Z. F., Lu, K. D., Yang, X. P., Liu, Y. H., Li, S. L., Li, X., Chen, S. Y., Novelli, A., Cho, C. M., Zeng, L. M., Wahner, A., and Zhang, Y. H.: Winter photochemistry in Beijing: Observation and model simulation of OH and HO2 radicals at an urban site, Sci Total Environ, 685, 85-95, 2019.

Nel, A.: Air pollution-related illness: Effects of particles, Science, 308, 804-806, 10.1126/science.1108752, 2005.

Nunnermacker, L. J., Weinstein-Lloyd, J. B., Hillery, B., Giebel, B., Kleinman, L. I., Springston, S. R., Daum, P. H., Gaffney, J., Marley, N., and Huey, G.: Aircraft and ground-based measurements of hydroperoxides during the 2006 MILAGRO field campaign, Atmos Chem Phys, 8, 7619-7636, 10.5194/acp-8-7619-2008, 2008.

Penkett, S. A., Jones, B. M. R., Brice, K. A., and Eggleton, A. E. J.: Importance of Atmospheric Ozone and Hydrogen-Peroxide in Oxidizing Sulfur-Dioxide in Cloud and Rainwater, Atmos Environ, 13, 123-137, doi 10.1016/0004-6981(79)90251-8, 1979.

Poschl, U., and Shiraiwa, M.: Multiphase Chemistry at the Atmosphere-Biosphere Interface Influencing Climate and Public Health in the Anthropocene, Chem Rev, 115, 4440-4475, 2015.

Qin, M., Chen, Z., Shen, H., Li, H., Wu, H., and Wang, Y.: Impacts of heterogeneous reactions to atmospheric peroxides: Observations and budget analysis study, Atmos Environ, 183, 144-153, 10.1016/j.atmosenv.2018.04.005, 2018.

Reeves, C. E., and Penkett, S. A.: Measurements of peroxides and what they tell us, Chem Rev, 103, 5199-5218, 10.1021/cr0205053, 2003.

Sillman, S.: The use of NO y, H2O2, and HNO3 as indicators for ozone-NO x-hydrocarbon sensitivity in urban locations, Journal of Geophysical Research: Atmospheres, 100, 14175-14188, 1995.

Sillman, S., He, D., Pippin, M. R., Daum, P. H., Imre, D. G., Kleinman, L. I., Lee, J. H., and Weinstein-Lloyd, J.: Model correlations for ozone, reactive nitrogen, and peroxides for Nashville in comparison with measurements: Implications for O3-NO x-hydrocarbon chemistry, Journal of Geophysical Research: Atmospheres, 103, 22629-22644, 1998.

Slater, E. J., Whalley, L. K., Woodward-Massey, R., Ye, C. X., Lee, J. D., Squires, F., Hopkins, J. R., Dunmore, R. E., Shaw, M., Hamilton, J. F., Lewis, A. C., Crilley, L. R., Kramer, L., Bloss, W., Vu, T., Sun, Y. L., Xu, W. Q., Yue, S. Y., Ren, L. J., Acton, W. J. F., Hewitt, C. N., Wang, X. M., Fu, P. Q., and Heard, D. E.: Elevated levels of OH observed in
419 haze events during wintertime in central Beijing, Atmos Chem Phys, 20, 14847-14871, 10.5194/acp-20-14847-2020,
420 2020.

421 Stockwell, W. R., Kirchner, F., Kuhn, M., and Seefeld, S.: A new mechanism for regional atmospheric chemistry modeling,
422 J Geophys Res-Atmos, 102, 25847-25879, 1997.

423 Su, H., Cheng, Y. F., Oswald, R., Behrendt, T., Trebs, I., Meixner, F. X., Andreae, M. O., Cheng, P., Zhang, Y., and Poschl,
424 U.: Soil Nitrite as a Source of Atmospheric HONO and OH Radicals, Science, 333, 1616-1618, 2011.

425 Tan, Z. F., Fuchs, H., Lu, K. D., Hofzumahaus, A., Bohn, B., Broch, S., Dong, H. B., Gomm, S., Haseler, R., He, L. Y.,
426 Holland, F., Li, X., Liu, Y., Lu, S. H., Rohrer, F., Shao, M., Wang, B. L., Wang, M., Wu, Y. S., Zeng, L. M., Zhang, Y. S.,
427 Wahner, A., and Zhang, Y. H.: Radical chemistry at a rural site (Wangdu) in the North China Plain: observation and
428 model calculations of OH, HO2 and RO2 radicals, Atmos Chem Phys, 17, 663-690, 10.5194/acp-17-663-2017, 2017.

