EPA-650/2-75-028
January 1975
Environmental Protection Technology Series
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EPA-650/2-75-028
IMPROVEMENT OF INSTRUMENTATION
AND METHODOLOGY FOR COLLECTION
AND ANALYSIS OF MERCURY
by
D. J. Sibbett, R. H. MoyerandT. R. Quinn
Geomet Incorporated
2814 A Metropolitan Place
Pomona, California 91767
Contract No. 68-02-1282
ROAP No. 26-AEK-38
Program Element No. 1AA010
EPA Project Officer: Eva Wittgenstein
Chemistry and Physics Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
WASHINGTON, D.C. 20460
January 1975
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EPA REVIEW NOTICE
This report has been reviewed by the National Environmental Research
Center - Research Triangle Park, Office of Research and Development,
EPA, and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names ox- commercial
products constitute endorsement or recommendation for use.
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U .S. Environ-
mental Protection Agency, have’ been grouped into series. These broad
categories were established to facilitate further development and applica-
tion of environmental technology. Elimination of traditional grouping was
consciously planned to foster technology transfer and maximum interface
in related fields. These series are:
1. ENVIRONMENTAL HEALTH EFFECTS RESEARCH
2. ENViRONMENTAL PROTECTION TECHNOLOGY
3. ECOLOGICAL RESEARCH
4. ENVIRONMENTAL MONITORING
5. SOCIOECONOMiC ENVIRONMENTAL STUDIES
6. SCIENTIFIC AND TECHNICAL ASSESSMENT REPORTS
9. MISCELLANEOUS
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to
develop and demonstrate instrumentation, equipment and methodology
to repair or prevent environmental degradation from point and non-
point sources of pollution. This work provides the new or improved
technology required for the control and treatment of pollution sources
to meet environmental quality standards.
This document is available to the public for sale through the National
Technical Information Service, Springfield, Virginia 22161.
Publication No. EPA-650/2-75028
ii
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TABLE OF CONTENTS
2. 1
2. 2
2. 3
3.0 DETAILED
3. 1
3. 2
3.2. 1
3.2. 1. 1
3.2. 1.2
3.2.2
3.2.3
3.2.3. 1
3.2.3.2
3.2.4
3.2.4. 1
3.2.4.2
3.2.5
3.2.6
2-1
2-5
2-5
3-1
3-1
3-14
3-14
3-14
3-16
3-23
3-25
3-25
3-30
3-31
3-31
3-32
3-38
3-38
1.0 BACKGROUND AND OBJECTIVES
2.0 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
Page
1—1
2-1
Summary
Conclusions
R ecommeridations
TECHNICAL REPORT
Miniaturization of the Collection Device
Experimental Techniques
Operation of the Sampler
Assembly of the Sampler
Experimental
Canister Air Flow Calibration
Processing of Elemental Mercury Absorbent
Analysis of Elemental Mercury
Unsuccessful Procedures
Processing of Combined (Organic) Mercury
Absorbent
Introduction
Analytical Procedures
Processing of Particulate Samples
Analysis of Liquid Aliquots
11
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TABLE OF CONTENTS (Continued)
Page
3. 3 Results 3-39
3. 3. 1 Screening Tests for Absorbents 3-39
3. 3. 2 Elemental Mercury Collection Tests 3-43
3. 3. 3 Collection of Dimethyl Mercury 3-47
3. 3. 4 Collection of Particulate Mercury 3-50
3. 3. 5 Tests for Effects by Interferences 3-54
3. 3. 5. 1 Introduction 3-54
3. 3. 5. 2 Effects of Hydrogen Sulfide 3-55
3. 3. 5. 3 Effects of Sulfur Dioxide 3-59
3. 3. 5. 4 Effects of Nitrogen Dioxide 3-59
3. 3. 5. 5 Summarized Effects of Interferences 3-60
3. 3. 6 Environmental Tests 3-64
3. 3.6. 1 Results 3-64
3. 3. 6. 2 Detectability Limits 3-66
3. 3. 7 Environmental Effects 3-67
3. 3. 8 Transportability of Samples 3-68
3. 3. 9 Estimates of Collection Capacity 3-69
111
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INDEX OF FIGURES
Figure Page
3-1 Schematic of Collection Assembly 3-2
3-2 Mercury Collection in Hi-Vol Sampler 3-3
3-3 Canister End Pieces and Screens 3-5
3-4 Canister Tube 3-6
3-5 Orifice Housing No. 2 3-7
3-6 Retaining Ring No. 2 3-8
3-7 Large Orifice Plate 3-9
3-8 Pressure Tube 3-10
3-9 Orifice Disc 3-11
3-10 Canister Clamp 3-12
3-11 Schematic of Collection Assembly 3-17
3-12 Air Flows in Sampling System 3-19
3-13 Elemental Mercury Vapor Source 3-20
3-14 Air Flow Calibration of Canister 3-24
3-15 Calibration of Canister Air Flow 3-26
3-16 Calibration of Silver-Alumina System 3-29
3-17 Schematic Diagram, Charcoal Combustion System 3-34
3-18 Calibration of Dimethyl Mercury in Iodine
Monochloride Bubblers 3-36
3-19 Calibration of Charcoal Absorbent System
Dimethyl Mercury Added to Charcoal 3-37
3-20 Schematic of Analytical System 3-40
3-21 Collection of Elemental Mercury by Absorbent
Canister 3-46
3-22 Collection of Dimethyl Mercury on Charcoal 3-49
3-23 Collection of Particulate Mercury on Glass
Fiber Filters 3-53
iv
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INDEX OF TABLES
Table Page
1 Collection of Elemental Mercury on 10%
Silver-Alumina Granules 3-44
2 Collection of Dimethyl Mercury 3-48
3 Collection of Particulate Mercuric Sulfide 3-52
4 Collection of Elemental and Organic Mercury in
Presence of 1. 2 PPM Hydrogen Sulfide 3-56
5 Collection of Elemental and Organic Mercury in
Presence of 5. 0 PPM SO 2 3-57
6 Collection of Elemental and Organic Mercury in
Presence of 3.2 PPM NO 2 3-58
7 Recovery of Elemental and Dimethyl Mercury by
Canister Absorbents in the Presence of H 2 S,
SO 2 and NO 2 3-61
8 Recovery of Elemental Mercury by 10% Silver on
Alumina in the Presence of H 2 S, SO 2 and NO 2 3-62
9 Recovery of Dimethyl Mercury by Charcoal (TCA,
Barneby-Cheney) in Presence of H 2 S, SO 2 and
NO 2 3-63
10 Ambient Tests at GEOMET Pomona Laboratory 3-65
v
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Section 1.0
BACKGROUND AND OBJECTIVES
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Section 1. 0
BACKGROUND AND OBJECTIVES
This contract was a continuation of effort originated under
EPA Contract No. 68-02-0578 for the development of a collector for
all forms of atmospheric mercury which operated in conjunction with
a conventional High-Volume particle sampler. In this procedure, mer-
cury is collected in particulate and vapor forms. The latter is further
separated into elemental mercury and all other mercury compound vapors.
The technical objectives of the current program included (1)
miniaturization of the vapor sampling techniques which utilized absorbents,
so that the High-Volume sampler package might be operated without the
addition of complex or bulky modifications and, (2) simplification of the
techniques for recovery and analysis of the three forms of mercury in
ambient air. Commercially available instrumentation is required in
analysis and quantitation of mercury-containing samples. The latter
are extracted from ambient air over a range extending from a few nano-
grams per cubic meter to 100 micrograms per cubic meter. To verify
achievement of these objectives, full descriptions of (1) the modified
collector, (2) experimental operating and analytical procedures and (3)
supportive test data are required. Section 3. 1 details the miniaturiza-
tion, Section 3. 2 describes the experimental techniques which were applied
in testing and sample analysis and Section 3.3 contains the data which were
collected to establish the utility of the methods.
1 -1
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Section 2. 0
SU1 MARY, CONCLUSIONS AND RECOMMENDATIONS
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Section 2. 0
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
2. 1 SUMMARY
The technique of collecting vaporized forms of mercury by
utilization of absorber canisters in conjunction with a High-Volume sam-
pler which collects mercury-bearing particulates has been miniaturized
to fit the entire added assembly within the normal configuration of such
instruments. As adapted, vapors from elemental mercury and organo-
mercury compounds are collected by passage of air through a canister
containing two selective absorbents which is positioned within the col-
lector funnel of a High-Volume sampler. A fully assembled cylindrical
collection canister measures 11.74 cm (high) x 3. 18 cm (diameter) in-
cluding its screen-containing end pieces. It may be conveniently trans-
ported by mail to laboratories for analysis in standard 12. 7 cm x 4. 45 cm
mailing tubes.
Each sampling canister consists of two cylindrical sections,
2. 54 cm (i. d.) x 5. 08 cm (high), fabricated from polyvinyl chloride (VT-
36) plastic tubes which are joined together by a screen holder and closed
off at each end by another screen holder. Canister sections are filled
separately by absorbents which are selective for vapors of elemental
mercury and combined mercury, respectively.
Canisters are supported within the High-Volume sampler
assembly by a large orifice plate which has six, 0. 64 cm (diameter)
holes spaced equally on a 7. 14 cm radius. In normal operations at an
air sampling rate of 24 CFM, two of these air flow orifices are closed
off. The orifice plate supports a canister orifice housing, a retaining
2-1
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ring, a canister flow orifice, differential pressure taps and a canister
clamp. Air flow through the central canister portion of the sampler is
controlled by the canister flow orifice; the flow rate is measured, after
calibration, by placing a differential pressure meter across this orifice.
The canister support assembly is fixed in position when the knurled ring
which attaches the High-Volume sampler funnel to the blower housing is
tightened.
With a conventional glass fiber filter positioned on top of the
sampler funnel and a canister placed in the added assembly, the High -
Volume sampler may be used to sample air for mercury particulates,
elemental mercury and vapors of mercury compounds.
Three absorbents were tested in a laboratory apparatus for
suitability for collection of elemental mercury: (1) silver wool, (2) 10%
silver on alumina support and (3) a silver zeolite. Silver wool collected
efficiently at air flows of approximately 200 ml/min. The granular ma-
terials collected effectively to rates of approximately 10 liters/mm. How-
ever full recovery of mercury from the silver zeolite was not achieved.
Therefore, the absorbent consisting of 10% silver on alumina was selected
for testing.
Collection efficiency tests were run with the High-Volume
sampler operating at 24 CFM and the canister sampler at 8. 0-9.8 liters!
mm. Five different types of tests were conducted including collection and
analysis of: (1) elemental mercury, alone, (2) dimethyl mercury, alone
(3) mercury-bearing (HgS) particulates diluted in silica, (4) elemental
mercury and dimethyl mercury together in the presence of hydrogen sul-
fide, sulfur dioxide and nitrogen dioxide and (5) ambient air samples.
2-2
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Elemental mercury was sampled in the concentration range
from 0.044 to 201 pg/rn 3 with the canister operating at 9.8 liters/minute.
In tests, recovery averaged 104%; the standard deviation of the results
was 18. 8%.
Collection of mercury organics utilized dimethyl mercury as
the test compound. Laboratory efficiency tests were conducted at levels
from 0.57 to 113.2 pg/rn 3 . Recovery of dimethyl mercury averaged 96.3%
in ten tests; the standard deviation of these results was ± 11.5%.
Collection of particulate mercuric sulfide diluted in fumed
silica (Cab-O-Sil) was conducted with a total particle loading on the
glass fiber filter varying between 2610 and 19200 pg. This range was
equivalent to 384.2 to 471. 1 pg/rn 3 . In eleven tests, recovery averaged
101% with a standard deviation of ± 5. 1 %.
