Explore the Wild | Wetland
The wetland in Explore the Wild was once a quarry owned by the city of
Durham. Tons of rock were taken out and crushed to make gravel for the
city's dirt roads. Eventually the pit was so deep that it began to fill
with groundwater. For a while the water was pumped out, then the quarry
was abandoned in the 1930s. Rainwater draining off the surrounding land
filled the deserted quarry with even more water. Plants began to grow
and animals made this newly formed wetland their home.
The rain that flows to wetlands isn’t just water. It carries fertilizer, pollutants, sediments and everything else that is in its path. A team of volunteer Youth Partners, guided by staff, tested four parameters of water quality to see how well this wetland purifies runoff.
pH: The pH in our wetland ranges from seven to ten. That means it is neutral to alkaline, not acidic (which would make the pH fall below seven). Three factors could influence the pH of the wetland: dissolving diabase minerals from the rock quarry could increase pH, acid rain could decrease pH, and excessive nutrients from stormwater runoff could cause pH to fluctuate.
Nitrate: Stormwater, decaying organic matter, and air pollution bring nitrates to the wetland. Nitrates can cause excessive plant growth, which shades and can kill aquatic life. Nitrates decreased 12-fold as the water moved through the wetland. The decrease in nitrate demonstrates that the wetland is functioning properly.
Dissolved oxygen (DO): At the inlet to the wetland, the DO levels were too low to support aquatic life. Levels increase through photosynthesis and agitation. By the time water reaches the observation deck, DO levels are high enough to support fish, macroinvertebrates, plants, and bacteria.
Fecal colliform and E. coli: Fecal colliform is a collection of microorganisms found in animals’ intestines. In the wetland, it could come from pets, wild animals and possibly exhibit animals. We tested a particular type of fecal colliform, E. coli. As the water moved through the wetland, E. coli levels decreased to below recreational water standards.
It took a lot of testing, but the Youth Partners were able to assess the health of the wetland. The results were good: all four tests showed that the wetland is healthy and purifies the water that flows through it.