The formation of sulfate (SO42−) in the atmosphere is linked chemically to its direct precursor, sulfur dioxide (SO2), through several key oxidation paths for which nitrogen oxides or NOx (NO and NO2) play essential roles. Here we present a coherent description of the dependence of SO42– formation on SO2 and NOx under haze-fog conditions, in which fog events are accompanied by high aerosol loadings and fog-water pH in the range of 4.7–6.9. Three SO42– formation regimes emerge as defined by the role played by NOx. In the low-NOx regime, NOx act as catalyst for HOx, which is a major oxidant for SO2, whereas in the high-NOx regime, NO2 is a sink for HOx. Moreover, at highly elevated NOx levels, a so-called NO2-oxidant regime exists in which aqueous NO2 serves as the dominant oxidant of SO2. This regime also exists under clean fog conditions but is less prominent. Sensitivity calculations using an emission-driven box model show that the reduction of SO42– is comparably sensitive to the reduction of SO2 and NOx emissions in the NO2-oxidant regime, suggesting a co-reduction strategy. Formation of SO42− is relatively insensitive to NOx reduction in the low-NOx regime, whereas reduction of NOx actually leads to increased SO42– production in the intermediate high-NOx regime.
Subscribe to Journal
Get full journal access for 1 year
only $15.58 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
The datasets generated during and/or analysed during the current study are available at https://github.com/xuejianust/NGsulfate/blob/master/NG.zip.
The computer code used to generate the results in this manuscript is available from the corresponding authors on request.
Stein, A. F. & Lamb, D. Chemical indicators of sulfate sensitivity to nitrogen oxides and volatile organic compounds. J. Geophys. Res. 107, 13–11 (2002).
Stein, A. F. & Lamb, D. Empirical evidence for the low- and high-NOx photochemical regimes of sulfate and nitrate formation. Atmos. Environ. 37, 3615–3625 (2003).
Tao, J., Zhang, L. M., Cao, J. J. & Zhang, R. J. A review of current knowledge concerning PM2.5 chemical composition, aerosol optical properties and their relationships across China. Atmos. Chem. Phys. 17, 9485–9518 (2017).
Wang, J. D. et al. Particulate matter pollution over China and the effects of control policies. Sci. Total Environ. 584, 426–447 (2017).
Yang, S. et al. Characteristics and formation of typical winter haze in Handan, one of the most polluted cities in China. Sci. Total Environ. 613, 1367–1375 (2018).
Lu, C. S. et al. Chemical composition of fog water in Nanjing area of China and its related fog microphysics. Atmos. Res. 97, 47–69 (2010).
Wang, G. H. et al. Persistent sulfate formation from London fog to chinese haze. Proc. Natl Acad. Sci. USA 113, 13630–13635 (2016).
Ronald, J. V. et al. Cleaning up the air: effectiveness of air quality policy for SO2 and NOx emissions in China. Atmos. Chem. Phys. 17, 1775–1789 (2017).
Shen, X. J. et al. Characterization of submicron aerosols and effect on visibility during a severe haze-fog episode in Yangtze River Delta, China. Atmos. Environ. 120, 307–316 (2015).
Cheng, Y. F. et al. Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China. Sci. Adv. 2, e1601530 (2016).
Xue, J., Yuan, Z. B., Yu, J. Z. & Lau, A. K. H. An observation-based model for secondary inorganic aerosols. Aerosol Air Qual. Res. 14, 862–882 (2014).
Xie, Y. N. et al. Enhanced sulfate formation by nitrogen dioxide: implications from in situ observations at the SORPES station. J. Geophys. Res. Atmos. 120, 12679–12694 (2015).
Xue, J. et al. Sulfate formation enhanced by a cocktail of high NOx, SO2, particulate matter, and droplet pH during haze-fog events in megacities in China: an observation-based modeling investigation. Environ. Sci. Technol. 50, 7325–7334 (2016).
Hagler, G. S. et al. Source areas and chemical composition of fine particulate matter in the Pearl River Delta region of China. Atmos. Environ. 40, 3802–3815 (2006).
Pathak, R. K., Wu, W. S. & Wang, T. Summertime PM2.5 ionic species in four major cities of China: nitrate formation in an ammonia-deficient atmosphere. Atmos. Chem. Phys. 9, 1711–1722 (2009).
Wang, Y. et al. The ion chemistry and the source of PM2.5 aerosol in Beijing. Atmos. Environ. 39, 3771–3784 (2005).
Tian, Y. Z. et al. Spatial, seasonal and diurnal patterns in physicochemical characteristics and sources of PM2.5 in both inland and coastal regions within a megacity in China. J. Hazard Mater. 342, 139–149 (2018).
Li, P. F. et al. Fog water chemistry in Shanghai. Atmos. Environ. 45, 4034–4041 (2011).
