Rain is a good thing.

I have come to realize that summer in Williamsburg is a little eerie.  The brick walk ways throughout campus are commonly empty, except of course if you happen to trip on an out-of-place brick…in that case there is always a dog walker or tour group around.  The basement of the Sadler Center is dark, the Market Place is closed, WaWa rarely has a line, and the terrace on a sunny Friday afternoon has open tables.  And for those who have never seen Swem in the Summer…trust me, it’s like nothing you have ever seen before.

So how have I been keeping busy in Williamsburg this summer?  The short answer is that I have been collecting a lot of rain.  I have four rain collectors outside of McGlothlin Street Hall.  Every time it rains (which is often in Williamsburg in the Summer) or snows (which is rare in Williamsburg in the Summer), I bring in and filter the water that has been obtained by the collectors.  A substantial Williamsburg storm can give us anywhere from 6 to 12 gallons of rain sample.  Over the course of a month, these rainwater samples really add up which makes for a very crowded geochemistry lab.  In February I collected 45 liters of rain, in March and April combined I collected 83 liters, and in May I collected 68 liters.

While it only takes a small vial of rain sample to measure the concentrations of major cations (sodium, ammonium, potassium, magnesium, and calcium) using ion chromatography, I need to collect really large samples in order to detect the extremely low concentrations of sodium-22.  Thankfully, I don’t have to deal with these huge water samples for too long.  Cation-exhange resin is a substance that looks like a bunch of small, gold beads.  These beads are packed with H+ ions, and when in contact with the water, the H+ ions will switch out with the major cations.  Therefore, when the resin is removed from the sample about ten days later, all the of the major cations that were present in these huge rain samples are concentrated into a small, much more manageable  25 mL container of resin.  I can then put the resin directly in the gamma ray spectrometer to measure the cosmogenic radionuclides.  In addition to sodium-22, I have been able to measure the average monthly concentrations of other cosmogenic radionuclides such as beryllium-7 and lead-210.

I also have been attempting to better understand how the concentrations of these radionuclides, as well as the major cations, vary between individual storms.  For example, in Williamsburg, we are exposed to both convective thunderstorms and tropical storms, such as tropical storm Beryl which Williamsburg felt the effects of at the end of May.  By analyzing these two types of storms separately, I can get a better idea of how and why the geochemistry of rain water varies from storm to storm.  Generally speaking, major differences in rainwater geochemistry at a given latitude is a function of where the storm is coming from, how high up into the atmosphere the storm reaches, and the actual amount of rain or snowfall.

With only a few months of data so far, it is difficult to determine any significant patterns, but obtaining my first few months’ worth of data has been both interesting and exciting!

Happy Summer!!!