Chemical species' contributions to the upper extremes of aerosol fine mass

Frequency distributions of the major chemical components of aerosol fine ma ss are shown to illustrate the respective species' contributions to the ran ge of observed fine particle mass concentration. The magnitude of a species ' contribution to the upper extremes of aerosol fine mass is relevant to co ntrol scenarios that seek to improve worst day fine particle conditions, or in many cases worst day visibility. We summarize the relative contribution s of fine particle sulfate, nitrate, carbon, and soil plus sea salt to the upper extremes of aerosol fine mass based on Interagency Monitoring of PROt ected Visual Environments (IMPROVE) data collected at monitoring locations across the United States during 1995 through 1999. The data show that the s patial pattern of a given chemical species' contribution to the upper extre mes of aerosol fine mass is often quite different than at lower fine mass c oncentrations. In some cases, the monitoring data suggest a casual relation ship between specific aerosol source regions and the magnitude in which a s pecies' contribution to the upper extremes of fine mass is elevated above t he contribution to median fine mass concentrations. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.