scholarly journals Influence of biomass burning plumes on HONO chemistry in eastern China

2014 ◽  
Vol 14 (6) ◽  
pp. 7859-7887 ◽  
Author(s):  
W. Nie ◽  
A. J. Ding ◽  
Y. N. Xie ◽  
Z. Xu ◽  
H. Mao ◽  
...  
Keyword(s):  
Surface Area ◽  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Eastern China ◽  
Yangtze River Delta ◽  
Mean Value ◽  
Surface Areas ◽  
Agricultural Burning ◽  
Conversion Efficiencies

Abstract. Nitrous acid (HONO) plays a key role in atmospheric chemistry via influencing the budget of hydroxyl radical (OH). In this study, a two-month measurement period of HONO and related quantities were analyzed during a biomass burning season in 2012 at a suburban site in the western Yangtze River delta, eastern China. An overall high HONO concentration with the mean value of 1.1 ppbv was observed. During biomass burning (BB) periods, both HONO concentration and HONO / NO2 ratio were enhanced significantly compared with non-biomass burning periods. A correlation analysis showed that the HONO concentration was not associated potassium (a tracer of BB) in BB plumes, but showed a high correlation with the NO2 concentration, suggesting a principle role of secondary production rather than direct emissions in elevated HONO concentrations. A further analysis based on comparing the surface area at similar PM levels and HONO / NO2 ratios at similar surface area levels suggested larger specific surface areas and higher NO2 conversion efficiencies of BB aerosols. A mixed plume of BB and anthropogenic fossil fuel (FF) emissions was observed on 10 June with even higher HONO concentrations and HONO / NO2 ratios. The strong HONO production potential (high HONO / NO2 to PM2.5 ratio) was accompanied with a high sulfate concentration in this plume, suggesting a promotion of mixed aerosols to HONO formation. In summary, our study suggests an important role of BB in atmospheric oxidation capacity by affecting the HONO budget. This can be especially important in eastern China, where agricultural burning plumes are inevitably mixed with urban pollutions.

scholarly journals Influence of biomass burning plumes on HONO chemistry in eastern China

2015 ◽  
Vol 15 (3) ◽  
pp. 1147-1159 ◽  
Author(s):  
W. Nie ◽  
A. J. Ding ◽  
Y. N. Xie ◽  
Z. Xu ◽  
H. Mao ◽  
...  
Keyword(s):  
Surface Area ◽  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Eastern China ◽  
Yangtze River Delta ◽  
Mean Value ◽  
Air Masses ◽  
Surface Areas ◽  
Agricultural Burning ◽  
Conversion Efficiencies

Abstract. Nitrous acid (HONO) plays a key role in atmospheric chemistry by influencing the budget of hydroxyl radical (OH). In this study, a two-month measurement of HONO and related quantities were analyzed during a biomass burning season in 2012 at a suburban site in the western Yangtze River delta, eastern China. An overall high HONO concentration with the mean value of 0.76 ppbv (0.01 ppbv to 5.95 ppbv) was observed. During biomass burning (BB) periods, both HONO concentration and HONO/NO2 ratio were enhanced significantly (more than a factor of 2, p < 0.01) compared with non-biomass burning (non-BB) periods. A correlation analysis showed that the HONO in BB plumes was more correlated with nitrogen dioxide (NO2) than that with potassium (a tracer of BB). Estimation by the method of potassium tracing suggests a maximum contribution of 17 ± 12% from BB emission to the observed HONO concentrations, and the other over 80% of the observed nighttime HONO concentrations during BB periods were secondarily produced by the heterogeneous conversion of NO2. The NO2-to-HONO conversion rate (CHONO) in BB plumes was almost twice as that in non-BB plumes (0.0062 hr−1 vs. 0.0032 hr−1). Given that the residence time of the BB air masses was lower than that of non-BB air masses, these results suggest BB aerosols have higher NO2 conversion potentials to form HONO than non-BB aerosols. A further analysis based on comparing the surface area at similar particle mass levels and HONO/NO2 ratios at similar surface area levels suggested larger specific surface areas and higher NO2 conversion efficiencies of BB aerosols. A mixed plume of BB and anthropogenic fossil fuel (FF) emissions was observed on 10 June with even higher HONO concentrations and HONO/NO2 ratios. The strong HONO production potential (high HONO/NO2 to PM2.5 ratio) was accompanied with a high sulfate concentration in this plume, suggesting a promotion of mixed aerosols to the HONO formation. In summary, our study suggests an important role of BB in atmospheric chemistry by affecting the HONO budget. This can be especially important in eastern China, where agricultural burning plumes are inevitably mixed with urban and industrial pollution.

