Arsenic and Zinc Distributions in Streams Near Park City, Utah
It is hard to believe that it has been almost a year since Park City, Utah, hosted part of the 2002 Winter Olympic Games. Long before the Olympic Games, Park City was a small silver-mining town, founded in 1864. Since the early 1990s, Park City has undergone tremendous growth. Like other resort towns in the western United States, Park City's growth has resulted in a number of emerging environmental problems associated with water quality and quantity. These include high nutrient and high salt concentrations in streams, explosive residue in snow, and high concentrations of trace metals in surface water (Giddings et al., 2001).
My concern for these environmental issues really kicked in about 14 months ago in my freshman honors biology class. During a field assignment for this class at the wetlands near our school, I observed an absence of wildlife. I wanted to study the environment in this area with equipment that would help me measure the potentially "invisible" environmental contaminants in this area. With the assistance of my biology teacher, I used a field kit to measure phosphate in the water from the wetlands near our school. I found the phosphate concentrations were as high as 12 milligrams per liter. This level of phosphate could be part of the problem in the wetlands near our school by accelerating plant growth beyond natural conditions, resulting in eutrophication and extreme depletion of the oxygen in the water. This was the first step in my expedition to uncover the unseen factors affecting the water quality in my town.
Research Objectives and Approach
In May 2002, I attended a Park City water forum that outlined the city's plans for water distribution, addressed emerging water-quality issues, and made time for citizens to ask questions. Elevated trace-metal concentrations in the streams of Park City were a big concern for those at the meeting. The two metals that seemed to pose the greatest threat to the environment, and to humans, were arsenic and zinc. From discussions at the meeting, I learned that elevated arsenic concentrations were in the drinking water coming out of Spiro Tunnel, and that toxic concentrations of zinc were showing up in Silver Creek.
After the meeting, I contacted the people at Park City Water Maintenance and talked with them about the sources of arsenic in our city's water supply. I found that most of the drinking water used by Park City comes out of tunnels constructed by past mining operations. After the mines closed, the tunnels were allowed to flood, providing an easy drinking-water source for the city. Spiro Tunnel, one of the main supplies of drinking water, contains the highest concentration of arsenic.
Arsenic, an element widely distributed throughout the Earth's crust, is very harmful to humans and other organisms, and poses the greatest threat to humans when it shows up in drinking water (World Health Organization, 2001). In parts of India, there are millions of reported cases of acute arsenic poisoning from drinking water (Harder, 2002). Scientists at the University of California at Berkeley have conducted arsenic toxicity studies in Argentina, Chile, and India, and found that prolonged exposure to elevated levels of arsenic in drinking water caused cancer and resulted in death for 1 out of every 10 people (Smith, 2001). Another study found that arsenic concentrations comparable to 10 micrograms per liter (µg/L) in water had hormone-disrupting effects in people (Wang, 2001). This level of arsenic concentration is well below the current EPA drinking-water standard of 50 µg/L (USEPA, 2002). There is also evidence that arsenic consumed over a period of 15 to 30 years may shrink the blood vessels that carry blood to the brain (Harder, 2002).Zinc, the second trace metal of concern, has been found at elevated levels in Silver Creek. The probable source of zinc is from abandoned mine tailings left over from Park City's historic silver mining. Preliminary studies by the U.S. Geological Survey found that zinc concentrations in Silver Creek exceeded the Ambient Water Quality Criteria of 388 µg/L by up to four times (Giddings et al., 2001). Elevated concentrations of zinc are absorbed by the gill tissues of fish, eventually preventing their intake of oxygen from the water (Hogstrand, 2000).
After gathering this background information on arsenic and zinc, I could now plan and carry out my research expedition. Phase 1 would include finding my data collection sites and obtaining water samples to determine changes in arsenic and zinc concentrations over time. Phase 2 would include conducting preliminary laboratory investigations on how to remove trace metals passively from the surface waters of Park City.
