has not been as thoroughly covered. A few years ago, the author suggested that 

 some heavy metals such as hexavalent chromium, which is toxic to humans, 

 might be released by corrosion of car bodies and move into surface and 

 groundwaters. Little progress has been made in evaluating the validity of this 

 idea, but preliminary field studies indicate that corrosion of home water systems 

 is potentially a serious problem. Although corrosion occurs mainly by oxidation, 

 the process is enhanced in the presence of solutions containing chloride. 45 



A typical home-water system involves pumping from a stone or concrete Hned 

 dug well or drilled well with steel casing, through a plastic or iron pipe, to a 

 dwelling where flow is into copper tubing through an iron pressure tank, back 

 into copper tubing. Iron and copper and impurities may be released, and, in 

 addition, zinc and cadmium may be released if galvanized piping is involved. In a 

 state such as New Hampshire where groundwater tends to be in the pH 5.5-7.5 

 range, the end result can be considerable corrosion of copper as well as other 

 metals, thereby causing deterioration of the water system and posing a health 

 hazard. Added chloride can only make the problem worse. 



A sampling for chemical analysis including iron, zinc, copper, lead, and 

 hexavalent chromium of a pond, a stream, and 18 wells along U.S. 4, from Great 

 Bay four miles east of Durham, to Northwood Ridge 15 miles west of Durham, 

 was undertaken in the summer of 1972. The results must be treated carefully 

 because of the small number of samples, lack of knowledge about the water 

 systems, and problem of determining in some cases, whether chloride was from 

 road deicing salt or a septic tank. Also, with the exception of iron, which is more 

 unsightly than a health hazard, all values are lower than accepted standards. 



Nevertheless, one domestic well close to the highway had water with 174 

 mg/£^ of chloride, a pH of 6.0, and 0.395 mg/^ hexavalent chromium which is 

 uncomfortably high. There is a definite tendency in the samples for high 

 chloride to be associated with lowpH and fairly high zinc and copper. Lead levels 

 are low and appear to represent natural background. Iron ranges from 0.09 mg/£ 

 to 19 mg/£, but relationships to chloride are not obvious. An interesting point is 

 that during the study, many people complained about corrosion of their own 

 water system or remarked on similar problems of others. Clearly, additional 

 work needs to be done to assess what is happening and to pose corrective 

 measures for both economic and health reasons. 



ELEMENTS ACCOMPANYING CHLORIDE 



Apart from the chloride itself, the accompanying constituents may produce 

 problems. Considerable emphasis has recently been placed on sodium which is 

 the other major component of most road deicing salt.*^" Several aspects have 

 already been discussed in the section on vegetation and soils. Also, there has 

 been considerable controversy over whether or not hard (high in calcium and 

 magnesium) or soft (high in sodium and low in calcium and magnesium) drinking 

 waters have implications for health. A hard water can have considerable sodium 



45 



Id. 



'^^TERRY 38^1. 



24 



