4 Oct 2007
Group Members: Clark Barlow, Oliver Obregon,
Sample Sites: Upstream Hobble Creek, Downstream Hobble Creek
Summary
We measured phosphate and nitrite at both sites. The tests went as outlined in the procedures. One concern was that there were no kimwipes to wipe down the sample bottles so the colorimeter readings may have been slightly affected by the clarity of the sample bottles. We tried our best to wipe them down with Oliver’s jeans, and the bottles looked clean, but it’s hard to say how clean. At the downstream site, where samples were gathered from a bucket sampler, we decided to run the same nitrite sample several times successively in the colorimeter. The number that appears in the results table is the average of those readings. When we ran the phosphate sample at the downstream site, we noticed that the readings varied from 0.04 to 0.09, a range quite similar to the reading at the upstream site. There was also no identifiable trend in the readings either, so we decided to prepare a second sample from the same bucket. This time we got a much more reasonable average reading of 0.28 ppm. We have no idea why the readings were so different between the two samples.
Another note is that the nitrite-nitrogen reading can be used to derive nitrite. The conversion is shown in the Lamotte procedures.