The sound of the car door slamming shut cuts through the frigid air. The ice and snow that collected on the car overnight plummet downward and shatter on the driveway below. The car is loaded and ready to go for another sample day. Inside, I have a hydrolab mini-monitor for measuring water temperature, pH, and specific conductance (which is directly proportional to salt concentration); a camera; my field journal; and acid-rinsed sample bottles. It is December 21, the day after school let out for the holiday break. The time on my watch reads 11:15. While most of my friends and classmates are sleeping or skiing, I am preparing for another day of exploring, collecting samples, and gathering data. I like doing this stuff; it's relaxing and makes me feel like I am accomplishing something worthwhile, or trying something new that no one has ever done before. This is what drives me to do my best.
I pull out of my driveway and head for the water maintenance building in town, about 10 miles from my house. This is my first site, and the place from which most of Park City's water comes. It is widely known to contain high levels of arsenic, barely below the EPA's standard for drinking water. Currently the standard is 50 µg/L; however, as of January 2006, the new standard will be 10 µg/L (USEPA, 2002). I walk up to the gray concrete building, ring the doorbell, and am greeted by, "Are you the science-fair kid?" I respond with a Yes and walk in the door. I go to the familiar spigot, which receives water from three miles away through the abandoned mine tunnel. I rinse my sample bottle three times, fill it to the brim, and rush out the door with a quick thanks. I rush back to my car to measure the water's temperature, specific conductance, and pH. Then I drive to my next site.
I arrive on the snow-covered dirt road, which is now blinding white rather than its usual reddish-brown color. Site 1 is on Silver Creek. During the silver mining days in Park City, a railroad ran along Silver Creek, and toxic mine tailings were dumped in and around the creek, contaminating the water with trace metals. This site is known to have high levels of zinc that could potentially harm fish (Giddings et al., 2001). I turn off the car, gather up all of my supplies, and walk down to the stream. I break the ice with my heel and submerge the hydrolab into the frigid water flowing beneath. The water is at the lowest level I've ever seen, and I quickly make a note of this in my field journal. With the exception of an abandoned beaver dam, there are no signs of wildlife at this site. I record the data from the spinach-colored screen on the hydrolab and plunge my hand into the frigid water for my sample. After what seems like an eternity, the bottle is full, and I quickly remove my hand from the icy water. The stabbing wind burns my hand as I dry it off on my ski pants.
My hand gradually warms up as I drive to the last of my three monitoring sites. Site 2 is below a sewage treatment plant that discharges sewage into Silver Creek. According to my previous four samples, Site 2 has higher arsenic levels than Site 1. Site 2 has lower zinc concentrations than Site 1, possibly because of dilution by the treated sewage effluent. The nasty smell of treated sewage singes my nostrils as I open the car door. Although the smell is horrible, I look forward to sampling at this site. The water temperature at Site 2 is about 9°C. warmer than the water at Site 1. It makes perfect sense when you think about it—the water is coming from people's houses, where it is warmed. I also notice small bubbles floating by as I collect my sample, think to myself, "This is odd," and quickly snap a picture.
On the way home I ponder the origin of the small white bubbles (foam), and I come to the conclusion that it may be detergents from the houses in Park City, that was flushed into the sewage treatment plant and then released into Silver Creek. This question, however, will have to wait for another expedition. I have enough to do with analyzing my arsenic and zinc samples.
I finally arrive home after almost two hours of sampling. I unpack my supplies and place my new bounty of samples on the garage workbench. I first measure the zinc concentration in each of the samples, using my field kit and a battery-powered photometer. I first pour 25 milliliters of sample water into a beaker and then place eight drops of the indicator solution into the sample. Next, I stir the sample and then break off the vacu-vial ampoule inside the beaker. If there is any zinc in the sample, a red color forms in the ampoule. The intensity of the red color is directly proportional to the amount of zinc in the water. I measure the color intensity with a portable field photometer.
