Characteristics and Formation Mechanisms of Fine Particulate Nitrate in Typical Urban Areas in China

Ge, Xinlei; He, Yanan; Sun, Yele; Xu, Jianzhong; Wang, Jun Feng; Shen, Yafei; Chen, Mindong

doi:10.3390/atmos8030062

Cited by 67 publications

(35 citation statements)

References 46 publications

(67 reference statements)

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“…Similar to several previous reports, the chemical compositions of PM2.5 during winter of 2017 in Beijing changed significantly Elser et al, 2016;Ge et al, 2017;Huang et al, 2017;Wang et al, 2017). The major inorganic ions of PM2.5 in Beijing during 2017 winter were ammonium (3.3±4.4μg/m 3 ), nitrate (7.1±9.6μg/m 3 ), sulfate (4.5±5.9μg/m 3 ) and chloride (2.4±2.3μg/m 3 ).…”

Section: Pm25 Chemical Compositionssupporting

confidence: 87%

Observation of nitrate dominant PM<sub>2.5</sub> and particle pH elevation in urban Beijing during the winter of 2017

Xie¹,

Wang²,

Wang³

et al. 2019

Preprint

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Particle acidity is crucial to understand secondary formation processes in pollution events since acidity has substantial impacts on the physiochemical properties of PM2.5. Quantification of particle acidity with simulated pH yielded various values range from 0-7 and conflicting conclusions on sulfate formation mechanisms in China 15 recently. In this article, we found that particle pH could increase to near neutral (5.4) as a result of effective sulfur emission control. Benefit from strict pollution control actions, average PM2.5 concentration reduced to a low level (39.7μg/m 3 ) in urban Beijing during winter of 2017. Compare to history record (2014-2017), SO2 gradually decreased to a low level (3.2ppbv in 2017 winter) while NO2 kept increasing (21.4ppbv in 2017 winter). As a response, nitrate's contribution (23.0μg/m 3 ) to PM2.5 become dominant over sulfate (13.1μg/m 3 ) during PM2.5 20 pollution episodes. The nitrate to sulfate molar ratio significantly increased from 1 to 2.7 (value of 1999 and 2017).As nitrate's fraction significantly elevated, particle pH was also found to increase in winter Beijing given sufficient ammonia (average concentration 7.1μg/m 3 , 12.9μg/m 3 during pollution). During PM2.5 pollution episodes, the particle pH predicted increased from 4.4 (moderate acidic) to 5.4 (near neutral) as nitrate to sulfate molar ratio increased from 1 to 5. It is found that the major H + contributor S(VI) was mostly in the form of sulfate, indicating 25 that anions were more neutralized as nitrate content elevated. In the final part, future prediction of particle acidity change was discussed via sensitivity tests: On one hand, nitrate rich particles would absorb more water compared to the sulfate rich particles. This absorption contrast doubles with low to moderate RH (20%~50%). On the other hand, increased level of nitrate and ammonia would have synergetic effects leading to rapid elevation of particle pH to merely neutral (above 5.6). As moderate haze might occur more frequently with high ammonia and particulate 30 nitrate concentration, the major chemical processes during haze events and the control target shall be re-evaluated to obtain the most effective control strategy.

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Section: Pm25 Chemical Compositionssupporting

confidence: 87%

Observation of nitrate dominant PM<sub>2.5</sub> and particle pH elevation in urban Beijing during the winter of 2017

Xie¹,

Wang²,

Wang³

et al. 2019

Preprint

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“…As for the inorganic species, SO 4 2− concentration is~17% higher during daytime, and the difference between day and night samples regarding NO 3 − is very striking, being consistent with day-night variability of nitrate observed in Kanpur, India [35]. The remarkably low levels of nitrate in the day are likely attributed to the evaporation of NH 4 NO 3 due to higher temperature during daytime and/or condensation of nitrate under relatively low temperatures and high RH during nighttime [36]. Overall, the enhancement of secondary aerosol formation is likely a dominant cause for the increase of PM 2.5 concentrations during daytime.…”