Tests of collection and analysis of both gas phase components
were carried out in the presence of added gases which might potentially
interfere with the performance of the collector canister. Hydrogen sul-
fide (1. 2 ppm), sulfur dioxide (5. 0 ppm) and nitrogen dioxide (3. 2 ppm)
were added in tests of collection of elemental mercury and dimethyl mer-
cury. Essentially, the collection and recovery characteristics were not
changed by the added gases. Total recovery of elemental and dimethyl
mercury averaged 99. 4% (a= ± 6. 3%) in 28 tests. Elemental mercury
recovery was 99. 9% (o ± 7. 0%); dimethyl mercury recovery was 98. 2
(° ± 7. 9%) for the same runs. These data confirm the ability of the
canister collection method to operate successfully in reasonably con-
taminated atmospheres.
2-3
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A series of 8 - 24 hours tests of the collection procedures
were run in ambient atmospheres characteristic of the environment of
the laboratory. In the room used for storage of elemental mercury and
dimethyl mercury, levels of 0. 023 - 0. 028 ug/m 3 of elemental mercury
and 0.015 to 0.026 pg/rn 3 of dimethyl mercury were detected. In the
shop area levels from 0.025 to 0.049 pg/rn 3 of elemental mercury were
obtained. Organic mercury was not detected. At the building entrance,
levels from 0.010 to 0.024 ug/m 3 in elemental mercury were measured.
Although measurable deposits of particles were obtained in all locations,
mercury bearing particulates were very low varying from 7x10 5 to
1. 2x10 3 ,ug/m 3 .
The environmental factors, temperature and relative humidity
were measured for the major portion of the test data. No effects on col-
leçtion or analysis were observable.
In order to test for factors of the total procedure relating to
handling, storage and shipping, a set of canisters (a blank and a controlled
sample) were shipped by mail from the west coast to the EPA Research
Triangle Center, opened, inspected and returned. On return, the silver-
alumina and charcoal absorbents were reanalyzed. No significant change
in mercury content of either material was detectable. Thus, this simple
procedure of sample transmission by mail appears adequate to send field
samples to a central analytical laboratory.
Procedures have been developed and tested for the analysis
of elemental mercury absorbed on silver-alumina, dimethyl mercury on
charcoal and mercury-bearing particulates on the standard 8 x 10 inch
2-4
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glass fiber filter used by High-Volume air samplers. The precision
of these analytical methods is indicated by the standard deviation of
the results, which is in the ± 6-8% range, normally. The methods
developed utilize standard laboratory instrumentation including an
atomic absorption spectrophotometer and an induction combustion
Lu r na ce.
2.2 CONCLUSIONS
A prototype field procedure for collecting particulate mercury
and the vapors of elemental mercury and organic mercury compounds from
air samples by utilization of a standard High-Volume air sampler has been
developed and tested. Samples collected by the technique may be shipped
in simple mailing tubes to a central laboratory for analysis. Analytical
procedures for laboratory analysis have also been developed and tested.
Initial testing of all aspects of the method is complete. The methods
applied appear to form a sound basis for batch sampling of mercury under
a variety of field conditions.
2.3 RECOMMENDATIONS
Testing of the collector method under a variety of conditions
should be conducted to establish acceptance of the methods which have
been developed. The limits of the field uses which may be appropriate
have not been determined. However, the techniques and methods which
have been developed have no obvious limitations.
In short, the recommendation arising from this work, is,
that the technique be used wherever mercury evaluations are required.
The method is not appropriate for real-time or nearly real-time deter-
minations.
2-5
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Section 3. 0
DETAILED TECHNICAL REPORT
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Section 3. 0
DETAILED TECHNICAL REPORT
3. 1 MINIATURIZATION OF THE COLLECTION DEVICE
The collection device previously developed under Contract No.
68-02-0578 has been redesigned so that collection of the various forms of
vapor which contain mercury is achieved by a miniaturized canister array
positioned within a standard Hi-Vol sampler. Particulate collection re-
mains, as previously demonstrated on the standard glass fiber filter of
the Hi-Vol sampler.
Schematically, the arrangement utilized is shown in Figure 3-1.
The mercury vapor sampling assembly has been installed within the funnel
of a Hi-Vol sampler so that no external modifications of the sampler are
required. The components which are added within the shell of the sampler
are shown in more detail in Figure 3-2. The components are identified by
part numbers which refer to Figures 3-3 through 3-10. These figures show
all the details necessary to fabricate the canister and its support sections.
In routine operation, the two component, plastic absorption
canister sits in an aluminum socket provided in an orifice housing. The
assembly has two sets of orifices: one under the canister housing to con-
trol the flow of air through a canister, a second, comprising a series of
six 0.64 cm (1/4 inch) holes in the plate which supports the orifice housing.
These latter orifices control the total air flow through the Hi-Vol sampler.
To achieve desired air flow rates through the Hi-Vol funnel and the canisters,
the 0. 64 cm holes were blocked as required. With two holes blocked, a 24
CFM air flow through the sampler w a s achieved, while simultaneously a
9. 5 1pm air flow through the canister resulted when the orifice plate under
the canister had a 0. 13 cm (.052 inch) diameter opening.
3-1
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3AMPLE
1
P B OR% fl
LUMft JUM CAN 1 R..
kOL R
CANY V p
co oL/5t )cDpoY v
P MPL
Figure 3-1
Schematic of Collection As sembly
1
3- 2
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/
Particle Filter
Screen and Holder
P/N 1514- 1, -3, -4
3
#2-121 “0” Ring
#2-216 11011 Ring
#2-221 “0” Ring
Orifice Plate
P/N 1515
Canister
P/N 1511
Orifice
Absorbent
Canister
P/N 1510
Absorbent
Canister
P/N 1510
Orifice For Orifice For
Hi-Vol Air Control Canister Air Control
P/N 1343
Figure 3-2
Mercury Collection in Hi-Vol Sampler
Hi-Vol
Collector Cone
P/N 1344
Pressure Tube
2 req.
P/N 1513
Retainer
Stud
8-32 x 2. 8
long, thread
3 req.
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The dimensions of the canister components are shown on Fig-
ures 3-3 and 3-4. Each cylindrical section of the canister is 2. 54 cm in
internal diameter (0. 998” i. d.) and 5. 08 cm (2”) in height. The volume per
section is 25. 6 ml. In use, these sections are each charged with 24 ml of
granular absorbent.
The canisters are assembled with screens and screen retainers
(Figure 3-3) separating the two absorbent sections. Screens are made of
20 mesh stainless steel and sealed into the recessed end of one of the re-
tainers by use of Permabond No. 120 adhesive. The divider between the
two sections of the canister is fabricated from 1 screen holder with recess
(Figure 3-3, 1) and 1 screen holder without recess (Figure 3-3, ). The
screen is sealed to the recessed holder, then the two sections are cemented
together, face to face. Finally, two canister sections as shown in Figure
3-4 are cemented to the ends of this divider and the absorbent charge is
added separately to each section. On addition of each absorbent, the cor-
responding acrylic end pieces were sealed to the cylinder sections by use
of a drop of adhesive on each side of an end screen holder. In order to
make canisters easily openable for analysis, use of too much adhesive
must be avoided in this last operation.
The aluminum canister holder assembly which is simultane-
ously a housing for the orifice controlling flow through the canister is
shown in Figure 3-2. It consists of seven parts. These are (1) the Orifice
Housing (Figure 3-5), (2) the Retaining Ring No. 2 (Figure 3-6), (3) the
Large Orifice Plate (Figure 3-7), (4) Pressure Tubes (two) Figure 3-8),
(5) the Canister Flow Control Orifice Disc (Figure 3-9), (6) the Canister
Clamp (Figure 3-10) and (7) the canister bolts (three) (not shown).
3-4
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3-5
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3-12
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Differential pressure taps for calibration of air flow rates have been in-
cluded. (These are capped when measurements are not required.) The
canister holder bolts to the large orifice plate and the retainer. The large
orifice plate functionally supports the canister holder and also controls the
total air flow through the Hi-Vol sampler. The large orifice plate is placed
under the flange of the Hi-Vol funnel during assembly of the sampler. Tighten-
ing of the large knurled ring then fixes both the Hi-Vol funnel and the canister
sampler in position for use.
The retainer (Figure 3-6) supports the canister air control ori-
fice plate (Figure 3-9) from the bottom side of the assembly. Canisters are
fastened to the canister holder and orifice housing by three bolts and a can-
ister clamp. The clamp fits around the middle section of the canister and
is fastened on the upper side of the canister divider. The clamp is shown
in Figure 3-10; the method of assembly in Figure 3-2. A canister is solidly
positioned when the bolts are tightened into the orifice housing. The bolts
are 0.64 cm (0.25 inch) thread stock 7.11 cm (2.8 inches) in length.
Seals at the bottom of the collection canister, between the ori-
fice housing and the retainer and between the retainer and large orifice
plate are achieved by the use of rubber IIQI! rings.
SUMMARY
A relatively simple two section canister collector was designed
and installed in a Hi-Vol sampler without modification of the standard sampler
envelope. This assembly is then applicable to the collection of mercury
in all its airborne forms, particulate and vapor. Vapor collection has been
separated into elemental and combined form by use of a two section canister,
each section of which is specific in collection of either type of vapor. In
3-13
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principle this collection technique may be employed for a variety of gaseous
and particulate pollutants by modification of the absorbent species.
3.2 EXPERLMENTAL TECHNIQUES
In principle, operation of the collection system involves setting
up and drawing air through the sampler, removal of the resultant samples
from the collector followed by analysis of the solid absorbents and filter
for mercury. All of these operations must be carried out with adequate
care to achieve results of useful accuracy.
Discussions of the experimental methods employed include (I)
operation of the sampler, (2) canister air flow calibration, (3) processing of
elemental mercury absorbents, (4)processing combined mercury absorbents,
(5) processing of mercury particulates, and (6) analysis of processed sam-.
pies by the atomic absorption spectrophotometer.
3. 2. 1 Qperation of the Sampler
3. 2. 1. 1 Assembly of the Sampler
The miniaturized absorbent canisters described in the preced-
ing section were prepared for use by weighing an appropriate volume of ab-
sorbent into each half. The elemental mercury absorbent was placed in the
upper half into which the air passes initially. F a r t h e 1 0 % s jive r on
alumina absorbent which was 8-14 mesh, 24. Og were weighed into the upper
section. A canister end piece was added and sealed onto the canister body
with a minimum amount of Permaborid No. 102. The absorbent for corn-
bined mercury vapor was added similarly to the lower end of the canister.
Using Barneby-Cheney TCA Grade charcoal (6-10 mesh) 12. 5 g was required
to fill the lower section of the canister.
3-14
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With the High-Volume Air Sampler disassembled, assembly
for use involved the following steps:
(1) Insertion of the end of the absorbent canister into the ori-
fice housing and support assembly, followed by assembly arid tightening
of the retaining clamp.
(2) Placement of the large disc, canister and canister support
assembly of top of the blower housing.
(3) Positioning of High-Volume Sampler funnel in position atop
the blower housing. The canister and its assembly extends upward within
the funnel but not as far as the level of the filter support.
(4) Tightening of the knurled ring at the funnel base onto the
threads of the blower housing. This action fixes the canister and its flow
controls in position.
(5) Placement of the particulate filter* on top of the stainless
support screen of the air funnel arid positioning of the retaining frame on
the edge of the filter.
On completion of the assembly process, the pressure taps
indicated in Figure 3-2 should be connected to a Magnehelic Differential
Pressure Gage***. This gage may be used to measure flow through the
canister after calibration. The method of calibration is indicated in the
following section.
The High Volume Air Sampler used in the program was the Precision
Scientific Model, obtained from Van Waters and Rogers Scientific,
Catalog No. 10300-306.
