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.
Diurnal trend for Class A NPF days, regular days, and PB days. Data correspond to 5 min time average integrated SMPS concentration for 5–10 and 10–40 nm size range. Solid lines are the median concentration. Shades are the interquartile range. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
