EPA-600/3-77-007
January 1977
Ecological Research Series
ABIOLOGICAL METHYLATION OF MERCURY
IN SOIL
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
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal
species, and materials. Problems are assessed for their long- and short-term
influences. Investigations include formation, transport, and pathway studies to
determine the fate of pollutants and their effects. This work provides the technical
basis for setting standards to minimize undesirable changes in living organisms
in the aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service. Springfield. Virginia 22161.
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EPA-600/3-77-007
January 1977
ABIOLOGICAL METHYLATION OF
MERCURY IN SOIL
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 constitute
endorsement or recommendation for use.
ii
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ABSTRACT
The results from this work define several factors influencing the meth-
ylation of mercuric ion in soil. Two of the most important findings were that
it is possible to extract the mercury methylating factor from soil with a
solution of 0.511 sodium hydroxide (NaOH) and that this factor is responsible
for the abiological methylation of mercury in the soils under investigation.
The ability of the soil extract to methylate mercury is influenced by
temperature, mercuric ion concentration, and solution pH. In addition, it
was found that the methylating ability of the soil extract was stable at high
temperatures (121° C), but was lost after exposure to ultraviolet radiation.
When the 0.511 NaOH extract of soil was separated into a soluble fraction
and an insoluble precipitate, the ability to methylate mercuric ion remained
with the soluble fraction. It was found that the methylating factor was lost
when the 0.5N NaOH extract was dialyzed against distilled water. Other work
showed that the methylating factor passes through dialysis tubing into the
distilled water.
iii
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ACKNOWLEDGMENTS
The work and dedication of Mr. Gene Butler are gratefully acknowledged.
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INTRODUCTION
In an earlier work (Rogers, 1975), it was shown that mercuric ion is meth-
ylated under a variety of conditions in alkaline, agriculture soils. That study
confirmed the work of Beckert et_ al. (1974) who found methylmercury in desert
soils which had been amended with mercuric nitrate. In neither study was the
mechanism for the methylation of mercury discovered. However, it was suggested
that there was a possibility for an abiotic process (Rogers, 1975).
Since it has been established that mercuric ion can be abiotically meth-
ylated by a variety of substances (Bertilsson and Neujahr, 1971; Imura et al.,
1971; DeSimone, 1972; Brinckman, Iverson, and Blair, 1975), an abiotic pathway
seemed probable. A partial confirmation of the necessity of soil organic matter
for the abiotic methylation of mercury in soil came as a result of two prelim-
inary experiments. A silty clay loam soil which had been used in a previous
study (Rogers, 1975) was ignited at 600° C for 24 hours. The ashed soil was
then amended with mercuric ion at the rate of 25,000 micrograms of mercury
(yg Hg) per 50 grams (g) of ashed soil. After one week of incubation, these
soils contained no methylmercury, while an unashed control soil did contain
significant quantities of methylmercury. Soil was also exposed to a process
of wet oxidation. Such a treatment can sterilize soil. However, only after
several repeated oxidation steps was it possible to destroy the methylating
ability of the soil, which suggested that methylation was not biological and
that the methylating factor was associated with soil organic material.
While attempting to extract organic material from the above soil, it was
discovered that a 0.5fl[ NaOH extract of the soils was capable of methylating
introduced mercuric ions. This report is the results of studies involving
mercury reactions with NaOH extracts of soil.
CONCLUSIONS
The following conclusions were drawn from the current study:
1. A constituent can be extracted from soil which will methylate mercuric
ion abiologically.
2. The methylating substance is associated with the lower molecular
weight fraction of the soil organic matter.
3. Soil extracts exposed to ultraviolet (UV) radiation lose the ability
to methylate mercury.
4. The rate of conversion of mercury into methylmercury is dependent
upon mercuric ion concentration, solution pH, and temperature.
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RECOMMENDATIONS FOR FUTURE RESEARCH
Further experimental refinements and identification of the compound respon-
sible for the methylation of mercury in sodium hydroxide extracts of soils are
required. Once identified, it will be possible to analyze other soils and even
aquatic systems for the compound. With those findings it should be possible to
identify areas where significant methylation of mercury is likely to occur.
MATERIALS AND METHODS
Agricultural soils used for this investigation were obtained from the area
in southeastern Nevada. The soils were of three different textural types.
