- Area: Science
- Program: GeoScience
- Type of Writing: Scientific (writing to communicate scientific research results)
- Course Level: 2000
- English Speaking Nativeness: Native
- Year: 2017
- Paper ID: S.G.S.2.N.2.6
Soil Screening Assessment of Mineral Fork Canyon 2
Utah’s historic mines were abandoned long before there were safety regulations put in place to prevent threats to health and safety, and environmental degradation. The working hypothesis for this study is that heavy metals from the Wasatch Mine, are direct contributors to environmental contamination in the canyon. Seven of ten soil samples exceed BLM Risk Management Criteria, or RMC, for arsenic in relation to the recreational use of the land. Only three of the collection locations detected lead levels that exceed RMC acceptable concentration levels for recreational users. Of those three locations, none had levels exceeding the RMC level of 2000 ppm that is acceptable for workers and surveyors. The arsenic levels detected from each collection site exceeds natural background levels and the RMC acceptable concentration levels for recreational users of 20 ppm. The arsenic level detected at the mine opening was over 8900. These results show that while lead levels are not high enough to be of a concern, the arsenic levels in the environment are high enough to pose serious health risks to most humans and wildlife in contact with the area.
With over two hundred mining districts and thousands of abandoned mine openings, the Utah landscape is littered with the remnants of its mining history. Most of the mines were closed before the Utah Mined Land Reclamation Act enacted by the Utah Legislature in 1975 (Utah 1975). The mine reclamation process restores land that has been mined, to a natural or economically usable state. The present safety threats posed by the unreclaimed historical mines are the accessible mine openings, abandoned infrastructure, ground surface instability, and exposed waste rock and tailings (James 1979). Utah currently has over four hundred mine cleanups in progress and nearly two thousand waiting to be analyzed by the BLM (BLM 2014). The Bureau of Land Management (BLM), has developed an acceptable concentration level criterion, called Risk Management Criteria (RMC) for the chemicals of concern (heavy metals) as they relate to recreational use and wildlife habitat on BLM lands (Ford 2004).
Lead and arsenic pose serious cancer and non-cancer threats. The potential exposure pathways include soil and sediment ingestion, vegetation ingestion, surface water ingestion, and airborne dust inhalation. Lead is a bio-accumulative toxin, resulting in the “secondary poisoning” of top consumers in a food web (Ford 2004). Lead poisoning is a serious and often fatal condition that results from the buildup of the toxic metal in the body. Natural levels of lead in soil range from 50 to 400 parts per million. Cancers directly linked to arsenic exposure are lung, bladder, liver, and skin melanomas. Arsenic is a Group 1 cancer causing, carcinogen. Serious illness and deaths have been reported at exposure levels of 600 ppm per day or higher (Gomez-Caminero et al., 2004). Typical arsenic concentrations for uncontaminated soils range from 1 to 18 parts per million (NAOMI 2008). Mining and smelting site activities result in a substantial increase of arsenic and lead levels in the environment (Ford 2004).
The waste rock and tailings from the Wasatch Mine have been left exposed to the elements and have likely increased levels of the heavy metal contamination in the soil and water in the area. The Wasatch Mine has a runoff stream draining the heavy metals directly out of the mine before converging with the Mineral Fork stream. The Mineral Fork stream then carries the heavy metals further downslope into Big Cottonwood Creek that serves as a water source for Salt Lake City. To evaluate this assumption, several soil samples were collected along the mine runoff and brought back to the classroom for analysis. This paper presents the results of the tests conducted to determine the levels of heavy metal contamination found in the soil collected around Mineral Fork trail and the Wasatch Mine.
Research Question and Hypothesis
If the soil in Mineral Fork canyon contains heavy metal levels that exceed the EPA’s natural screening levels for lead and arsenic, and the increased levels of the metals directly correlates to the runoff coming out of the Wasatch Mine, it could be established that the historic unreclaimed mine is a direct contributor of the environmental contamination in the canyon.