scholarly journals Thermodynamics of manganese oxides: Sodium, potassium, and calcium birnessite and cryptomelane

2017 ◽  
Vol 114 (7) ◽  
pp. E1046-E1053 ◽  
Author(s):  
Nancy Birkner ◽  
Alexandra Navrotsky
Keyword(s):  
Surface Energy ◽  
Surface Area ◽  
Oxidation State ◽  
Manganese Oxides ◽  
Lower Surface ◽  
Surface Energies ◽  
Surface Areas ◽  
Bulk Thermodynamics ◽  
Lower Surface Energy

Manganese oxides with layer and tunnel structures occur widely in nature and inspire technological applications. Having variable compositions, these structures often are found as small particles (nanophases). This study explores, using experimental thermochemistry, the role of composition, oxidation state, structure, and surface energy in the their thermodynamic stability. The measured surface energies of cryptomelane, sodium birnessite, potassium birnessite and calcium birnessite are all significantly lower than those of binary manganese oxides (Mn3O4, Mn2O3, and MnO2), consistent with added stabilization of the layer and tunnel structures at the nanoscale. Surface energies generally decrease with decreasing average manganese oxidation state. A stabilizing enthalpy contribution arises from increasing counter-cation content. The formation of cryptomelane from birnessite in contact with aqueous solution is favored by the removal of ions from the layered phase. At large surface area, surface-energy differences make cryptomelane formation thermodynamically less favorable than birnessite formation. In contrast, at small to moderate surface areas, bulk thermodynamics and the energetics of the aqueous phase drive cryptomelane formation from birnessite, perhaps aided by oxidation-state differences. Transformation among birnessite phases of increasing surface area favors compositions with lower surface energy. These quantitative thermodynamic findings explain and support qualitative observations of phase-transformation patterns gathered from natural and synthetic manganese oxides.

scholarly journals Application of SCIAMACHY and MOPITT CO total column measurements to evaluate model results over biomass burning regions and Eastern China

2011 ◽  
Vol 11 (12) ◽  
pp. 6083-6114 ◽  
Author(s):  
C. Liu ◽  
S. Beirle ◽  
T. Butler ◽  
J. Liu ◽  
P. Hoor ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Eastern China ◽  
Central Africa ◽  
Satellite Observations ◽  
Anthropogenic Sources ◽  
Data Sets ◽  
Vertical Column ◽  
Data Set ◽  
Vertical Column Density

Abstract. We developed a new CO vertical column density product from near IR observations of the SCIAMACHY instrument onboard ENVISAT. For the correction of a temporally and spatially variable offset of the CO vertical column densities we apply a normalisation procedure based on coincident MOPITT (version 4) observations over the oceans. The resulting normalised SCIAMACHY CO data is well suited for the investigation of the CO distribution over continents, where important emission sources are located. We use only SCIAMACHY observations for effective cloud fractions below 20 %. Since the remaining effects of clouds can still be large (up to 100 %), we applied a cloud correction scheme which explicitly considers the cloud fraction, cloud top height and surface albedo of individual observations. The normalisation procedure using MOPITT data and the cloud correction substantially improve the agreement with independent data sets. We compared our new SCIAMACHY CO data set, and also observations from the MOPITT instrument, to the results from three global atmospheric chemistry models (MATCH, EMAC at low and high resolution, and GEOS-Chem); the focus of this comparison is on regions with strong CO emissions (from biomass burning or anthropogenic sources). The comparison indicates that over most of these regions the seasonal cycle is generally captured well but the simulated CO vertical column densities are systematically smaller than those from the satellite observations, in particular with respect to SCIAMACHY observations. Because SCIAMACHY is more sensitive to the lowest part of the atmosphere compared to MOPITT, this indicates that especially close to the surface the model simulations systematically underestimate the true atmospheric CO concentrations, probably caused by an underestimation of CO emissions by current emission inventories. For some biomass burning regions, however, such as Central Africa in July–August, model results are also found to be higher than the satellite observations.