Section: Total Concentration and Compositions Of Pm 25supporting

confidence: 75%

Summertime Day-Night Differences of PM2.5 Components (Inorganic Ions, OC, EC, WSOC, WSON, HULIS, and PAHs) in Changzhou, China

et al. 2017

Atmosphere

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increase during daytime, while NO 3 − concentration decreases by a factor of three from nighttime to daytime due to its semi-volatile nature. PAHs, EC, and WSON show higher mass concentration in the night too. Mass ratios of WSOC to OC are high in both day and night, indicating that secondary organic aerosol (SOA) formation could occur throughout the day, while the slightly higher ratio during daytime suggests a more significant contribution from daytime photochemical oxidation. Strong positive correlations between HULIS-C and WSOC, and HULIS-C with O 3 both in day and night, imply that HULIS-C, similar to WSOC, is mainly composed of secondary species. HULIS-C accounted for a large fraction of WSOC, with an average of~60%. Moreover, the average WSON concentrations are 1.08 and 1.46 µg/m 3 , constituting~16% and~18% of water-soluble total nitrogen in day and night, respectively. Correlation analyses suggest that WSON is also predominantly produced from secondary processes. PAHs concentrations are found to be very low in summer aerosols. Overall, our findings highlight the dominant contribution of secondary processes to the major aerosol components in Changzhou, suggesting proper measures to effectively reduce gaseous precursors are also important to improve air quality.

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“…Nanjing implemented a series of air quality control measures around the 2014 Youth Olympics Games period (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). Nevertheless, the mass concentration of PM 2.5 in summer in this work appeared to be high.…”

Section: Seasonal Differencesmentioning

confidence: 88%

Chemical and Light Extinction Characteristics of Atmospheric Aerosols in Suburban Nanjing, China

Zhang

et al. 2017

Atmosphere

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This work reports the chemical and light extinction characteristics of the atmospheric particles collected from January to November 2014 in suburban Nanjing. Size-segregated measurement results showed that more than 80% of the major aerosol components were concentrated in PM 2.5 . The concentration of PM 2.5 was highest in winter and lowest in autumn. Specifically, K + concentration peaked in late spring indicating heavy influences from straw burning, while sulfate concentration was highest in summer and its daytime concentration was also higher than its nighttime concentration, both reflecting a significant role of photochemical production. Nevertheless, except for sulfate, all other components had higher concentrations during nighttime, signifying the role of unfavorable meteorological conditions in exacerbating the air pollution. The IMPROVE formula was employed, which can reconstruct the PM 2.5 mass and light extinction well. The light extinction was mainly contributed by (NH 4 ) 2 SO 4 and NH 4 NO 3 (together 58.3%). Mass concentrations of all PM 2.5 components increased significantly with the increase of pollution levels, but nitrate increased most rapidly; correspondingly, the contribution of nitrate to light extinction also increased quickly when pollution became heavy. Such results were different from those observed in Beijing-Tianjin-Hebei where sulfate increased most quickly. Our results thus highlight that reduction of vehicular NO 2 is likely a priority for air quality improvement in Nanjing. Back trajectory analysis showed the dominance of the local air mass and the one from Huanghai, yet the air mass originated from Bohai, and passed though Shandong and north of Jiangsu province could deliver highly-polluted air to Nanjing, as well.

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Characteristics and Formation Mechanisms of Fine Particulate Nitrate in Typical Urban Areas in China

Cited by 67 publications

References 46 publications

Observation of nitrate dominant PM<sub>2.5</sub> and particle pH elevation in urban Beijing during the winter of 2017

Observation of nitrate dominant PM<sub>2.5</sub> and particle pH elevation in urban Beijing during the winter of 2017

Summertime Day-Night Differences of PM2.5 Components (Inorganic Ions, OC, EC, WSOC, WSON, HULIS, and PAHs) in Changzhou, China

Chemical and Light Extinction Characteristics of Atmospheric Aerosols in Suburban Nanjing, China

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Characteristics and Formation Mechanisms of Fine Particulate Nitrate in Typical Urban Areas in China

Cited by 67 publications

References 46 publications

Observation of nitrate dominant PM&lt;sub&gt;2.5&lt;/sub&gt; and particle pH elevation in urban Beijing during the winter of 2017

Observation of nitrate dominant PM&lt;sub&gt;2.5&lt;/sub&gt; and particle pH elevation in urban Beijing during the winter of 2017

Summertime Day-Night Differences of PM2.5 Components (Inorganic Ions, OC, EC, WSOC, WSON, HULIS, and PAHs) in Changzhou, China

Chemical and Light Extinction Characteristics of Atmospheric Aerosols in Suburban Nanjing, China

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Observation of nitrate dominant PM<sub>2.5</sub> and particle pH elevation in urban Beijing during the winter of 2017

Observation of nitrate dominant PM<sub>2.5</sub> and particle pH elevation in urban Beijing during the winter of 2017