Standard High Volume Sampler glass fiber filters measuring 8 x 10
inches, Van Waters and Rogers Cat. No. 10300-420 were used.
** Magnehelic Gage Model Z100C measuring 0-100 inches of water dif-
ferential pressure.
3-15
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Total air flow through the High-Volume Air Sampler is dis-
played on the gage attached into the base of the blower. With four of the
six orifices in the orifice plate open, air flows of approximately 24 CFM
were achieved. Under these conditions, an air flow of 8. 0-9. 5 1pm through
the canister resulted.
3. 2. 1. 2 Experimental
The apparatus set up to monitor introduction and collection of
controlled mercury vapor samples is shown schematically in Figure 3-11.
A domed section was constructed to close off the air inlet above the parti-
culate filter of a Hi-Vol sampler. The dome was bolted to the top of the
sampler using a rubber gasket to effect a seal. Air under ambient cond-
itions was brought into the dome through a 3t1 (7. 62 cm) 1. d., side arm.
Mercury vapor was brought from a controlled source into a sample inlet
tube 3/8” (0.95 cm, i.d.) which extended inside the side arm. (This tech-
nique is indicated in Section 3. 1. 3.) Thus, mixing of the sample stream
and the ambient air occurred in the side arm. The mixed sample was
pulled through the apparatus by the Hi-Vol blower. By adjustment of the
air control orifices in the canister support in the neck of the Hi-Vol about
1. 4% of the total air flow through the sampler was diverted through the
collection canister. Constancy of air flow through the canisters was checked
by means of a Magnehelic gage during sampling operations. Air sampling
probes (teflon) were positioned at the inlet end (Probe 1) of the canister
and in the outlet (Probe 2) stream. The latter probe was positioned im-
mediately under the charcoal-containing section but above the orifice plate
under the canister. Samples at both positions were pulled into bubblers
for evaluation during all runs. The mercury concentration value obtained
3-16
-------
Figure 3-11
Echematic of Collection Assembly
TO
-v p._ ,zs t
c —/ uw’ o v
W oc 4 -\/cL.
4 -VOL
7RO6
T0 L ’$
I
3-17
-------
at the upper probe was used to define the level of the source stream. The
lower probe (No. 2) was used to check the efficiency of the collection.
The various air flows utilized in the sampling assembly are
shown in Figure 3-12. The Hi-Vol sampler was operated at 24 CFM
679 1/rn). The inlet stream air which contained controlled levels of
mercury vapor was added to the ambient air at 2. 8 1/mm. Mixing was
carried out in the side arm of the inlet. A total of 9. 5-9. 8 1/mm. of the
total inlet flow was passed through the canister. At the upper end of the
canister samples were taken at 1. 0 1/mm. into two KMnO4-HNO 3 bubblers
when elemental mercury alone was sampled; iodine monochioride was used
for total mercury when organic mercury compounds were present. Results
of analysis of the mercury trapped in these bubblers were used as the source
level. At the lower end of the canister another gas sample to two bubblers
was taken at a flow of 1. 5 1/mm. Analytical results from this position were
used to define the performance efficiency of the canisters.
Air flow was measured as follows: (1) the total sampler flow
was monitored from the air flow gage placed below the instrument blower*.
(2) The inlet and outlet bubbler flows were measured with rotameters which
were placed between the second bubbler in each set and the vacuum pumps
(Neptune Dyria Pumps, either Model 2 of Model 4K) used to draw the air.
Flow was adjusted by valves placed between the rotameters and the pumps.
(3) Air flow from the mercury source was measured by rotameter placed
on the outlet side of a Dyna Pump which was used to push air through the
mercury source. Figure 3-13 shows this arrangement. From the rota-
meter, air passed over a pool of mercury held in a U tube and thence
directly to the sample inlet in the side arm of the dome over the Hi-Vol.
* The Hi-Vol is a Precision Scientific Model, Cat. No. 63083. This
gage reads directly in. CFM.
3-18
-------
MPL -R V& L W
CPM
t.O L/M
0. 5 - 9. 8 L/M
Figure 3-12
Air Flows in Sampling System
ERCUP P MPL
AU - ‘FL V’J 2. L/W\
t.5 L/M
3-19
-------
Vapor to Hi-Vol
for Challenges
Pyrex U-Tube
Mercury)
0-12 1/mm.
Flowniete r
Control Valve
Figure 3-13 Elemental Mercury Vapor Source
3-20
Reference ‘Temp.
Thermometer
1
Heating
Tape
Variac
Air Pump
r c
Activated Char coal
Air Filter
Air Inlet
-------
Mercury vapor levels from this source were controlled by adjustment of
power to a heating tape placed around the U tube. (4) Air flow through
the canister was measured by use of a differential pressure gage with all
components in position and operating within the Hi-Vol. Calibration of
the flow is discussed in Section 3. 2. 2.
Bubblers for collection of mercury contained the following:
First bubbler: 13. 5 ml volume, comprised of
0. 5 ml KMnO4 (0. 25M)
4.0 ml HNO3 (1:1)
9.0 ml H 2 0
Second bubbler: 15. 1 ml volume, containing
0. 1 ml KMnO 4 (0. 25M)
l.OrnlHNO 3 (1:1)
14 ml H 2 0
In analysis of mercury, aliquots of the total bubbler volume were used.
In general, 1. 0, 2. 0 or 5. 0 ml were employed.
Dimethyl mercury was supplied to the mixing plenum of the
test assembly from a bubbler which served as a vaporizer.
The procedure utilized in supplying dimethyl mercury was as
follows: Prior to each test run a 10 pl volume of dimethyl mercury was
diluted in methanol and 1.0 ml was placed in the bottom of a standard
Smith-Greenberg bubbler. The concentration used was based on the aver-
age air concentration desired for the test and its planned duration. The
estimated concentration was based on a series of trials which had demon-
strated that approximately 55-60% of the dimethyl mercury placed in the
vaporizer was recoverable in the source bubbler operating from Probe 1
3-21
-------
at the top of the canister. In all operations the dimethyl mercury solu-
tion placed in the vaporizer was completely exhausted during a test. The
vaporizer was placed in a constant temperature water bath to control the
rate of sample evaporation. Air flow through the vaporizer was adjusted
to prolong the total vaporization time so that it approached the duration
of the test. However, no rate of vaporization has been estimated.
In order to avoid fluctuating air flow rates through the vapor-
izer an aliquot of the dimethyl mercury solution measuring no more than
1. 0 ml was employed. This volume remained below the level of the nozzle
in the bubbler/vaporizer, thus permitting smooth air flow.
Measurement of the quantity of dimethyl mercury placed in the
vaporizer was carried out volumetrically: First, utilizing a capillary pi-
pette, 10 p1 of dimethyl mercury was added to 5. 0 ml of methanol. A
volume of 1. 0 ml of this solution contains 5340 pg of dimethyl mercury
(as Hg). This solution was generally used as the dimethyl mercury source
for the tests in which levels greater than 30 pg/rn 3 were desired. For the
lower test levels a 0. 5 ml volume of the first solution was diluted to 8. 0 ml.
This solution contains 334 pg/ml of dimethyl mercury as Hg. Adjustments
to achieve the desired average air concentrations were made by adjusting
the air flow rate through the bubbler.
Actual values for the concentration of dimethyl mercury (as
Hg) which were used in the analyses of the data, were always based on
the values obtained through the upper probe and its bubbler. This is
indicated in the data tabulation under the heading of “Source Analysis”.
Both bubblers used to evaluate the absorption of dimethyl
mercury on charcoal contained 10. 0 ml of 0. ION iodine monochloride.
3-22
-------
The air flow rate through the upper bubbler (Probe 1) which was used to
measure the input mercury level was 1. 0 1/mm. The lower bubbler oper-
ating from Probe 2 sampled the air coming through the absorbent at 1. 5
1/mm.
Although a bubbler sample was taken after the canister ab -
sorbent at Probe 2, for every test run, no evidence of any dimethyl mer-
cury was obtained in any of these bubblers. Thus, within the limits of
detection of mercury in this modified Hatch and Ott method, it may be
stated with complete conlidence that the dimethyl mercury was quantita-
tively absorbed by the charcoal.
The procedures utilized in analysis of the results of the tests
are outlined in Sections 3. 3, 3. 4 and 3. 6. All analyses were calibrated
against controls comprising the same silver-alumina and charcoal ab-
sorbents to which controlled volumes of mercury-containing vapors were
added in closed containers. The full analytical procedure was then carried
out on these synthetically prepared samples.
3. 2. 2 Canister Air Flow Calibration
Independent calibration of air flow through the canister as-
sembly was achieved by use of a rotameter and air pump. Figure 3-14
is a schematic of the set up.
Using the standard canister holder assembly with the 0. 132
cm (.052’) flow orifice in position, air was pulled through the canister
and orifice opening by use of a separate air pump. The pressure drop
across the opening was measured by a Magnehelic gage* with a 0-100
* Magriehelic Model 2100C, Dwyer Instruments, Inc. Michigan City, Indiana.
3-23
-------
Figure 3-14
Air Flow Calibration of Canister
E - E\-1 .L C ..
GP E.
PLP T
CAN\SVE .
\/ALVa
EX -l U$ 1
LO\N W\
3-24
-------
inches of water differential pressure range. By adjustment of the valve
positioned in front of the pump easy control of the air flow rate was
achieved. Air flow was measured by a rotameter*. Figure 3-15 shows
typical air calibration data.
The air flow calibration achieved as indicated, was used to
determine air flow through the canister for each test run. The differ-
ential pressure value as measured by the same Magnehelic gas was read
at the start, finish and at hourly intervals, where appropriate, during
each run. The average value was referred to the calibration chart (Figure
3-15) for determination of the average air flow rate during each test.
3. 2. 3. Processing of Elemental Mercury Absorbent
3. 2. 3. 1 Analysis of Elemental Mercury
A number of methods were tested for analysis of elemental
mercury after absorption on 10% silver-alumina absorbent and other ab-
sorbents. The 10% Ag/A1 2 0 3 absorbent material shows capability to per-
form under adverse conditions which have apparently deactivated other
elemental mercury absorbers. It also exhibits high capacity for mercury.
Its good absorbent properties do, however, appear to make mercury re-
covery relatively difficult. Nevertheless, a procedure has been estab-
lished which works efficiently even in the presence of contaminants. Ini-
tial efforts with contaminants such as aromatics which absorb in the wave
length (253. 7 rim) utilized for mercury analysis showed that a purification
step was required. The following procedure was developed.
A riffled (representative) 10 gram sample of the 10% silver on
alumina granules (8-14 mesh) contained in the top section of the absorbent
* Roger Gilmont Instruments, Inc.; Cat. No. F 1300, Size No.3, Air Flow
Range 200-12, 000 mI/mm.
3-25
-------
Figure 3-15
Calibration of Canister Air Flow
Air Flow, 1pm
3-26
Pressure
Drop,
Inches of
Water
80
70
60
50
40
30
20
10
0
I-i--
t i I - E r
Ii =c :
--
i T* _ 1
:
-r- --—r
.
/ — --- --——
/ - r
7 1 +
Ii T---()-- ’H’
il
2 4 6 8 10 12
-------
canister* were placed in a 125 ml Erlerimeyer flask. To the solid, 7. 0 ml
of 0. 25M potassium permanganate solution and 15. 0 ml of concentrated nit-
ric acid were added. The flask was covered lightly with parafilm and agi-
tated gently overnight on a platform shaker. If the solution is clear after
shaking, the sample size was too large and the procedure should be re-
peated with a smaller sample, 5. 0 grams. It has been found that recovery
is low when the oxidizing reagents are used up.