Semi-quantitative understanding of source contribution to nitrous acid (HONO) based on 1 year of continuous observation at the SORPES station in eastern China

2020 ◽  
Author(s):  
Yuliang Liu
Keyword(s):  
Atmospheric Chemistry ◽  
Nitrous Acid ◽  
Heterogeneous Reaction ◽  
Total Concentration ◽  
Eastern China ◽  
Mean Value ◽  
Budget Analysis ◽  
Conversion Frequency ◽  
Yearly Average ◽  
Quantitative Understanding

&lt;p&gt;Nitrous acid (HONO), an important precursor of the hydroxyl radical (OH), has long been recognized as of significance to atmospheric chemistry, but its sources are still debated. In this study, we conducted continuous measurement of HONO from November&amp;#160;2017 to November&amp;#160;2018 at the SORPES station in Nanjing of eastern China. The yearly average mixing ratio of observed HONO was&amp;#160;&lt;span&gt;0.69&amp;#177;0.58&lt;/span&gt;&amp;#8201;ppb, showing a larger contribution to OH relative to ozone with a mean OH production rate of 1.16&amp;#8201;ppb&amp;#8201;h&lt;span&gt;&lt;sup&gt;&amp;#8722;1&lt;/sup&gt;&lt;/span&gt;. To estimate the effect of combustion emissions of HONO, the emitted ratios of HONO to&amp;#160;&lt;span&gt;NO&lt;sub&gt;&lt;em&gt;x&lt;/em&gt;&lt;/sub&gt;&lt;/span&gt;&amp;#160;were derived from 55 fresh plumes (&lt;span&gt;NO&amp;#8725;NO&lt;sub&gt;&lt;em&gt;x&lt;/em&gt;&lt;/sub&gt;&lt;/span&gt;&amp;#8201;&gt;&amp;#8201;0.85), with a mean value of 0.79&amp;#8201;%. During the nighttime, the chemistry of HONO was found to depend on RH, and the heterogeneous reaction of &lt;span&gt;NO&lt;sub&gt;2&lt;/sub&gt;&lt;/span&gt;&amp;#160;on an aerosol surface was presumably responsible for HONO production. The average nighttime&amp;#160;&lt;span&gt;NO&lt;sub&gt;2&lt;/sub&gt;&lt;/span&gt;-to-HONO conversion frequency (&lt;span&gt;&lt;em&gt;C&lt;/em&gt;&lt;sub&gt;HONO&lt;/sub&gt;&lt;/span&gt;) was determined to be&amp;#160;&lt;span&gt;0.0055&amp;#177;0.0032&lt;/span&gt;&amp;#8201;h&lt;span&gt;&lt;sup&gt;&amp;#8722;1&lt;/sup&gt;&lt;/span&gt;&amp;#160;from 137 HONO formation cases. The missing source of HONO around noontime seemed to be photo-induced, with an average&amp;#160;&lt;span&gt;&lt;em&gt;P&lt;/em&gt;&lt;sub&gt;unknown&lt;/sub&gt;&lt;/span&gt;&amp;#160;of 1.04&amp;#8201;ppb&amp;#8201;h&lt;span&gt;&lt;sup&gt;&amp;#8722;1&lt;/sup&gt;&lt;/span&gt;, based on a semi-quantitative HONO budget analysis. An over-determined system of equations was applied to obtain the monthly variations in nocturnal HONO sources. Besides the burning-emitted HONO (accounting for about 23&amp;#8201;% of the total concentration), the contribution of HONO formed heterogeneously on ground surfaces to measured HONO was an approximately constant proportion of 36&amp;#8201;% throughout the year. The soil emission revealed clear seasonal variation and contributed up to 40&amp;#8201;% of observed HONO in July and August. A higher propensity for generating HONO on aerosol surfaces occurred in severe hazes (accounting for 40&amp;#8201;% of the total concentration in January). Our results highlight ever-changing contributions of HONO sources and encourage more long-term observations to evaluate the contributions from varied sources.&lt;/p&gt;

scholarly journals Application of SCIAMACHY and MOPITT CO total column measurements to evaluate model results over biomass burning regions and Eastern China

