General Report

General Audience Report

Donald Millar

The water quality in San Diego county streams is very important to the health of our community and the plants and animals that live within it. Water possesses properties such as temperature, dissolved salt content (salinity), dissolved oxygen content, and pH. These parameters dramatically alter the nature of a stream and subsequently the life that depends on it. Tecolote Canyon is an urban canyon in central San Diego that serves to drain rain and runoff water from public parks, private residences and even a golf course. The water that enters the canyon collects in Tecolote creek where it flows to the ocean via Mission Bay. As a community that is highly concerned with the health of our marine ecosystem, it is important to understand the dynamics of the local creeks and watersheds that empty into the Pacific.

The water of Tecolote Creek was found to be at a temperature of ~17.5 degrees Celsisus and featured little salt content: 1 part salt per trillion parts water. These values are normal for a stream in Southern California. However, the amount of dissolved oxygen recorded in the water samples was significantly lower than would have been expected for a water sample of the same temperature. Organic pollution in the water is produced by the improper disposal and use of nitrogen and phosphorous fertilizers. The presence of organic pollution can be tested by analyzing the demand for oxygen present in a sample due to the need for oxygen in the metabolic processes of these organic bacteria. Measurements of this demand for oxygen, called Biological Oxygen Demand (BOD) found that the levels of organics were very low; a fact that was surprising due to the proximity to a golf course and

Tecolote Canyon near the sampling site

residential area. The BOD levels recorded in Tecolote Canyon were similar to those that would be found in a pristine wilderness waterway. This means that pollution due to overuse and improper disposal of fertilizers is not a significant problem in Tecolote Canyon.

Graph showing the expected dissolved oxygen (DO) and the recorded DO values.

Acid rain is an environmental problem caused by rainfall that has too low of a pH (an elevated concentration of H+ molecules). The acidity of the rain can cause a change in the pH levels of streams and lakes that dramatically alters the natural chemistry of these waterways. Soils and clays contain elements such as calcium, which is effective at neutralizing the acidic content of acid rain, helping to maintain normalcy in the ecosystem. Soils were collected from throughout Dan Diego county and each was tested for its ability to neutralize the effects of acid rain. Soils collected from Tecolote Canyon at the electrical power station and at the mouth of Tecolote creek were able to remove over 99% of H+ ions from the acid that was applied. The soil collected from Tecolote Creek was more effective at neutralizing acid than even pure limestone.

Soil Samples that were collected were tested for their metal content using an atomic analyzer machine. Each sample was tested for the presence of several metals, magnesium, lead, zinc, calcium, and copper. The most common metal found in the samples was calcium, a natural component of soils that did not come as a surprise to be present in such large amounts. The second most numerous metal observed was magnesium. The metal found in the least concentrations in San Diego soils was Zinc. Lead, which can pose a health risk, was found in very low concentrations; below the threshold of health risks.

The atomic analyzer instrument

The water samples that were collected from Tecolote Creek were analyzed using a Gas Chromatography/ Mass Spectroscopy instrument that is capable of determing if any toxic compounds were present in the water tested. Two compounds were discovered albeit in low concentrations: hexadecanoic acid (palmitic acid) and methoxyphenyloxime. Hexadecanoic acid is also known as palmitic acid and is commonly found in palm trees, seeing as though this canyon contains many palms it can be assumed that the contamination by hexadecanoic acid is due to natural leaching from palm trees. Methoxyphenyloxime is a compound known as an oxime, oximes are often used in the synthesis of nylon fabrics and in the production of artifical sweeteners.

Overall, the health of Tecolote Creek and the canyon itself is excellent. Little pollution due to organics or toxic compounds was found in the water. The soil has an excellent buffering ability against acid rain and has very little concentration of harmful metals such as lead. The dissolved oxygen content of the water tested in Tecolote Canyon was low, but this may have been due to the stagnant nature of the tested pool. Overall, the health of the canyons soil and water is exemplary and should be looked to as an example of stewardship by the local community.