These were a loamy sand, fine sandy loam, and silty clay loam. For convenience
these soils will be referred to as sand, loam, and clay. The soils contained
0.53%, 1.30%, and 3.44% organic carbon, respectively. A more complete descrip-
tion of the soils and their processing is found elsewhere (Rogers, 1975).
Extraction of organic material from the soils was done by Stevenson's
(1965) method for the extraction of soil humus with two modifications. The
soils were not acid-washed prior to extraction and 50 grams (g) of soil were
used instead of 40 g. The resulting sodium hydroxide (NaOH) extracts had the
following optical densities at pH 13: sand, 0.07; loam, 0.18; and clay, 0.56.
The solutions resulting from the extraction process were stored in amber glass
bottles.
Unless noted otherwise, the 0.5IJ NaOH extract obtained from these soils
was used for each phase of this study. The extracts were amended with mercuric
nitrate [Hg(N03)2] at the rate of 25,000 micrograms (yg) Hg as Hg(N03)2 per 50
milliliters (ml) of extract (500 ppm Hg). The extracts were prepared for amend-
ment with mercuric nitrate as follows. Before mercury was added, the extract pH
was decreased below 7 by adding concentrated nitric acid (HN03). After the
pH of the extract had been adjusted, 2 ml of a solution containing 12,500 ppm
Hg were added to 50 ml of extract. The pH of the amended extract was then ad-
justed to the desired pH with further additions of either concentrated HN03 or
20% NaOH while the extract was being stirred with a magnetic stirrer. Unless
noted otherwise, there were four replications per treatment of the mercury-
extract solutions. These solutions were incubated at 23 C on a shaker.
After incubation, methylmercury was extracted from these solutions using a
modified Westoo method (1966) discussed in a previous study (Rogers, 1975).
With the 0.51* NaOH extracts, however, the solution pH was lowered to 1 with
concentrated hydrochloric acid (HC1). Benzene which was used to extract the
methylmercury was analyzed as previously described (Rogers, 1975) using gas
chromatography and a nickel-63 linear electron capture detector. For addi-
tional confirmation of methylmercury, a random sample of the extracts was sub-
mitted to analysis by a gas chromatograph equipped with an element-specific
microwave emission spectrometric detector systems (Talmi, 1975).
In order to evaluate the effectiveness of the extraction procedure,
standard solutions consisting of 1 yg Hg as methylmercury chloride (CH3HgCl)
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In distilled water were added to the 0.5!* NaOH extract of the three soils.
These solutions were extracted using the above method and the quantity of
the extracted methylmercury was compared to the amount initially added. Using
this method it was determined that the extract from the sand had a 66% recovery
of mercury as methylraercury, loam extract, 49%, and clay extract, 53%. In addi-
tion, no methylmercury was founded in zero time extractions of Hg(N03>2 amended
NaOH extracts of the three soils.
Either one-way analysis of variance (ANOV) or polynomial regression was
used for the statistical testing of the data. When ANOV indicated a signi-
ficant difference between treatments, an orthogonal comparison was then used
to identify differences between individual treatment means.
RESULTS
EFFECT OF pH
The solubility of mercury in solution, especially at the concentration
used, is mediated by solution pH. For a solution extract of soils, pH not
only affects the solubility of mercury, but also the sorption of mercury by
organic complexes. It was assumed that the availability of mercuric ion
would increase as the soil extract became acidic. If this were true, the
methylation of mercury should be enhanced by the increased availability of
mercuric ions. An experiment was initiated to determine the methylating
ability of the 0.5N NaOH extracts of the three soils at various pH's. Ex-
tracts of each of the soils were adjusted to pH 2.0, 4.5, 5.5, 7.5, and 9.0
with concentrated HNOg. After the extracts had been amended with 25,000 yg
Hg asHg(N03)2, the solution pH was checked and any necessary corrections
were made. The amended solutions were then shaken at 25° C for 1 day.
Data from this study show the effect pH has on the production of methyl-
mercury in these extracts (Figure 1). In all extracts there was a decrease
in the occurrence of methylmercury when the solution pH was above 4.5. There
was a continued decrease in methylmercury with increasing pH in both the clay
arid loam extracts with the least amount of methylmercury being obtained at
pH 9.0. The sand extract remained static from pH 5.5 through the end point.
