Aged particles derived from emissions of coal-fired power plants: The TERESA field results

Abstract

The Toxicological Evaluation of Realistic Emissions Source Aerosols (TERESA) study was carried out at three US coal-fired power plants to investigate the potential toxicological effects of primary and photochemically aged (secondary) particles using in situ stack emissions. The exposure system designed successfully simulated chemical reactions that power plant emissions undergo in a plume during transport from the stack to receptor areas (e.g., urban areas). Test atmospheres developed for toxicological experiments included scenarios to simulate a sequence of atmospheric reactions that can occur in a plume: (1) primary emissions only; (2) H₂SO₄ aerosol from oxidation of SO₂; (3) H₂SO₄ aerosol neutralized by gas-phase NH₃; (4) neutralized H₂SO₄ with secondary organic aerosol (SOA) formed by the reaction of α-pinene with O₃; and (5) three control scenarios excluding primary particles. The aged particle mass concentrations varied significantly from 43.8 to 257.1 µg/m³ with respect to scenario and power plant. The highest was found when oxidized aerosols were neutralized by gas-phase NH₃ with added SOA. The mass concentration depended primarily on the ratio of SO₂ to NO_x (particularly NO) emissions, which was determined mainly by coal composition and emissions controls. Particulate sulfate (H₂SO₄ + neutralized sulfate) and organic carbon (OC) were major components of the aged particles with added SOA, whereas trace elements were present at very low concentrations. Physical and chemical properties of aged particles appear to be influenced by coal type, emissions controls and the particular atmospheric scenarios employed.

Keywords::

• Aged particles
• coal-fired power plant emissions
• atmospheric scenarios
• Secondary Organic Aerosol
• TERESA study

Acknowledgements

We acknowledge the efforts of Denise Lamoureux, Erick Vlassidis, and Dr. Yang Liu for field and laboratory support; Dr Euripides Stephanou for the SOA speciation; and all the people who helped with the field tests at the power plants.

Declaration of interest

This project was supported by the Electric Power Research Institute (Contract EP-P10983/C5530/56546), the US Environmental Protection Agency Center, for Particle Health Effects at the Harvard School of Public Health (grant R827353), and the Harvard NIEHS Center for Environmental Health (grant ES00002). This work was also prepared with the support of the US Department of Energy (DOE) under award DE-FC26-03NT41902, and a grant from the State of Wisconsin. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the authors, and do not necessarily reflect the views of the US EPA or the DOE.