Abstract View
The Relative Influence of Roadway and Harbor Particle Sources before and during COVID-19 Related Lockdown in Charleston, South Carolina
ROBY GREENWALD, Eleanor Clarke, Georgia State University
Abstract Number: 545
Working Group: Urban Aerosols
Abstract
We PM2.5 number and mass concentration and black carbon (BC) mass concentration at a waterfront site in downtown Charleston, South Carolina during the time period surrounding the COVID-19 related lockdown in February-March 2020. In addition to particle and meteorological measurements, we collected roadway traffic data from the South Carolina Department of Transportation and ship transponder data from the Marine Traffic company. Similar to other regions of the world, we observed sharp reductions in motor vehicle traffic following stay-at-orders associated with the pandemic response. Roadway traffic decreased 50% as assessed by the number of vehicles crossing the Cooper River approximately 2 km from the sample site. Ship traffic in Charleston harbor during this time period however did not follow the same pattern as roadway traffic. Some types of ship traffic were temporarily reduced or ceased altogether. For example, cruise ship operations were discontinued, and passenger boats for tourism purposes operated on a reduced schedule. On the other hand, commercial and cargo ship traffic continued operations. We constructed a simple model to identify plumes from ships moving in the harbor based on wind direction and speed and ship GPS data. PM2.5 data collected at the sample site typically showed temporal trends consistent with regional ambient air quality monitors with notable exceptions. BC concentrations was temporally inconsistent with PM2.5 trends but frequently corresponded to wind direction blowing from local sources, including harbor traffic. Occasional increases in BC concentration were observed to occur when wind direction was from the largest highway in the immediate vicinity; however, more frequent increases in BC were observed when wind direction was from nearby ship traffic, including large vehicle carriers and smaller tour boats. Numerous increases in BC did not temporally correspond to any known source near the sample site. These results are consistent with both roadway and harbor traffic influencing BC concentration in downtown Charleston.