EPA-600/3-78-046
Apri! 1978
Ecological Research Series
VOLATILITY OF MERCURY
FROM SOILS AMENDED WITH
VARIOUS MERCURY COMPOUNDS
it
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Las Vegas, Nevada 89114
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
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EPA-600/3-78-046
April 1978
VOLATILITY OF MERCURY FROM SOILS
AMENDED WITH VARIOUS MERCURY COMPOUNDS
By
Robert D. Rogers
Monitoring Systems Research and Development Division
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
LAS VEGAS, NEVADA 89114
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DISCLAIMER
This report has been reviewed by the Environmental Monitoring and Support
Laboratory—Las Vegas, U.S. Environmental Protection Agency, and approved for
publication. Mention of trade names or commercial products does not consti-
tute endorsement or recommendation for use.
11
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FOREWORD
Protection of the environment requires effective regulatory actions
which are based on sound technical and scientific information. This
information must include the quantitative description and linking of pollutant
sources, transport mechanisms, interactions, and resulting effects on man and
his environment. Because of the complexities involved, assessment of specific
pollutants in the environment requires a total systems approach which trans-
cends the media of air, water, and land. The Environmental Monitoring and
Support Laboratory-Las Vegas contributes to the formation and enhancement of
a sound monitoring data base for exposure assessment through programs designed
to:
• develop and optimize systems and strategies for moni-
toring pollutants and their impact on the environment
• demonstrate new monitoring systems and technologies by
applying them to fulfill special monitoring needs of
the Agency's operating programs
This study was conducted to determine the rate of mercury volatilization
from soils freshly amended with mercury. Different mercury compounds were
used in conjunction with three different soil types. Mercury was evolved
from all treatments but volatilization was dependent upon the solubility of
the mercury compound and the texture of the soil. The conclusions can be
beneficial in designing experiments dealing with mercury compounds and soils
and also in the interpretation of data gathered by other investigators.
Users who should find the report of value include the Office of Air Programs,
Office of Toxic Substances, laboratories within the Office of Research and
Development, other Federal agencies, and university and industrial research
staffs.
George B. Morgan
Director
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada
111
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ABSTRACT
A study was conducted to determine the rate of mercury volatilization
from soils freshly amended with mercury compounds. Mercuric nitrate,
mercuric chloride, mercuric acetate, mercuric oxide, and mercuric sulfide
were used in conjunction with three soils: a loamy sand, a sand loam, and
a clay loam. Mercury was evolved from all combinations and was shown to be
dependent upon the solubility of the mercury compound and the texture of the
soil.
iv
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INTRODUCTION
Studies involving the transformation and fate of mercury (Hg) in the
environment have been intensely pursued in recent years. Investigations
have been conducted involving both aquatic and terrestrial environments in
which mercuric ion (Hg++) is added to the environment of interest and its
transformation with time is determined. One transformation which is often
overlooked is that Hg++ can rapidly be reduced and lost from the study system
as elemental Hg.
Some work on the volatilization of reduced Hg++ from aquatic systems has
been conducted (Avotins and Jenne, 1975), and it has also been noted that Hg
applied to soil can be volatilized as elemental Hg (Alberts et al., 1974;
Kimura and Miller, 1964; Hitchcock and Zimmerman, 1957). However, since
large losses of Hg have not been suspected, no effort has generally been
made to monitor the amount of Hg liberated from either deliberately or
accidentally contaminated soils. In addition, work is necessary to determine
the actual loss rate of Hg from several soil types as a function of various
inorganic mercuric sources.
Because of the need for more information, a study was conducted to
determine the effect of inorganic mercuric sources on Hg volatilization from
soil. Since the possibility exists that soil type could influence Hg loss,
because of chemical and/or physical properties, three different soil types
were amended with solutions of a variety of inorganic mercury compounds.
CONCLUSIONS
The following conclusions can be drawn from the study:
1. Considerable amounts of Hg can be volatilized from soil but the
loss depends on the soil type and the inorganic form of Hg used. These
data indicate that mercury can be volatilized from soil amended with any of
the water-soluble Hg compounds used.
2. The maximum loss of Hg occurred within the first week after amendment
of the soil with such Hg compounds.
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RECOMMENDATIONS FOR FUTURE RESEARCH
Future work to determine the mechanism causing volatilization of Hg
applied to soil is needed.
MATERIALS AND METHODS
Three soils, a loamy sand, a sandy loam, and a clay loam, were used for
this study. They were collected from an agricultural area in southern Nevada.
Depth of the soil collections was limited to the upper 10 centimeters of the
Ap horizon (plow layer). The moist soil was processed through a 2-millimeter
sieve and stored at room temperature in plastic bags. The physical and
chemical properties of the soils are found in Table 1.
