Distilled water has a pH of 7. Basic or alkaline solutions i. Acidic solutions i. Each unit change in pH is equal to a fold 10 times change in the pH. The table shows the approximate pH value for some common substances. Rain and snow the principal sources of ground water have pH values near 5. Acid rain can have pH values near 4.
There are concerns that acid rain is having effects on vegetation and aquatic fauna. This measurement includes orthophosphate as well as any phosphorus incorporated with organic or inorganic suspended sediment in the water sample. Excessive phosphorus can lead to algal blooms and the resulting depletion of dissolved oxygen in surface- water and karst groundwater systems.
There are no health-based water-quality standards for total phosphorus in water. The Kentucky Division of Water recommends that total phosphorus be less than 0. Polychlorinated biphenyls PCBs Polychlorinated biphenyls PCBs , also known as chlorinated hydrocarbons, consist of man-made, organic compounds with up to 10 chlorine atoms that are attached to a biphenyl molecule with two benzene rings. PCBs were banned in the United States in , but may still be present in industrial products produced before that time, such as electrical equipment, hydraulic system fluids, oil-based paints, and some plastics.
PCBs have been demonstrated to be a carcinogen. Pesticides Pesticides are substances used to control, prevent or destroy any type of pest undesirable species of animals. A large number of synthetic organic pesticides have been developed and applied in agricultural and urban settings. Some, such as the organochlorine insecticide DDT, were banned decades ago but still persist in soils and sediments and can still be found in groundwater.
Most recently developed pesticides are less persistent in natural environments; however, they may still have undesirable impacts on human health and groundwater-quality. According to recent agriculture sales data, atrazine, glyphosate, metolachlor, and simazine are the top four animal pesticides sold in Kentucky. Alachlor and cyanazine have also been used extensively in the past.
Toxicological information for pesticides was obtained from the Extension Toxicology Network ace. Alachlor map image Alachlor is used to kill crabgrass and broadleaf plants that occur among various agricultural crops, including peanuts, sorghum, beans, and tobacco. The three primary breakdown products of alachlor ethanesulfonic acid, alachlor oxanlic acid, and 2,6-diethylanaline may be found in groundwater and surface water at higher levels than the alachlor itself; however, their health effects are not well established.
Alachlor has not been shown to cause cancer in humans, but can cause cancer in laboratory animals. Atrazine map image Atrazine is used as both an agricultural and domestic herbicide for broadleaf and grassy weeds. It is a widely used pesticide throughout Kentucky. Short-term health effects for exposure to atrazine include congestion of heart, lungs, and kidneys; low blood pressure; muscle spasms; weight loss, and damage to the adrenal glands. Long-term exposure can result in cancer, weight loss, cardiovascular damage, retinal and some muscle degeneration.
Cyanazine map image Cyanazine belongs to the chemical class of triazines. It is used mainly to control annual grasses and broadleaf weeds in corn. It has low to moderate persistence in soils and is rapidly degraded by microbial activity. Cyanazine has a half-life of 2 to 14 weeks, depending on soil type, and is stable in water. There is no Maximum Contaminant Level for cyanazine; however the Kentucky Division of Water has set a health advisory limit of 0.
Metolachlor map image Metolachlor belongs to the chemical class of amides. It is mainly used to control broadleaf and grassy weeds in field corn, soybeans, peanuts, grain sorghum, potatoes, pod crops, cotton, safflower, stone fruits, and nut trees, highway rights-of-way, and woody ornamentals. It is moderately persistent in soils with a half-life of 15 to 70 days, and is highly persistent in water. There is no Maximum Contaminant Level for metolachlor; the Kentucky Division of Water has set a health advisory limit of 0.
Simazine map image Simazine belongs to the chemical class of triazines. It is predominantly used to control broadleaf weeds and annual grasses in fields where berry fruits, nuts, vegetables, and ornamental crops are grown, and on turfgrass. It is moderately persistent in soils, with a half-life of about 60 days, and is moderately persistent in water, with a half-life that depends on the amount of algae present. The Maximum Contaminant Level for simazine is 0.
