January Number Four - High Levels of Uranium in SW Kansas Water

Watershed Restoration and Protection Strategy

I lived in Deerfield and Lakin, Kansas for many years and having higher than acceptable levels of uranium in the drinking water had been a problem for years. After a multitude of health issues and elevated cases of cancer plagued the region, many locals citing the bad water as the cause, I decided I wanted to find out why the levels of uranium were so high in this area.  

Below is a section that relates to why the levels are higher in this area than in surrounding areas.  It appears to me that the drought SW Kansas has been suffering with for the past 20 years is taking its toll on everything from humans to plant life.

I included the link to the entire project at the top of the page, if reading this kind of stuff is your idea of a good time.  It was for me and I'm definitely not a geologist or scientist of any kind.

Upper Ark – Lake McKinney Watershed

2008

Trace constituents of concern

The process of evapotranspiration concentration of dissolved salts in Arkansas River water not only increases concentrations of the major constituents such as sulfate and sodium but also of minor and trace constituents. The concentrations of some minor and trace inorganic substances dissolved in the river water become limited by chemical reactions such as adsorption on sediments, whereas the levels of other constituents continue to increase with rising salinity. The elements boron (B), selenium (Se), and uranium (U) can increase to concentrations that exceed either recommended or regulated levels for particular uses.

Boron is an element that occurs in water primarily in the form of boric acid (H3BO3). The boron level in most Kansas streams is usually less than a few tenths of a mg/L (a few hundred μg/L). However, boron is concentrated with other dissolved constituents in Arkansas River water and has exceeded 0.75 mg/L (750 μg/L), the maximum level listed in the Kansas surface-water quality standards for irrigation use, in low river flows. Boron concentrations above this level can be toxic to selected sensitive crops such as onions, and levels within the range 0.76-1 mg/L can begin to become toxic to wheat, barley, and sunflowers. The highest boron concentration observed in the Arkansas River within the Lake McKinney watershed is nearly always less than one mg/L.

Selenium is a trace constituent that is also concentrated with dissolved salts in Arkansas River water. Selenium occurs in stream water primarily in the form of selenite (SeO3) or selenate (SeO4) ions. Dissolved selenium concentration is typically less than a few μg/L in Kansas streams but usually has exceeded 5 μg/L, the chronic toxicity level for aquatic life use listed in the Kansas surface-water quality standards, in lower flows of the Arkansas River in the Lake McKinney watershed. High levels of selenium can be toxic to aquatic life, such as fish and invertebrates, and to birds that eat aquatic life containing excessive selenium content. The selenium concentration of Arkansas River water has exceeded 20 μg/L, the acute toxicity level for aquatic life, for some low flows in the watershed. Selenium in the Arkansas River has not been observed to exceed 30 μg/L, therefore it is not a drinking-water concern because the maximum contaminant level for potable water is 50 μg/L.

Uranium is another trace element concentrated with salinity in the Arkansas River. Uranium dissolved in stream water occurs primarily in the form of uranyl ion (UO2) complexed with hydroxyl (OH) and carbonate (CO3) ions. Uranium concentration in most stream waters is less than a few μg/L but has been measured as high as over 60 μg/L in the Arkansas River. For example, a river water sample collected at Garden City in 1999 contained a uranium concentration of 68 mg/L; the sulfate content of this sample was 2,280 mg/L. The U.S. EPA established a maximum contaminant level (MCL) of 30 μg/L for uranium in drinking water at the end of 2003 and Kansas adopted this as a regulated standard in 2004. Chemical data for the Arkansas River in southwest Kansas indicate that the uranium concentration usually exceeds 30 μg/L when the sulfate content is greater than 1,400 mg/L, a common condition for moderate to low river flows.

The selenium/sulfate and uranium/sulfate ratios are both within a limited range in water from John Martin Reservoir in southeastern Colorado downstream in the Arkansas River valley to Dodge City (Figure 11). These ratios are useful for comparing how these trace elements change relative to sulfate, the major constituent in greatest concentration. The ratios show some variation in central Colorado then become relatively constant from the John Martin Reservoir downstream, thus there is little relative change due to hydrological and geochemical processes or any additional sources downstream from this location. The ratios indicate that the saline water crossing the state line generally changes very little for these constituents as it moves downstream to and within Kansas. A selenium/sulfate ratio in the range of 0.7 x 10-5 plus or minus 0.2 x 10-5 indicates that when the sulfate concentration is above about 600-900 mg/L in the Arkansas River, the selenium content generally exceeds 5 μg/L. A uranium/sulfate ratio in the range of 2.5 x 10-5 plus or minus 0.5 x 10-5 indicates that when the sulfate level is greater than about 1,000-1,500 mg/L, uranium concentration generally exceeds 30 μg/L. Based on the distribution of sulfate levels with flow shown in Figure 10, Arkansas River water usually contains selenium and uranium concentrations that exceed the chronic toxicity level for aquatic life use and the MCL for drinking water, respectively, when the flow is less than 300 ft3/sec, a condition that is typical for the river.

The drinking water standard for uranium is based on the toxicity of the element. However, uranium is also a radioactive element. Other trace elements that are radionuclides and contribute to the radioactivity of stream water include radium. The main radioactivity concern for the Arkansas River is alpha radiation for which there is a maximum contaminant level of 15 pCi/L (picocuries per liter) for adjusted gross alpha (excluding radon and uranium) in drinking water. KDHE is currently examining gross alpha radiation in the Arkansas River. The radionuclide levels are higher in the Arkansas River than in other Kansas surface waters due to the source and high concentration of uranium and other dissolved constituents in the river water.