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8.0 GROUND -WATER QUALITY -- Continued
<br />8.3 Minor Dissolved Constituents
<br />Concentrations of Several Minor Dissolved Constituents
<br />Exceed Water - Quality Standards
<br />Concentrations of boron, fluoride, iron, manganese, mercury, nitrate nitrogen,
<br />selenium, and zinc are increased locally by geologic processes and
<br />human activities.
<br />Water - quality standards established by the U.S.
<br />Environmental Protection Agency (EPA) for human
<br />and livestock consumption and crop irrigation serve
<br />as a basis for appraisal of the concentrations of
<br />minor dissolved constituents (usually present in con-
<br />centrations of less than 10 milligrams per liter) in
<br />terms of their limiting effects on the intended use of
<br />the water (table 8.3 -1�. Several studies in Area 61
<br />considered minor dissolved constituents in the
<br />ground water, but the sampling was sparse and the
<br />selection of analyzed constituents was inconsistent
<br />from study to study. Minor dissolved constituents
<br />that were analyzed include aluminum, arsenic, bo-
<br />ron, bromide, cadmium, copper, fluoride, iodide,
<br />iron, lead, manganese, mercury, molybdenum, nick-
<br />el, nitrate - nitrogen, phosphate - phosphorus, seleni-
<br />um, silver, uranium, vanadium, and zinc. Concentra-
<br />tions of several of these constituents locally exceed
<br />EPA standards, in some instances by three to four
<br />times; the selenium concentration may be as much as
<br />100 times the standard (figs. 8.3 -1 and 8.3 -2).
<br />Abnormally high concentrations of minor dis-
<br />solved constituents in ground water result from the
<br />dissolution of uncommon minerals in bedrock, other
<br />hydrogeologic processes, or contamination from hu-
<br />man activities. Large concentrations of fluoride
<br />occur in water in the Poison Canyon and Raton
<br />Formations probably as a result of the dissolution of
<br />detrital fluorite, a calcium fluoride mineral (Howard,
<br />1982, p. 56 -57). The coincident enrichment of fluo-
<br />ride and boron in water in the Cretaceous Dakota
<br />Sandstone near the southern edge of the area is a
<br />common occurrence in areas with thermal activity
<br />and suggests a local magmatic origin for these con-
<br />stituents (Griggs, 1948, p. 53 -55). Large concentra-
<br />tions of iron and manganese occur principally in
<br />water in the Raton and Vermejo Formations, and
<br />also in the Poison Canyon Formation and alluvium,
<br />probably from the dissolution of coal, pyrite (an iron
<br />sulfide mineral), and siderite (an iron carbonate
<br />mineral) (Howard, 1982, p. 53 -56). Large selenium
<br />concentrations occur principally in the Cretaceous
<br />Smoky Hill Marl Member of the Niobrara Formation
<br />in the northeastern corner of the basin and randomly
<br />in other formations as a result of the dissolution of
<br />selenium- containing salt minerals in shale. Nitrate -
<br />nitrogen enrichment in the ground water occurs in
<br />most formations, principally in stream valleys and
<br />the eastern plains where farming and ranching are the
<br />most common land uses. Animal wastes and fertiliz-
<br />ers apparently add nitrogen to the ground water,
<br />although some of the nitrogen enrichment may result
<br />from the dissolution of organic -rich shale or other
<br />rocks with large nitrogen contents. Large mercury
<br />and zinc concentrations in ground water occur ran-
<br />domly and cannot be attributed to specific origins.
<br />Table 8.3 -1 Water - quality standards.
<br />Constituent
<br />Recommended
<br />Concentration Limit
<br />(milligrams per liter)
<br />Effect of Excess Constituent
<br />0.75
<br />Damages fruit and nut trees
<br />Baron
<br />Chloride
<br />250
<br />Kills fish
<br />Fluoride
<br />1.8
<br />Mottles teeth
<br />Hardness (calcium and magnesium as calcium carborate)
<br />120
<br />Inhibits sudsing and encrusts pipes _
<br />0.3
<br />Imparts undesirable taste to water and stains laundry
<br />Iron
<br />0.05
<br />Same as iron effects
<br />Manganese
<br />10
<br />Causes lethal blood disease in infants
<br />Nitrogen
<br />0.01
<br />Causes gastrointestinal and skin damage and mental disorders
<br />Selenium
<br />250
<br />Causes laxative effect
<br />Sulfate
<br />Zinc
<br />5.0
<br />Imparts bitter taste to water and damages crops
<br />1. Sources are Freeze and Cherry (1979, P. 386), U.S. Environmental Protection Agency (1977a, 1977b), and Hem, 1970, p. 224 -226
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