An anomaly occurred with the clay extract at pH 2.0. There was a lower con-
centration of methylmercury at this pH than at pH 4.5. It was noted that
these solutions contained a considerable amount of organic precipitate (humic
acid). It is probably that complexing of the humic acid rendered some of the
mercury or methylation factors unavailable for reaction. Because of the
possible problem of complexing the mercury and the relative ease of adjust-
ing and maintaining the soil extracts at pH 4.5, this pH was selected for
the other studies. It should be noted that controls containing everything
except soil extract (but including 50 ml of 0.5N NaOH) failed to produce
methylmercury.
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60
(B
en
u
e>
600
550
500
450-
400
350-
300-
250-
200-
150-
100-
50-
0
CLAY EXTRACT
LOAM EXTRACT
SAND EXTRACT
—r
3
—r-
5
PH
—r
8
—r
10
Figure 1. Methylmercury in O.SN^ NaOH extracts of soil at various pH values
INCUBATION TIME
The extent of mercury methylation by the three soil extracts was deter-
mined for 1, 3, and 7 days of incubation (Table 1). The loam and sand ex-
tracts had significant (at the 1% level) increases in methylmercury content
between days 1 and 3. The content of methylmercury in the loam extract did
not change significantly from day 3 to day 7, while the sand extract decreased
in methylmercury by day 7. Analysis of the clay extract revealed no signifi-
cant increase in methylmercury occurrence between days 1 and 3, but a signi-
ficant increase (at the 1% level) between days 3 and 7.
The conclusions to be drawn from these data are that the loam and sand
extracts reach a maximum methylmercury content within a relatively short
period of time. The clay extract requires a longer period of time before
significant increases in methylmercury above initial quantities are observed.
These data also indicate that methylmercury formation in different soils is
not a uniform process.
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TABLE 1. METHYLMERCURY OCCURRENCE IN 0.5IJ NaOH EXTRACT
INCUBATED 1, 3, AND 7 DAYS AT 25° C
Concentration
(ng CH3Hg+/50 ml Extract)
Extract 1 Day 3 Days 7 Days
Clay
Loam
Sand
622.6
196.0
65.5
646.3
299.7*
204.9*
803.0*
268.8
144.8*
* Indicates significance at the 1% level between the same extract with
increasing time.
INCUBATION TEMPERATURE
Extracts of the soils were amended with mercuric ions and then shaken at
5 C, 25° C, and 40° C for 1 day. All amended extracts increased in methyl-
mercury content with increased temperature (Figure 2). Regression coefficients
for this plot are 13.9, 5.1, and 2.2, for the clay, loam, and sand extracts,
respectively, with a significance of 1% for all (F values of 84.9, 92.6, and
38.9; 1, 10 df). From these data it can be seen that the production of methyl-
mercury in the clay extract is substantially elevated.
MERCURY CONCENTRATION
Extracts of the soils were amended with 12,500 yg Hg, 25,000 yg Hg, and
37,500 yg Hg as HgN03 per 50 ml extract. These solutions were then incubated
for 1 day.
Figure 3 shows the effect of increased mercury concentration extracts.
Regression coefficients for these data are 22.3, 7.6, and 4.9 for the clay,
loam, and sand extracts, respectively. Both the clay and loam extracts are
significant at the 1% level while the sand extract was not significant at the
5% level (F values of 321.5, 22.1, and 4.9; 1, 10 df). The lack of signifi-
cance of the sand data was because of a high variability between treatment
replications. The clay extract had a good response to increased mercury con-
centration and this response clearly indicates that the clay extract could
methylate mercury under even greater mercury concentrations. The data for the
loam and sand extracts indicate that these extracts may have had their meth-
ylation factor saturated at the 25,000 yg and 37,500 yg Hg levels.
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Fig 2 METHYLMERCURY OCCURRENCE IN 0.51 NaOH EXTRACTS
INCUBATED AT VARIOUS TEMPERATURES FOR ONE DAY
900
800
700
600
500
B»
« 400
D)
x 300
PO
*jj> 2001
100
0
CLAY EXTRACT y
LOAM EXTRACT y
SAND EXTRACT y
13.9x . 288.2
Six * 114.9
2.2x * 43.9
10 15 20 25
Temperature °C
30
35
40
45
Figure 2. Methylmercury occurrence in Q.5Q NaOH extract incubated at
various temperatures for 1 day
900
800
700-
600
500
1 400
M
IB
+» 300-
CO
1, 200
E
TOO
0-
CLAY EXTRACT y = 22.3x + 35.4
— LOAM EXTRACT y = 7.6x * 61.9
SAND EXTRACT y = 4.9x * 5.9
1
12,500
25,000
37,500
Concentration
as Hg
Figure 3.
