grab samples

SECTION 6
CHEMICAL ANALYSIS
This section describes methods of chemical analysis which can be used to acquire the necessary data
prescribed in the Regulations to the Ocean Dumping Control Act. In some cases, there is more than one method
which can provide the information, and references are given for alternative methods. Many of the methods are
for bulk analysis, so they do not provide information on the chemical species present, reactivity with seawater,
ease of solution in seawater, or relative toxicity. Since elutriate tests are, at present, often required, methods
which are suitable for both sediment and seawater analyses are included.
Other chemical groups may be added to the list of scheduled substances from time to time. The methods
included here are for items included in Canadian legislation as of March, 1977.
For compara tive purposes, values for" rivers, " " typical offshore seawater," and " nearshore sediments"
have been included when available.
It is essential that the results of chemical analyses submitted with applications under the Ocean Dumping
Control Act be placed in context of the precisions and accuracies of the analytical procedures. Estimates of
precision and accuracy assist in assessing the validity of analytical results especially in judging whether the
levels of chemical constituen ts in sediment sam pies exceed the limi t of detection of the method em ployed.
Accuracy can best be determined by the analyses of standard materials having matrices, or composition,
approximating those of the sample material to be analysed. Thus accuracies for sediment analysis for inorganic
constituents are best determined by the analysis of standard rock or sediment samples. Suitable standard rock
samples are now available in Canada from Canada Centre for Mineral and Energy Technology, 555 Booth St.,
Ottawa, Ontario K IA OG I.
Each laboratory submitting data for inclusion in an ocean dumping application should report the basis
upon which they have assessed the accuracy of their procedures.
Precisions should be determined for each batch of samples analysed for a particular application. For the
purposes of the Ocean Dumping Control Act four replicate analyses of a particular sample will suffice. The
precision for each constituent reported can be expressed as the standard deviation of these replicate
determ ina tions.
Laboratories should establish the limits of detection of their procedures. This is needed to avoid reports of
concentrations which are below the sensitivity of the method. It is recommended that the detection limit be
defined as three times the standard deviation of analysis of normal (uncontaminated) environmental samples.
Thus a few analyses ofa normal sediment sample will suffice to estimate the precisions and detection limits for
the constituents to be determined for purposes of the Ocean Dumping Control Act.
6.1 Preliminary Preparation of Sediment Samples
Carry through the following preliminary steps separately for sediments in each of the three sample
containers (See Sections 2.2.2 and 2.2.3) (i.e., samples for inorganics, oils and greases, and pesticides and
organohalogens ).
( I) Ifsamples as received contain much " free" water, allow to stand overnight. Carefully decant any
clear supernatant liquid that may separate.
(2) If clear supernatant does not separate on standing, centrifuge at about 4 000 rpm. Remove any
clear supernatant that may separate.
(3) Washing the sediment sample with distilled water is not generally recommended since some
"fines" may be lost in the washing process with possible loss of contaminants. In some cases, however,
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