At higher levels, long-term exposure can cause tremors; damage to testes, kidneys, liver, and thyroid; and gene mutations. There is some evidence that simazine may have the potential to cause cancer from a lifetime exposure at levels above the MCL.
Petroleum Hydrocarbons Petroleum hydrocarbons are complex mixtures of chemicals that are the primary constituents in oil, gasoline, diesel fuel, and other solvents or types of oil. Radionuclides A radionuclide is an atom with an unstable nucleus, which emits gamma radiation or subatomic particles ionizing radiation.
They may occur naturally or can be produced artificially. Also referred to as radioactive isotopes or radioisotopes, radionuclides are primarily used either for their chemical properties, such as in tracing the movement of water, or as radiation sources, such as in food preservation.
Residues In chemistry, a residue is any material remaining after the distillation or evaporation of a larger molecule. In groundwater research, residues called total solids are substances remaining after a water sample has been evaporated to dryness. Total Suspended Solids TSS is the portion of total solids that are retained on a filter, usually with 0.
Total dissolved solids TDS is the portion of total solids that has passed through a filter, and the remaining water then evaporated, leaving the TDS residue. TDS is often used as an indicator of the suitability of that groundwater for various uses. It can be calculated by adding all the solute concentrations from a complete chemical analysis, or measured as the weight of residue remaining after water has been evaporated to dryness. Total dissolved solids values typically increase with sample depth or the distance that groundwater has traveled from recharge area to sample site.
Total dissolved solids values are a general indicator of the suitability of groundwater for various uses. A common classification for total dissolved solids is. Water having a value greater than this has an unpleasant taste and may stain containers or precipitate scale in pipes and faucets. Total Suspended Solids map image Total suspended solids refers to particulate material in water. Total suspended solids values are typically higher where there is rapid water flow karst springs, wells that intercept a fracture or karst conduit and in water from uncased wells that has been stirred during purging prior to sample collection, and lower where groundwater flows slowly through porous media such as sand or sandstones.
Total suspended solids values may also include any solids that formed in the sample bottle after collection and prior to analysis. There are no health standards or cosmetic limits for total suspended solids in water. Some metals and pesticides are readily bound to suspended material, so water high in total suspended solids may also contain important amounts of metals or synthetic organic chemicals which may have health or safety implications.
High amounts of suspended material can clog plumbing systems and stain clothing and water containers. Semivolatile Organic Compounds SVOC's A semivolatile organic compound has a boiling point higher than that of water degrees Fahrenheit , and may vaporize at temperatures higher than that of room temperature.
PAH compounds occur in oil and coal deposits and are byproducts of burning either fossil or biomass fuels. Volatile Organic Compounds VOC's Volatile organic compounds are carbon-based substances having boiling points lower than those of semivolatile organic compounds, and therefore readily produce gases or vapors at room temperature. They include gasoline and solvents used in many industrial applications The volatile organic compounds benzene, ethylbenzene, toluene, and xylene are characterized by a pale to colorless appearance, sweet odor, and high volatilization.
They are used as solvents and in the production of plastics, rubber, and resins. They are also components of gasoline and are most commonly introduced to the environment through spills from leaking gasoline-storage tanks, fumes and exhaust from gas-power engines, and runoff from gasoline- or oil-contaminated surfaces such as highways and parking lots.
Local groundwater contamination from these compounds can also result from improper disposal of used oil. MTBE methyl tertiary-butyl ether is an oxygenate additive used to promote fuel combustion and reduce carbon monoxide and ozone emissions from vehicles. Releases to the environment are most commonly the result of leaking underground storage tanks and pipelines, other spills, and, to a lesser extent, from air deposition around refineries or urban areas. Benzene map image Benzene is a clear, colorless, aromatic organic compound that is highly flammable.
It is used in the manufacture of gasoline, plastics, rubber, resins, and synthetic fabrics. It is also used as a solvent in printing, paints, and dry cleaning. The most common sources of benzene in groundwater are leaks from underground gasoline- storage tanks and landfills. Benzene is released to the air by fumes and vehicle exhaust. Industrial discharges and losses during fuel spills can release benzene to soils and water supplies.
