This autumn, I have begun water quality monitoring on Antipoison Creek, a small tributary of the Chesapeake Bay, located on Virginia’s Northern Neck. I have been collecting and preparing water samples for analysis of nitrates, phosphates, ammonium, and chlorophyll, and working with the University of Maryland Center for Environmental Studies’ Nutrient Analytical Services Laboratory (NASL) on advanced analytical services for these water chemistry results.
Water sampling bottles are prepared using an acid wash procedure, to ensure that no remaining particles from manufacturing or previous water samples corrupt the results. When the bottles are ready, I collect samples from four locations via kayak along Antipoison Creek (2 samples per location, using a three-sample rinse method).
The first location is upstream from the beach from where I depart; the second location is several feet in front of the beach. The third and fourth locations are further downstream, at the mouth of Little Bay, (shown on the map below as Fleet’s Bay- Little Bay lies just between Fleet’s Bay and the mainland).
Once the samples are collected, they are filtered and divided into auto analyzer cups to be tested for nitrate, phosphate, and ammonium levels at NASL. (See photo below). Samples are frozen until they can be transported to the lab.
The samples must be filtered differently for chlorophyll- the lab receives just a filter pad for this, no water samples.
It took a little longer to get all of the supplies for the chlorophyll filtering procedure, and I have yet to send in samples for chlorophyll testing. However, the first results for nitrates, phosphates and ammonium recently came in. The ammonium test results have to be crosschecked with the pH levels of the samples, but I was able to read the phosphate and nitrate results.
According to North Carolina State University, phosphate designated use limits for estuaries, in order to support maximum diversity of aquatic life, must be 0.01 mg/L; for moderate diversity the phosphate limit is 0.1 mg/l.
Recommended nitrate limits are 0.1 mg/l for maximum diversity, and 1.0 mg/l for moderate diversity.
The results we received for phosphate (PO4) and nitrates (NO23) from Antipoison Creek were as follows (see bolded figures):
The results for phosphates and nitrates are significantly lower than limits set for water quality standards– which is a good thing- it means there is not an excess level of nutrients in the water, which can impair aquatic life. There is a significant amount of oyster production taking place in this sample area- oysters are natural filterers of nutrients and sediment. Perhaps this has an impact on our results. This is only one month’s results, however, (September), and results from following months must be compared before further analysis can be made.
Future chlorophyll readings will give an indication of algae levels in the sample region. Ammonium is another type of nitrogen in waters- it is produced when plants and animals decompose, and is present in animal waste. It acts as a pollutant when levels are too high, impacting local aquatic species. We should be seeing low results for ammonium as well to indicate good water quality in this portion of Antipoison Creek.