Methylmercury occurrence in 0.5N NaOH extract incubated for 1
day with amendments of varying mercuric nitrate concentrations
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CHARACTERISTICS OF THE METHYLATING FACTOR
The mechanism for mercury methylation in these soil extracts is nonbiolog-
ical. Four petri plates containing 1 ml of extract and 15 ml glucose nitri-
ent agar showed no microbial growth after 1 week of incubation. In a similar
experiment, extracts containing 25,000 yg Hg as Hg(N03)2 had no microbial con-
tamination after 1 week of solution incubation. Apparently the combination
of high Na and Hg concentration did not allow for microbial growth. In addi-
tion, quantities of each of the extracts were autoclaved at 121° C and 15 psi
for 30 minutes. These sterile extracts were then amended with mercury at the
standard rate of 25,000 yg Hg as Hg(N03>2 per 50 ml extract and incubated 1
day. Methylmercury was found in all the amended solutions (Table 2). These
values showed the same trend as those of non-autoclaved solutions (Table 1).
TABLE 2. METHYLMERCURY OCCURRENCE IN AUTOCLAVED
0.5N NaOH EXTRACT INCUBATED 1 DAY
Concentration
Extract (ng CH_Hg+/50 ml Extract)
Clay 551.3* ± 29.6**
Loam 296.9 ± 26.5
Sand 121.0 ± 19.7
* Mean of four replications.
** ± standard deviation.
Alkaline extracts of soil are routinely separated by acidification into
two different fractions (Stevenson, 1965). The precipitated fraction is
designated as humic acids, and the soluble fraction is known as fulvic acid.
A study was initiated to determine which of these fractions was responsible for
the methylation. The humic acid fraction of the soil extracts was removed.
The fulvic acid fraction of each soil was then amended with 25,000 yg Hg as
Hg(N03)2 per 50 ml extract and was incubated for 1 day. Analysis of these
solutions showed that mercuric ions were methylated at approximately the
same rate as prior to fraction separation (Table 3). These data suggest that
the methylation process is mediated by some of the low-molecular-weight
material which composes the fulvic acid fraction.
The corollary to the fulvic acid study was also performed. Samples of
four commercially available humic acid precipitations were obtained from
Mr. George Baughman of the EPA's laboratory in Athens, Georgia. These mate-
rials were designated: Aldrich humic acid, technical grade; Humussauve
7821; Fluka Ag, Buchssg; and Humussauve Naturiumsatz. Sufficient amounts of
each of these humic acids were dissolved in 0.51* NaOH so that the resulting
mixtures had the same optical density at pH 13 as the clay extract at the same
pH. These solutions were then amended with mercury at the rate of 25,000 yg
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Hg as Hg(N03)2 per 50 ml solution. After 1 day of incubation at pH 4.5 none
of the solutions contained methylmercury. More concentrated solutions of the
humic materials also failed to produce methylmercury. It was therefore con-
cluded that the methylating factor was not associated with the higher molecular
weight humic acid fraction.
TABLE 3. METHYLMERCURY OCCURRENCE IN 0.5N NaOH EXTRACT AND
0.05N NaOH EXTRACT WITH HUMIC ACID REMOVED
CHsHg+ Detected
(ng/50 ml Extract)
Extract Complete Extract Humic Acid Removed
Clay 515.0 427.3**
Loam 172.4 137.2*
Sand 76.6 75.7
* or ** Indicates significance at the 5% or 1% level between the same extract
with and without humic acid.
In order to aid in the long-term storage, molecular analysis, and concen-
tration studies, quantities of the 0.51$ NaOH extracts from the clay, loam,
and sand were freeze dried. The method for drying (Stevenson, 1965) involved
the dialysis of the solutions to remove the excess NaOH. Three 500-ml quan-
tities of each solution were dialyzed for 3 days against 30 liters of moving
distilled water. The water was changed daily and maintained at a temperature
of 50° C. At the end of this period of dialysis the solutions were tested
to determine their methylating potential. Incubation of these dialyzed solu-
tions with mercury failed to produce methylmercury. Subsequent dialyzed
solutions also failed to produce methylmercury. At first, it was thought
that the NaOH was required in the methylation process. To test this hypoth-
esis, NaOH was added to the dialyzed soil extracts so that the resulting
solutions contained the same NaOH concentration as before dialysis. Incuba-
tion of these soil solutions with mercury also failed to produce methylmercury.
