Choi Daniel, Huangfu Yibo, Fredj Erick, Li Qian, Yuan Bin, Zhang Xiaoxiao, He Xianjun, Liu Huizhi, Tas Eran
The Robert H. Smith Faculty of Agriculture, Food and Environment, Department of Soil and Water Sciences, The Hebrew University of Jerusalem, Rehovot, Israel.
College of Environment and Climate, Institute for Environmental and Climate Research, Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou, China.
Sci Total Environ. 2025 Oct 15;999:180347. doi: 10.1016/j.scitotenv.2025.180347. Epub 2025 Sep 1.
Tropospheric ozone (O) is a major air pollutant that negatively affects human health and vegetation, and plays a central role in climate change and atmospheric chemistry. Current simulations of tropospheric O concentrations in climate and air-quality models are significantly limited by the inaccurate representation of O dry deposition rate-particularly in urban areas, where field measurements remain scarce. We hypothesize that O dry deposition in the urban environment is controlled by factors similar to those over vegetation, albeit via potentially different mechanisms. Accordingly, we performed O and reactive nitrogen oxide (NO = [NO] + [NO]) flux measurements using eddy covariance (EC) technique from a meteorological tower in an urban area of Beijing (IAP) during the spring and summer, complemented by EC flux measurements of volatile organic compounds (VOCs) using Vocus-PTR-TOF-MS. Our analyses indicated that the downward ozone velocity (Vdw,O) at the IAP measurement site is controlled by both gas-phase chemical reactions and surface uptake, with comparable contributions. The reaction of O with NO emissions dominated the chemical contribution to Vdw,O, with a significant contribution of NO near the ground, particularly in the morning. The effect of relative humidity (RH) on Vdw,O, likely via surface wetness accumulation similar to its effect on non-stomatal O deposition over vegetation, showed a logarithmic and hyperbolic dependency of Vdw,O on RH, for 5 % < RH < 30 % and RH > 70 %, respectively. Both NO emissions from elevated sources and RH < 30 %-conditions associated with a higher frequency of positive O flux events-dramatically limited Vdw,O.
对流层臭氧（O）是一种主要的空气污染物，对人类健康和植被产生负面影响，并且在气候变化和大气化学中起着核心作用。目前，气候和空气质量模型中对流层O浓度的模拟受到O干沉降速率表示不准确的显著限制，特别是在城市地区，那里的实地测量仍然很少。我们假设，城市环境中的O干沉降受与植被上空类似的因素控制，尽管其潜在机制可能不同。因此，我们在春季和夏季利用北京城区（IAP）一座气象塔上的涡度相关（EC）技术进行了O和活性氮氧化物（NO = [NO] + [NO]）通量测量，并辅以使用Vocus-PTR-TOF-MS对挥发性有机化合物（VOCs）进行的EC通量测量。我们的分析表明，IAP测量站点的向下臭氧速度（Vdw,O）受气相化学反应和表面吸收的控制，二者贡献相当。O与NO排放的反应主导了对Vdw,O的化学贡献，地面附近的NO贡献显著，尤其是在早晨。相对湿度（RH）对Vdw,O的影响，可能是通过类似于其对植被非气孔O沉降的影响的表面湿度积累，分别在5% < RH < 30%和RH > 70%时，显示出Vdw,O对RH的对数和双曲线依赖性。高空源的NO排放以及RH < 30%（与较高频率的正O通量事件相关的条件）都极大地限制了Vdw,O。
