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    Courtesy of Dara Salcedo

From: Dara Salcedo
T0, March 15, 2006

The other side of the wall

As I promised in my last postcard, I am showing what is in "the other side of the wall". We have several instruments to measure particle properties, all of the them connected to the inlet. The one on the left is called a SMPS (Scanning Mobility Particle Sizer). The SMPS measures the number of particles in ambient air as a function of particle size. On the left, there is another similar instrument called nano-SMPS, which measures the number of the very small particles (in the nanometer range). There is also a CCN counter. CCN stands for "cloud condensation nuclei" and refers to those particles that can grow and become clouds. Finally, in front of the table, we have an AMS (Aerosol Mass Spectrometer), which measures the composition of the particles. The data from the instruments is automatically saved in computers so it can be analyzed later. Most of the instruments belong to Prof. Jose Luis Jimenez from the University of Colorado at Boulder.

We have been recording data from all the instruments continuously for the last four days. The air has been very dirty with episodes of high concentrations of organic compounds, probably due to fires occurring around Mexico City.

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