429 Tan, Z., Lu, K., Jiang, M., Su, R., Dong, H., Zeng, L., Xie, S., Tan, Q., and Zhang, Y.: Exploring ozone pollution in
430 Chengdu, southwestern China: A case study from radical chemistry to O3-VOC-NOx sensitivity, Sci Total Environ, 636,
431 775-786, https://doi.org/10.1016/j.scitotenv.2018.04.286, 2018.

432 Vermeuel, M. P., Novak, G. A., Alwe, H. D., Hughes, D. D., Kaleel, R., Dickens, A. F., Kenski, D., Czarnetzki, A. C.,
433 Stone, E. A., and Stanier, C. O.: Sensitivity of Ozone Production to NOx and VOC Along the Lake Michigan Coastline,
434 Journal of Geophysical Research: Atmospheres, 124, 10989-11006, 2019.

435 Walker, S. J., Evans, M. J., Jackson, A. V., Steinbacher, M., Zellweger, C., and McQuaid, J. B.: Processes controlling the
436 concentration of hydroperoxides at Jungfraujoch Observatory, Switzerland, Atmos Chem Phys, 6, 5525-5536, DOI
437 10.5194/acp-6-5525-2006, 2006.

438 Wang, X., Gemayel, R., Hayeck, N., Perrier, S., Charbonnel, N., Xu, C., Chen, H., Zhu, C., Zhang, L., and Wang, L.:
439 Atmospheric photosensitization: a new pathway for sulfate formation, Environ Sci Technol, 2020.

440 Wang, Y., Chen, Z. M., Wu, Q. Q., Liang, H., Huang, L. B., Li, H., Lu, K. D., Wu, Y. S., Dong, H. B., Zeng, L. M., and
441 Zhang, Y. H.: Observation of atmospheric peroxides during Wangdu Campaign 2014 at a rural site in the North China
442 Plain, Atmos Chem Phys, 16, 10985-11000, 10.5194/acp-16-10985-2016, 2016.
443 Wang, Y. X., Zhang, Q. Q., Jiang, J. K., Zhou, W., Wang, B. Y., He, K. B., Duan, F. K., Zhang, Q., Philip, S., and Xie, Y.

444 Y.: Enhanced sulfate formation during China's severe winter haze episode in January 2013 missing from current models, J Geophys Res-Atmos, 119, 2014.

445 Geophys Res-Atmos, 119, 2014.

446 Watanabe, K., Yachi, C., Nishibe, M., Michigami, S., Saito, Y., Eda, N., Yamazaki, N., and Hirai, T.: Measurements of atmospheric hydroperoxides over a rural site in central Japan during summers using a helicopter, Atmos Environ, 146, 174-182, 10.1016/j.atmosenv.2016.06.074, 2016.

447
448
449
Watanabe, K., Yachi, C., Song, X. J., Kakuyama, S., Nishibe, M., and Michigami, S.: Measurements of atmospheric hydroperoxides at a rural site in central Japan, J Atmos Chem, 75, 71-84, 2018.

450
451
452
Watanabe, K., Yachi, C., Song, X. J., Kakuyama, S., Nishibe, M., and Michigami, S.: Measurements of atmospheric hydroperoxides at a rural site in central Japan, J Atmos Chem, 75, 71-84, 2018.

453
454
455
Watson, J. G., Chow, J. C., and Houck, J. E.: PM2.5 chemical source profiles for vehicle exhaust, vegetative burning, geological material, and coal burning in Northwestern Colorado during 1995, Chemosphere, 43, 1141-1151, 2001.

456
457
458
Wiedinmyer, C., Akagi, S. K., Yokelson, R. J., Emmons, L. K., Al-Saadi, J. A., Orlando, J. J., and Soja, A. J.: The Fire INventory from NCAR (FINN): a high resolution global model to estimate the emissions from open burning, Geosci. Model Dev., 4, 625-641, 10.5194/gmd-4-625-2011, 2011.

459
460
461
462
Xue, C., Ye, C., Zhang, C., Catoire, V., Liu, P., Gu, R., Zhang, J., Ma, Z., Zhao, X., Zhang, W., Ren, Y., Krysztofiak, G., Tong, S., Xue, L., An, J., Ge, M., Mellouki, A., and Mu, Y.: Evidence for Strong HONO Emission from Fertilized Agricultural Fields and its Remarkable Impact on Regional O3 Pollution in the Summer North China Plain, ACS Earth and Space Chemistry, 10.1021/acsearthspacechem.0c00314, 2021.