TABLE 1. PHYSICAL AND CHEMICAL PROPERTIES OF SOIL
Soil
(Texture
classification)
Series
Sand Clay
Cation
Organic exchange
carbon capacity
PH
Sand
(Loamy sand)
Loam
(Fine sandy
loam)
Calico—a member of
the coarse-loamy,
over clayey, mixed
(calcareous), thermic
family of Aquic Xero-
fluvents
Bluepoint—a member 79.8
of the mixed, thermic
family of Typic
Torripsamment
3.5 0.53
53.9 10.8 1.30
_meq/100g
4.3
12.7
9.0
8.6
Clay
(Silty clay
loam)
Overton—a member of
the fine montmoril-
lonitic, calcareous,
thermic family of
Mollic Haplaguepts
14.7 34.4 3.44
29.0
7.8
Five different Hg compounds were used as Hg sources. These included
mercuric nitrate [HgfNOsJal/ mercuric chloride (HgCla), mercuric acetate
[Hg(C2H302)2~l, mercuric oxide (HgO), and mercuric sulfide (HgS). All were
soluble in water except HgS which was made up in 0.1N_ (NaaS) sodium sulfide.
To each soil (50 grams), 50 micrograms of Hg in the desired compound was
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added and stirred. This resulted in a concentration of 1 part per million
Hg in each soil. The study was arranged so that the three soils were amended
with the same Hg compound for the ensuing week's study. In all cases the
studies were carried out in triplicate.
After the soil was poured into a flask it was amended with Hg and suffi-
cient water was then added to bring the moisture content to 50% of the soil's
moisture holding capacity. The moistened soil was thoroughly mixed and care
was taken to prevent soil from being spread on the sides of the flask. A
rubber stopper containing connections for inlet and outlet air lines was used
to cap the flask. The flasks were connected to an air supply manifold and
the outlet was connected to a mercury adsorption trap. Air flow through the
flasks was maintained at 20 cubic centimeters per minute. All soils were
incubated inside a darkened growth chamber maintained at 25° C.
Mercury adsorption traps were made from 1-milliliter volumetric pipets
cut to length with the bulb being filled with gold-coated 40/60-mesh glass
beads. The beads were coated using the method of Braman and Johnson (1974).
To determine the amount of mercury being volatilized, a clean trap was placed
in the exit flow from the flask and after 1 hour the trap was replaced with
another trap to safely contain the vented Hg until time for the next 1-hour
collection.
Analysis for Hg was carried out by heating the collection traps to 600° C
in a block heater. After the trap had been heated for 30 seconds, the desorbed
Hg was flushed from the trap with helium into a Hg detector. The detector used
in this study was an Isotope Zeeman Atomic Absorption Spectrophotometer (IZAA)
(Hadeishi and McLaughlin, 1975).
Analyses were performed in triplicate for each soil treatment. Results
for the replicate treatments agreed within 10% and were averaged and express-
ed as nanograms of Hg evolved per hour.
RESULTS AND DISCUSSION
Mercury was volatilized from soil amended with the different Hg compounds,
but the amount volatilized appeared to be affected by the solubility of the
compounds (Table 2). Over a 144-hour period of time the three Hg compounds
most soluble in water [i.e., Hg(NOs)2, HgCla, and Hg(C2H302)z] had a greater
loss of Hg from the three soils (12 to 38%) followed by the less soluble HgO
(6 to 19%) with the insoluble HgS losing only a minor amount of applied Hg
(0.2 to 0.3%). These data also indicate that.the form of Hg added to the
soil has an effect on the initial volatilization of applied Hg.
In all cases the Hg volatilization rate for all treatments, except the
HgS, decreased to a minimum within the first week after amendment (Figures
1 through 4). However, in the case of the HgS amended soils, there was
minimal volatilization throughout the duration of the study. Whether the
decrease in Hg volatilization was due to the loss of a soluble Hg fraction
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Hg CI2
o>
O)
c
425-
400
40 50 60 70 80 90 100 110 120 130 140 150
Sand
Loam
Clay
i i i
10 20 30
Time (hrs.)
Figure 1. Evolution of Hg from soils amended to 1 ppm Hg with HgCl2.
4
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Hg (N03)2
CD
x
en
Sand
Loam
Clay
I I I I I I I I [ ^ I \ \ \ I
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
Time (hrs.)
Figure 2. Evolution of Hg from soils amended to 1 ppm Hg with Hg(NOa)2
5
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Hg (C2 H3 02)2
• Sand
* Loam
• Clay
I I I I I
10 20 30 40 50
60
I I I I I I I I I •
70 80 90 100 110 120 130 140 150
Time (hrs.)
Figure 3. Evolution of Hg from soils amended to 1 ppm Hg with
6
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HgO
o>
Sand
Loam
Clay —
I I I
10 20 30 40 50
I
60
III I I I I
70 80 90 100 110 120 130
I I
140 150
Time (hrs.)
Figure 4. Evolution of Hg from soils amended to 1 ppm Hg with HgO.
7
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or was the result of the Hg becoming more bound with time could not be
determined with this experiment.