A 5. 0 ml aliquot of the extract was removed from the shaken
Erlenmeyer and added to 50 ml of 1M sodium ascorbate. The metallic
silver aggregated slowly; a wait of about one minute was adequate to com-
plete precipitation. Then the silver ( and mercury) was filtered out on a
25 mm disc of Whatman GF/D glass fiber held on a vacuum filter. The
residue was washed with distilled water and the glass fiber and residue
- *
were transferred to a crucible’ for ignition in a high frequency induction
* Reference throughout is to the canister of dimensions l i. d. x 4-5/8”
high, which contains 23. 2g of 10% Ag on A1 2 0 3 (23 ml) and 11.5 g (23 ml)
of activated charcoal. This canister can be used at relatively high air
flow rates without loss in collection efficiency. One tested sampling rate
utilized is 8.0 liters/mm. (hourly space velocity 20870 vol/vol-hr) which
allows sampling of levels as low as 1 nanogram/rn 3 in a 24 hr. day when
the sampled volume is equal to 11, 520 liters and the mercury collected
would be 11.5 nanograms. Materials requiring longer sampling intervals
cannot conveniently be sampled. This is one of the difficulties encoun-
tered with silver wool as an elemental mercury collector. It requires a
low flow rate.
crucible such as the Leco N528-11 may be used. The induction furnace
utilized was the Leco 52 1-000.
3-27
-------
furnace. The following set-up was used:
Air was pulled into the induction furnace at 1.0 liter/minute. (Dry nitro-
gen may also be used.) The bubbler contained 9. 0 ml of 1M nitric acid
and 1. 0 ml of 0. 025 M potassium permanganate. The solid sample was
heated for 3 minutes at maximum furnace grid current.
After collection of the mercury in the bubbler, 1. 0 ml of 20%
stannous chloride in 6N HC1 was added to the bubbler. Using the same
air flow, the reduced mercury was pulled through into the optical cell of
the atomic absorption spectrophotometer operating in the flarneless mode.
Section 3. 2. 6 describes this operation.
The calibration data are shown in Figure 3-16. For calib-
ration, mercury vapor was absorbed onto the solid in a clean flask which
was closed by a rubber septum. Various volumes of equilibrated mercury
vapor were added by hypodermic syringe to such flasks containing samples
of the absorbent. The solid was then processed as indicated above. Ex-
perimental notes relative to the procedure:
3-28
Sample in crucible
Induction Furnace
Bubbler
Air at 1 1/mm.
-------
. TO. .._ _NTII 18
KEUFFEL & ESSER CO. NAO( IN US_A.
Nanograms of Mercury on Absorbent
LW 151L
:i:i1UI 1 Ii
.:::.::.;;tj 11
.1
IL T t: i ::
II i:
f I1
EEIE Ec t
!! ±±± L
HF±:
dffF ft J
U
Iftii UP 1lft Ri
14;
us
I
;and
ur iir a ‘Sy tern
.rd” Samples
tI UI ‘IHI t
i.tf _I _t _1 _iI
I ; : :: :
LI
:1::
I1
‘:: f f : i , . . H
h
FflItt1it
tTF HiTt T
/
•1
/
:1.:
/
t:12 LL-i 4 ; -;
7
: ::: T Fth
. : : : ;;
[ I
tHttt
ti hI I
ii
c : 1 4 !.
T iw
. .
‘ r H:!;
.
T L
141
ZOO,
I I I I t L I I LiFi [ t IJ
: .:
-------
1. Mercury in the extract obtained after treatment of the
solid may be absorbed onto the manganese dioxide. Therefore it is im-
portant to mix the contents of the flask prior to removal of the aliquot
used in the analysis.
2. if the aliquot taken is less than 5. 0 ml, silver nitrate
should be added to keep the quantity of silver on the filter relatively con-
stant. The procedure utilized has been to add 0. 2 ml of a 40% silver nit-
rate solution for every 1. 0 ml the aliquot is below 5. 0 ml. For example,
if the aliquot is 3. 0 ml, 0. 4 ml of the 40% silver nitrate should be added.
This increment is added to sodium ascorbate immediately prior to addi-
tion of the sample. By this technique, heating of the silver in the induc-
tion furnace is kept uniform from sample to sample. Variations in the
amount of silver present will modify the temperature achieved.
3. Where excessive amounts of oxidizable materials have
become absorbed onto the Ag/Al 2 0 3 absorbent, larger volumes of the
oxidizing components may be used. Calibrations have been run with 15 ml
of 0. 25M KMnO 4 and 30 ml of conc. HNO 3 . Identical results were obtained.
This procedure has been qualitatively checked on addition of
sulfur compounds such as H 2 S, SO 2 and aromatics such as xylene to the
calibration flask. Interferences were observed when the bubbler step
was omitted. The bubbler process also concentrates the mercury re-
lease producing sharper absorbance peaks than would be achieved without
it.
3. 2. 3. 2 Unsuccessful Procedures
A considerable number of trial experiments were carried out
in development of the specific method indicated above. Some of the less
3-30
-------
useful attempts included:
(1) Thermal Desorption of Mercury
Typical of the problems encountered, included a trial with
450 nanograms of elemental mercury on 10 grams of silver/alumina
granules. Air at 50 ml/min was pulled through a glass trap containing
the sample which was supported in a resistance furnace maintained at
600 650°C. Mercury was collected in 2 bubblers each of which con -
tamed 10 ml of 0. 5N HNO 3 . Various periods alter commencement of
heating were checked. A 3 hour sample showed release of only 10-20
nanograms of mercury after 3 hours of heating. Samples collected alter
6-1/2 hours of heating showed 45-50 nanograms of mercury still in the
process of desorption. In addition, the glass showed considerable softening.
It may be concluded that standard resistance furnace heating
of mercury on silver-alumina absorbent does not bring about sufficiently
rapid desorption of the mercury for use in a short analytical procedure.
(2) Nitric Acid Extraction
A considerable variety of procedures were examined in attempts
to avoid heating to desorb the mercury. For example, the silver was re-
moved from the granules with HNO 3 and an aliquot was reduced with SnCl 2
and tested directly. Silver precipitated in the reduction step appeared to
hold the mercury. No Hg vapor emission resulted. No other liquid ex-
traction was found to work effectively.
3. 2. 4 Processing of Combined (Organic) Mercury Absorbent
3. 2. 4. 1 Introduction
In use of the two section canister collection method, the silver/
alumina tiabsorbentU removes the elemental portion of total mercury from
3-31
-------
sampled gases. The second section containing activated charcoal (Barneby-
Cheney, TCA, 6-10 mesh) removes vapors of compounds of mercury. These
latter are considered to be mainly mercury organics such as dimethyl mercury.
Analysis of the charcoal presented several problems:
(1) All combustion and high temperature procedures resulted in
the release of gases which interfered with analysis in the atomic absorption
spectrophotometer set at the mercury wave length, 253. 7 nm.
(2) Release of the mercury compounds by direct heating in a
resistance furnace was very slow (requiring about an hour for a 1 gm sam-
ple at 600 _7000C) and was also accompanied by the release interfering vapors.
(3) Use of bubbler collectors containing either KMriO 4 /HNO 3 or
ICl solutions to trap the mercury after high temperature removal of the vapors
from charcoal did not separate Hg from the interference. That is, use of the
bubbler extract in direct Hatch and Ott type procedure showed interference
still, although on a diminished scale.
The following procedure was established which circumvented
the interference problems.
3. 2. 4. 2 Analytical Procedures
Analysis of the charcoal absorbent samples was carried out as
follows:
(1) The total charcoal sample was riffled carefully to separate
a representative 1. 0 gram sample of the solid.
(2) The charcoal sample was transferred to the combustion
chamber of an induction furnace where it was heated to redness in a nitro-
gen atmosphere. The temperature was approximately 1000°C. The nitro-
gen flow rate was 1.5 1/mm. Under these conditions, the mercury
3-32
-------
absorbate was rapidly released. After approximately 7 minutes, release
of mercury was complete. Figure 3-17 shows the arrangement used for
combustion.
(3) The gases released during the heating are passed through
a small bore alumina tube maintained at 1000°C. This step is included to
complete reduction of any mercury compounds which may have been de-
sorbed from the charcoal absorbent without alteration. A high quality
alumina tube* measuring l/l6tt (1. d.) x 5-3/22” (o. d.) x 18” (length) is
heated in a 14” electric furnace. This small volume tube design is uti-
lized to minimize mercury vapor hold-up.
(4) The gases from the alumina tube were passed to a KMnO 4 -
HNO 3 bubbler which removes the mercury from the gas. These bubblers
contained 0. 2 ml, 0. 25M KMnO4, 1. 0 ml, 8.3 N (1:1) HNO 3 and 13. 8 ml
H 2 0.
(5) The system was purged into the bubbler for three minutes
with nitrogen prior to analysis of the contents of the bubbler.
(6) The bubbler contents were reduced with 2. 0 ml of 20%
SnC1 2 in 6N HC1. Upon addition of the stannous chloride solution, the
bubbler was immediately connected to the remainder of the analytical
apparatus line. Care was taken to avoid mixing the reagents until the
bubbler containing the sample was reconnected to the remainder of the
apparatus. Mixing was provided by passage of air at 1. 0 1/mm. through
* The Alumina tube was obtained from Thermal American Fused Quartz
• Co. It is specified as “high purity recrystallized” alumina, nominal
bore -2. 0 mm, nominal wall -1. 0 mm, maximum outside diameter
-4. 5 mm, length -375 mm.
3-33
-------
Induction
Coil
“0” Ring
Closure
Moveable
Pedestal
N gel
Supply
Midget
Bubbler
Schematic Diagram,
Charcoal Combustion System
Al urn in a
Tube
Sample
in
Crucible
l 3
LECO
Model 521
Induction
Furnace
Liridberg
Hevi - Duty
Furnace
Type 55035A
=
Figure 3-17
-------
the sample bubbler. Released vapors passed to a second bubbler con-
taining a solution of 0. 5 g sodium borohydride in 15 ml of water and thence
to the optical cellin the atomic absorption spectrophotometer which quanti-
tates the mercury vapor.
(7) Calibrations:
(a) Samples of dirnethyl mercury used for quantitation
with the iodine monochioride procedure were added
directly to 10 ml of 0. 10 N IC1 in a bubbler. Freshly
prepared methanol solutions of varying dilutions were
used. In general, 10-40 /il volumes were used. The
contents of the bubblers were then analyzed as mdi -
cated in (6). A typical calibration is shown in Figure
3-18.
(b) Calibrations of the charcoal absorbent system were
carried out by the addition of dimethyl mercury (in
MeOH) directly to 1. 0 g of charcoal. The charcoal
was then analyzed in accordance with the total pro-
cedure indicated in (1) - (6). An example of a calib-
ration is shown in Figure 3-19 where various amounts
of mercury added to charcoal samples are indicated
on the abscissa, absorbance is plotted on the ordinate.
The intercept is a measure of the blank value assoc-
iated with charcoal samples to which no added mer-
cury is associated.
3-35
-------
Figure 3-18
Calibration of Dimethyl Mercury
in Iodine Monochloride Bubblers
1.. .
