Tuesday, March 6, 2012

Student Questions from San Pedro, California!

Questions from Ms. Elissa Eastvedt’s 9th grade Conceptual Physics class at Rolling Hills Preparatory School, San Pedro, California

What are atmospheric trace gases?  How does the ice affect the gases in the air?
Dry air contains 78.09% nitrogen (N2), 20.95% oxygen (O2), ~0.93% argon (Ar), and small (trace) amounts of other gases, including carbon dioxide (CO2) and ozone (O3).  Since they exist in only small quantities in the atmosphere, these other gases are termed “atmospheric trace gases”.  However, despite their small quantities, they can have large impacts on air quality (example – negative human health impacts of high ozone days) and climate (example – increasing carbon dioxide levels lead to warming).  In the Arctic, we are studying interactions between the sea ice and atmosphere to understand how trace gases in the atmosphere are impacted by the sea ice.  When the seawater freezes, the salts, such as sodium chloride (NaCl – what we know as table salt), precipitate out on the ice surface and can be lofted into the air.  Elements including the halogens chlorine (Cl), bromine (Br), and iodine (I) can react on the ice surface or on ice particles in the air to form gases.  These halogen gases can then react with ozone, for example, in the atmosphere, changing the composition of the air.

Why do you have go to Alaska for this research (instead of having samples shipped back to Indiana)?
In this study, our instruments are automated to do on-line sampling, meaning that air is continuously drawn through tubing to our instruments sitting inside a trailer.  Kerri’s mass spectrometer samples with data points every 10 seconds!  Kyle’s gas chromatograph samples 200 milliliters of air every 50 minutes, giving ~28 data points per day.  We need to sample the hourly patterns of these gases to investigate how they change with wind direction, wind speed, temperature, and light.  This sampling rate would be like taking home 28 cans of air each day totaling ~1.5 gallons of air for each day; even if we did do this, reactions would take place in the cans, changing the gases inside and providing incorrect results.  These recently developed “real-time” measurement techniques are helping to improve scientists’ understanding of the chemistry of atmospheric trace gases.  However, we will collect and take home snow and sea ice samples to measure their chemical composition.  This will be a significant challenge though because we have to make sure the snow and sea ice doesn’t melt!  If it melts, chemical reactions may occur, changing the chemistry of the ice.  So, we will use dry ice (frozen carbon dioxide, CO2) to help transport the snow back to Indiana!

Thank you to the students at Rolling Hills for great questions!  We hope that you enjoy reading our field research blog!

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