Role of gas-particle conversion of ammonia in haze pollution under ammonia-rich environment in Northern China and prospects of effective emission reduction

Xueting Zou; Shanshan Wang; Jiaqi Liu; Jian Zhu; Sanbao Zhang; Ruibin Xue; Chuanqi Gu; Bin Zhou

doi:10.1016/j.scitotenv.2024.173277

Role of gas-particle conversion of ammonia in haze pollution under ammonia-rich environment in Northern China and prospects of effective emission reduction

Sci Total Environ. 2024 Jul 15:934:173277. doi: 10.1016/j.scitotenv.2024.173277. Epub 2024 May 15.

Authors

Xueting Zou¹, Shanshan Wang², Jiaqi Liu¹, Jian Zhu¹, Sanbao Zhang¹, Ruibin Xue¹, Chuanqi Gu¹, Bin Zhou³

Affiliations

¹ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China.
² Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Institute of Eco-Chongming (IEC), No. 20 Cuiniao Road, Shanghai 202162, China. Electronic address: shanshanwang@fudan.edu.cn.
³ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Institute of Eco-Chongming (IEC), No. 20 Cuiniao Road, Shanghai 202162, China; Institute of Atmospheric Sciences, Fudan University, Shanghai 200433, China. Electronic address: binzhou@fudan.edu.cn.

PMID: 38754510
DOI: 10.1016/j.scitotenv.2024.173277

Abstract

As an important precursor of secondary inorganic aerosols (SIAs), ammonia (NH₃) plays a key role in fine particulate matter (PM_2.5) formation. In order to investigate its impacts on haze formation in the North China Plain (NCP) during winter, NH₃ concentrations were observed at a high-temporal resolution of 1 min by using the SP-DOAS in Tai'an from December 2021 to February 2022. During the observation period, the average NH₃ concentration was 11.84 ± 5.9 ppbv, and it was determined as an ammonia-rich environment during different air quality conditions. Furthermore, the average concentrations of sulfate (SO₄^2-), nitrate (NO₃^-) and ammonium (NH₄⁺) were 9.54 ± 5.97 μg/m³, 19.09 ± 14.18 μg/m³ and 10.72 ± 6.53 μg/m³, respectively. Under the nitrate-dominated atmospheric environment, aerosol liquid water content (ALWC) was crucial for NH₃ particle transformation during haze aggravation, and the gas-particle partitioning of ammonia played an important role in the SIAs formation. The reconstruction of the molecular composition further indicated that ammonium nitrate (NH₄NO₃) plays a dominant role in the increase of PM_2.5 during haze events. Consequently, future efforts to mitigate fine particulate pollution in this region should focus on controlling NH₄NO₃ levels. In ammonia-rich environments, NO₃^- formation is more dependent on the concentration of nitric acid (HNO₃). The sensitive analysis of TNO₃ (HNO₃ + NO₃^-) and NH_X (NH₃ + NH₄⁺) reduction using the thermodynamic model suggested that the NO₃^- concentration decreases linearly with the reduction of TNO₃. And the concentration of NO₃^- decreases rapidly only when NH_X is reduced by 50-60 %. Reducing NO_X emissions is the most effective way to alleviate nitrate pollution in this region.

Keywords: Aerosol liquid water content; Ammonia; DOAS; Gas-particle partitioning; Reduction potential.