Over hill and dale

To the field!


If rain water was time zero, a stream can be considered time final. Water is rained down, moves over or under the ground, and ends up in a stream. Previous William & Mary geology students tested stream water, and I followed in their footsteps.


I inherited my study area from research students before me: the Pagonia watershed. A sub watershed located within the larger Matoaka watershed, the Pagonia watershed is largely forested and is home to the Pagonia stream. The students before me found an age for this stream (~10-12 years old), but I’m using a different method and wanted to build on their research and confirm their results.



Collecting water from the Pagonia stream


I processed the stream samples in much the same way I processed the rain samples, but ran into some difficulties along the way. Obtaining the water from the stream was a challenge in and of itself. I pulled a wagon of supplies out through the woods – doing some off roading! I pumped water directly from the stream into the collection tank, through two sets of filters. This ensured I minimized the amount of organic matter entering the tank.


048 049


Once I had pumped all the water into the tank, I carted the whole setup back to campus for analysis in the lab.


Precious cargo!

One factor I had to consider was the amount of ion exchange resin I added to the tank. The research students prior to me either added the resin to the sample and let it sit, or slowly filtered the sample through tubes packed with the resin. My method of using a magnetic stir bar requires less manual oversight and a faster processing time. Additionally, I was able to improve the efficiency of the quantity of resin needed to uptake ions. For an approximate 90% efficiency, I was able to use a smaller mass of resin per mmol of charge as compared to previous research – see table below.


Stream water also often had a higher concentration of ions than rain water. This extra charge often complicated our calculations, and required a larger amount of resin to be used. This extra resin then often took longer to burn, or did not properly leach sodium from it.


All in all, testing different types of water required constant adjustments in my technique. Tinkering with how I processed each individual sample could be a headache, but ultimately it allowed me to dig into a deeper understanding of my research method.