2011 ◽  
Vol 11 (1) ◽  
pp. 1265-1331 ◽  
Author(s):  
C. Liu ◽  
S. Beirle ◽  
T. Butler ◽  
J. Liu ◽  
P. Hoor ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Eastern China ◽  
Central Africa ◽  
High Sensitivity ◽  
Satellite Observations ◽  
Anthropogenic Sources ◽  
Vertical Column ◽  
Data Set ◽  
Vertical Column Density

Abstract. We developed a new CO vertical column density product from near IR observations of the SCIAMACHY instrument onboard ENVISAT. For the correction of a temporally and spatially variable offset of the CO vertical column densities we apply a normalisation procedure based on coincident MOPITT (version 4) observations over the oceans. The resulting normalised SCIAMACHY CO data are well suited for the investigation of the CO distribution over continents, where important emission sources are located. We use only SCIAMACHY observations for effective cloud fractions below 20%. Since the remaining effects of clouds can still be large (up to 100%), we applied a cloud correction scheme which explicitly considers the cloud fraction, cloud top height and surface albedo of individual observations. We compared our new SCIAMACHY CO data set, and also observations from the MOPITT instrument, to the results from three global atmospheric chemistry models (MATCH, EMAC at low and high resolution, and GEOS-Chem); the focus of this comparison is on regions with strong CO emissions (from biomass burning or anthropogenic sources). The comparison indicates that over most of these regions the seasonal cycle is generally captured well but the simulated CO vertical column densities are systematically smaller than those from the satellite observations, in particular with respect to SCIAMACHY observations. Because of the high sensitivity of the SCIAMACHY observations to the lowest part of the atmosphere, this indicates that especially close to the surface the model simulations systematically underestimate the true atmospheric CO concentrations, probably caused by an underestimation of CO emissions by current emission inventories. For some biomass burning regions, however, such as Central Africa in July–August, model results are also found to be higher than the satellite observations.

scholarly journals Measurement of Amount of Invaginated Membrane in Mammalian Platelets by Osmotically-Induced Spherocyte Formation

1977 ◽  
Author(s):  
John G. Milton ◽  
M.M. Frojmovic
Keyword(s):  
Surface Area ◽  
Quantitative Estimation ◽  
Platelet Rich Plasma ◽  
Membrane Damage ◽  
Personal Communication ◽  
Dark Field ◽  
Mean Value ◽  
Test Tube ◽  
Lactate Dehydrogenase Activity ◽  
Surface Areas

Invaginated membrane of the surface-connected canalicular system (SCCS) of the resting platelet can be potentially externalized. We have estimated the SCCS surface area by carefully swelling platelets in hypotonic media. Platelets were osmotically stressed by either interfacing a drop of platelet-rich plasma (PRP) with distilled water on a siliconized glass slide or directly in a test tube by careful additions of 60-80% by volume water. Surface areas of the platelets were estimated from a cinematographic analysis of freely rotating platelets. Within five minutes of the addition of water, large smooth spheres (spherocytes) are formed. Soluble, cytoplasmic lactate dehydrogenase activity is not released and visible membrane damage as estimated from dark-field microscopy observations does not occur for at least one hour. The mean value of the spherocyte diameters was 3.9 ± 0.6 um (3 human donors) and did not change over 5 - 60 minutes. It is estimated that the volume of the spherocyte is ~550% greater than that of the original disc and that the surface area has increased by ~300%. Similar results were obtained for rabbit platelets.Since platelet swelling induced osmotically has been shown to yield large spheres with the disappearance of SCCS (J.G. White, personal communication), it is concluded that: 1) the SCCS of the resting platelet can be easily externalized, and 2) osmotic spherocyte formation allows a quantitative estimation of the SCCS surface area.

