Sample Collection, Analytical Methods, and Data Interpretation for Mercury Analyses


In Reply Refer To:                              February 15, 1994
Mail Stop 412

OFFICE OF WATER QUALITY TECHNICAL MEMORANDUM 94.10

Subject:  Sample Collection, Analytical Methods, and Data
          Interpretation for Mercury Analyses

                          PURPOSE

The purpose of this memorandum is to inform Division personnel
that determinations of aqueous mercury should be carefully
evaluated prior to interpretation and publication.

                         BACKGROUND

Recently, a number of hydrologic studies have been conducted on
aqueous mercury that have  adapted previously developed clean
protocols (Patterson and Settle, 1976; Bloom and Crecelius, 1983;
and Bloom, 1989) for the field and laboratory.  The studies have
covered streams and rivers (Southworth and others, 1992; Hurley,
Andren, and others, 1994), lakes (Fitzgerald and Watras, 1989;
Lent and Krabbenhoft, unpublished data, 1991-93), and ground
waters associated with lakes (Lindqvist and others, 1991;
Krabbenhoft and Babiarz, 1992; Hurley, Krabbenhoft, and
others, 1994).  These studies have demonstrated that for surface
waters, the mercury concentrations in remote, unpopulated areas are
generally less than 10 nanograms per liter (ng/L) (see
table 1).  In comparison, during 1986-1990, mercury levels
measured at the NASQAN Program sites using standard field and
laboratory methods ranged up to 41,000 and 61,000 ng/L,
respectively, for filtered and unfiltered samples.  At Benchmark
Program sites, the maximum values using standard methods were
11,000 (filtered) and 300 (unfiltered) ng/L.

The current reporting limit for mercury at the National Water
Quality Laboratory (NWQL) is 0.1 microgram per liter (ug/L)
(100 ng/L).  Only about 5 percent of the samples annually
submitted to the NWQL for mercury analyses show values above
the reporting limit.  Because of the reported findings of the
clean protocol studies, samples which exceed the NWQL reporting
limit for mercury should be regarded with caution.  These mercury
concentrations may result from contamination from a variety
of sources during sample collection, field processing, and
laboratory handling and analysis.

Mercury is unique among trace elements in its physical-
chemical characteristics and sources of contamination.
Therefore, mercury is not covered in the new Protocol for
Collecting and Processing of Surface-Water Samples for Subsequent
Determination of Trace Elements, Nutrients, and Major Ions in
Filtered Water, Office of Water Quality (OWQ) Technical
Memorandum No. 94.09.

                            ACTIONS

The OWQ and NWQL are exploring two alternatives to enable
the Division to obtain accurate, low-level measurements of
mercury. These are:

1. Develop and implement Division field and laboratory
protocols to acquire low-level mercury data.  This alternative
would include specification of supplies and suitable cleaning
procedures for both the field and the NWQL, and suitable
training for the Division on the protocols.

2. Seek a commercial source of precleaned, one-use, prepackaged
supplies for collecting and processing mercury samples, plus
a contract laboratory to run low-level mercury analyses.
For this alternative, the OWQ would develop an abbreviated
field protocol to support use of the supplies and provide
training on using the protocol.  The NWQL would develop and
monitor contracts for both the supplies and analyses.

As the OWQ and NWQL select and implement an alternative,
Division personnel should observe the following guidelines
for sample collection and measurement of mercury in water:

1.  Collect water samples for mercury analyses according to OWQ
Technical Memorandum No. 94.09.  Although the protocol is not designed
to include mercury, using the protocol should reduce the amount of
contamination that now occurs in water samples collected for mercury
analysis.

2.  Develop a quality-assurance plan for all mercury work consistent with
project data quality objectives and the capabilities of Division-approved
field and laboratory methods to determine mercury.  Pay particular attention
to using equipment blanks and field blanks to determine the possibility of
contamination from equipment, supplies, sample collection, and sample
processing.  Guidelines for developing quality-assurance plans are provided
in Shampine and others (1992).

