Road deicing

Evaporites are important sources of economic minerals that have been exploited for at least the past 6000y. For example, the evaporite mineral trona (NaHCOj -Na2C03 2H2O) was used by the ancient Egyptians to preserve mummies. Evaporite salts continue to be used for food preservation, construction, road deicing, and in industrial processes. The marine evaporites of Saskatchewan (Canada) are the world s largest source of potash (KCl), which is used as an agricultural fertilizer. In the United States,... 

Uses of calcium chloride include road deicing (40%), where it competes with sodium chloride, road dust control and roadway base stabilization (20%), industrial processing (20%), oil and gas wells (10%), and concrete... 

Road deicing and its effect on local plant life 5 3... 

Storm water runoff from cities and villages presents another problem. This runoff contains salts from road deicing, street refuse, animal waste, food litter, residue from atmospheric deposition of sulfuric and nitric acid, metals, asbestos from automobile brakes, rubber from tires, hydrocarbons from motor vehicle exhaust condensates, oil and grease, soil and inorganic nutrients from construction sites, and a variety of other chemicals. Research shows a heavy impact of urban nonpoint pollution on freshwater quality (World Resources Institute, 1988). 

Sodium occurs extensively in feldspars, clay minerals, etc., but is extracted as NaCl from the oceans, in which Na+ is the most abundant cation (10,500 mg kg-1 or parts per million, ppm), and from rock salt deposits. The compounds NaCl, NaHCC>3, Na2C03, Na2S04, and NaOH are used in food processing, road deicing, water treatment, glass manufacture, paper making, and the chemical industry. 

Box 12.4 Winter road deicing and controlling dust on roads... 

A number of methods have been employed for determining the contamination of the atmosphere by aerosol transported chlorides, for example, sea salt and road deicing salts. The wet candle method, for... 

One of the most evident modem corrosion disasters is the present state of degradation of the North American infrastructure, particularly in the snow belt where the use of road deicing salts rose from 0.6M ton in 1950 to 10.5M tons in 1988. The structural integrity of thousands of... 

The environmental problems with calcium chloride in its deicing application, as with salt, are that when used in excess it can harm roadside vegetation and contaminate water supplies. Howard and Beck (1993) have studied the effect of road deicing chemicals upon the springs, wells, groundwater and aquifers near... 

Bubeck, R. C., and Burton, R. S. (1989). Effect of Decreased Use of Road Deicing Salts (1974-1984) on the Chloride Concentration, Mixing and Stratification of Irondequoit Bay, New York. Water Resour. Invest., U.S. Geol. Surv. Rept. WRI 87-4223, 52 pp. 

The galvanic corrosion of aluminum is usually mild, except in highly conductive media such as seawater, wind-blown sea spray, and salted slush from road deicing salts, when corrosion can be appreciable. In natural surface waters and nonsaline atmospheres, the galvanic corrosion of aluminum is rarely significant, although rain mnoff from copper and its alloys pit aluminum qtpreciably. 

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