Runoff from roads or parking lots, and improper disposal of gasoline and oil products around the home, can also contribute benzene to the groundwater system. Benzene does not degrade by reaction with water, but can be degraded by microbes in soil and water. CO 2 from the air dissolves in the water. Carbonic acid is a principal agent of chemical weathering. This mixture of carbonic acid in water makes most natural surface waters slightly acidic.
As slightly acidic water infiltrates the ground to become part of the groundwater system it causes weathering of the rocks. The abundant silicate minerals are chemically weathered into clay minerals and soluble byproducts. A few common minerals dissolve into soluble weathering products that are removed with the slowly flowing groundwater, leaving little solid residue.
But the most common soluble minerals are calcite CaCO3 , the principal mineral in the rocks limestone and marble, and the related mineral dolomite Ca Mg CO 3 2 , the principal mineral in the rock dolostone also simply called dolomite. These carbonate rocks are abundant in the upper crust in many areas. They are susceptible to dissolution. Chlorides in high concentrations present a health hazard to children and other young mammals. Aluminum Al is derived from bauxite and other clays.
Although present in many rocks, aluminum is not highly soluble and precipitates readily. There is no evidence that it affects use of water for most purposes. Acid water low pH often contains greater amounts of aluminum. Such water is troublesome for boiler feed because of the formation of scale. Dissolved from practically all rocks and soils, silica SiO 2 is generally found in small amounts from 1 ppm to 30 ppm.
Higher concentrations generally occur in highly alkaline water. Silicas form a hard scale in pipes and boilers. Carried over in steam of high-pressure boilers, silicas form damaging deposits on the delicately balanced blades of steam turbines.
Silica also inhibits the deterioration of zeolite-type water softeners, but does not affect water for domestic purposes. Groundwater generally contains more silica than surface water. Extremely common, iron Fe is dissolved from practically all rocks and soils.
Water having a low pH tends to be corrosive and may dissolve iron in objectionable quantities from pipe, pumps, and other equipment. More than 1 ppm to 2 ppm of soluble iron in surface water generally indicates the presence of acid wastes from mine drainage or other sources. More than about 0. Objectionable for food processing, beverages, dyeing, bleaching, ice manufacturing, brewing, and other processes, moderately large quantities cause unpleasant taste and favor the growth of iron bacteria under slight oxidizing conditions and typical groundwater temperatures.
On exposure to air, iron in groundwater is readily oxidized and forms a reddish-brown precipitate. Iron can be removed by oxidation, sedimentation, and fine filtration, or by precipitation during removal of hardness by ion exchange not a recommended practice.
Sources of nitrate NO 3 - are decaying organic matter, legume plants, sewage, nitrate fertilizers, and nitrates in soil. Nitrate encourages growth of algae and other organisms that cause undesirable tastes and odors. Concentrations much greater than the local average may suggest pollution.
Nitrate in water may indicate sewage or other organic matter. In amounts less than 5 ppm, nitrate has no effect on the value of water for ordinary uses. Chiefly, "dissolved solids" is the total quality of mineral constituents dissolved from rocks and soils, including any organic matter and some water of crystallization. Water containing more than 1, ppm of dissolved solids is unsuitable for many purposes. The amount and character of dissolved solids depend on the solubility and type of rocks with which the water has been in contact.
The taste of the water often is affected by the amount of dissolved solids. In most water, nearly all the hardness is due to calcium and magnesium carbonates. All of the metallic cations other than the alkali metals deposit soap curd on bathtubs. Hard water forms scale in boilers, water heaters, and pipes. Hardness equivalent to the bicarbonate and carbonate is called carbonate or "temporary" hardness because it can be removed by boiling.
Any hardness in excess of this is called noncarbonate or "permanent" hardness. Noncarbonate hardness is caused by the combination of calcium and magnesium with sulfate, chloride, and nitrate.
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