3.  When sample results from the NWQL are reported at > 0.1 ug/L, resample
the site (if possible) and also collect equipment and field blanks for
analysis.

4.  Because of the limits of the current Division sampling and analytical
methods, exercise care and be conservative when interpreting mercury
results from water samples.

                           REFERENCES

Bloom, N.S., 1989, Determination of picogram levels of
methylmercury by aqueous phase ethylation, followed by cryogenic
gas chomotography with cold vapour atomic fluorescence detection:
Canadian Journal of Fisheries and Aquatic Science, v. 46,
p. 1131-1140.

Bloom, N.S., and Crecelius, E.A., 1983, Determination of
mercury in seawater at sub-nanogram per liter levels: Mar.
Chemistry, v. 14, p. 49-59.

Fitzgerald, W.F., and Gill, G.A., 1979, Subnanogram determination
of mercury by two-stage gold amalgamation and gas phase detection
applied to atmospheric analysis: Analytical Chemistry, v. 51,
n. 11, p. 1714-1720.

Fitzgerald, W.F., and Watras, C.J., 1989, Mercury in surficial
waters of rural Wisconsin lakes: Total Environment, v. 87/88,
p. 223-232.

Hurley, J.P., Andren, A.W., Babairz, C.L., and Benoit, J.M.,
1994, Mercury and methyl-mercury levels in Wisconsin streams,
Third International Conference on Mercury, July 10-14,
Vancouver, British Columbia, Canada.

Hurley, J.P., Krabbenhoft, D.P., Babiarz, C.L., and Andren, 1994,
Cycling processes of mercury across sediment/water interfaces in
seepage lakes, in  Baker, L.A., editor, Environmental chemistry
of lakes: American Chemical Society, Washington, D.C., in press.

Krabbenhoft, D.P., and Babiarz, C.L., 1992, The role of
groundwater transport in Aquatic Mercury Cycling: Water Resources
Research, v. 28, n. 12, p. 3119-3128.

Lindqvist, O., Johansson, K., Aastrup, M., Anderson, A.,
Bringmark, L., Hovenius, G., Hakanson, L., Iverfeldt, A., Meili,
M., and Timm, B., 1991, Mercury in the Swedish environment-
Recent research on causes, consequences, and corrective methods:
Water Air and Soil Pollution, v. 55, p. 1-261.

Patterson, C.C., and Settle, D.M., 1976, The reduction of orders
of magnitude of errors in lead analyses of biological materials
and natural waters by evaluating and controlling the  extent and
sources of industrial lead contamination introduced during sample
collection,  handling, and analysis, in  Laflaur, P.D., editor,
Accuracy in trace analysis--sampling, sample handling, and
analysis: Special Publication 422,  National Institute of
Standards and Technology, Gaithersburg, Maryland, 1976,
p. 321-351.

Shampine, W.J., Pope, L.M., and Koterba, M.T, 1992, Integrating
quality assurance in project work plans of the U.S. Geological
Survey: U.S. Geological Survey Open-File Report 92-162, 12 p.

Southworth, G.R., Turner, R.R., and Nourse, B.D., 1992, Site-
specific water quality criterion of total mercury in East
Fork Popular Creek downstream from the Oak Ridge y-12 plant:
Report to the Office of Environmental Restoration and Waste
Management, U.S. Department of Energy, Report Y/ER-126.

Turner, R.R., and Lindberg, S.E., 1978, Behavior and transport
of mercury in a river-reservoir system downstream of an inactive
chloralkalai plant: Environmental Science and Technology, v. 12,
p. 918-923.


                    David A. Rickert
                    Chief, Office of Water Quality

Attachment (not included on electronic copy)

This memorandum does not supersede any other Office of
Water Quality Technical Memorandum.

Key Words:  Analytical methods, data interpretation,
            sample collection, mercury

Distribution:  A. B, S, FO, PO, AH