PM2.5 acidity and secondary nitrate formation during typical pollution episodes of four seasons in Beijing

WANG You-feng; JING Kuan; SHEN Xiu-e; WANG Qin; WANG Chen-jing; FU Jia-ming; ZHANG Bo-tao; ZHANG Jian; CAO Yang; ZHANG Ke; LIU Bao-xian

PDF(2142 KB)

China Environmental Science ›› 2024, Vol. 44 ›› Issue (8) : 4167-4178.

Air Pollution Control

PM_2.5 acidity and secondary nitrate formation during typical pollution episodes of four seasons in Beijing

WANG You-feng^1,2, JING Kuan^1,2, SHEN Xiu-e^1,2, WANG Qin^1,2, WANG Chen-jing^1,2, FU Jia-ming^1,2, ZHANG Bo-tao^1,2, ZHANG Jian^1,2, CAO Yang^1,2, ZHANG Ke^1,2, LIU Bao-xian^1,2

Author information +

History +

Abstract

Based on the online monitoring data from urban sites in Beijing during 2022, the ISORROPIA-II model was used to analyze the acidity of PM_2.5 during four typical pollution episodes, namely haze pollution in winter, dust pollution in spring, high ozone pollution in summer, and PM_2.5 and O₃ combined pollution in autumn. The evolution of aerosol pH with the rapid formation of nitrate was obtained. The results show that the aerosol pH in Beijing was moderately acidic, in ranges of 3.59~5.07, 3.70~7.76, 2.44~6.15, and 2.80~4.69 for the four episodes, respectively. The aerosol pH exhibited normal distribution for the four pollution episodes with median values of 4.60, 4.59, 3.91 and 4.09, respectively. During winter haze pollution, aerosol water content and the aerosol pH were the highest. During spring dust pollution, the aerosol pH presented bimodal distribution, affected by both anthropogenic and natural sources. The acidity of PM_2.5 in summer and autumn episodes was the strongest and the second strongest respectively, which might be related to the oxidation of acid gas enhanced by strong atmospheric oxidation conditions. During high ozone pollution in summer, with high temperature and low pH, HNO₃ tended to be distributed in the gas phase, and the nitrate proportion in PM_2.5 was the lowest (22%). For PM_2.5 and O₃ combined pollution in autumn, pH was low in the daytime and high in the nighttime, conducive to the nitrate accumulation at night after the gaseous HNO₃ formation in the daytime. The nitrate proportion was comparable to that during pollution episodes in winter and spring, reaching 27%~28%. Gaseous NH₃ was abundant, and the neutralization (homogenization) reaction between HNO₃and NH₃ was the main formation mechanism of NO₃^-. Abundant of NH₄⁺, (NH₄)₂SO₄, NH₄NO₃ and NH₄Cl in aerosol could also be fully coupled. This research shows that high aerosol water content and aerosol pH were responsible for the rapid growth of nitrate during pollution. Further reduction of the precursors NH₃ and NO_x would be an effective means to control the fine particles in Beijing.

Key words

aerosol pH / Beijing / ISORROPIA-II model / secondary nitrate formation mechanism / typical pollution episodes

Cite this article

EndNote

Ris (Procite)

Bibtex

Download Citations

WANG You-feng, JING Kuan, SHEN Xiu-e, WANG Qin, WANG Chen-jing, FU Jia-ming, ZHANG Bo-tao, ZHANG Jian, CAO Yang, ZHANG Ke, LIU Bao-xian. PM_2.5 acidity and secondary nitrate formation during typical pollution episodes of four seasons in Beijing[J]. China Environmental Science. 2024, 44(8): 4167-4178