- - - 0
: :t ±1 H
-- ---
_ _ft 0
40 80 120
160 200 240 280
Nanograms of Mercury added to IC1 as Diniethyl Mercury
=
Absorbance
0. 4
3
0 ’
0. 3
0. 2
0. 1
-F
-------
I ; ,
Figure 3-19
Calibration of Charcoal Absorbent System
Dimethyl Mercury Added to Charcoal
Nanograms of Mercury Added to Charcoal as Dirnethyl Mercury
-1
.13
Absorbarice
0. 4
0. 3
0. 2
0. 1
H::
H:: IT1 f
40 80 120 160 200 240 280
-------
3. 2. 5 Processing of Particulate Samples
For testing the collection, recovery and analysis of particu-
lates, synthetic mixtures of powdered mercuric sulfide were compounded
with Cab-O-Sil (Grade M-5Y. The mixtures were homogenized in a small
tube by a Vortex mixer. With the particulate filter in place in the operating
collection assembly, the solid sample was vibrated into the air stream at
the air inlet. Figure 3-11 shows the arrangement which was used. In
general, particle preparations in which 1. 0 mg of powdered HgS was mixed
with 83. 2 mg of Cab-O-Sil were typical of the proportion between the mer-
curic compound and the diluent. -
After collection, the glass fiber filter was carefully removed
from the collector, folded and placed in a cleaned, wide-mouth bottle which
was capped and used for storage until needed: Analysis was commenced
by the addition of the 35 ml of 0. 25M KMnO 4 and 75 ml of concentrated
HNO 3 to the sample on the filter. A glass stirring rod was used to break
up the filter. The macerated filter-reagent mixture was allowed to sit for
at least one hour alter addition of the acid KMnO 4 , when 90 ml of distilled
water was added and stirred.
For analysis, a 10 ml aliquot of the liquid was removed and
placed a 35 ml Greenberg-Smith impinger equipped with a standard tip.
The sample was reduced with 2. 0 ml of 20% SnCl 2 in 6 N HC1 and the stan-
dard analytical determination described in the following section.
3. 2. 6 Analysis of Liquid Aliquots
All processed samples were analyzed by the same modified
* Fumed Silica manufactured by the Cabot Corporation. Grade M-5 has an
averag e particle diameter of 0. 014 microns; an average surface area of
200 m 1g.
3-38
-------
Hatch and Ott method: (1) An aliquot of the dissolved sample was placed
in a Greenberg-Smith impinger modified by use of a standard nozzle in
place of impinger tip; (2) The volume was made up to 10 ml with ZN nitric
acid; (3) The sample was reduced with 2. 0 ml of 20% SnC1 2 in 6N HC1 and
(4) connected to a train which consists in series of a bubbler containing
10 ml of 2% sodium borohydride (NaBH 4 ), an empty impinger, an optical
cell set in the optical path of a Perkin-Elmer Model 303 atomic absorp-
tion spectrophotometer, a rotameter and a vacuum pump. The arrange-
ment is shown schematically in Figure 3-20. Air was pulled at 1-2 1pm
through the system. Peak signals read as % absorption were converted to
absorbance and quantitated by comparison against calibrations constructed
by analysis of the various substrates.
Calibrations for each of the three main procedures which were
tested, elemental mercury on Ag/Al 2 0 3 ; (CH 3 ) 2 Hg on charcoal and HgS
(Diluted) on the glass fiber filter were normally constructed end-to-end.
That is, known quantities of mercury, in the appropriate form were added
to the solid in the case of the absorbents, and the entire analysis was car-
ried out with known samples to obtain a calibration for determination of
unknown collector samples. Typical calibration curves have been shown
in the sections which described the processing of each absorbent.
3.3 RESULTS
3. 3. 1 Screening Tests for. Absorbents
Three absorbents were tested for suitability in elemental mer-
cury collection by the canister method: (1) Silver wool, (2) 10% silver on
alumina and (3) a silver zeolite. These materials had been demonstrated
3-39
-------
Figure 3-20
Schematic of Analytical System
Spray
Trap
L U1
NaB H 4
Bubbler
Vuum
Pump
Valve
R otameter
Optical
Cell
in AAS
S am pie
3-40
-------
as most promising in previous tests.
The silver wool used was Baker Catalog No. V007, for micro
analytical applications. It is described as silver wire, approximately 5
microns in diameter, containing not 1 e s s than 99. 99% silver after
degreasing.
The silver-alumina absorbent was made by adding 30 ml of a
silver nitrate solution which contained 0. 6 7g AgNO 3 per g H 2 0 to 100 g
of 8-14 mesh, Alcoa F-i, activated alumina. With shaking, this solution
was dripped slowly through a separatory funnel into an evacuated vacuum
flask which contained the alumina. After the solution was completely added,
the granules were dried at 100°C and then calcined at 700°C for several hours.
The silver was not further reduced.
The silver zeolite was a 100% silver exchanged, Type 13X, 12-
16 mesh, chromatographic grade molecular sieve purchased from Coast
Engineering Laboratory. Its silver content is the result of completely
exchanging the sodium of the zeolite by silver.
These materials were screened in simple tube (1/2” 1. d.)
configuration using relatively low levels of mercury vapor: 5-20 pg/rn 3 .
Qualitatively, the following results were obtained. The silver
wool (2 grams) after cleaning and activation, collected mercury vapor effi-
ciently at low flow rates. For example, at 200 mi/mm. collection effi-
ciency was excellent and no mercury was detected passing to the detector
positioned below the test bed. At 400 mi/minute, 2-5% of the mercury
was detectable. At higher flow rates, larger percentages passed the ab-
sorbent. A simple calculation for ambient levels, i.e. 5 nanograms/m 3
3-41
-------
indicates that very long runs would be required at the effective flow rates
to utilize silver wool. To collect 5 nanograms, a detectable quantity by
an atomic absorption spectrophotometer, a 5000 minute collection cycle
would be required. Even a tenfold improvement in collection parameters
such as by use of a ZOg sample in a half-canister configuration, would
probably not be adequate to qualify silver wool for use in the projected
operations. Therefore, testing with wool was discontinued.
A ten gram portion of the 10% silver on Alcoa alumina pre-
paration was tested similarly, initially. It passed no mercury at flow
rates up to 10 liters per minute in the laboratory screening device.
The silver zeolite was technically a most promising material.
It collected mercury as effectively as the Ag/A1 2 0 3 preparation. However,
its particle size (12-16 mesh) made achievement of 1-2 1/mm flow rates
difficult. In analysis of the solid, however, the zeolite held tenaciously
to its silver and mercury. At all levels of mercury complete recovery
proved impossible to achieve. Testing of the zeolite was discontinued.
Considerations in terms of equal quantities of silver shows
that the 10% silver/alumina absorbent is vastly superior to silver wool.
A 24g canister charge of Ag/A1 2 0 3 contains approximately 2. 4g of silver.
A silver wool packing for a canister requires approximately 15g of silver
as a minimum. The latter still requires operation at low air throughputs.
In addition, screening tests of the silver/alumina absorbent
showed complete passage of dimethyl mercury vapor without measurable
retention. Thus, it exhibited the selectivity required for the top section
of the two part canister absorber. On the basis of the three materials
screened, the 10% silver on alumina was selected for more complete
3-42
-------
testing in the canister and High-Volume sampler.
Previous testing of the Barneby-Cheney TCA Grade charcoal
had shown this material to have the desired properties for an absorber of
organic mercury compounds. It fully removes organic mercury vapors as
exemplified by dimethyl mercury under the desired flow parameters. It
does not collect elemental mercury as demonstrated in laboratory screen-
ing tests. In addition, it is the only charcoal tested which can be heated
directly in the Leco induction furnace. On the basis of these properties,
the TCA Grade charcoal was selected for use in the lower section of the
canister absorber.
3. 3. 2 Elemental Mercury Collection Tests
Tests of the 10% silver on alumina absorbent were run with
synthetically generated mercury vapor concentrations ranging from the
ambient level in the laboratory to approximately 200 pg/rn 3 . Those util-
izing the ambient level were run over 5 to 6 hour intervals; all others
were run for one hour. Analyses were run in duplicate or in triplicate.
That is, aliquots of the riffled solid absorbent, 3-lOg each, were run
separately to obtain reasonable agreement. Separate calibrations were
run for each day. Bubbler samples which determined the elemental mer-
cury level in the source were analyzed in the same way as those result-
ing from induction furnace heating, followed by collection in KMnO 4 -HNO 3
bubblers.
The data for test runs at elemental mercury vapor concentra-
tions ranging from 0.044 to 201 pg/rn 3 are collected in Table 1. The High-
Volume air sampler was operated in the range 24. 0-24. 8 CFM for these
tests. The sample air through the canister was controlled at 9.8 1pm.
3-43
-------
Table 1
Collection of Elemental Mercury on 10% Silver-Alumina Granules
Elem. Mercury High-Vol. Source Air
Dur- Elern. Mercury Aver. Value Average Bubbler Sample Sample Sample
ation Canister Anal. Canister Anal. Air Sample Anal. Air Vol Humidity Temp.
(mm.) (pg/rn 3 ) (pg/rn 3 ) Rate (CFM) (jig/rn 3 ) (liters) (RH) (°F) Recovery
60 1. 98 2. 0 24. 8 1. 19 590 35 75 168
2.50
1. 54
60 2.09 1.9 24.7 1.36 590 38 77.5 140
1.76
60 1. 92 2. 3 24. 5 2. 62 590 42 79. 5 88
2.50
2.37
2.75 2.3 24.0 2. 56 590 28 81 90
1. 92
2.69
1.85
60 8.51 9.0 24.0 10.3 590 30 74 87
9. 55
60 8. 73 9. 6 24. 0 10. 3 590 32 74 92
10. 43
60 118 118 24.0 111 590 52 76 106
118
60 201 201 24.0 188 590 58 78 107
201
392 0.044 0.044 24.0 0.055 3840 62 76 80
343 0. 049 0. 049 24. 0 0. 058 3360 57 75 84
Average 104 %
%Standard Deviation + 18. 8%
=
-------
The column labelled Source Bubbler Anal, refers to the results obtained
in analysis of the bubbler which extracted air at 1. 0 1pm from the stream
immediately prior to its entry into the canister sampler. In all cases the
sample obtained from the bubbler located below the canister was indistin-
guishable from the reagent-absorbent blank. Thus, it may be concluded
that the canisters were, within the limits of the analytical procedure, 100%
efficient in extraction of mercury from air under the conditions of these
experiments.
More precisely, the reagent -absorbent blank was equal to
1-2 divisions on the strip chart of the atomic absorption spectrophoto-
meter. The system response to the samples obtained from the No. 2
bubbler was not greater than that blank, or the mercury equivalent of
a few nanograms /meter 3 of air. This value was constant regardless of
the level of the mercury in the air sample.
Figure 3-21 shows the results of these runs plotted on a log-
log scale. The ordinate units are the results obtained from analysis of
the bubbler contents sampled at the top of the absorbent canisters. The
abscissa shows the results obtained from analyses of the canister absor-
bents. That is, the air concentrations sampled and analyzed extended
from approximately 40 nanograms of mercury/meter 3 to 200 micrograms/
meter 3 . The diagonal dotted line shows the theoretical equivalence of
these data. The recovery averaged 104% with a standard deviation of
± 18. 8%. The high values of the standard deviation are generally attri-
butable to values obtained at the lower levels of mercury vapor concentra-
tion. In evaluation of these data it should be recognized that a finite esti-
mate of probable error is associated with each of the coordinates.
3-45
-------
Figure 3-21
Collection of Elemental Mercury by Absorbent Canister
Mercury
Mercury Source vs. Mercury Collected /
Source
.nograms
r r meter 3 -
i0 5
/
Source Measurement by Bubbler /
Collection Measurement by Canister
/
/
0”
:: /
Canister Concentration of Mercury, nanograms/meter 3
3-46
-------
On the basis of these data, it may be concluded that 10% silver
on alumina is an effective collector of elemental mercury over the full range
of mercury concentrations near ambient to 200 jig/rn 3 .