Temperature-induced changes in nuclear pore complex frequencies nuclear envelope surface areas and nuclear volumes in light-synchronized Euglena

1981 ◽  
Vol 59 (10) ◽  
pp. 802-809 ◽  
Author(s):  
John S. Greenwood ◽  
John N. A. Lott
Keyword(s):  
Nuclear Envelope ◽  
Surface Area ◽  
Nuclear Pore Complex ◽  
Temperature Shift ◽  
Mean Value ◽  
Nuclear Pore ◽  
Nuclear Surface ◽  
Envelope Surface ◽  
The Third ◽  
Surface Areas

An autotrophic culture of Euglena, synchronized using a day: night (D:N), 14:10-h cycle, was subjected to a 21.5 → 31.5 °C temperature shift and then to a reversed shift in temperature after three D:N cycles at 31.5 °C. Nuclear pore complex (NPC) number per square micrometre and nuclear surface area and volume determinations were made on G1 cells at various intervals. Cells sampled immediately prior to the 21.5 → 31.5 °C shift had a mean value of 37.68 NPC∙μm−2 nuclear envelope surface area, 30.40 NPCs/μm2 after three D:N cycles at.31.5 °C and 39.98 NPCs/μm2 after three D:N cycles at the resumed culture temperature of 21.5 °C. Thus temperature changes affect NPC numbers per square micrometre and these changes are reversible.Mean nuclear surface area was 125.76 μm2 immediately prior to the 21.5 → 31.5 °C shift, and decreased over two D:N cycles at 31.5 °C to 101.30 μm2 by the end of the third D:N cycle. Nuclear envelope surface area, one and two D:N cycles after the 31.5 → 21.5 °C shift, was approximately equal that prior to the 21.5 → 31.5 °C shift. After the third D:N cycle, however, nuclear surface area had increased to 173.05 μm2. The changes in nuclear surface area resulted in large differences in the estimates of the total number of NPCs per nucleus. Euglena immediately prior to the 21.5 → 31.5 °C temperature shift had 4739 NPCs/nucleus; immediately prior to the 31.5 → 21.5 °C shift had 3079 NPCs/nucleus; and had 6919 NPCs/nucleus at 21.5 °C and three D:N cycles after the 31.5 → 21.5 °C shift. Estimates of the number of NPCs per cubic micrometre of nuclear volume were almost identical between these samples.

scholarly journals Semi-quantitative understanding of source contribution to nitrous acid (HONO) based on 1 year of continuous observation at the SORPES station in eastern China

2019 ◽  
Vol 19 (20) ◽  
pp. 13289-13308 ◽  
Author(s):  
Yuliang Liu ◽  
Wei Nie ◽  
Zheng Xu ◽  
Tianyi Wang ◽  
Ruoxian Wang ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Nitrous Acid ◽  
Heterogeneous Reaction ◽  
Total Concentration ◽  
Eastern China ◽  
Mean Value ◽  
Budget Analysis ◽  
Conversion Frequency ◽  
Yearly Average ◽  
Quantitative Understanding

Abstract. Nitrous acid (HONO), an important precursor of the hydroxyl radical (OH), has long been recognized as of significance to atmospheric chemistry, but its sources are still debated. In this study, we conducted continuous measurement of HONO from November 2017 to November 2018 at the SORPES station in Nanjing of eastern China. The yearly average mixing ratio of observed HONO was 0.69±0.58 ppb, showing a larger contribution to OH relative to ozone with a mean OH production rate of 1.16 ppb h−1. To estimate the effect of combustion emissions of HONO, the emitted ratios of HONO to NOx were derived from 55 fresh plumes (NO∕NOx > 0.85), with a mean value of 0.79 %. During the nighttime, the chemistry of HONO was found to depend on RH, and heterogeneous reaction of NO2 on an aerosol surface was presumably responsible for HONO production. The average nighttime NO2-to-HONO conversion frequency (CHONO) was determined to be 0.0055±0.0032 h−1 from 137 HONO formation cases. The missing source of HONO around noontime seemed to be photo-induced, with an average Punknown of 1.04 ppb h−1, based on a semi-quantitative HONO budget analysis. An over-determined system of equations was applied to obtain the monthly variations in nocturnal HONO sources. Besides the burning-emitted HONO (accounting for about 23 % of the total concentration), the contribution of HONO formed heterogeneously on ground surfaces to measured HONO was an approximately constant proportion of 36 % throughout the year. The soil emission revealed clear seasonal variation and contributed up to 40 % of observed HONO in July and August. A higher propensity for generating HONO on aerosol surfaces occurred in severe hazes (accounting for 40 % of the total concentration in January). Our results highlight ever-changing contributions of HONO sources and encourage more long-term observations to evaluate the contributions from varied sources.