References

[1] Pye H O T, Nenes A, Alexander B, et al. The acidity of atmospheric particles and clouds [J]. Atmospheric Chemistry and Physics, 2020, 20(8):4809-4888.
[2] Kanakidou M, Myriokefalitakis S, Tsigaridis K. Aerosols in atmospheric chemistry and biogeochemical cycles of nutrients [J]. Environmental Research Letters, 2018,13(6):063004.
[3] Rengarajan R, Sudheer A K, Sarin M M. Aerosol acidity and secondary organic aerosol formation during wintertime over urban environment in western India [J]. Atmospheric Environment, 2011, 45(11):1940-1945.
[4] Fang T, Guo H, Zeng L, et al. Highly acidic ambient particles, soluble metals, and oxidative potential: A link between sulfate and aerosol toxicity [J]. Environmental Science & Technology, 2017,51(5):2611- 2620.
[5] Mahowald N, Jickells T D, Baker A R, et al. Global distribution of atmospheric phosphorus sources, concentrations and deposition rates, and anthropogenic impacts [J]. Global Biogeochemical Cycles, 2008, 22(4).doi:10.1029/2008GB003240.
[6] Metzger S, Abdelkader M, Steil B, et al. Aerosol water parameterization: long-term evaluation and importance for climate studies [J]. Atmospheric Chemistry and Physics, 2018,18(22):16747- 16774.
[7] Zhao Q, Nenes A, Yu H, et al. Using high-temporal-resolution ambient data to investigate gas-particle partitioning of ammonium over different seasons [J]. Environmental Science & Technology, 2020,54(16):9834-9843.
[8] 肖致美,武婷,卫昱婷,等.天津市PM_2.5中二次硝酸盐形成及防控[J]. 环境科学, 2021,42(6):2616-2625. Xiao Z M, Wu T, Wei Y T, et al. Formation and prevention of secondary nitrate in PM_2.5 in Tianjin [J]. Environmental Science, 2021,42(6):2616-2625.
[9] Liu M, Song Y, Zhou T, et al. Fine particle pH during severe haze episodes in northern China [J]. Geophysical Research Letters, 2017, 44(10):5213-5221.
[10] Pathak R K, Wang T, Ho K F, et al. Characteristics of summertime PM_2.5organic and elemental carbon in four major Chinese cities: Implications of high acidity for water-soluble organic carbon (WSOC) [J]. Atmospheric Environment, 2011,45(2):318-325.
[11] Du H, Kong L, Cheng T, et al. Insights into ammonium particle- to-gas conversion: non-sulfate ammonium coupling with nitrate and chloride [J]. Aerosol and Air Quality Research, 2010,10(6):589-595.
[12] Li W, Shao L, Shi Z, et al. Mixing state and hygroscopicity of dust and haze particles before leaving Asian continent [J]. Journal of Geophysical Research-Atmospheres, 2014,119(2):1044-1059.
[13] Shi X, Nenes A, Xiao Z, et al. High-resolution data sets unravel the effects of sources and meteorological conditions on nitrate and its gas-particle partitioning [J]. Environmental Science & Technology, 2019,53(6):3048-3057.
[14] Weber R J, Guo H, Russell A G, et al. High aerosol acidity despite declining atmospheric sulfate concentrations over the past 15 years [J]. Nature Geoscience, 2016,9(4):282-285.
[15] Ito T, Nenes A, Johnson M S, et al. Acceleration of oxygen decline in the tropical Pacific over the past decades by aerosol pollutants [J]. Nature Geoscience, 2016,9(6):443-447.
[16] Ding J, Zhao P, Su J, et al. Aerosol pH and its driving factors in Beijing [J]. Atmospheric Chemistry and Physics, 2019,19(12):7939- 7954.
[17] Guo H, Sullivan A P, Campuzano-Jost P, et al. Fine particle pH and the partitioning of nitric acid during winter in the northeastern United States [J]. Journal of Geophysical Research-Atmospheres, 2016,121(17):10355-10376.
[18] 安欣欣,曹阳,王琴,等.北京城区PM_2.5各组分污染特征及来源分析[J]. 环境科学, 2022,43(5):2252-2261. An X X, Cao Y, Wang Q, et al. Chemical characteristics and source apportionment of PM_2.5 in urban area of Beijing [J]. Environmental Science, 2022,43(5):2251-2261.
[19] 张蒙,韩力慧,刘保献,等.北京市冬季重污染期间PM_2.5及其组分演变特征[J]. 中国环境科学, 2020,40(7):2829-2838. Zhang M, Han L H, Liu B, et al. Evolution of PM_2.5 and its components during heavy pollution episodes in winter in Beijing [J]. China Environmental Science, 2020,40(7):2829-2838.
[20] Rindelaub J D, Craig R L, Nandy L, et al. Direct measurement of pH in individual particles via Raman microspectroscopy and variation in acidity with relative humidity [J]. Journal of Physical Chemistry A, 2016,120(6):911-917.