It has been shown that low-molecular-weight components of fulvic acid are
lost through dialysis tubing (Mortensen and Himes, 1964; Stevenson and Butler,
1969). Knowing this, an effort was then made to determine if the methylating
factor had indeed permeated the dialysis membrane, which according to the
manufacturer, Union Carbide, would pass molecules with molecular weights of
up to 12,000. In this study, 500 ml of the 0.5N NaOH clay extract was placed
into the dialysis tubing. The full tube was suspended in a graduated cylinder
and the cylinder was then filled with 500 ml of distilledQwater. The complete
apparatus was then placed in an oven and maintained at 50 C for 24 hours. At
the end of this time it was noted that the distilled water had acquired a straw
8
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yellow color. This solution was then amended with 25,000 pg Hg as
per 50 ml and incubated for 1 day. Upon analysis the solution was found
to contain 303 ng CH3Hg+ per 50 ml solution and thus confirmed that the meth-
ylating factor was lost during dialysis, but remained active when separated
from the higher molecular weight soil organics.
The photosensitivity of the methylating factor was determined by exposing
samples of the 0.5N. NaOH extract of clay to ultraviolet (UV) radiation. A
quartz immersion well was used in conjunction with a small, medium-pressure
mercury lamp. With 50 ml of the clay extract in the water-cooled immersion
well, the UV source was turned on for 16 hours. At the end of this time the
extracted solution was bleached and appeared water clear. This solution was
amended with 25,000 yg Hg as Hg(N03)2 and incubated for 1 day. No meth-
ylmercury was found in the mixture at the end of this time. The experiment
was repeated and the same results were obtained.
DISCUSSION
The results from this work define several as yet unknown factors influ-
encing the methylation of mercuric ion in soil. Two of the most important
findings are that the methylation reaction is abiological and that it is pos-
sible to extract the methylating factor from soil. The occurrence of methyl-
mercury was confirmed by both an electron capture detector and an element-
specific microwave emission spectrometer detector system (Talmi, 1975).
It had previously been found that mercury could be methylated by non-
biological processes. Bertilsson and Neujahn (1971) and Imura et al. (1971)
showed that methylcobalamin was capable of transferring methyl groups to mer-
curic ions. DeSimone (1972) was able to demonstrate the methylation of mer-
cury by trimethylsilyl salts. It is also known that there can be a transfer
of methyl groups from other methylated metals to mercuric ion (Brinckman,
Iverson, and Blair, 1975). So, the occurrence of an abiotic mechanism for the
methylation of mercury in active environmental systems should not be surprising.
While the substance in the soil extracts responsible for the methylation
of mercury is not known, the reaction can be defined by the following factors.
The reaction produces significant amounts of methylmercury within a 24-hour
period (Table 1). Increasing temperature increased the rate of reaction
(Figure 2), and increasing concentration of mercury substrate increased the
amount of resulting methylmercury (Figure 3). Some variability was noted with
the loam and sand extracts when amended with various concentrations of mercury.
The production of methylmercury in these solutions is also dependent upon
solution pH. The greatest amount of methylmercury was found in those solutions
maintained below pH 5.5. The lower pH is thought to allow for a greater
availability of the mercury ion.
Through this study it has been possible to delineate several facts about
the methylating substance. It was evident from all of the studies that the
methylating substance is more available in the clay followed by the loam and
then the sand extracts. These results are consistent with data on the
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occurrence of methylmercury in the complete soils (Rogers, 1975). The meth-
ylating factor can be destroyed by photo-oxidation, thus indicating that it is
an organic compound. Temperatures of at least 121° C have no effect on the
methylating ability of the soil solutions (Table 2). The molecular weight of
the substance is apparently within the range of that material commonly found
in the fulvic acid fraction of the soil. This is known because fulvic acid
preparations of the soils methylate mercury at the same rate as solutions con-
taining both fulvic and humic acids (Table 3). Also, solutions containing only
humic acid were not capable of mercury methylation. And lastly, since the
methylating factor passed into distilled water via dialysis tubing it should
be possible to further define it.
