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Mercury in the EnvironmentSurficia I Materials of the 

Conterminous United States 

Mercury in the EnvironmentSurficial Materials of the 

Conterminous United States 

By Hansford T. ShackleHe, Josephine G. Boerngen, and 

Robert L. Turner 

GEOLOGICAL SURVEY CIRCULAR 6 4 4 

Washington J 97J 
United States Department of the Interior 

ROGERS C. B. MORTON, Secretary 

Geological Survey 

William T. Pecora, Director 

Free on application to the U.S. Geological Survey, Washington, D.C. 20242 
Mercury 1n the Environment-Surficial Materials of the 

Conterminous United States 

By Hansford T. Shacklette, Josephine G. Boerngen, and Robert L. Turner 

ABSTRACT 

Mercury determinations for 912 samples of soils and 

other regoliths from sites approximately 50 miles apart 

throughout the United States are represented on a map 

by symbols showing five ranges of concentration. A histogram of mercury concentrations in the samples is also 

given. The geometric mean concentration of mercury is 

71 parts per billion for all samples, 96 ppb for samples 

from the Eastern United States, and 55 ppb for samples 

from Western United States. Twelve samples contained 

at least 1,000 ppb mercury; the greatest concentration 

found was 4,600 ppb. 

INTRODUCTION 

The concentrations of 34 elements ( excluding mercury) in samples of soils and other regoliths from sites about 50 miles apart on routes 

of travel throughout the conterminous United 

States were reported by Shacklette, Hamilton, 

Boerngen, and Bowles (1971). Only after that 

report had been prepared were analytical methods made available for detecting mercury and 

some other elements in surficial materials collected for this study. Because of the current 

widespread interest in the mercury concentration in natural materials, the samples from the 

earlier study, as well as some additional samples, have been analyzed for mercury. The samples were collected and prepared for analysis in 

the same manner as reported earlier (Shacklette and others, 1971) and were analyzed in 

randomized sequence. Mercury concentrations 

in the samples were determined by using the 

method described by Vaughn and McCarthy 

(1964). The lower detection limit of this method 

1 

for these materials is 10 ppb (parts per billion, 

1 X 10-9 gram per gram) . 

Mercury analyses of soils and other surficial 

materials that were reported in the literature 

commonly were performed for use in mineral 

exploration or for detecting areas of suspected 

mercury contamination. A summary of the reports of mercury in natural materials was given 

by Fleischer (1970). References to reports of 

mercury in rocks, soils, and stream sediments 

were prese~ted by Pierce, Botbol, and Learned 

(1970), who stated, "Statistics for only four 

sets of soil samples are available, and these suggest a background value of 500 ppb mercury for 

soils in Western United States." Shacklette 

(1965, p. C10) reported that soils overlying cinnabar deposits may contain as much as 40,000 

ppb mercury in their A2 and B horizons. In a 

study of roadside contamination in Missouri, 

mercury concentrations in samples of soils were 

found to range from 40 to 650 ppb ( Shacklette, 

1970). Worldwide "average" (presumably, 

arithmetic mean) concentration of mercury in 

soils was reported by Vinogradov ( 1959, p. 184) 

to be 10 ppb and by Hawkes and Webb (1962, p. 

369) to range from 30 to 300 ppb. 

Although most samples of this study were collected along roads, the specific sampling sites 

were selected to represent surficial materials 

that were, insofar as possible, but little altered 

from their natural condition. Some samples, of 

necessity, were collected in cultivated fields; the 

degree of contamination of these samples, and 
of some from roadsides, cannot be evaluated 

from the data at hand. Surficial materials analyzed in this study were ordinarily sampled at a 

depth of 8 inches. We believe that soils and other 

regoliths from this depth commonly show little 

or no effects of surficial contamination that may 

have occurred. 

Many geologists and others of the U.S. Geological Survey assisted this study by collecting 

samples along routes of travel to areas of other 

kinds of field studies; this assistance, and that 

of computer specialists, was acknowledged in 

the earlier report of this sampling program 

(Shacklette and others, 1971). Additional samples for this study of mercury in surficial materials were collected by R. N. Eicher, R. F. 

Gantnier, J. A. Erdman and J. R. Keith, and 

J. J. Connor and H. T. Shacklette. The mercury 

analyses were performed by R. L. Turner. 

RESULTS OF ANALYSES 

The mercury values were transformed to a 

logarithmic form because the frequency distribution is more nearly symmetrical on a logarithmic scale than on an arithmetic scale. The best 

measure of central tendency in a lognormal distribution is given by the geometric mean, which 

is the antilogarithm of the mean logarithm. An 

estimate of the arithmetic mean was derived 

from the data by the use of Sichel's (1952) technique. These methods of statistical evaluation 

are the same as those used for evaluating other 

elements in the samples ( Shacklette and others, 

1971). 

We measured the precision of the analytical 

method for mercury by analyzing 4 7 randomly 

selected samples in duplicate. The 47 duplicates 

were randomly interspersed among the other 

912 samples and were unknown to the analyst. 

The logarithmic variance of the analytical 

method is 0.0689. This means that the analyses 

are reproducible within a factor of 1.83 at the 

68-percent level of confidence, or within a factor 

of 3.35 at the 95-percent level. 

