How Geologic Features, Watersheds, Topography, and Climate
Affect Oregon’s Mercury Levels
Natural Inputs of Mercury into the Environment
Mercury is a naturally occurring element and most commonly found in it's ore form. Large deposits of cinnabar (mercury sulfide) have been mined in Oregon (Oregongeology.org). Some examples are the Independent and Mother Lode mines near Prineville, Oregon in the Ochoco Creek watershed. These mines have since been abandoned, but were in operation from 1930 until the mid 1950's (Oregon Department of Geology and Mineral Industries, n.d.). The mining operations are shown to have increased the natural input of mercury and raised background levels (Oregon DEQ, 2014). These cinnabar deposits occur in the Ochoco Mountains where the headwaters for Ochoco Creek originate. This natural input of mercury into the environment and aquatic ecosystems affects three other major Oregon river systems. Ochoco Creek is a tributary to the Crooked River, which is a tributary of the Deschutes River, which is a tributary of the Columbia River. The Oregon Department of Environmental Quality has been conducting an ongoing study to clean up and monitor levels. Further site details can be found here.
Mercury is a naturally occurring element and most commonly found in it's ore form. Large deposits of cinnabar (mercury sulfide) have been mined in Oregon (Oregongeology.org). Some examples are the Independent and Mother Lode mines near Prineville, Oregon in the Ochoco Creek watershed. These mines have since been abandoned, but were in operation from 1930 until the mid 1950's (Oregon Department of Geology and Mineral Industries, n.d.). The mining operations are shown to have increased the natural input of mercury and raised background levels (Oregon DEQ, 2014). These cinnabar deposits occur in the Ochoco Mountains where the headwaters for Ochoco Creek originate. This natural input of mercury into the environment and aquatic ecosystems affects three other major Oregon river systems. Ochoco Creek is a tributary to the Crooked River, which is a tributary of the Deschutes River, which is a tributary of the Columbia River. The Oregon Department of Environmental Quality has been conducting an ongoing study to clean up and monitor levels. Further site details can be found here.
Cinnabar deposits occurring naturally in the Ochoco Mountains contribute to the mercury levels in Oregon's major river systems (Oregon DEQ, 2014).
Ore deposits enter the headwaters of Ochoco Creek naturally, although mining has increased the total amount...
Ochoco Creek flows into the Deschutes River...
Deschutes River flows into the Columbia River...
Columbia River flows into the ocean, further polluting coastal ecosystems.
Oregon is home to nineteen volcanoes (volcanodiscovery.com). Mercury, classified as a volatile element lives mostly in the Earth's crust.
Its geochemical cycle starts with volcanic activity as magma invades sedimentary rocks. Mercury vapors and compounds rise toward the surface, condensing in porous rocks mostly as the sulfide HgS, cinnabar (Alden, 2014).
Heat, fracturing, and erosion either by natural or anthropogenic causes release the mercury into the atmosphere, soil and waterways (Elaw, 2010).
Mercury and conveyance mechanisms through the hydrological cycle
As shown in the above image, mercury discharged by coal fired power plants is broadcast by the atmosphere and enters the hydrological cycle as vapor. Following the path of water vapor through the transportation, radiative exchange (oxidizing the elemental mercury), and precipitation stages, this inorganic mercury is distributed alongside precipitation to the earth's surface where it accumulates in sediments and waterbodies. Just like the rest of the precipitation it accompanies, mercury is either stored in ice and snow or goes through infiltration or runoff upon meeting the soil. Through the same transport mechanisms as water, mercury is directed by the regional topography, soil structure, and geology to various waterbodies in the watershed basin. Beyond mercury's natural occurrence in sediment, the additional land disturbances from large runoff events and anthropogenic sources such as clearcut logging, mining, and charging of new reservoirs yields a disproportionate deposition of mercury into the hydrological cycle (Van Furl, Chad, John A. Colman, and Michael H. Bothner, 2010). This accelerates the presence of mercury in freshwater systems, and increases the bioaccumulation of mercury in fish, which in turn increases the risk and volume of human consumption.
The Mercury Cycle. Image: http://www.mercury.utah.gov/atmospheric_transport.htm
As shown in the above image, mercury discharged by coal fired power plants is broadcast by the atmosphere and enters the hydrological cycle as vapor. Following the path of water vapor through the transportation, radiative exchange (oxidizing the elemental mercury), and precipitation stages, this inorganic mercury is distributed alongside precipitation to the earth's surface where it accumulates in sediments and waterbodies. Just like the rest of the precipitation it accompanies, mercury is either stored in ice and snow or goes through infiltration or runoff upon meeting the soil. Through the same transport mechanisms as water, mercury is directed by the regional topography, soil structure, and geology to various waterbodies in the watershed basin. Beyond mercury's natural occurrence in sediment, the additional land disturbances from large runoff events and anthropogenic sources such as clearcut logging, mining, and charging of new reservoirs yields a disproportionate deposition of mercury into the hydrological cycle (Van Furl, Chad, John A. Colman, and Michael H. Bothner, 2010). This accelerates the presence of mercury in freshwater systems, and increases the bioaccumulation of mercury in fish, which in turn increases the risk and volume of human consumption.
The Mercury Cycle. Image: http://www.mercury.utah.gov/atmospheric_transport.htm
How Mercury Gets into fish
1. Chemical Emissions from industrial plants and other point and non point sources.
2. Surface water runoff fueled by precipitation
3. Deposition of run off into ocean
4. Mercury (Hg) transforms to methlymercury (CH3Hg) through chemical reactions of hydrogen ion accumulation from water (H2O) and the present soil texture.
5. Once the mercury has been transformed it can accumulate inside fish. The older, and larger the fish the more potential for mercury accumulation it can have.
6. Fishermen then catch the fish for economic distribution, or for consumption.
2. Surface water runoff fueled by precipitation
3. Deposition of run off into ocean
4. Mercury (Hg) transforms to methlymercury (CH3Hg) through chemical reactions of hydrogen ion accumulation from water (H2O) and the present soil texture.
5. Once the mercury has been transformed it can accumulate inside fish. The older, and larger the fish the more potential for mercury accumulation it can have.
6. Fishermen then catch the fish for economic distribution, or for consumption.
- Pregnant women are worried not to consume large quantities of fish due to possible mercury contamination.