Participating Students-Levi Mielke

Levi Mielke

Purdue University

BART Enrollment Year: 2007

Email: lhmielke at purdue.edu

 

Atmospheric Mentor: Paul Shepson, Alex Guenther

Biospheric Mentor: Peter Curtis

 

Research Topics:

 

Secondary organic aerosol formation from biogenic VOCs and feedbacks to the climate system

 

Emission of VOCs from white pine trees (Pinus Strobus) is dominated by the monoterpenes a- and ß-pinene. Oxidation of these monoterpenes yields low vapor pressure products that lead to the formation and growth of secondary organic aerosol. These particles promote primary productivity by increasing diffuse radiation. Increased light scatter by biogenic aerosols also introduces a negative climate feedback. The University of Michigan Biological Station (UMBS) forest is uniquely situated as a forest undergoing succession in which white pine will become a more dominant species. Monoterpene emission is exponentially correlated to air temperature. As global surface temperatures are expected to increase monoterpene emission will also increase. Additionally forest succession at UMBS favors the increase in numbers of white pine trees. These two effects will only serve to increase the role that monoterpenes have in the local chemistry and ecology of the UMBS and related forests. Our research will examine the role of a- and ß-pinene photochemistry in secondary organic aerosol growth and feedbacks to climate and biosphere health at UMBS. This will be accomplished through the measurement of a- and ß-pinene, and the primary oxidation products pinonaldehyde and nopinone, to use the terpene oxidation products as a proxy for aerosol growth. VOC measurements will be conducted using our newly developed proton transfer reaction – linear ion trap (PTR-LIT) mass spectrometer. Additionally, we will measure the number and size of aerosols. This will allow us to quantify the impact of a- and ß-pinene oxidation on secondary organic aerosol in this environment. This project will complement not only the forest succession experiment planned for UMBS but also the PROPHET commitment to studying BVOC photooxidation chemistry and its biosphere-atmosphere impacts.