A study of the green area effect in the Black Hills of South Dakota

Abstract

Bimonthly sampling of Aitken and larger particles for a twelve-month period in the Black Hills of South Dakota has revealed several possible particle removal mechanisms. The measurements were made using a Gardner small particle counter at thirteen stations surrounding and within the Black Hills proper. The results indicate that the Black Hills area is a significant source of clean air and that observed low levels of particle concentrations are primarily the result of precipitation and in-cloud scavenging, elevation variation, and the particle removal mechanism of vegetation (greenarea effect). After correcting the data for elevation changes, precipitation scavenging, and local pollution sources, present analysis suggests the operation of a significant particulate filtering mechanism by the heavy vegetation of the Black Hills. The green area effect alone may serve to reduce ambient Aitken particle concentrations by as much as 50%.