Particulate Organic Carbon

In Reply Refer To:
Mail Stop 412                            April 28, 2000


Subject:  Particulate Organic Carbon

The purpose of this memo is to give early guidance on new National Water
Quality Laboratory (NWQL) methods for determining particulate (suspended)
organic and inorganic carbon in water.  These new methods will be an
alternative to, and ultimately a replacement for the traditional U.S.
Geological Survey (USGS)/NWQL wet-oxidation suspended organic carbon method
(SOC, parameter code 00689, lab code 0305).  A copy of the new analytical
methods is available from the NWQL web site
( in PDF format.

At the same time the new particulate carbon methods are implemented there
will be a change in the sample filtration and preservation procedures for
dissolved organic carbon (DOC) analysis.  The analytical method for DOC
will not change however.  This memo briefly outlines the new methods and
lists the new equipment and supplies needed to collect and process the
samples when the method becomes available. This will enable field
operations to have the necessary supplies on hand when the method becomes

There will be an Office of Water Quality (OWQ) Technical Memorandum
describing the new field sample processing protocol for SOC issued prior to
the implementation of the new SOC method by the NWQL.  This will be
followed by a revision of Chapter 5 of the National Field Manual for the
Collection of Water-Quality Data.


On June 1, 2000, a new analytical method for particulate (suspended) carbon
(PC), parameter code 00694, particulate (suspended) inorganic carbon (PIC),
and parameter code 00688 is scheduled to be available at the NWQL.
Particulate (suspended) organic carbon (POC) is determined in the new
analytical method as the difference between PC and PIC. The new PC
analytical method will require significant changes in type and size of
filter media, filtration unit, number of filters submitted for analysis,
and filter handling procedures.

Also on June 1, 2000, samples for analysis of dissolved organic carbon
samples (DOC, parameter code 00681) will no longer be required to be
filtered using the silver filter. Field and lab studies have shown the
there is no significant difference in dissolved organic carbon content in
samples filtered with a 0.45 micron silver filter, a 0.45 micron capsule
filter, or the 0.7 micron glass fiber filter used for the new PC method.
Samples for DOC analysis may be taken directly from the capsule filter
(Gelman Supor capsule filter, Ocala, Florida, QW Supply Unit part number
Q398FLD).  As an alternative to the capsule filter the filtrate from the
0.7 micron glass-fiber filter can be submitted or the 0.45 micron silver
filters be used.  The DOC sample, except those filtered using a silver
filter, will be preserved using sulfuric acid (Ocala, Florida, QW Supply
Unit part number Q438FLD).  This is the same acid vial currently used to
preserve nutrient samples.


New pressure filtration units to be used with the 25 mm glass fiber filters
can be purchased from Savillex Corporation, 6133 Baker Road Minnetonka,
Minnesota, 55345, and phone number 612-935-5427. The price for the DOC-25
(part number DOC-25) is $175.00 each.  Orders can be placed with the
Savillex Corporation starting on May 1, 2000.


The new PC methods will require a 25-millimeter diameter glass fiber filter
medium that has an effective pore size of 0.7 micrometers. The
"precombusted" or "baked" glass fiber filter media can be ordered from the
USGS ONE STOP SHOPPING?analytical supplies (NWQL) (
Each sample will require three separate filters.


The POC samples need to be packaged for shipment as follows:
     The filter media containing the sample should be folded in half with
     the sample side on the inside of the fold as is currently performed on
     the SOC silver filters. The folded filter should then be wrapped in a
     6-inch x 6-inch aluminum foil square.  The labeled aluminum foil
     envelope is to be put into a small whirl pack bag and then inside a
     larger whirl pack bag for shipment to the NWQL.


    DOC-25 filtration unit--available from Savillex Corporation
    Precombusted" or "baked" 25 mm diameter glass fiber filters--available
through USGS One Stop
        Shopping?analytical supplies (NWQL)
    Aluminum foil?Use only the aluminum foil squares available though USGS
One Stop Shopping?analytical
        supplies (NWQL)
    Small whirl pack bag?One Stop Shopping?water quality supplies (OCALA)
part number Q22FLD
    Large whirl pack bag?One Stop Shopping?water quality supplies (OCALA)
part number Q21FLD
    Two filter media forceps?One Stop Shopping?water quality supplies
(OCALA) part number Q347BACT
    Labeling tape


    Gelman Supor capsule filter?One Stop Shopping?water quality supplies
(OCALA) part number Q398FLD
    Sulfuric acid vial?One Stop Shopping?water quality supplies (OCALA)
part number Q438FLD

                      Janice R. Ward /s/
                      Acting Chief, Office of Water Quality

This memorandum does not supercede any other OWQ Technical Memorandum.

Distribution: All WRD Employees

(See attached file: techmemo.poc.0005)
Janice Ward
Acting Chief, Office of Water Quality
US Geological Survey
Reston, VA