[21] Hennigan C J, Izumi J, Sullivan A P, et al. A critical evaluation of proxy methods used to estimate the acidity of atmospheric particles [J]. Atmospheric Chemistry and Physics, 2015,15(5):2775-2790.
[22] Kim Y P, Seinfeld J H, Saxena P. Atmospheric gas-aerosol equlibrium. 2. Analysis of common approximations and activity-coefficient calculation methods [J]. Aerosol Science and Technology, 1993,19(2): 182-198.
[23] Metzger S, Dentener F, Pandis S, et al. Gas/aerosol partitioning: 1. A computationally efficient model [J]. Journal of Geophysical Research- Atmospheres, 2002,107(D16).doi:org/10.1029/2001JD001102.
[24] US EPA Office of Research and Development: CMAQ (Version 5.3), Zenodo, https://doi.org/10.5281/zenodo.3379043, 2019.
[25] Fountoukis C, Nenes A. ISORROPIA II: a computationally efficient thermodynamic equilibrium model for K⁺-Ca²⁺-Mg²⁺-NH₄⁺-Na⁺- SO₄^2--NO₃^--Cl^--H₂O aerosols [J]. Atmospheric Chemistry and Physics, 2007,7(17):4639-4659.
[26] Nenes A, Pandis S N, Pilinis C. ISORROPIA: A new thermodynamic equilibrium model for multiphase multicomponent inorganic aerosols [J]. Aquatic Geochemistry, 1998,4(1):123-152.
[27] 高洁,史旭荣,卫昱婷,等.基于天津市在线数据评估ISORROPIA- Ⅱ模式结果及气溶胶pH的影响因素[J]. 环境科学, 2020,41(8): 3458-3466. Gao J, Shi X R, Wei Y T, et al. Evaluation of different ISORROPIA-Ⅱ modes and the influencing factors of aerosol pH based on Tianjin online data [J]. Environmental Science, 2020,41(8): 3458-3466.
[28] Zellner R. John H. Seinfeld and Spyros N. Pandis: Atmospheric chemistry and physics, from air pollution to climate change [J]. Journal of Atmospheric Chemistry, 2000,37:212-214.
[29] Xue J, Lau A K H, Yu J Z. A study of acidity on PM_2.5in Hong Kong using online ionic chemical composition measurements [J]. Atmospheric Environment, 2011,45(39):7081-7088.
[30] Song S, Gao M, Xu W, et al. Fine-particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models [J]. Atmospheric Chemistry and Physics, 2018,18(10):7423-7438.
[31] Battaglia M A Jr, Douglas S, Hennigan C J. Effect of the urban heat island on aerosol pH [J]. Environmental Science & Technology, 2017,51(22):13095-13103.
[32] Guo H, Liu J, Froyd K D, et al. Fine particle pH and gas-particle phase partitioning of inorganic species in Pasadena, California, during the 2010 CalNex campaign [J]. Atmospheric Chemistry and Physics, 2017,17(9):5703-5719.
[33] Young A H, Keene W C, Pszenny A A P, et al. Phase partitioning of soluble trace gases with size-resolved aerosols in near-surface continental air over northern Colorado, USA, during winter [J]. Journal of Geophysical Research-Atmospheres, 2013,118(16):9414- 9427.
[34] Bougiatioti A, Nikolaou P, Stavroulas I, et al. Particle water and pH in the eastern Mediterranean: source variability and implications for nutrient availability [J]. Atmospheric Chemistry and Physics, 2016, 16(7):4579-4591.
[35] Zhang T, Lu B, Quan X, et al. PM_2.5 acidity during haze episodes in Shanghai, China [J]. Environmental Chemistry, 2021,18(4):168-176.
[36] Pathak R K, Louie P K K, Chan C K. Characteristics of aerosol acidity in Hong Kong [J]. Atmospheric Environment, 2004,38(19):2965- 2974.
[37] Pathak R K, Wu W S, Wang T. Summertime PM_2.5 ionic species in four major cities of China: nitrate formation in an ammonia-deficient atmosphere [J]. Atmospheric Chemistry and Physics, 2009,9(5):1711- 1722.
[38] 刘湘雪,蒲维维,马志强,等.北京地区大气氨时空变化特征[J]. 中国环境科学, 2021,41(8):3473-3483. Liu X X, Pu W W, Ma Z Q, et al. Study on the temporal and spatial variation of atmospheric ammonia in Beijing [J]. China Environmental Science, 2021,41(8):3473-3483.
[39] Wang Y, Zhuang G, Zhang X, et al. The ion chemistry, seasonal cycle, and sources of PM_2.5 and TSP aerosol in Shanghai [J]. Atmospheric Environment, 2006,40(16):2935-2952.
[40] Zhang Y, Huang W, Cai T, et al. Concentrations and chemical compositions of fine particles (PM_2.5) during haze and non-haze days in Beijing [J]. Atmospheric Research, 2016,174-175:62-69.