Arsenic is much more difficult to measure. To measure arsenic levels, I use a Hach PermatchemTM kit. The lengthy instructions for measuring arsenic are burned into my memory. I only periodically check the methodology posted on the wall in front of me. I am constantly swirling the sample, adding reagents, and letting the sample react. After the final reaction is complete, I use a color-matching method to determine the amount of arsenic in the water. Today, December 21, my analytical results are higher than usual. I have found higher arsenic concentrations at Spiro Tunnel than on previous measurements. I have also measured an elevated arsenic concentration at Site 1, coming in at 20 µg/L. I have noticed that the arsenic concentration has been increasing at Site 1; this may be due to lower flows in Silver Creek as winter begins to exert its icy grip on Park City.
Data Analysis and Conclusions
Through my research, I have found that there are higher arsenic concentrations in Silver Creek below the sewage treatment plant (Site 2) than above it (Site 1). My research has also shown that the drinking water in Park City has elevated arsenic concentrations. I can conclude from my field observations and measurements that arsenic from the Spiro Tunnel is reaching the sewage treatment plant after people use this water for their day-to-day activities, such as flushing toilets, washing dishes, taking showers, etc. Once this high-arsenic water reaches the sewage treatment plant, it is treated and then contributes arsenic to Silver Creek at Site 2.
In contrast to the arsenic results, my research indicates that zinc concentrations are diluted by the sewage effluent discharging into Silver Creek. The zinc concentrations in the drinking water from Spiro Tunnel are relatively low, and when this low-zinc water is discharged into Silver Creek, it actually dilutes the zinc concentrations below the Ambient Water Quality Criteria for zinc.
I can conclude from this part of my research that the sewage treatment plant is both good and bad for Silver Creek. It helps to dilute the high zinc levels, but it is bad because it increases the concentration of arsenic. If only I could find a way to remove the arsenic before it gets into the Park City water supply and then into Silver Creek...
Passive Remediation of Surface Water Contaminated With Arsenic
After identifying that there was a serious problem concerning arsenic in the streams and possibly in the drinking water of Park City, I decided to see if there was a natural and cost-effective way to remove it. I found many references to permeable reactive barriers (PRBs) and how they could remove trace elements from water. I decided to see if PRBs could remove arsenic from water in the Spiro Tunnel. After further research, I found that almost all PRBs had been used to treat groundwater (Conca, et al., 2002), not surface water. It still was worth a try. I had a feeling that it just might work. I decided to use iron pellets in my PRB. Other researchers had found that iron was useful in removing trace metals from water by absorption (Joye, et al., 2002).
I built a miniature chamber containing nine PRBs in which I could test my theory. I collected five gallons of water from the Spiro Tunnel to use in my experiment. To simulate water flowing through the PRBs, I used a peristaltic pump to cycle the water through the reaction chamber.
It is December 25, and I am finally prepared to conduct my arsenic remediation study. I pour the five gallons of water from Spiro Tunnel into the test chamber and place both ends of the tubing into the water to create an artificial stream. Before contacting the iron pellets, my control sample contains 40 µg/L arsenic, a normal value for the Spiro Tunnel site. I flip on the pump, whose constant whirr quickly lets me know that it's functioning correctly. I find myself collecting water samples for almost four hours and finally stop at 6:45 pm. My gut feeling was right—the iron pellets removed 63 percent of the arsenic during the three-hour-and-48-minute experiment. If these PRBs could be installed throughout Spiro Tunnel, they just might remove enough arsenic to get the concentration below the future standard of 10 µg/L; or they could act as a pretreatment filter to help remove arsenic before it reaches the water treatment facility. I still have a lot of unanswered questions, but I feel like I have made some real progress in my research.
Questions for Further Research
- Is there a way to remove zinc using iron pellets or some other reactive media?
- Can the high concentrations of nutrients (phosphate, nitrate) that are present in Silver Creek and other streams, be removed by PRBs?
- Can I measure the fish, bacteria, and pathogen populations in Silver Creek? In addition, are these organisms impacted by the high trace-metal concentrations in Silver Creek?