It is hoped that this work will add emphasis to the importance of the
abiotic methylation of mercury not only in soil environments, but also aquatic
environments. It is now possible to have at hand a solution which can be not
only chemically modified in many ways, but can also be used as a standard in
determining the impact on mercury methylation by many of the inorganic compounds
of mercury.
REFERENCES
Beckert, W. F., A. A. Moghissi, F. H. F. Au, E. W. Bretthauer, and J. C. McFar-
lane. 1974. Methylmercury: Evidence for its formation in a terrestrial
environment. Nature 249;674-675.
Bertilsson, L. and H. Y. Neujahr. 1971. Methylation of mercury compounds by
methylcobalamin. Biochemistry 10;2805-2808.
Brinckman, F. E., W. P. Iverson, and W. Blair. 1976. Approaches to the study
of microbial transformations of metals. In Shapley and Kaplan (ed.) Biodeteri-
oration of Materials. Vol. 3, paper 98. Applied Science Publications. Essex,
England. In Press.
DeSimone, R. E. 1972. Methylation of mercury by common nuclear magnetic
resonance reference compounds. Chemical Communique 780.
Imura, N., E. Sukegawa, S. Pan, K. Nagae, J. Kim, T. Kwan, and T. Ukita. 1971.
Chemical methylation of inorganic mercury with methylcobalamin, a vitamin 812
analog. Science 172;1248-1249.
Mortensen, J. L. and F. L. Himes. 1964. Soil Organic Matter, pp. 206-241.
In F. E. Bear (ed.) Chemistry of the Soil, 2nd ed. Reinhold Publications.
New York.
Rogers, R. D. 1975. Methylation of mercury in a terrestrial environment.
U.S. Environmental Protection Agency. Report No. EPA-600.3-75-014. Las Vegas.
Stevenson, F. J. 1965. Gross chemical fractionation of organic matter. In
C. A. Black (ed.) Methods of Soil Analysis. Part 2. Chemical and Micro-
biological Properties. Agronomy 9;1409-1421.
10
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Stevenson, F. J. and J. H. A. Butler. 1969. Chemistry of humic acids and
related pigments, pp. 534-557. In G. Eglinton and M. T. J. Murphy (ed.).
Organic Geochemistry. Springer-Verlag. New York.
Talmi, V. 1973. The rapid sub-picrogram determination of volatile organo-
mercury compounds by gas chromatography with a microwave emission spectrom-
etric detector system. Analytica Chimica Acta 74;107-117.
Westoo, G. 1966. Determination of methylmercury in foodstuffs. (I) Methyl-
mercury compounds in fish, identification and determination. Acta Chemica
Scandivica 20:2131-2137.
11
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-77-007
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
ABIOLOGICAL METHYLATION OF MERCURY IN SOIL
5. REPORT DATE
January 1977
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Robert D. Rogers
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Las Vegas, NV 89114
1O. PROGRAM ELEMENT NO.
1AA602
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Same as above
13. TYPE OF REPORT AND PERIOD COVERED
Final
and
Ecological Effects
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This work defines several factors influencing the methylation of mercuric ion in
soil. Two of the most important findings were that it is possible to extract the
mercury methylating factor from soil with a solution of 0.51$ sodium hydroxide and
that this factor is responsible for the abiological methylation of mercury in the
soils under investigation.
The ability of the soil extract to methylate mercury is influenced by temperature,
mercuric ion concentration, and solution pH. The methylating ability of the soil
extract was stable at high temperatures (121° C), but was lost after exposure to
ultraviolet radiation.
When the 0.5N sodium hydroxide extract of soil was separated into a soluble and
insoluble fraction, the ability to methylate mercuric ion remained with the
soluble fraction. It was found that the methylating factor was lost when the
0.5N sodium hydroxide extract was dialyzed against distilled water. Further
work showed that the methylating factor passes through dialysis tubing into
the distilled water.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
mercury
mercury inorganic compounds
mercury organic compounds
methylation
soil chemistry
06F
07B, C
08G
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RELEASE TO PUBLIC
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UNCLASSIFIED
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16
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EPA Form 2220-1 (t-73)
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