Chemical Character of Ground Water
The chemical character of ground water in Marshall County is indicated by the analyses in Table 3. The analyses were made by Howard Stoltenberg in the Water and Sewage Laboratory of the Kansas State Board of Health. Samples of water for chemical analysis were collected from 30 wells distributed as uniformly as possible within the county and representing the principal water-bearing formations of the area. Analyses of the water from several municipal wells are also given. The effect of the geologic character of the aquifer upon the quality of water is discussed in the section on quality of water in relation to water-bearing formations. The results of the analyses of the water samples are given in parts per million. Factors for converting parts per million of mineral constituents to equivalents per million are given in Table 4.
Table 4--Factors for converting parts per million of mineral constituents to equivalents per million.
|Cation||Conversion factor||Anion||Conversion factor|
Chemical Constituents in Relation to Use
The following discussion of the chemical constituents of ground water has been adapted in part from publications of the Federal Geological Survey and the State Geological Survey of Kansas.
Dissolved solids--When water is evaporated, the residue consists mainly of the mineral constituents listed in the tables of analyses and generally includes a small quantity of organic material and a little water of crystallization. Water containing less than 500 parts per million of dissolved solids generally is satisfactory for domestic use except for difficulties resulting from hardness or excessive content of iron. Water containing more than 1,000 parts per million is likely to include enough of certain constituents to cause a noticeable taste or to make the water unsuitable in some other respects.
The dissolved solids in samples of water from Marshall County ranged from 193 to 3,887 parts per million. About 27 percent of the samples contained less than 500 parts per million and about 40 percent of the samples contained between 500 and 1,000 parts per million (Table 5). Ten of the 30 samples contained more than 1,000 parts per million.
Table 5--Dissolved solids in samples of water from wells in Marshall County.
|More than 1,000||10|
Hardness--The hardness of water, which is the property that generally receives the most attention, is recognized most commonly by its effects when soap is used with the water. Calcium and magnesium cause almost all the hardness of ordinary waters. These constituents are also the active agents in the formation of the greater part of the scale formed in steam boilers and other vessels used to heat or evaporate water.
In addition to the total hardness, the table of analyses shows the carbonate hardness and the noncarbonate hardness. The carbonate hardness is due to the presence of calcium and magnesium bicarbonates and can be almost completely removed by boiling. In some reports this type of hardness is called temporary hardness. The permanent or noncarbonate hardness is due to the presence of sulfates or chlorides of calcium and magnesium and cannot be removed by boiling. With reference to use with soap, the carbonate hardness and noncarbonate hardness do not differ. In general, the noncarbonate hardness forms harder scale in steam boilers.
Water having a hardness of less than 50 parts per million is generally rated as soft, and treatment for the removal of hardness is not necessary under ordinary circumstances. Hardness between 50 and 150 parts per million does not seriously interfere with the use of water for most purposes, but the hardness does increase the amount of soap used and removal by a softening process is profitable for laundries or other industries using large quantities of soap. Water having hardness in the upper part of this range will cause considerable scale on steam boilers. Hardness above 150 parts per million is very noticeable, and if the hardness is 200 or 300 parts per million, water for household use is commonly softened. Where municipal water supplies are softened, an attempt is made generally to reduce the hardness to 80 to 100 parts per million. The additional improvement by further softening of a public supply generally is not deemed worth the increase in cost.
Water samples collected in Marshall County ranged in total hardness from 136 to 2,709 parts per million. Only one sample had a hardness of less than 200 parts per million (Table 6); nearly two-thirds of the samples had hardnesses between 200 and 600 parts per million. Four samples had hardnesses of 700 to 900 parts per million, and 6 had hardnesses of more than 1,000 parts per million.
Table 6--Hardness of samples of water from wells in Marshall County.
|More than 1,000||6|
Iron--Next to hardness, iron is the constituent of natural water that generally receives the most attention. The quantity of iron in ground water may differ greatly from place to place, although the water may be derived from the same formation. If a water contains more than 0.1 part per million of iron, the excess may settle out as a reddish precipitate. Iron present in sufficient quantity to give a disagreeable taste and to stain cooking utensils and plumbing may be removed from most water by simple aeration and filtration, but some water requires the addition of lime or some other substance.