Wu, D. et al. Study on the chemical characteristics of polluting fog in Guangzhou area in spring. J. Trop. Meteorol. 15, 68–72 (2009).
Benedict, K. B., Lee, T. & Collett, J. L. Cloud water composition over the southeastern Pacific Ocean during the VOCALS regional experiment. Atmos. Environ. 46, 104–114 (2012).
Sillman., S. The relation between ozone, NOx and hydrocarbons in urban and polluted rural environment. Atmos. Environ. 33, 1821–1845 (1999).
Wennberg, P. O. Let’s abandon the “high NOx” and “low NOx” terminology. IGACnews 50, 3–4 (2013).
Straub, D. J., Hutchings, J. W. & Herckes, P. Measurements of fog composition at a rural site. Atmos. Environ. 47, 195–205 (2012).
Meng, Z. Y. et al. Vertical distributions of SO2 and NO2 in the lower atmosphere in Beijing urban areas, China. Sci. Total Environ. 390, 456–465 (2008).
Liu, M. X. et al. Fine particle pH during severe haze episodes in northern China. Geophys. Res. Lett. 44, 5213–5221 (2017).
Clifton, C. L., Altstein, N. & Huie, R. E. Rate-constant for the reaction of NO2 with sulfur(iv) over the pH range 5.3–13. Environ. Sci. Technol. 22, 586–589 (1988).
He, P. Z. et al. Isotopic constraints on heterogeneous sulfate production in Beijing haze. Atmos. Chem. Phys. 18, 5515–5528 (2018).
Gao, M. et al. Improving simulations of sulfate aerosols during winter haze over northern China: the impacts of heterogeneous oxidation by NO2. Front. Environ. Sci. Eng. 10, 16 (2016).
Li, M. M. et al. Formation and evolution mechanisms for two extreme haze episodes in the Yangtze River Delta region of China during winter 2016. J. Geophys. Res. Atmos. 124, 3607–3623 (2019).
Huang, L. et al. Enhanced sulfate formation through SO2 + NO2 heterogeneous reactions during heavy winter haze in the Yangtze River Delta region, China. Atmos. Chem. Phys. Diss. https://doi.org/10.5194/acp-2019-292 (2019).
Lee, Y. N. & Schwartz, S. E. Kinetics of oxidation of aqueous sulfur(iv) by nitrogen dioxide. In Proc. 4th International Conference, Santa Monica, California (eds Pruppacher, H. R. et al.) Vol. 1 (Elsevier, 1982).
Shen, C. H. & Rochelle, G. T. Nitrogen dioxide absorption and sulfite oxidation in aqueous sulfite. Environ. Sci. Technol. 32, 1994–2003 (1998).
Warneck, P. The relative importance of various pathways for the oxidation of sulfur dioxide and nitrogen dioxide in sunlit continental fair weather clouds. Phys. Chem. Chem. Phys. 1, 5471–5483 (1999).
Fairlie, T. D. et al. Impact of mineral dust on nitrate, sulfate, and ozone in transpacific asian pollution plumes. Atmos. Chem. Phys. 10, 3999–4012 (2010).
Trebs, I. et al. Relationship between the NO2 photolysis frequency and the solar global irradiance. Atmos. Meas. Tech. 2, 725–739 (2009).
Bott, A. & Carmichael, G. R. Multiphase chemistry in a microphysical radiation fog model—a numerical study. Atmos. Environ. 27, 503–522 (1993).
Herckes, P., Chang, H., Lee, T. & Collett, J. L. Air pollution processing by radiation fogs. Water Air Soil Poll. 181, 65–75 (2007).
Robert, M. A., Kleeman, M. J. & Jakober, C. A. Size and composition distributions of particulate matter emissions: part 2—heavy-duty diesel vehicles. J. Air Waste Manag. Assoc. 57, 1429–1438 (2012).
Wild, R. J. et al. On-road measurements of vehicle NO2/NOx emission ratios in Denver, Colorado, USA. Atmos. Environ. 148, 182–189 (2017).
Tan, Z. F. et al. Wintertime photochemistry in Beijing: observations of ROx radical concentrations in the north China plain during the BEST-ONE campaign. Atmos. Chem. Phys. 18, 12391–12411 (2018).
This study was supported in part by the Research Grants Council of Hong Kong (grant nos. 615406 and 16122017). We acknowledge air quality data from the Atmospheric Research Center, Institute of Environment at HKUST.
The authors declare no competing interests.
Peer review information Primary Handling Editor(s): Xujia Jiang
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Xue, J., Yu, X., Yuan, Z. et al. Efficient control of atmospheric sulfate production based on three formation regimes. Nat. Geosci. 12, 977–982 (2019). https://doi.org/10.1038/s41561-019-0485-5
Proceedings of the National Academy of Sciences (2020)