TOTAL SUSPENDED PARTICULATES, PM10, AND PM2.5 MEASUREMENTS FOR USE IN BIOGEOCHEMICAL STUDIES; THE ROLE OF LARGE PARTICLES IN AEROSOL CONCENTRATIONS AND FLUX ESTIMATES

The composition of atmospheric aerosols is an important issue for urban and rural environments. Most existing aerosol monitoring networks focus on the small particle-size classes of less than 2.5 and 10 μm. These size classes are an emphasis in federal environmental law because they have a major potential impact on human health. Particles > 10 μm can also be a significant component of the atmospheric aerosol load and biochemical inputs to ecosystems. For estimates of elemental flux or mass transport through the atmosphere, these large suspended particulates can represent an important flux that may not be captured in existing observational networks even though they can significantly impact visibility. In this study we compare PM 2.5 and 10 aerosol concentrations detected by an Interagency Monitoring of Protected Visual Environments (IMPROVE) network sampler to a Hi-Volume Total Suspended Particulate (TSP) sampler over a two-year period in Canyonlands National Park, UT. In some instances TSP concentrations exceed < 10 μm particle concentrations by 300 percent, while at other times the particles present are mainly in the sub-10-μm size class. Some of the variation in aerosol particle size and chemical concentration appears to be related to the influence of seasonal wind transport patterns on mineral aerosol load and the influence of seasonality on biological aerosol production. For element-flux estimates, and particularly for some major and biogeochemically relevant elements such as P and N, we suggest that the large particles embedded in the TSP category of aerosols may represent a biologically significant flux of material to ecosystems.