State Key Laboratory of Loess and Quaternary Geology, Key Lab of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710061, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
State Key Laboratory of Loess and Quaternary Geology, Key Lab of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710061, China; Key Lab of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai, 210062, China; Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China; University of Chinese Academy of Sciences, Beijing, 100049, China; School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, 710049, China.
Environ Pollut. 2019 Jan;244:877-884. doi: 10.1016/j.envpol.2018.10.019. Epub 2018 Oct 29.
To identify the sources and heterogeneous reactions of sulfate and nitrate with dust in the atmosphere, airborne particles in Xi'an, inland China during the spring of 2017 were collected and measured for chemical compositions, along with a laboratory simulation of the heterogeneous formation of ammonium nitrate on the dust surface. Our results showed that concentrations of Ca, Na and Cl in the TSP samples were enhanced in the dust events, with the values of 41.8, 5.4 and 4.0 μg m, respectively, while NO (7.1 μg m) and NH (2.4 μg m) remarkably decreased, compared to those in the non-dust periods. During the dust events, NH correlated only with NO (R = 0.52) and abundantly occurred in the coarse mode (>2.1 μm), in contrast to that in the non-dust periods, which well correlated with sulfate and nitrate and enriched in the fine mode (<2.1 μm). SO in Xi'an during the dust events existed mostly as gypsum (CaSO·2HO) and mirabilite (NaSO·10HO) and dominated in the coarse mode, suggesting that they were directly transported from the upwind Gobi Desert region. Our laboratory simulation results showed that during the long-range transport hygroscopic salts in the Gobi dust such as mirabilite can absorb water vapor and form a liquid phase on the particle surface, then gaseous NH and HNO partition into the aqueous phase and form NHNO, resulting in the strong correlation of NH with NO and their accumulation on dust particles. The dry deposition flux of total inorganic nitrogen (NH + NO) in Xi'an during the dust events was 0.97 mg-N m d and 37% higher than that in the non-dust periods. Such a significant enhanced N-deposition is ascribed to the heterogeneous formation of NHNO on the dust particle surface, which has been ignored and should be included in future model simulations.
为了识别大气中硫酸盐和硝酸盐与灰尘的来源和异质反应，我们于 2017 年春季在中国内陆的西安市采集并测量了空气悬浮颗粒的化学成分，同时还进行了实验室模拟实验，以研究灰尘表面上硝酸铵的异质形成。结果表明，TSP 样品中的 Ca、Na 和 Cl 浓度在扬尘事件中升高，分别为 41.8、5.4 和 4.0μg/m，而 NO（7.1μg/m）和 NH（2.4μg/m）浓度明显降低。与非扬尘期相比，NH 在扬尘事件中仅与 NO（R=0.52）相关，并且大量出现在粗模态（>2.1μm）中，而在非扬尘期，NH 与硫酸盐和硝酸盐密切相关，并且在细模态（<2.1μm）中富集。西安市扬尘期间的 SO 主要以石膏（CaSO·2HO）和芒硝（NaSO·10HO）的形式存在，且主要分布在粗模态中，这表明它们是直接从上风戈壁荒漠地区输送而来。我们的实验室模拟结果表明，在长途运输过程中，戈壁灰尘中的吸湿盐类，如芒硝，可以吸收水蒸气并在颗粒表面形成液相，然后气态 NH 和 HNO 进入液相并形成 NHNO，导致 NH 与 NO 强烈相关，且在灰尘颗粒上积累。西安市扬尘期间总无机氮（NH+NO）的干沉降通量为 0.97mg-N/m·d，比非扬尘期高 37%。这种显著增强的 N 沉降归因于灰尘颗粒表面上 NHNO 的异质形成，这在过去的模型模拟中被忽略，而应在未来的模型模拟中加以考虑。
