NITRIC-ACID SCAVENGING BY MINERAL AND BIOMASS BURNING AEROSOLS

The abundance of gas phase nitric acid in the upper troposphere is ove restimated by global chemistry-transport models, especially during the spring and summer seasons. Recent aircraft data obtained over the cen tral US show that mineral aerosols were abundant in the upper troposph ere during spring. Chemical reactions on mineral dust may provide an i mportant sink for nitric acid. In regions where the mineral dust abund ance is low in the upper troposphere similar HNO3 removal processes ma y occur on biomass burning aerosols. We propose that mineral and bioma ss burning aerosols may provide an important global sink for gas phase nitric acid, particularly during spring and summer when aerosol compo sition in the upper troposphere may be greatly affected by dust storms from east Asia or tropical biomass burning plumes.