Field Methods/Research Methods
To test the levels of heavy metals present in the soil, samples were collected along the stream flowing from the Wasatch Mine. Ten collection sites were predetermined based on accessibility using the USGS topographic map Dromedary Peak, Utah. At each collection location, sample numbers, date, time, and GPS coordinates were recorded in the field journal along with detailed description notes of the collection site. The collection sites were positioned at various points along the streambed with the focus areas being at the Wasatch Mine entrance, at the intersection of the mine runoff and Mineral Fork stream, and at the end of the Mineral Fork stream before it converges with Big Cottonwood Creek. The collected samples were slowly dried out in aluminum pans before being sifted to remove the larger debris present in the samples. The soil samples were then taken to the geology lab at Salt Lake Community College where they were sieved on U.S. Sieve #30, #40, #50, and #80 in accordance with industry standards. The samples were then analyzed with the non-destructive handheld X-ray fluorescence machine (XRF), which scatters the innermost orbital electrons of the atoms and counts in parts per million as the outer electrons jump to fill back in the inner shell. The XRF reference number and parts per million counts were recorded in the field journal next to their respective sample location numbers. The XRF results were then uploaded onto the computer and reference numbers were matched up to sample numbers on a spreadsheet.
Data Analysis: Concentrations of Metals in Soil
During the collection phase, ten soil samples were collected and tested to determine the levels of heavy metals present in the soils in the Mineral Fork Mine runoff area. The samples were collected at depths of less than one foot where the metals were suspected of contaminating the soil. The locations of the collection sites are illustrated in figure 4 of this report. The soil samples were analyzed for arsenic and lead. Table 1 summarizes the screening level of the arsenic and lead detected from each of the collection sites.
Arsenic and lead were detected in all ten samples. The acceptable level criteria for the chemicals of concern, heavy metals, as they relate to residential and non-residential use on BLM lands, is listed in Table 2. Heavy metal concentrations exceeding the BLM contaminant of concern levels, called the Risk Management Criteria, RMC, is considered to indicate contamination in relation to the recreational use of the land. Acceptable lead levels for nonresidential recreational use is over 1000 ppm. Only three of the collection locations detected lead levels that exceed RMC contamination levels for recreational users. Of those three locations, none had levels exceeding the RMC level of 2000 ppm that is acceptable for workers and surveyors. The arsenic levels detected from each collection site exceed the highest natural background level of 40 ppm. The arsenic levels at three collection locations exceed the Risk Management Criteria (RMC) contamination levels for all users except ATV drivers and surveyors. There are seven collection sites where the arsenic levels exceed all RMC contamination levels.
The results of the soil analysis show that while lead levels are not high enough to be of a serious concern, the arsenic levels in seven of the ten collection sites are. All ten of the collection sites in the Mineral Fork hiking area contained arsenic levels that exceeded the highest acceptable background level of 40 ppm. Most samples far exceeded the BLM’s RMC acceptable levels of arsenic for residents (1 ppm), campers (20 ppm), and workers (12 ppm). The detected levels of arsenic in the environment are high enough to pose serious health risks to most wildlife and humans in contact with the area. The potential exposure pathways include soil and sediment ingestion, vegetation ingestion, surface water ingestion, and airborne dust inhalation (Ford 2004). Serious illness and deaths have been reported at exposure levels of 600 ppm per day or higher (Gomez-Caminero et al., 2004). There were three collection sites that the arsenic levels were detected higher than 600 ppm.
Conclusion and Future Study
The data gathered is conclusive enough to determine that lead levels do not exceed BLM acceptable concentration levels for recreational use. However, toxic levels of arsenic are present in soils collected in Mineral Fork Canyon. It is recommended that soil samples from background areas be collected and analyzed to determine the natural level of arsenic present in the canyon. Additional sites along the trail should be analyzed to determine the extent of the toxic levels of arsenic, and if the concentrations can be directly linked to the mine runoff. It is also recommended that the study be extended further up the canyon to the remnants of the Regulator Johnson Mine. The results from this analysis could be used in conjunction with future data to determine the extent of contamination the Wasatch Mine contributes to the environment and how the data relates to the background levels of arsenic.
Keywords: soil screening, lead levels, arsenic levels
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