3. 3. 3 Collection of Dimethyl Mercury
Tests for collection of mercury organic compounds were run
with dimethyl mercury. The absorbent tested was charcoal, Barneby-
Cheney, TCA Grade. Synthetic samples were generated in the laboratory
as indicated in Section 3. 2. Laboratory samples were varied from 0. 57
to 113.2 jig/rn 3 (as Hg) in concentration. Collection intervals varied from
7 to 207 minutes in these tests. Analyses of the solid absorbents were all
run in duplicate. The bubbler samples taken at Probe 1 (Figure 3-11) were
also analyzed in duplicate. The average value of the mercury trapped by
these iodine monochloride bubblers is included in Table 2, which summa-
rizes the operating parameters and the results obtained.
The results of the tests have been represented in Figure 3-22
with a log-log plot of the canister concentrations plotted against the re-
sults obtained from the source bubbler sample taken above the canister.
The results for the data fall appropriately, on the 45° line indicating rio
noticeable bias in collection of organic mercury in either the ICl bubbler
or the charcoal. The average recovery of dimethyl mercury was 96. 3%;
the standard deviation of the recovery was ± 11.5%.
If the runs at (CH 3 ).Hg levels ‘1 pg/rn 3 are considered ex-
clusively, the collection efficiency defined as
Recovery of (CH 3 )2 Hg from charcoal
x 100%
Recovery of (CH 3 )2 Hg from source bubbler
3-47
-------
Duration
(mm)
10
7
8
26
r
41
45
95
139
207
Average
Total Air
Sampling
Rate(CFM)
24. 0
24. 0
24. 0
24. 0
24. 0
24. 0
24. 0
24. 0
24. 0
24. 0
Table 2
Collection of Dimethyl Mercury
Organic
Mercury Analysis
Individual
Tests Average
(pg/rn 3 ) (pg/rn 3 )
29.8 30.5
31.2
4.4 4.8
5. 2
35.0 36.7
38. 4
3.8 3.8
3.8
2.4 2.4
2. 4
105.0 110.4
115.8
114.9 114.9
114. 9
1.48 1.61
1. 74
0.42 0.48
0.54
0.42 0.49
0.56
Average
Canister
Air Sampling
Rate (1/mm)
Air
Sample
Temp (OF)
Air
Sample
Humidity
(RH)
Source
Analysis
(pg/rn 3 )
%
Recovery
Source
Air Flow
Rate
(mi/mm)
9.5
73
33
28.4
107.4
400
9.5
71
35
5. 1
94. 1
400
9. 5
73
35
32. 5
112. 9
400
9. 5
74
35
4. 3
88. 4
100
9. 5
71
41
2. 2
109. 1
60
9.5
77
42
113.2
97.5
60
9.5
70
51
111.1
103.4
60
9.5
77
48
1.82
83.9
40
9.5
78
46
0.60
80.0
60
9.5
75
51
0.57
86.0
20
Average
Recovery
96. 3%
% Standard
Deviation
11. 4%
=
-------
Figure 3-22
Collection of Dimethyl Mercury on Charcoal
r
/
/
100
/
/
/
/
/
/
/
/
lv
0 +)
/
—
o
.—
14
cd
4.)
C
ri
/
Cw /
014
C) C.)
,
/
1 /
/
/
/
/
/
/
0 1 10 100
Canister Concentration of Mercury
(micrograms /meter 3 )
3-49
-------
averages 100. 1%. However, the standard deviation for the recovery is
± 9. 9%. The two determinations obtained at levels less than 1
showed lower recoveries.
In all of the tests indicated, dimethyl mercury collection was
quantitated from the charcoal section of canisters which contained both
absorbents. That is, the 10% Ag/A1 2 0 3 absorbent and the TCA charcoal
were both exposed to the dimethyl mercury vapor in that order. Thus,
the results also indicate that the absorber for elemental mercury does
not extract dimethyl mercury from the gas stream.
On the basis of these data it may be concluded that TCA Grade
charcoal is an effective absorber for organic mercury (Dimethyl mercury)
vapors over a range of concentrations from ambient to those in excess of
100 iig/m 3 . Silver on alumina is not active in extraction of mercury or-
ganics as exemplified by collection of dimethyl mercury from air streams.
3. 3. 4 Collection of Particulate Mercury
Laboratory collection tests for particulate mercury were
carried out with powdered mercuric sulfide diluted in Cab-O-Sil. The
experimental technique has been indicated in Section 3. 2. 5.
Tests varied in duration from 10 minutes to one hour under
conditions where the total final particle loading on the glass fiber filter
varied from 2610 to 19200 pg on the basis of the weight of charge re -
leased into the collector air stream. This is equivalent to a particle
concentration range of 384.2 jig/rn 3 to 471. 1 )lg/m 3 . In terms of HgS
(as Hg) the particle loading on the filters varied from 3 1 pg to 228 pg
or 4. 56 to 5. 59 pg/rn 3 of air. During all experiments, the High-Volume
sampler was operated at 24 CFM.
3-50
-------
Individual run data are collected in Table 3. A plot of charge
weight vs. recovery has been constructed as Figure 3-23. Recoveries for
the tests were centered about the 450 theoretical recovery line, indicating
no experimental bias in the method. Recovery of mercuric sulfide (as Hg)
for the tests averaged 101% with a standard deviation of ± 5. 1%.
On the basis of the results, it may be concluded that low-level
mercury particulate concentrations are determinable by use of the High-
Volume air sampler and the analytical methods outlined in Section 3. 2.
3-51
-------
Table 3
Collection of Particulate Mercuric Sulfide
Total
High - Vol Particulate Particulate
Average Air Charge Charge Collection
Duration Sample Rate to Filter as Hg Temp. Humidity Recovery Efficiency
(mm.) (CFM) (rig) ( ig) (OF) (RH) (21g-Hg) (%)
10 24.0 2610 31 72 35 29 94
10 24.0 2610 31 72 38 34 110
25 24.0 5305 63 75 42 66 105
25 24.0 5305 63 74 43 68 108
60 24.0 16000 190 72 52 194 102
60 24.0 16000 190 73 55 192 101
60 24.0 18270 217 73 57 210 97
60 24. 0 18270 217 75 60 220 101
60 24.0 18270 217 74 48 230 106
60 24.0 19200 228 72 49 230 101
60 24.0 19200 228 70 50 230 101
0 Blank 1
Average Coil. Eff. 101%
% Standard Deviation 4. 9%
1
-------
Figure 3-23
Collection of Particulate Mercury
on
Glass Fiber Filters
jig of Mercury particulates/test Recovery
3-53
Charge pg of Hg
Particulates per
Test
.:.,t.:.:. - -
— -t
.
TT .:.
Tfl:...
..:j:.TT
I
.::E1:::
•
—L :1 ._r:_
__
...;
—
;-
=
-
—
:
—. -—
- -
—---
. -
.
: .
—
—
—
V
—
•
-- --
/
-- - — -
V
— —
- ----1-
—
4-
, - - —r-
—
,
.. -
——
I
__ L___
-:::4::: . -. . - . ::
— — -— -4—-
:::
-H -
—
-
- —
:: .I /
/
-/ -
-
-
.. V
- ---- - -
—-- -— ± I —-
i
- --
----—- ---1-
111 1 1_III1ILIIiIE
I
- ““
Iti IiIIII
i . .—,
1
-t-- -H-
tff t
----
V.-
240
220
200
180
160
14Q
120
100
80
60
40
20
0
20 40 60 80 100 120 140 160 180 200 220 240
-------
3. 3. 5 Tests for Effects by Interferences
3. 3. 5. 1 Introduction
Tests for the effects of interferences were carried out utilizing
simultaneous collection of elemental and dimethyl mercury from syntheti-
cally generated inputs. In addition, the candidate interferences, hydrogen
sulfide, sulfur dioxide and nitrogen dioxide were metered in at concentra-
tions of 1. 2, 5. 0 and 3. 2 PPM, respectively.
In the conduct of these experiments, initial tests were run with
two bubblers monitoring the inlet gases at the position of Probe 1 in Figure
3-11. That is, a bubbler containing 0. iN iodine monochloride was set up
to sample for total mercury in the air stream, while the nitric acid-per-
manganate bubbler was installed for measurement of elemental mercury
input. It became rapidly apparent that canister recoveries based on anal-
yses of the iodine monochioride bubblers were too high, leading to the not
surprising conclusion that the performance of iodine monochioride as a
collection medium particularly in the presence of SO 2 was erratic. Thus,
another procedure for calibrating the input of elemental mercury and di-
methyl mercury in the presence of the added, interfering gases was de-
vised. Basically, it consisted of setting up separate experiments with
each of the vapor sources while excluding the interfering gases and the
canister collectors from the apparatus. Thus, at least four determin-
ations of the inputs of elemental mercury and dimethyl mercury were
made separately under each set of conditions planned for the interference
tests. Dimethyl mercury was determined by analysis of the iodine mono-
chloride collector. For the analysis of elemental mercury, the acidic
permanganate medium was used. For elemental mercury the vapor
3-54
-------
concentration was adjusted by varying the temperature of the vaporizer!
generator (Figure 3-13). Dimethyl mercury was varied by addition of
methanol solutions of varying concentrations to the source bubbler (Page
3-21). The average values obtained under the appropriate set of gener-
ator conditions were recorded as the vapor source concentration. In
Tables 4, 5 and 6 the columns headed, “Organic Mercury Source’ 1 and
“Elemental Mercury Source” contain the vapor concentrations determined
prior to the test with the interferences.
3. 3. 5. 2 Effects of Hydrogen Sulfide
The data obtained in a series of tests of collection of elerrien-
tal mercury and dimethyl mercury by the canister method in the presence
of 1. 2 PPM hydrogen sulfide are tabulated in Table 4. Tests were con-
ducted for 46-50 minutes under flow conditions of 24 CFM through the Hi-
Vol sampler. Of the total air flow 8. 0 1pm was diverted through the can-
ister collectors. Dimethyl mercury-elemental mercury concentration
pairs which were used were (1) 1. 75 Mg/rn 3 (CH 3 ) 2 Hg with 2. 2 pg/rn 3
elemental mercury, (2) 3.75 pg/rn 2 (CH 3 ) 2 Hg with 10.5 ftlg!m 3 elemental
Hg and (3) 44.5 pg/rn 3 (CH3) 2 Hg with 300 pg/rn 3 elemental mercury. These
three pairs of concentrations were tested four times each.
The twelve tests evidenced an average recovery of total mer-
cury from both sources of 98. 2% ( a = ± 5. 0%). Elemental mercury re-
covery was 99. 6% (a = ± 6. 1%). Dimethyl mercury recovery was 92. 8%
(a ± 6. 0%). From these data it may be concluded that the presence of
hydrogen sulfide is without effect on the collection of elemental mercury
by the silver falumina absorbent. The significance of the slightly low
recovery of dirnethyl mercury on charcoal is not determinable.