The type of soil had a distinct effect on the amount of mercury volatil-
ized. In all cases except sand and loam soils amended with Hg(C2Hs02)2 and
the HgS amended soils, the loss rates were sand>loam>clay (Table 2).
TABLE 2. PERCENT OF APPLIED Hg EVOLVED FROM SOILS WITHIN 144 HOURS
Hg
Compound
HgCl2
Hg(N03)2
Hg(C2H302)2
HgO
HgS
Sand
38.3
36.5
26.4
19.6
0.2
Soil
Loam
% evolved
32.9
24.1
30.5
15.0
0.3
Clay
14.2
13.4
12.1
6.4
0.2
These soils decreased in clay and organic matter in the same order. Since
Hg is bound to both clay and organic matter this could explain the decreased
volatility.
With both the loam and clay soil, maximum volatilization of Hg followed
immediately after amendment. However, with the sand soil there was a 22 to
29-hour lag before a maximum volatility rate was obtained. The cause of this
phenomenon was not ascertained.
This study amply shows that substantial quantities of Hg can be lost due
to volatilization from soils amended with a variety of inorganic Hg compounds.
The species of Hg being lost from the soil was not determined. However, work
with these soils (Rogers 1977, 1976) has shown that the rate of Hg being
transformed into a volatile organic compound (methylmercury) is not suffi-
cient to account for the amounts of Hg lost. Other investigators have shown
that elemental Hg is the species being volatilized from treated soils (Alberts
et al., 1974; Kimura and Miller, 1964; Hitchcock and Zimmerman, 1957). Whether
the reason for this loss was the result of chemical or biochemical reduction
of Hg was not determined. However, the percent clay and/or organic matter in
the soil does mediate the loss rate.
The data presented here clearly show that there can be large, unsuspect-
ed losses of Hg from amended soils. In addition, this loss of Hg is not
related to nor would it be detected in experiments designed to detect the
transformation of Hg compounds into organic species. These data also indicate
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methods which can be used to decrease the volatile loss of Hg from contaminated
sites. That is, clay and/or organic material could be added to the soil or the
available Hg could be bound as HgS by additions of sulfur. Both treatments
would result in a substantial decrease in the volatile loss of Hg, especially
the sulfur treatment.
LITERATURE CITED
1. Alberts, J. J., J. E. Schindler, R. W. Miller, and D. E. Nutter, Jr.
Elemental Mercury Evolution Mediated by Humic Acid. Science 184:895-
897, 1974.
2. Avotins, P., and E. A. Jenne. The Time Stability of Dissolved Mercury
in Water Samples II. Chemical Stabilization. J. Environ. Qual. 4_:515-
519, 1975.
3. Braman, R. D., and D. L. Johnson. Selective Adsorption Tubes and
Emission Techniques for Determination of Ambient Forms of Mercury in
Air. Environ. Sci. Tech. 8_: 996-1003, 1974.
4. Hadeishi, T., and R. D. McLaughlin. Isotope Zeeman Atomic Absorption:
A New Approach to Chemical Analysis. Amer. Lab. 7^:57-61, 1975.
5. Hitchcock, A. E., and P. W. Zimmerman. Toxic Effects of Vapors
of Mercury and of Compounds of Mercury on Plants. Ann. N.Y. Acad. Sci.
65_: 474-497, 1957.
6. Kimura, Y., and V. L. Miller. The Degradation of Organomercury Fungi-
cides in Soil. Agri. and Food Chem. 3.2^253-257, 1964.
7. Rogers, R. D. Abiological Methylation of Mercury in Soil. J. Environ.
Qual. 61463-466, 1977.
8. Rogers, R. D. Methylation of Mercury in Agricultural Soils. J. Environ.
Qual. 5:454-458, 1976.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-78-046
2.
3. RECIPIENT'S ACCESSIOf»NO.
4. TITLE AND SUBTITLE
VOLATILITY OF MERCURY FROM SOILS AMENDED WITH VARIOUS
MERCURY COMPOUNDS
5. REPORT DATE
April 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Robert D.
8. PERFORMING ORGANIZATION REPORT NO.
Rogers
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Las Vegas, Nevada 89114
10. PROGRAM ELEMENT NO.
1AA602
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency—Las Vegas, NV
Office of Research and Development
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/07
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A study was conducted to determine the rate of mercury volatilization from soils
freshly amended with mercury compounds. Mercuric nitrate, mercuric chloride,
mercuric acetate, mercuric oxide, and mercuric sulfide were used in conjunction
with three soils: a loamy sand, a sand loam, and a clay loam. Mercury was
evolved from all combinations and was shown to be dependent upon the solubility
of the mercury compound and the texture of the soil.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
mercury
mercury volatilization
soil chemistry
mercury vapor collection]
mercury transformation
mercuric nitrate
mercuric chloride
mercuric acetate
mercuric oxide
mercuric sulfide
07B
07D
08M
18B
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
16
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
*TJ.S. GOVERNMENT PRINTING OFFICE: 1978 - 785-724/1902M, 1170. 9-1
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