The only sites monitored in the region that exceed the median zinc concentrations at Cedar Creek are two very urban streams in Asheville where urban runoff is a significant issue.  Other sites in the region with unusually high median zinc concentrations also show excessive stream sedimentation, are downstream from wastewater treatment plants, or in one case, are downstream from several trout farms.  The possibilities for introduction of zinc into Cedar Creek should be investigated. No other site in the Glenville area exhibited zinc concentrations similar to those at Cedar Creek, and zinc at the control site was virtually non-existent.

D. Nutrients (Orthophosphate (PO₄), Ammonia-Nitrogen (NH₃), and Nitrate/Nitrite-Nitrogen (NO₂/NO₃)

Orthophosphate: Phosphorus is an essential nutrient for aquatic plants and algae. It occurs naturally in water and is, in fact, usually the limiting nutrient in most aquatic systems. In other words, plant growth is restricted by the availability of phosphorus in the system. Excessive phosphorus inputs stimulate the growth of algae and diatoms on rocks in a stream and cause periodic algal blooms in reservoirs downstream. Slippery green mats of algae in a stream, or blooms of algae in a lake are usually the result of an introduction of excessive phosphorus into the system that has caused algae or aquatic plants to grow at abnormally high rates. Eutrophication is the term used to describe this growth of algae due to an over abundance of a limiting nutrient. Sources of phosphorus include soil, disturbed land, wastewater treatment plants, failing septic systems, runoff from fertilized crops and lawn, and livestock waste storage areas.  Phosphates have an attraction for soil particles and phosphorus concentrations can increase greatly during rains where surface runoff is a problem.  In this report orthophosphate (PO₄) is reported as concentrations of PO₄. To isolate phosphorus (P) from the measurement, divide the reported amount by three.  Note that the four lake samples are also analyzed for total phosphorus. The median results are reported as both PO₄ and as P.  Orthophosphate is a measure of the dissolved phosphorus which is immediately available to plants or algae. Orthophosphate is also referred to as phosphorus in solution. There is no legal water quality standard, but generally levels must be below 0.05 mg/l to prevent downstream eutrophication. The normal ambient level of orthophosphate in undisturbed streams is about 0.01 to 0.03 mg/l. Total phosphorus is the measure of all the chemical forms of phosphorus including dissolved orthophosphate, phosphorus bound to particulate matter, and phosphorus locked up biologically in algae and bacteria.

Ammonia Nitrogen (NH₃) and Nitrate/nitrite Nitrogen (NO₃/NO₂): Ammonia-nitrogen is contained in the remains of decaying wastes of plants and animals. Some species of bacteria and fungi decompose these wastes and NH₃ is formed. The normal ambient level is approximately 0.10 mg/l, and elevated levels of NH₃ can be toxic to fish. Although the actual toxicity depends on the pH of the water, the proposed ambient standard to protect trout waters is 1.0 mg/l in summer and 2.0 mg/l in winter. The most probable sources of ammonia nitrogen are agricultural runoff, livestock farming, septic drainage and sewage treatment plant discharges.  In Western North Carolina, streams where extensive trout farming occurs may also show elevated ammonia-nitrogen concentrations.

Like phosphorus, nitrate/nitrite-nitrogen serves as an algal nutrient contributing to excessive stream and reservoir algal growth. In addition, nitrate is highly toxic to infants and the unborn causing inhibition of oxygen transfer in the blood stream at high doses. This condition is known as "blue-baby" disease. This is the basis for the 10 mg/L national drinking water standard. The ambient standard to protect aquatic ecosystems is 10 mg/L as well. The most probable sources are septic drainage, fertilizer runoff from agricultural land and domestic lawns, and livestock. Nitrates from land sources end up in streams more quickly than other nutrients such as phosphorus because they dissolve in water more readily and can travel with ground water into streams. Consequently, nitrates are a good indicator of the possibility of sources of pollution from sewage or animal waste during dry weather.  

This graph shows median orthophosphate concentrations at each site compared with the average median for the region. Orthophosphate concentrations are of particular concern because of the potential for contributing to algae blooms in Lake Glenville.  Limiting concentrations of nutrients to normal levels is important.  Regional trend analysis shows a strong seasonal trend for more elevated orthophosphate concentrations in summer and fall.  This is related to the amount of vegetation washed into streams where it decomposes and adds nutrients to the aquatic ecosystem. This process is natural, but phosphorus concentrations can become unnaturally high with the introduction of plant and animal waste or fertilizer from human activities.  Phosphorus in topsoil also becomes a problem for streams when surface runoff increases because land has been cleared.

 Median phosphorus concentrations are well below the average median for the region at all of the Glenville sites.  Median concentrations of phosphorus at all sites are similar to those at the control site. Although phosphorus concentrations have fluctuated somewhat, none of the sites appear to be significant regular contributors of phosphorus to Lake Glenville.  There is insufficient data to determine if the fluctuations are related to stream flow, thus indicating point or non-point sources.

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