3-55
-------
Table 4
Collection of Elemental and Organic Mercury in Presence of I. 2PPM Hydrogen Sulfide
Air Air
Dura- Average Air Canister Sample Sample IC1 Source KMno 4 -HNO Organic Hg Elern Hg Canister Analysis %
tion Sampling Rate Air Sampling Humidity Temp. Bubbler Anal Bubbler Anal Source Source Elem Hg Organic Hg Recovery Recovery Recovery
(mm.) Hi-Vol (CFM) Rate (1pm) (RH) (OF) ( pg/rn 3 ) (pg/rn 3 ) (pg/rn 3 ) (pg/rn 3 ) (pg/rn 3 ) (pg/rn 3 ) (Total) (Elemental) (Organic)
50 24.0 8.0 38% 72°F 3. 52 1.75 2.2 2.06 1.66 94.2 93.6 94.8
50 24.0 8.0 40 70 3.52 1.75 2.2 2.42 1.66 103.2 110.0 94.8
50 24.0 8.0 38 73 3.40 1.75 2.2 2.06 1.59 94.2 92.4 90.9
50 24.0 8.0 36 71 3.47 1.75 2.2 2.22 1.65 98.0 100.9 94.3
47 24.0 8.0 39 77 13. 5 3.75 10.5 10.8 3.70 101.8 102.9 98.7
g 47 24.0 8.0 40 76 15.1 3.75 10.5 10.7 3.62 101.2 101.9 96.5
47 24.0 8. 0 42 75 10. 0 3.75 10. 5 9. 9 3. 40 93.3 94. 3 90. 7
47 24.0 8.0 44 73 10.6 - 3. 75 10. 5 10. 4 3. 53 97.8 99. 0 94. 1
46 24.0 8.0 45 75 356.5 327.7 44.5 300 311.6 38.2 101.5 103.9 85.8
46 24.0 8. 0 42 74 339. 1 308.2 44. 5 300 325. 4 46. 3 107.9 108. 5 104.0
46 24.0 8.0 48 72 277.2 277.2 44.5 300 273.8 38.2 90.6 91.3 85.8
46 24.0 8.0 46 75 202.2 281.1 44.5 300 289.2 36.7 94.6 96.4 82.5
Average %Recovery 98.2 99.6 92.8
Standard Deviation 5.0 6.1 6.0
-------
Table 5
Collection
of
Elemental and
Organic Mercury
In
Presence
of 5. OPPM SO 2
Dura-
tion
(mm.)
Average Air
Sampling Rate
Hi-Vol (CFM)
Canister
Air Sampling
Rate (1pm)
Air
Sample
Humidity
(RH)
Air
Sample
Temp.
(OF)
IC! Source
Bubbler Anal
(pg/m 3 1
KMno4 HN
Bubbler Anal
(pg/rn 3 )
Organic
Source
( g/m 3 )
Hg
Elem Hg
Source
(pg/rn 3 )
55
24.0
8.0
41%
71°F
5.96
3.53
1.93
3.7
55
24.0
8.0
38
74
5.59
3.75
1.93
3.7
55
24.0
8.0
40
72
2.91
2.47
1.93
3.7
55
24. 0
8.0
42
72
2. 73
2. 52
1. 93
3. 7
U I
,i
-1
44
44
44
24.0
24.0
24.0
8.0
8.0
8.0
36
39
42
76
78
72
377.3
359. 1
231.8
303.4
276. 1
204. 5
46.7
46. 7
46. 7
300
300
300
44
24.0
8.0
37
74
211.4
177.3
46.7
300
Canister Analysis %
Elem Hg Organic Hg Recovery Recovery
(pg /m 3 ) ( g / m 3 ) (Total) (Elemental )
3. 59 2. 02 99. 6 97. 0
4.14 1.93 107.8 111.9
3. 26 1. 76 89. 2 88. 1
3.65 1.98 100.0 98.6
333.0 55.4 112.0 111.0
324.0 51.7 108.4 108.0
270.0 43. 7 90. 5 90.0
257.4 51.7 89. 1 85.8
R e cove ry
(Organic)
104. 7
100.0
91.2
102. 6
118.6
110.7
93.6
110.7
Average %Recovery
99.6
98.8
104.0
Standard Deviation
9. 3
10. 5
9. 2
-------
Table 6
Collection of Elemental and Organic Mercury in Presence of 3. ZPPM NO 2
Air Air
Dura- Average Air Canister Sample Sample IC1 Source KMno4 HNO 3 Organic Hg Elem Hg Canister Analysis To To
tion Sampling Rate Air Sampling Humidity Temp Bubbler Anal Bubbler Anal Source Source ElemHg Organic Hg Recovery Recovery Recovery
( mm.) Hi -Vol(CFM) Rate (1pm) (RH) (OF) (pg/rn 3 ) (pg/rn 3 ) (jig/rn 3 ) (pg/rn 3 ) ( pg/rn 3 ) (pg/rn 3 ) (Total) (Elemental) (Organic )
45 24.0 8.0 38 76°F 8. 00 6.04 1.94 6.6 6.22 1.89 95.0 94.2 97.4
45 24.0 8.0 42 74 8. 50 6.98 1.94 6.6 6.92 1.89 103.2 104.8 97. 4
45 24.0 8.0 45 77 8.10 6.20 1.94 6.6 6.45 1.87 97.4 97.7 96.4
45 24.0 8.0 46 71 8.72 6.42 1.94 6.6 6.64 1.67 97.3 100.6 86.1
45 24.0 8.0 45 75 357.8 316.7 45.3 300 318.6 47.4 106.0 106.2 104.6
45 24.0 8.0 47 73 382. 2 323. 3 45. 3 300 325.6 54.2 110. 0 108. 5 119.6
45 24.0 8.0 48 77 335. 5 300.0 45. 3 300 295. 7 44.3 98. 5 98.6 97. 8
45 24.0 8.0 36 79 345. 5 296. 7 45. 3 300 298.7 47.4 100. 2 99.6 104.6
Average%Recovery 101.0 101.3 100.5
Standard Deviation 5. 1 4. 8 9. 6
-------
Tentatively, a small inhibiting effect may be indicated by this result; on
the basis of the SO 2 and NO 2 results, the low (92. 8% ± 6. 0%) result appears
more probably an artifact of the experimental techniques.
3. 3. 5. 3 Effects of Sulfur Dioxide
A series of tests, similar to those run to test the collection
of elemental mercury on 10% silver on alumina and dimethyl mercury on
Barneby-Cheney TCA activated charcoal, respectively, in the presence
of hydrogen sulfide, were run in the presence of 5. 0 PPM of sulfur dio-
xide. Table 5 is a tabulation of the results. As before, a High-Volume
sample air flow rate of 24 CFM was used. Air at a rate of 8. 0 1pm of the
total was diverted through the canisters. The total recovery of both forms
of mercury by the canister averaged 99. 6% (a 9. 3%); elemental mercury
averaged 98.8% (a 10.5%); dimethyl mercury recovery was 104. 0%
(a =9. 2%). Under the conditions of the calibration, it was possible to
ascertain that neither the iodine monochloride nor nitric acid-permari-
ganate bubblers performed adequately in the presence of SO 2 . While
for iodine-monochloride this result conforms with previously published
results, the performance of the acid permanganate system is not explained.
On the basis of these data it may be concluded that the two
component absorbent canister performs effectively to remove elemental
mercury and dimethyl mercury from air in the presence of SO 2 . These
results are an improvement over the performance of the bubblers under
the same conditions.
3. 3. 5. 4 Effects of Nitrogen Dioxide
The canister collection system was further tested under the
same operating parameters in the presence of 3. 2 PPM of nitrogen
3-59
-------
dioxide. The data are compiled in Table 6. Total recovery was 101. 0%
(o=5. 1%); elemental mercury recovery averaged 101.3% (a= ± 4.8%);
dimethyl mercury recovery was 100. 5% (c 9. 6%). In addition, both the
iodine monochioride and acid permanganate bubblers performed very well
in the presence of NO 2 .
3. 3. 5. 5 Summarized Effects of Interferences
No effects of potential interferences are determinable oct the
basis of the data obtained in collection of elemental and dimethyl mercury.
by the canister technique in the presence of H 2 S, SO 2 and NO 2 . Three
sets of collection data are shown in Tables 7, 8 and 9. In Table 7, total
mercury recovery as determined by canister is recorded against calib-
ration levels in the presence of all three potential interferences. One
hundred percent collection efficiency is approached in the presence of
H 2 S, 502 and NO 2 . A similar treatment of the data for elemental mer-
cury recovery on 10% silver-alumina has been constructed in Table 8;
dirnethyl mercury recovery on charcoal is illustrated in Table 9. Con-
clusions for the latter are the same as for total Hg recovery. These
data individually and collectively confirm the results of Sections 3. 3. 2
and 3. 3. 3 which were obtained during separate collection of elemental
mercury and dimethyl mercury.
Averaging the resuits for all the 28 tests the following re-
coveries were achieved. The results are based oct the values obtained
by the indicated calibration procedures:
Recovery Standard Deviation
TotalMercury 99.4% ±6.3%
Elemental Mercury 99. 9% ± . 0%
Dimethyl Mercury 98. 2% ±7. 9%
3-60
-------
Table 7
Recovery of Elemental and Dimethyl Mercury by
Canister Absorbents in the Presence of H 2 S, SO 2 and NO 2
Concentration of
Hg arid (CH 3 ) 2 Hg Recovery by
Gas in Source Canister Absorbents
Added ( pg/rn 3 ) ( j ig/rn 3 )
H 2 S 3.95 3.72
(l.2PPM) 3.95 4.08
I I 3.95 3.65
3.95 3.87
II 14. 25 14. 50
I’ 14.25 14.32
14. 25 13. 30
14. 25 13. 93
344.5 349.8
I, 344.5 371.7
It 344.5 312.0
II 344.5 325.9
So. 2 5.63 5.61
(5. OPPM) 5.63 5. 07
II 5.63 5.02
5.63 5.63
1 346. 7 388. 4
U 346. 7 375. 7
346.7 313.7
346. 7 309. 1
NO 2 8.54 8.11
(3.2PPM) 8.54 8.81
8.54 8.32
H 8.54 8.31
It 345. 3 366. 0
I’ 345. 3 379. 8
II 345. 3 340. 0
‘I 345. 1 346. 1
Average Recovery (%) - 99. 2
Average Standard Deviation C ‘ %) ± “ 0
3-61
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Table 8
Recovery of Elemental Mercury by 10% Silver on Alumina
in the Presence of H 2 S, SO 2 and NO 2
Concentration of
Elemental Hg in Recovery by
Gas Source Silver-alumina
Added (jig/rn 3 ) (pg/rn 3 )
H 2 S 2.20 2.06
(1.2PPM) 2.20 2.42
2.20 2.06
1 2.20 2.22
‘I 10.5 10.8
10.5 10.7
I I 10.5 9.9
10.5 10.4
U 300.0 311.6
It 300. 0 325. 4
H 300.0 273.8
II 300.0 289.2
SO 2 3.70 3.59
(5. OPPM) 3. 70 4. 14
II 3.70 3.26
3.70 3.65
300.0 333.0
I’ 300.0 324.0
II 300.0 270.0
300.0 257.4
N02 6.60 6.22
(3.2PPM) 6.60 6.92
6.60 6.45
6.60 6.64
“ 300.0 318.6
300. 0 325. 6
II 300. 0 295. 7
II 300.0 298.7
Average Recovery (%) - 99.9
Average Standard Deviation ( a ,%) ± 6.3
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Table 9
Recovery of Dimethyl Mercury
by Charcoal (TCA, Barneby-Cheney)
in Presence of H 2 S, SO 2 and NO
Concentration of Recovery by
Gas (CH 3 ) 2 Hg in Source Charcoal
Added ( g ig/rn 3 ) ( g ig/rn 3 )
H 2 S 1.75 1.66
(1.2PPM) 1.75 1.66
1 1.75 1.59
1.75 1.65
II 3.75 3.70
3.75 3.62
3.75 3.40
II 3.75 3.53
tI 44.5 38.2
U 44.5 46.3
It 445 38.2
44.5 36.7
SOZ 1.93 2.02
(5.OPPM) 1.93 1.93
1 1.93 1.76
1.93 1.98
I’ 46.7 55.4
1 46.7 51.7
it 46.7 43.7
U 46.7 51.7
NO 2 1.94 1.89
(3.2PPM) 1.94 1.89
I’ 1.94 1.87
II 1.94 1.67
II 453 47.4
H 45.3 54.2
II 45.3 44.3
II 453 47.4
Average Recovery (%) - 98. 2
Average Standard Deviation ( a, %) ± 7. 9
3-63
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In conclusion, the canister collector utilizing 10% silver on
alumina and TCA Charcoal does provide a simple method for sampling
both ambient atmospheres and severely contaminated environments for
all forms of mercury.