The iron content of the water samples from wells in Marshall County ranged from 0.03 to 32 parts per million. One-fifth of the samples contained 0.1 part per million or less, half contained between 0.1 and 2 parts per million, and the remainder contained more than 2 parts per million. It is believed that the excessively high concentrations of iron shown in Table 7 are due to corrosion of the pumping equipment, and are not the natural iron content of the water.
Table 7--Iron content of samples of water from wells in Marshall County.
Fluoride--The fluoride content of water likely to be used by children should be known because fluoride in water is associated with the dental defect known as mottled enamel, which may appear on the teeth of children who drink water containing excessive amounts of fluoride during the period of formation of the permanent teeth. According to the Public Health Service (1946), water containing more than about 1.5 parts per million of fluoride should not be used for drinking. If the water contains as much as 4 parts per million of fluoride, 90 percent of the children drinking it are likely to have mottled enamel, and 35 percent or more of the cases will be classified as moderate or worse. Contents of fluoride up to 1 part per million are believed to be beneficial in reducing tooth decay, and fluoride is now being added to some municipal supplies to bring the content up to 1 part per million.
Twenty-one of 30 samples of water from wells in Marshall County had less than 0.5 part per million of fluoride, 6 had between 0.5 and 0.9 part per million, and 3 had between 1.0 and 1.4 parts per million.
Nitrate--The use of water containing an excessive amount of nitrate in the preparation of a baby's formula can cause cyanosis ("blue baby") or oxygen starvation. Some authorities advocate that water containing more than 45 parts per million of nitrate should not be used in formula preparation for infant feeding. Water containing 90 parts per million of nitrate generally is considered dangerous to infants, and water containing 150 parts per million may cause severe cyanosis. Cyanosis is not produced in adults and older children by the concentrations of nitrate found in drinking water. Boiling water high in nitrate content does not render it safe for use by infants; therefore, only water that is known to be free from high nitrate content should be used for this purpose.
The nitrate content of the water from some wells is somewhat seasonal, being highest in the winter and lowest in the summer (Metzler and Stoltenberg, 1950). In general, water from wells that are most susceptible to surface contamination is likely to be high in nitrate concentration.
The nitrate content of the water from wells sampled in Marshall County ranged from 0.40 to 1,084 parts per million (Table 8). About two-thirds of the samples contained less than 40 parts per million, about a quarter contained between 40 and 100 parts per million, and a tenth contained more than 100 parts per million of nitrate.
Table 8--Nitrate content of samples of water from wells in Marshall County.
|Range, parts per million||Number of samples|
|More than 200||3|
Sulfate--Sulfate (SO4) in ground water is derived principally from gypsum (calcium sulfate), and from the oxidation of pyrite (iron disulfide). Magnesium sulfate (Epsom Salts) and sodium sulfate (Glauber's Salts), if present in sufficient quantity, will impart a bitter taste to the water and may have laxative effect upon people who are not accustomed to drinking it.
The sulfate content of the water from wells sampled in Marshall County ranged from 8.2 to 1,689 parts per million. Two-fifths of the samples contained less than 50 parts per million, about a fourth of the samples contained between 50 and 200 parts per million, and about a third contained more than 200 parts per million of sulfate (Table 9).
Table 9--Sulfate content of samples of water from wells in Marshall County.
|More than 400||7|
The analyses of water given in Table 3 show only the amounts of dissolved mineral matter in the water and, except for fluoride and nitrate, are not considered generally to be indicative of the healthfulness of the water for human consumption.
An excessive amount of certain mineral matter, such as nitrate or chloride, may indicate pollution of the water. A well should not be constructed near sources of pollution, such as barnyards, privies, and cesspools, and every well should be tightly sealed to a level somewhat below the water table. The top of the well should be sealed to prevent the entrance of water, insects, and debris.
Kansas Geological Survey, Geologic History of Kansas
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Web version March 2004. Original publication date March 1954.