463
464
465
466
Xue, C. Y., Zhang, C. L., Ye, C., Liu, P. F., Catoire, V., Krysztofiak, G., Chen, H., Ren, Y. G., Zhao, X. X., Wang, J. H., Zhang, F., Zhang, C. X., Zhang, J. W., An, J. L., Wang, T., Chen, J. M., Kleffmann, J., Mellouki, A., and Mu, Y. J.: HONO Budget and Its Role in Nitrate Formation in the Rural North China Plain, Environ Sci Technol, 54, 11048-11057, 2020.

467
468
469
470
Xue, C. Y., Zhang, C. L., Ye, C., Liu, P. F., Catoire, V., Krysztofiak, G., Chen, H., Ren, Y. G., Zhao, X. X., Wang, J. H.,

471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
400
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
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
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
467 Xue, J., Yuan, Z. B., Griffith, S. M., Yu, X., Lau, A. K. H., and Yu, J. Z.: Sulfate Formation Enhanced by a Cocktail of High
468 NOx, SO2, Particulate Matter, and Droplet pH during Haze-Fog Events in Megacities in China: An Observation-Based
469 Modeling Investigation, Environ Sci Technol, 50, 7325-7334, 2016.

470 Ye, C., Liu, P., Ma, Z., Xue, C., Zhang, C., Zhang, Y., Liu, J., Liu, C., Sun, X., and Mu, Y.: High H2O2 Concentrations
471 Observed during Haze Periods during the Winter in Beijing: Importance of H2O2 Oxidation in Sulfate Formation,
472 Environmental Science & Technology Letters, 10.1021/acs.estlett.8b00579, 2018.

473 Ye, C., Chen, H., Hoffmann, E. H., Mettke, P., Tilgner, A., He, L., Mutzel, A., Brüggemann, M., Poulain, L., and Schaefer,
474 T.: Particle-Phase Photoreactions of HULIS and TMIs Establish a Strong Source of H2O2 and Particulate Sulfate in the
475 Winter North China Plain, Environ Sci Technol, 2021.

476 Yokelson, R. J., Crounse, J. D., DeCarlo, P. F., Karl, T., Urbanski, S., Atlas, E., Campos, T., Shinozuka, Y., Kapustin, V.,
477 Clarke, A. D., Weinheimer, A., Knapp, D. J., Montzka, D. D., Holloway, J., Weibring, P., Flocke, F., Zheng, W., Toohey,
478 D., Wennberg, P. O., Wiedinmyer, C., Mauldin, L., Fried, A., Richter, D., Walega, J., Jimenez, J. L., Adachi, K., Buseck,
479 P. R., Hall, S. R., and Shetter, R.: Emissions from biomass burning in the Yucatan, Atmos. Chem. Phys., 9, 5785-5812,
480 10.5194/acp-9-5785-2009, 2009.

481 Yu, D., Tan, Z., Lu, K., Ma, X., Li, X., Chen, S., Zhu, B., Lin, L., Li, Y., Qiu, P., Yang, X., Liu, Y., Wang, H., He, L.,
482 Huang, X., and Zhang, Y.: An explicit study of local ozone budget and NOx-VOCs sensitivity in Shenzhen China, Atmos
483 Environ, 224, 117304, https://doi.org/10.1016/j.atmosenv.2020.117304, 2020.

484 Zhang, Q., Liu, J., He, Y., Yang, J., Gao, J., Liu, H., Tang, W., Chen, Y., Fan, W., and Chen, X.: Measurement of hydrogen
485 peroxide and organic hydroperoxide concentrations during autumn in Beijing, China, J Environ Sci-China, 64, 72-81,
486 2018.

487 Zhang, Y., Bao, F., Li, M., Xia, H., Huang, D., Chen, C., and Zhao, J.: Photoinduced Uptake and Oxidation of SO2 on
488 Beijing Urban PM2.5, Environ Sci Technol, 10.1021/acs.est.0c01532, 2020.

489 Zheng, B., Zhang, Q., Zhang, Y., He, K. B., Wang, K., Zheng, G. J., Duan, F. K., Ma, Y. L., and Kimoto, T.: Heterogeneous
490 chemistry: a mechanism missing in current models to explain secondary inorganic aerosol formation during the January
491 2013 haze episode in North China, Atmos Chem Phys, 15, 2031-2049, 10.5194/acp-15-2031-2015, 2015.
492 Zuo, Y., and Hoigné, J.: Evidence for photochemical formation of H2O2 and oxidation of SO2 in authentic fog water,

493 Science, 260, 71-73, 1993.