Lien Justin, Hung Hui-Ming
Department of Atmospheric Sciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan.
Heliyon. 2021 Oct 19;7(10):e08210. doi: 10.1016/j.heliyon.2021.e08210. eCollection 2021 Oct.
The interaction between transport and chemistry is pivotal for local ozone (O) concentration, especially for a coastal region where the upstream sources might change diurnally. In the current emission control policy, most pollutants, such as particulate matter, SO, NOx, and CO, decrease while the annual O trend might increase due to the complex feedbacks of precursors. In this study, we investigate the influence of transport upon the wintertime O diurnal trend over ZuoYing Kaohsiung, an urban coastal site in southern Taiwan, by constructing a two-dimensional numerical model coupling both physical mechanisms and core chemical processes and provide a feasible emission control strategy. The transport process (i.e., import vs. export) for the daytime is determined using the Leighton Ratio (Φ), the ratio of O-production over O-loss rate, under the pseudo-steady-state condition. Φ shows a deviation of -9 to +13% from the photo-stationary state, and experiences a transition from import effect before 10:15 to weakening import or net export effect afterward associated with a net O production as sea breeze starts developing. The significantly higher Φ derived from observation than from simulation by a factor of 1.35 might be resulted from the over-reported NO due to NOy contribution on the NO measurement, and the influence of aerosol and cloud possibly reducing ∼30% on applied NO photolysis rate constant, associated with aerosol optical depth of 0.75 ± 0.15 and single scattering albedo of 0.85 ± 0.15. In this studied NOx-saturated regime, the addition of sea breeze convergence over the land enhances the maximal O by ∼10%, mainly due to the O accumulation (∼88%). Furthermore, the ozone isopleth analysis as a function of non-methane hydrocarbons and NOx emissions provides an achievable strategy to decrease both maximum daily ozone and the increment of ozone from morning to maximum by reducing hydrocarbons and NOx emissions, which can also eliminate the additional nitrate contribution on the aerosols.
传输与化学之间的相互作用对于局部臭氧（O）浓度至关重要，特别是对于上游源可能会随昼夜变化的沿海地区而言。在当前的排放控制政策中，大多数污染物，如颗粒物、二氧化硫、氮氧化物和一氧化碳，排放量都在减少，而由于前体物质的复杂反馈，臭氧的年变化趋势可能会增加。在本研究中，我们通过构建一个耦合物理机制和核心化学过程的二维数值模型，研究了传输对台湾南部城市沿海站点左营高雄冬季臭氧昼夜变化趋势的影响，并提供了一种可行的排放控制策略。在准稳态条件下，利用莱顿比率（Φ），即臭氧生成速率与臭氧损耗速率之比，确定白天的传输过程（即输入与输出）。Φ与光化学稳态相比有-9%至+13%的偏差，并且随着海风开始发展，经历了从10:15之前的输入效应到随后输入减弱或净输出效应的转变，同时伴随着臭氧的净生成。观测得到的Φ值比模拟值显著高出1.35倍，这可能是由于氮氧化物对一氧化氮测量的贡献导致一氧化氮报告值过高，以及气溶胶和云层的影响可能使应用的一氧化氮光解速率常数降低约30%，气溶胶光学厚度为0.75±0.15，单次散射反照率为0.85±0.15。在本研究的氮氧化物饱和状态下，陆地上海风辐合的增加使最大臭氧浓度提高了约10%，主要是由于臭氧的积累（约88%）。此外，作为非甲烷烃和氮氧化物排放函数的臭氧等值线分析提供了一种可行的策略，即通过减少碳氢化合物和氮氧化物排放来降低每日最大臭氧浓度以及从早晨到最大值的臭氧增量，这还可以消除气溶胶上额外的硝酸盐贡献。