3. 3. 6 Environmental Tests
3.3.6.1 Results
A series of tests of the environment at the GEOMET Pomona
Laboratory were carried out as a complete check of the collection and
analytical methodology under normal ambient conditions. These tests
were conducted over sampling intervals ranging from 7 to 24 hours with
the High-Volume sampler operating at 24 CFM. Three positions were
selected for tests: (1) a doorway leading to the external atmosphere, (2)
a shop area and (3) the laboratory in which the mercury experimentation
and analysis was conducted. Table 10 is a compilation of the data.
The initial ambient tests were conducted in the laboratory
where the reagents for the program were stored. Air was pulled through
the canisters at 9. 5 1/mm. The air was also sampled by an iodine mono-
chloride bubbler for these runs. Analysis of the canisters showed 0.022-
0.028 ( ig/m 3 ) of elemental mercury and 0.015-0. 026 ( ig/m 3 ) of combined
mercury (as Hg). For these tests, the iodine monochloride estimates of
total mercury were 0. 043-0. 049 ( tg/m 3 ). No particulate mercury was
detectable above the values determined as blanks.
Average analysis of the glass fiber filters shows a blank value
of 0. 67 jig as Hg. A value of 0. 05 jig of collected Hg particulates has been
selected as the detection threshold. In terms of the air sampled this value
has been expressed in various terms, i. e., for a 24 hour sample (978m 3 )
3-64
I1
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Table 10
Ambient Tests at GEOMET Pomona Laboratory
Canister Analyses Particle High-Vol Canister Air Independent
Duration Elem. Hg Comb. Hg Hg Anal. Air Sampling Air Sampling Temperature Humidity Hg Anal
Location (mm) (pg/rn 3 ) (pg/rn 3 ) (ug/m 3 ) Rate (CFM) Rate (1/rn) (°F) (RH) (ug/m 3 )
External
Doorway 1440 0.010 0.003 <5x10 5 24.0 8.0 48-70 21-68
1 1440 0.016 <0.003 <5x10 5 24.0 8.0 42-62 35-62 -
1440 0.021 <0.003 3.0x10 4 24.0 8.0 55-75 31-42 22. 7°
(14. 7-28. 1)
1 1440 0.015 <0.003 4.6x10 4 24.0 8.0 52-77 35-38 18.9°
(15.2-27.2)
1440 0.017 <0.003 7x10 5 24.0 8.0 50-74 35-50
(11.5-16.5)
1 1440 0.024 <0.003 l.7x10 4 24.0 8.0 52-77 36-42 16.9**
(12.2-21.0)
1440 0.013 <0.003 9.2x10 4 24.0 8.0 55-75 32-53 17.40*
(11.8-22.2)
1440 0.019 <0.003 l.2x10 3 24.0 8.0 51-75 30-47 18.20*
(11.7-25.0)
ShopArea 480 0.044 <0.003 1.5x10 4 24.0 8.0 70-73 52-60
ShopArea 480 0.044 <0.003 1.5x10 4 24.0 8.0 71-74 41-51
ShopArea 420 0.049 <0.003 1.7xlO 4 24.0 8.0 70-76 45-55
ShopArea 420 0.025 <0.003 l. 7 x10 24.0 8.0 69-72 33-39 -
Laboratory 480 0.023 0.016 1.5x10 4 24.0 9.5 75-77 51-59 0.049*
0.023 0.026
Laboratory 960 0.022 0.015 8x 10 5 24.0 9.5 73-75 45-49 0.043*
0.028 0.021
IC1 bubbler
by GEOMET Model 103 Air Monitor, average values. Values in parentheses are extremes of results obtained in 30 minute analyses.
-------
0. 05 jig is equivalent to 5 x l0 pg/rn 3 . For shorter determinations the
threshold is larger. Values for various sampling intervals are tabulated
in Column 5 of Table 10.
Determinations of mercury vapor concentrations in the shop
area indicated that the entire mercury content of the air was due to ele-
mental mercury. Values from 0.025 to 0.049 pg/m 3 of elemental mer-
cury were encountered. No determinations by other techniques were made
simultaneously.
A number of twenty-four hour tests were carried out in an
external doorway leading from the shop area to outdoors. In most of
these tests, independent evaluations of the mercury level were made by
use of the GEOMET, Model 103, Mercury Air Monitor. Elemental mer-
cury levels ranged from 0.010 to 0.024 jig/rn 3 in determinations by the
High-Volume method. No organic mercury above the blank was detect-
able. Particulate mercury ranged from 5 x l0 to 1. 2 x pg/rn 3
despite a moderately heavy dust loading on the glass fiber filters. The
GEOMET Model 103, set-up to measure elemental mercury exclusively
showed mercury levels varying from 0.0154 to 0.0227 pg/rn 3 on the aver-
age. The Model 103 sampled air at 18 1/mm. and produced a print-out
every 30 minutes during these operations.
3.3.6.2 Detectability Limits
In establishing the analytical methodology, calibrations of the
methods were established against samples of elemental mercury vapor and
dimethyl mercury in methanol solutions. The calibration samples were
added to the appropriate absorbent (i. e., 10% Ag on alumina in the case
of Hg vapor and TCA charcoal in the case of dimethyl mercury) and the
3-66
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entire extraction and combustion procedures were carried out. The use
of a soluble mercury standard added at the reduction step was generally
avoided.
On the basis of this full analytical procedure, it was deter-
mined that a collection of approximately 30 nanograms of mercury on an
absorbent (24 ml volume) represented a reliable detection threshold above
the blank values normally observed. That is, an absolute quantition of 30
nanograms of mercury added to the 10% silver-alumina absorbent could
be successfully determined with a standard deviation of an average result
of 10%. Thus, at a sampling rate of 8. 0 1/mm. through the canister,
levels of elemental mercury equivalent to 2. 6 nanograms per meter 3 are
detectable in 24 hour collection cycles. This value represents the de-
tection threshold. As in the case of the particulate detection threshold,
the value in terms of jig/rn 3 , varies with the amount of air collected.
The threshold for organic mercury is somewhat higher than
that for elemental vapor. The analytical procedure for charcoal utilizes
only one gram of material, representing 8.7% of the total canister charge,
whereas the elemental analysis utilizes 10 grams, which is 43% of the
total. Thus, the organic threshold is approximately 13 nanograms per
meter 3 in a 24 hour collection cycle.
3. 3. 7 Environmental Effects
During all portions of the experimental testing of the canister
method, values of the ambient temperature and relative humidity were
ompiled. Temperatures ranged from 42 to 81°F at the collection sites;
relative humidity varied from 21 to 68%. In the ambient tests described
in Section 3. 3. 6, temperature and humidity variations were relatively
3-67
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large over a period of 24 hours.
In no case was the efficiency of the collection process demon-
strably affected by these environmental variations.
3. 3. 8 Transportability of Samples
In order for the canister method of collection of mercury
samples to have field utility, samples must be mailable to a central labor-
atory in convenient packaging which is adequate to protect sample integrity
for relatively long periods of time. As a test of transportability, canisters
containing controlled amounts of mercury were mailed across country and
back in standard 13. 33 x 4. 45 cm mailing tubes. A common place 7. 62 x
35. 56 cm polyethylene bag* was used as an inner wrapping during the mail-
ing operation.
One blank canister containing no added mercury and one canister
which contained 29 nanograms of elemental mercury per gram of silver -
alumina absorbent and 29 nanograms of dimethyl mercury (as [ -ig) per gram
of TCA charcoal were sent.
Inspection at the end of the first portion of the trip showed that
one end of one mailer had been indented. However, the inner packaging
was intact. Some charcoal fines were visible in the inner envelope. Re-
turn to the point of origin was accomplished without damage. Thus, the
samples had been mailed a distance of approximately 6, 000 miles.
* Available from Bradley’s Plastic Bag Company, Downey,
California 90241, as Stock No. 3l4C, size 3 x 14 inches.
3-68
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Analysis on return of the canisters to the laboratory showed:
Return Start
Blank Canister
Ag/A1 2 0 3 Absorbent <1. 25ng/g < 1. 25ng/g
Charcoal Absorbent
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In testing absorbents during Contract No. 68-02-0578, ele-
mental mercury at levels of 100 pg/rn 3 was passed through a 6% Ag on
alumina preparation at flow rates of 20 CFM for 24 hours. Intermittent
sampling showed 99. 4% efficiency at the end of that period. In this test,
a total of-- 81.5 mg of mercury was passed through 800g of absorbent
without breakthrough. Or, in other units,’O. 1 mg of Hg/g of absorbent
was retained.
Interpolating the same figures to the scale utilized in the
current program, more than 2. 445 mg of mercury would be absorbable
in the 24 ml (24g) bed of silver/alumina absorbent. However, under the
conditions of current usage: 8 1/mm. flow @ 100 pg/rn 3 , 1. 15 mg of mer-
cury would be passed through the miniaturized bed in 24 hours. This is
less than one-half the amount retained by the 6% Ag/Al 2 0 3 preparation.
Thus, the current 10% Ag/A1 2 0 3 preparation should have an operating
capability well in excess of 24 hours at exposure levels of 100 pg/rn 3 .
The high efficiency-high capacity characteristics are the
major advantage of preparations of the type tested: silver on high surface
area supports.
3-70
4 j
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TECHNICAL REPORT DATA
(Please read IRSzrucnons on the reverse before completing)
1 REPORT NO.
EPA—650/2—75—028 12. •
3. RECIPI ENTS CCESSIOFNO.
4. TITLE AND SUBTITLE
IrnprovenEnt of InstnutEntation and Methodology for
Collection and Analysis of Mercury
5. REPORT DATE
Jan. 1975 Publication
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
D. J. Sibbett, R. H. Meyer, and T. R. Quinn
8. PERFORMING ORGANIZATION REPORT NO.
IF - 434
9 PERFORMING ORGANIZATION NAME AND ADDRESS
Geat t, Incorporated .
2814—A Metropolitan Place
Patona, California 91767
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68—02—1282 -
DRESS
12 SPO .ISORING AG
chemistr r A :atory
Environmental Protection Agency
Research iangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final, pril-Sept. 1974
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
,
16. ABSTRACT
A collection device for the sampling of atnospheric mercury in its three forms,
previously developed under EPA contract 68-02-0578, was miniaturized and streamlined
and methods for the recovery and analysis of the collected mercury were simplified.
The device consists of a t -section canister assembly which fits inside a
standard Hi-Vol sampler underneath the support screen for the particulate filter.
While particulate mercury is collected in the usual manner on glass fiber filter,
mercury vapors are trapped on specific absorbants, i.e. elemental mercury on silver-
impregnated alumina in the upper canister section and canbined mercury vapors on
charcoal in the lower section. With the Hi-Vol operating at 24 CEll, an airflow of
8 - 9.5 l n was obtained through the canister.
Recoveries averaged 101% for particulate mercury, 104% for elemental mercury
and 96.3% for organic mercury compounds. Gaseous *llutants such as SO 2 , NO 2 or H 2 S
did not affect the collection efficiency.
procedures have been developed and tested for the recovery and analysis of
elemental mercury, dimethyl mercury and mercury-bearing particulates. These methods
utilize standard laboratory instrumentation including an induction combustion
furnace and an atomic absorption spectrophotat ter. Thern precision of the methods is
indicated by the standard deviation of the results which is in the ± 6-8% range.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
C. COSATI Field/Group
Mercury
Air Pollution
Sampling
Particles
Vapors
analyzing
18 DISTRIBUTION STATEMENT
Release Unlimited
19 SECURITY CLASS (This Report)
Unclassified
21. NO OF PAGES
20 SECURITY CLASS (Thispage)
Unclassified
22 PRICE
EPA Form 2220-I (9.73)
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