Figure 4.
Diurnal variations of the 30 day mean PM2.5 concentrations averaged over all stations for pre-SD and SD.
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.