ABSTRACT
We use a machine learning algorithm combining information from the NASA GEOS composition forecast (GEOS-CF) model and surface observations of nitrogen dioxide (NO2) and ozone (O3) at more than 5,000 observation sites to assess the impact of COVID-19 restrictions on surface air quality in 46 countries. Our methodology removes the compounding impacts of meteorology, seasonality and atmospheric chemistry on air pollution, thus allowing for a quantitative estimate of the change in surface air quality following COVID-19 containment measures. Compared to GEOS-CF model predictions that do not include emission reductions related to COVID-19 restrictions, surface observations show a drop in surface NO2 of up to 60% after the implementation of lockdowns. Average NO2 concentrations between February 2020 to June 2020 were 18% lower than business as usual. The earliest and strongest declines are observed over China, followed by Europe and the US. While NO2 concentrations over China recovered within 2 months, the recovery has been slower over Europe and the US. The impact of COVID-19 restrictions on O3 is complicated by non-linear atmospheric chemistry. Locally, O3 can show a short-term increase of up to 50% as a result of the decrease in NO2, which leads to a reduction in night time titration. However, this effect is offset by a decrease in photochemical production during the day. Our results indicate that these two competing processes resulted in a net zero change in average surface ozone during the first 5 months of the pandemic. The results also indicate that the reduced photochemical production becomes increasingly important over time. Our analysis is based on surface observations and model simulations available in near real-time, and we will present an up-to-date view of the short and medium-term impacts of COVID-19 restrictions on air quality around the world.
ABSTRACT
Active learning, such as hands-on activities, provides students with opportunities to develop skills such as critical thinking, problem solving, and teamwork [1] [2]. Incorporating hands-on learning into the classroom environment involves several challenges including the design of the activities, building and setup of equipment, and reallocation of limited contact hours. While challenges exist for in-class hands-on learning, further hurdles, such as access to materials and activity scaffolding, are presented when adapting hands-on learning for remote course delivery. This paper describes the process of designing a series of remote hands-on activities, called Hands on Learning Days (HOLD), for an Introduction to Statics course based on materials that students have in their residences. Techniques to increase student access to the hands-on experiences included designing each activity using common materials that have many possible substitutions such as string, which is easily replaced with thread, floss or computer cables. Student-learning gains from the remote hands-on activities are presented and compared with those from an in-person hands-on instructional environment through the use of a midterm course evaluation and the Student Assessment of their Learning Gains (SALG) administered upon completion of the course. The vast majority (91%) of students had no or little difficulty finding the supplies needed to complete the HOLD activities. The findings suggest that, even under the extreme circumstances of the COVID-19 pandemic, HOLD had a positive effect on student learning. In 5 of the 14 learning outcomes assessed, the effect of HOLD was equal to or greater than the effect of attending lecture and had a compensatory effect, allowing similar learning to the average in-person, pre-pandemic learning environment. © American Society for Engineering Education, 2021