Role of Carbon in Oxidation of GR-S Vulcanizates

1947 ◽  
Vol 20 (2) ◽  
pp. 469-478 ◽  
Author(s):  
Hugh Winn ◽  
J. Reid Shelton ◽  
David Turnbull
Keyword(s):  
Carbon Black ◽  
Surface Area ◽  
Oxygen Absorption ◽  
Quantitative Correlation ◽  
Surface Areas ◽  
Rapid Absorption ◽  
Initial Stage ◽  
Different Types ◽  
Channel Type

Abstract 1. Carbon black is a catalyst for the oxidation of GR-S vulcanizates. The increased rate of oxygen absorption with increased loading is, however, a function of surface area rather than weight. Different types of carbons show different degrees of activity for a given surface area; the furnace carbons studied were, for example, only 55 per cent as active as channel black in promoting oxidation. 2. The rate constant for the initial rapid absorption of oxygen by GR-S tread stocks is independent of carbon loading. The presence of carbon is, however, essential to activate the centers involved in this initial stage, and the number of activated centers increases with carbon loadings, so that the amount of oxygen absorbed in a given time is also increased. 3. The second or linear stage of oxygen absorption involves two types of reaction with the remaining oxidizable centers in the polymer: a reaction with centers not under the catalytic influence of the carbon black, and a reaction catalyzed by carbon. 4. A theoretical equation was presented which permits the calculation of oxygen absorption by stocks containing either furnace- or channel-type carbons with various surface areas and loadings. The validity of the theory on which the derivation was based is supported by the quantitative correlation of calculated and observed rates of oxygen absorption for stocks containing carbons of both types, with surface areas ranging from 3.7 to 15.7 acres per pound and with loadings of 0 to 75 parts per 100 parts of GR-S. 5. The additional oxygen absorbed at higher loadings of carbon was shown to produce a correspondingly greater deterioration of physical properties.

scholarly journals Contributions of different sources to nitrous acid (HONO) at the SORPES station in eastern China: results from one-year continuous observation

2019 ◽  
Author(s):  
Yuliang Liu ◽  
Wei Nie ◽  
Zheng Xu ◽  
Tianyi Wang ◽  
Ruoxian Wang ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Nitrous Acid ◽  
Heterogeneous Reaction ◽  
Eastern China ◽  
Early Morning ◽  
Mean Value ◽  
Budget Analysis ◽  
Yearly Average ◽  
Heterogeneous Formation ◽  
One Year

Abstract. Nitrous acid (HONO), a reservoir of the hydroxyl radical (OH), has been long-standing recognized to be of significant importance to atmospheric chemistry, but its sources are still debate. In this study, we conducted continuous measurement of HONO from November 2017 to November 2018 at SORPES station in Nanjing of eastern China. The yearly average mixing ratio of observed HONO was 0.69 ± 0.58 ppb, showing a larger contribution to OH relative to ozone with a mean OH production rate of 0.90 ± 0.27 ppb/h. To estimate the effect of combustion emissions of HONO, the emitted ratios of HONO and NOx were derived from 55 fresh plumes (NO / NOx > 0.85), with a mean value of 0.79 %. The well-defined seasonal and diurnal patterns with clear wintertime and early morning concentration peaks of both HONO and NOx indicate that NOx is the critical precursor of HONO. During the nighttime, the chemistry of HONO was found to depend on RH, and heterogeneous reaction of NO2 on aerosol surface was presumably responsible for HONO production. The average nighttime NO2-to-HONO conversion frequency (CHONO) was determined to be 0.0055 ± 0.0032 h−1 from 137 HONO formation cases. The missing source of HONO around noontime seemed to be photo-induced with an average Punknown of 1.13 ± 0.95 ppb h−1, based on a semiquantitative HONO budget analysis. An over-determined system of equations was applied to obtain the monthly variations in nocturnal HONO sources. Except for burning-emitted HONO (approximately 23 % of total measured HONO), the contribution of heterogeneous formation on ground surfaces was an approximately constant proportion of 36 % throughout the year. The soil emission revealed clear seasonal variation, and contributed up to 40 % of observed HONO in July and August. A higher propensity for generating HONO on aerosol surface occurred in heavily polluted period (about 40 % of HONO in January). Our results highlight ever-changing contributions of HONO sources, and encourage more long-term observations to evaluate the contribution from varied sources.

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