EPRI Visibility Experiment Continues to Shed Light on Aerosol Properties
EPRI’s Advanced Visibility Measurements Experiment completed its measurement phase last summer, and several analyses are now under way.  The multiyear, multisite project is investigating the causes of aerosol light extinction in U.S. national parks, using intensive periods of collocated measurements at selected sites in the National Park Service’s Interagency Monitoring of Protected Visual Environments (IMPROVE) network.  Of particular note is an ongoing analysis by Liz Alexander, Pacific Northwest National Laboratory, using high-resolution aerosol mass spectrometer (AMS) data from the Mt. Rainier site.  In comparing the AMS data with measured hygroscopic growth factors for a 10-day period, she found that periods of increasing organic mass correlated with periods of decreasing water absorption.  The inverse relationship suggests that a significant fraction of the organic mass comes from biogenic organic compounds, which tend to be less-water absorbing.  Further research is under way to speciate the organic fraction.  For more information, contact Naresh Kumar, (650) 855-2990, nkumar@epri.com.