ABSTRACT

The Lake Michigan Ozone Study 2017 (LMOS 2017) in May and June 2017 enabled study of transport, emissions, and chemical evolution related to ozone air pollution in the Lake Michigan airshed. Two highly instrumented ground sampling sites were part of a wider sampling strategy of aircraft, shipborne, and ground-based mobile sampling. The Zion, Illinois site (on the coast of Lake Michigan, 67 km north of Chicago) was selected to sample higher NO_x air parcels having undergone less photochemical processing. The Sheboygan, Wisconsin site (on the coast of Lake Michigan, 211 km north of Chicago) was selected due to its favorable location for the observation of photochemically aged plumes during ozone episodes involving southerly winds with lake breeze. The study encountered elevated ozone during three multiday periods. Daytime ozone episode concentrations at Zion were 60 ppb for ozone, 3.8 ppb for NO_x, 1.2 ppb for nitric acid, and 8.2 μg m^-3 for fine particulate matter. At Sheboygan daytime, ozone episode concentrations were 60 ppb for ozone, 2.6 ppb for NO_x, and 3.0 ppb for NO_y. To facilitate informed use of the LMOS 2017 data repository, we here present comprehensive site description, including airmass influences during high ozone periods of the campaign, overview of meteorological and pollutant measurements, analysis of continuous emission monitor data from nearby large point sources, and characterization of local source impacts from vehicle traffic, large point sources, and rail. Consistent with previous field campaigns and the conceptual model of ozone episodes in the area, trajectories from the southwest, south, and lake breeze trajectories (south or southeast) were overrepresented during pollution episodes. Local source impacts from vehicle traffic, large point sources, and rail were assessed and found to represent less than about 15% of typical concentrations measured. Implications for model-observation comparison and design of future field campaigns are discussed.

Implications: The Lake Michigan Ozone Study 2017 (LMOS 2017) was conducted along the western shore of Lake Michigan, and involved two well-instrumented coastal ground sites (Zion, IL, and Sheboygan, WI). LMOS 2017 data are publicly available, and this paper provides detailed site characterization and measurement summary to enable informed use of repository data. Minor local source impacts were detected but were largely confined to nighttime conditions of less interest for ozone episode analysis and modeling. The role of these sites in the wider field campaign and their detailed description facilitates future campaign planning, informed data repository use, and model-observation comparison.

摘要

2017 年 5 月和 6 月进行的 2017 年密歇根湖臭氧研究 (LMOS 2017) 使得能够研究与密歇根湖气域臭氧空气污染相关的传输、排放和化学演化。两个高度仪器化的地面采样点是飞机、船载和地面移动采样的更广泛采样策略的一部分。伊利诺伊州锡安的站点（位于密歇根湖沿岸，芝加哥以北 67 公里）被选为对较高的 NO _{x进行采样}经过较少光化学处理的航空包裹。选择威斯康星州 Sheboygan 站点（位于密歇根湖沿岸，芝加哥以北 211 公里）是因为它的位置有利，可以在涉及南风和湖风的臭氧事件期间观察光化学老化的羽流。该研究在三个多日期间遇到了臭氧升高的情况。Zion 的日间臭氧事件浓度为臭氧 60 ppb、NO _x 3.8 ppb 、硝酸 1.2 ppb 和细颗粒物8.2 μg m ^{-3 。}在 Sheboygan 白天，臭氧浓度为 60 ppb 臭氧，2.6 ppb NO _x和 3.0 ppb NO _y. 为了促进 LMOS 2017 数据存储库的知情使用，我们在此提供全面的场地描述，包括活动期间高臭氧时期的气团影响、气象和污染物测量概述、来自附近大点源的连续排放监测数据的分析，以及特征描述车辆交通、大型点源和铁路对本地源的影响。与之前的实地活动和该地区臭氧事件的概念模型一致，在污染事件期间，来自西南、南部的轨迹和湖风轨迹（南或东南）的轨迹过多。来自车辆交通、大点源和铁路的本地源影响经过评估，发现代表不到典型测量浓度的 15%。

影响：2017 年密歇根湖臭氧研究 (LMOS 2017) 是在密歇根湖西岸进行的，涉及两个仪器齐全的沿海地面站点（伊利诺伊州锡安和威斯康星州希博伊根）。LMOS 2017 数据是公开的，本文提供了详细的场地特征和测量摘要，以便能够明智地使用存储库数据。检测到较小的本地源影响，但主要局限于夜间条件，对臭氧事件分析和建模不太感兴趣。这些站点在更广泛的实地活动中的作用及其详细描述有助于未来的活动规划、明智的数据存储库使用和模型观察比较。