- Are there other metals in Silver Creek besides arsenic and zinc, and can they be removed using PRBs?
Arsenic in Drinking Water Fact Sheet. World Health Organization. May 2001. Retrieved from the World Wide Web on December 9, 2002: http://www.who.int/imf-fs/en/fact210.html.
Conca, J., et al. "Treatability study of reactive materials to remediate groundwater contaminated with radionuclides, metals, and nitrates." Handbook of Groundwater Remediation Using Permeable Reactive Barriers: Applications to Radionuclides, Trace Metals, and Nutrients. New York: Academic Press (2002): 222-250.
Cravotta, C.A. and G.R. Watzlaf. "Design and performance of limestone drains to increase pH and remove metals from mine drainage." Handbook of Groundwater Remediation Using Permeable Reactive Barriers: Applications to Radionuclides, Trace Metals, and Nutrients. New York: Academic Press (2002): 20-62.
"Drinking Water Standards." USEPA. 2002. Retrieved from the World Wide Web on December 12, 2002: http://www.epa.gov/safewater/mcl.html.
Giddings, E.M., M.I. Hornberger, and H.K. Hadley. "Trace metal concentrations in sediment and water and health of aquatic microinvertebrate communities of streams near Park City, Summit County, Utah." Water Resources Investigations Report 01-4213. U.S. Geological Survey (2001): 22.
Harder, Ben. "Arsenic agriculture? Irrigation may worsen Bangladesh's woes." Science News Vol. 162, No. 21 (Nov. 23, 2002).
Harder, Ben. "Blood vessel poisoning: Arsenic narrows artery that feeds brain." Science News Vol. 161, No. 14 (April 6, 2002).
Hogstrand, Christer. "Transport mechanisms for zinc across gill and intestinal epithelia of fish." Retrieved from the World Wide Web on December 27, 2002: http://es.epa.gov/necr_abstracts/grants/97/envbio/hogstrand.html.
Joye, J.L., et al. "Development and performance of an iron oxide/phosphate reactive barrier for the remediation of uranium contaminated groundwater." Handbook of Groundwater Remediation Using Permeable Reactive Barriers: Applications to Radionuclides, Trace Metals, and Nutrients. New York: Academic Press (2002): 195-220.
Park City water meeting, Jim Santy Auditorium, May 2002.
Shelley, Kim. Environmental Engineer Division of Water Quality, Salt Lake City, UT. Written correspondence, 2002.
Smith, A.H. Arsenic Health Effects Research Program. University of California at Berkeley. 2001. Retrieved from the World Wide Web on September 27, 2002: http://ist-socrates.berkeley.edu/asrg/.
Standards of water quality for surface water. State of Utah. 2001. Retrieved from the World Wide Web on December 17, 2002: http://www.rules.state.ut.us/publicat/code/r317/r317-002.htm.
Wang, Linda. "Arsenic Pollution Disrupts Hormones." Science News Vol. 159, No. 11 (March 17, 2001).
More About This Resource...
This winning entry in the museum's Young Naturalist Awards 2003 examines water-quality issues. Doug's narrative essay, with illustrations and photographs, discusses:
- how his freshman honors biology class ignited his concern for environmental issues
- his expedition to uncover the unseen factors affecting the water quality in his town, including details about his research objective and approach
- his findings about arsenic and zinc levels and how they led him to the conclusion that the sewage treatment plant is both good and bad for Silver Creek
- his research to determine if there are natural and cost-effective ways to remove arsenic from the drinking water, as well as with his unanswered questions
Less than 1 period.
Supplement a study of ecology with an activity drawn from this winning student essay.
- Send students to this online article, or print copies of the essay for them to read.
- Divide the class into small groups and have them research permeable reactive barriers (PRBs), and how they are used in water treatment.
- Challenge the groups to prepare a five-minute oral report that creatively presents what they learned.
OriginYoung Naturalist Awards
SubtopicMinerals and Resources