What is “dust”? Three-decade observations of aerosol chemical
composition during dust storms over the continental United States
Abstract
This work presents 30-year observations of dust chemical composition by
the IMPROVE network in the United States. Analysis of 1,253 large dust
storms detected at the IMPROVE sites shows that dust PM2.5 (particles
less than 2.5 micrometers in fresh dust plumes) crustal materials
(64%), organic matter (13%), sulfate (7%), nitrate (2%), Cl, Br, and
heavy metals. Dust composition stays relatively stable during near
source transport. There are distinct spatial variations in dust
composition, including high carbon and sulfate in Oklahoma, high Cl in
Washington, and high fractions of heavy metals in Arizona. Compared to
the Earth’s crust, dust PM2.5 contains less crustal elements but more
OC, EC, sulfate, nitrate, and halogen elements due to influence by human
activities and biogeochemical processes. This rich pool of dust
composition data provides useful information to study the roles played
by dust in the Earth system and its effects on human society.