Statistics for the mercury concentration of all 

samples, as well as of samples from both east 

and west of the 97th meridian, are given in 

table 1. Shown in figure 1 are the distribution 

of the sampling sites throughout the conterminous United States and the mercury concentra2 

tions of the samples expressed in terms of five 

geometric ranges of concentration. 

TABLE !.-Concentrations of mercury, in parts per billion, in samples of soils and other surficial materials 

from the conterminous United States 

[Number of samples is given in parentheses after area] 

Geometric Geometric Arithmetic 

Area Range mean deviation mean 

Entire conterminous 

United States 

(912) ----------- < 10-4,600 71 2.60 112 

Western United I States, .west of the 

97th meridian 

(492) ----------- < 10-4.600 55 2.46 83 

Eastern United 

States, east of the 

97th meridian 

(420) ----------- 10-3,400 96 2.53 147 

DISCUSSION OF RESULTS 

The arithmetic mean concentration of mercury in the samples analyzed for this report 

( 112 ppb) falls within the range of values reported for Missouri soils by Shacklette ( 1970, 

p. 35) and for soils used in geochemical prospecting as reported by Hawkes and Webb (1962, 

p. 369). This concentration, however, is much 

greater than the average (10 ppb) reported for 

worldwide soils by Vinogradov (1959, p. 184). 

The difference in geometric mean concentrations of mercury in samples from the Eastern 

and Western United States (table 1) is statistically significant at the 99.9-percent confidence 

level. The mean concentration of mercury in 

surficial materials from the Western United 

States is much less than the background value 

( 500 ppb) suggested by Pierce, Botbol, and 

Learned (1970, p. 14) for soils from the same 

region. 

The greatest mercury concentration found in 

surficial materials was in a sample from Summit County, Utah, that contained 4,600 ppb. 

This sample contained no visible organic materials. The greatest concentration found in 

surficial materials from the Eastern United 

States was in a sample from Walton County, 

Fla., that contained 3,400 ppb mercury. This 

sample, which consisted of organic-stained sand, 

was from an area of humate deposits that were 

described by Swanson and Palacas (1965). An 

additional sample, collected at the same locality, 

contained 2,000 ppb mercury. 

Other high mercury concentrations were found 

in samples from Cameron Parish, La. (2,500 
ppb); Monterey County, Calif. (1,500 ppb); 

Eagle County, Colo. (1,300 ppb) ; Presque Isle 

County, Mich. (1,200 ppb); Menominee County, 

Mich. (1,200 ppb); Pacific County, Wash. 

(1,200 ppb); Chelan County, Wash. (1,200 

ppb); Charlton County, Ga. (1,000 ppb); Aitkin County, Minn. ( 1,000 ppb) ; and Santa Clara 

County, Calif. (1,000 ppb). These samples from 

Michigan, Minnesota, Louisiana, and Georgia 

were of mucks, bog soils, or dark organicstained sands, and their mercury contents suggest that this metal was enriched in the organic 

materials that were present. The samples from 

California, Colorado, and Washington were not 

noted to have a high organic content; their high 

mercury concentrations may be due to a high 

mercury content of underlying geologic materials or to pollution. 

REFERENCES CITED 

Fleischer, Michael, 1970, Summary of the literature on 

the inorganic geochemistry of mercury, in Mercury 

in the environment: U.S. Geol. Survey Prof. Paper 

713, p. 6--13. 

3 

Hawkes, H. E., and Webb, J. S., 1962, Geochemistry in 

mineral exploration: New York, Harper & Row, 

Publishers, 415 p. 

Pierce, A. P., Botbol, J. M., and Learned, R. E., 1970, 

Mercury content of rocks, soils, and stream sediments, in Mercury in the environment: U.S. Geol. 

Survey Prof. Paper 713, p. 14-16. 

Shacklette, H. T., 1965, Br~ ophytes associated with mineral deposits and solutions in Alaska: U.S. Geol. 

Survey Bull. 1198-C, 18 p. 

--- 1970, Mercury content of plants, in Mercury in 

the environment: U.S. Geol. Survey Prof. Paper 

713, p. 35-36. 

Shacklette, H. T., Hamilton, J. C., Boerngen, J. G., and 

Bowles, J. M., 1971, Elemental composition of surficial materials in the conterminous United States: 

U.S. Geol. Survey Prof. Paper 574-D. (In press.) 

Sichel, H. S., 1952, New methods in the statistical evaluation of mine sampling data: London, Inst. Mining 

and Metallurgy Trans., v. 61, p. 261-288. 

Swanson, V. E., and Palacas, J. G., 1965, Humate in 

coastal sands of northwest Florida: U.S. Geol. Survey Bull. 1214-B, 29 p. 

Vaughn, W. W., and McCarthy, J. H., Jr., 1964, An 

instrumental technique for the determination of 

submicrogram concentrations of mercury in soils, 

rocks, and gas, in Geological Survey research 1964: 

U.S. Geol. Survey Prof. Paper 501-D, p. D123-D127 

[1965]. 

Vinogradov, A. P., 1959, The geochemistry of rare and 

dispersed chemical elements in soils, [2d ed.]: New 

York Consultants Bur., Inc., 209 p. 
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