Measurement of contemporary and fossil carbon contents of PM2.5 aerosols: results from Turtleback Dome, Yosemite National Park.

The impact of aerosol particulate matter of mean mass aerodynamic diameter < or = 2.5 microm (PM2.5 aerosols) on health, visibility, and compliance with the U.S. EPA's regional haze regulations is a growing concern. Techniques that can help better characterize particulate matter are required to better understand the constituents, causes, and sources of PM2.5 aerosols. Measurement of the 14C/C ratio of the PM2.5 aerosols, the absence of 14C in fossil carbon materials, and the known 14C/C levels in contemporary carbon materials allow the use of a two-component model to derive contemporary and fossil carbon contents of the particulate matter. Such data can be used to estimate the relative contributions of fossil fuels and biogenic aerosols to the total aerosol loading. Here, the methodology for performing such an assessment using total suspended particulate hi-vol aerosol samplers to collect PM2.5 aerosols on quartz fiber filters and the technique of accelerator mass spectrometry to measure 14C/C ratios is presented and illustrated using PM2.5 aerosols collected at Yosemite National Park.