“平流层臭氧侵入例外事件”美国做法及其对我国臭氧污染防控的启示

The implementation of stratospheric ozone intrusion exceptional event in the United States and its implication for ozone control in China

平流层臭氧在特定气象条件下可侵入对流层,严重情况下会引发近地面监测点位的臭氧浓度超标。美国环境保护局(EPA)将上述事件称作"平流层臭氧侵入例外事件"(以下简称"例外事件"),并于2018年颁布了《关于可能影响臭氧浓度的平流层臭氧侵入例外事件申请陈述指南》(以下简称《指南》)。本文结合美国相关实操案例,详细阐述了"例外事件"的识别、判定技术和业务化处理流程及其对我国探索开展"例外事件"剔除工作的启示,以期为我国臭氧污染管控提供决策参考。研究发现以下结果:一是"例外事件"不定期发生,且影响范围较大,直接导致受影响区域近地面监测点位臭氧浓度异常超标,影响臭氧达标限值的设定,不利于客观公平地开展空气质量达标考核工作;二是美国依托多种监测手段和模式方法,已针对"例外事件"形成了一套完整的判定指标体系及规范的业务化流程,可直接扣除此类事件导致的臭氧超标数据;三是美国现有实操案例多为解决平流层臭氧侵入导致西部高海拔地区(如怀俄明州、犹他州等)近地面臭氧浓度超标的问题。地方空气质量管理机构只有在"例外事件"发生期间臭氧浓度处于年度排名前四位时,才会积极组织相关技术专家开展"例外事件"的证据搜集和申请工作。"例外事件"美国做法对我国的启示是:尽快组织力量深入开展我国"例外事件"的回溯分析,重点关注春末和冬初以臭氧为首要污染物的轻度污染天气,尽快形成我国"例外事件"的识别判定技术规范与要求,并建立健全"例外事件"管理机制,为打赢污染防治攻坚战提供有力支撑。

The intrusion of stratospheric ozone to the lower troposphere can occur occasionally under particular meteorological circumstances, inducing the exceedance of ozone concentration over relevant monitor sites.The events mentioned above are defined as Stratospheric Ozone Intrusion Exceptional Event( SOIEE) by the United States( US) Environmental Protection Agency(EPA), and the Guidance on the Preparation of Exceptional Events Demonstrations for Stratospheric Ozone Intrusions was further released on 2018.Based on the existing cases, this study elaborated the identification, criterion of SOIEE and the processing steps of SOIEE;suggestions on the exploration of SOIEE exclusion in China was further proposed for providing policy strategies of ozone pollution control.The main results were found as follows: firstly, SOIEE can happen irregularly and affect large-scale regions, leading to the exceedance of ozone concentration standard, namely the design value, which influence the fairness of ozone attainment determination;secondly, a complete system of SOIEE exclusion has been built in the US based on multiple monitoring approaches and modeling methods;thirdly, the existing cases mainly focus on the SOIEE occurred in high-altitude regions(i.e.Wyoming State, Utah State), which is due to the calculation of design value;the local Air Agency will only be motivated to prepare an "EE" demonstrations when the ozone concentration is beyond the fourth highest value in a year.In general, this study suggests that the trace-back analyses on the SOIEE in China warrant further investigations,especially for the days with light ozone pollution during late-spring and early-winter.In addition, the technical standards on the recognition of SOIEE as well as the management mechanisms of SOIEE should be formed timely, providing sufficient support to win the battle against pollutions.