grab samples

(5) Analyze" after" water sample as for" before" water sam pie.
(6) Analyze sediment remaining as for" before" sediment sample.
(7) A physical analysis of the "before" sediment is also necessary (sieve and pipette, -5 to + 9 phi).
This will assist in determining the dispersion qualities of the sediment at the dump site.
V. Analysis
The sediment and water samples from both before and after the elutriate test should be analyzed by the
methods outlined in this manual. A more complete discussion of trace metal analyses in seawater may be
found in such references as: Nix and Goodwin ( 1970), Brewer et al. ( 1969), and Brooks et al. ( 196'7).
Concentration levels of metals in seawater are likely to be low, therefore, solvent extraction will be required
and because of limitations of sample volume and desired detection limits, use of the f1ameless attachment
(only available for some models of atomic absorption spectrometers) is probably necessary. The analysis
for petroleum oils and for pesticides are essentially the same for water samples as for the sediment samples.
Although nutrient analyses have not been included in this manual, the methods for seawater analyses are
outlined in Strickland and Parsons ( 1972) in some detail. It is suggested that dredge material from some
areas should be analyzed for nutrient concentrations (P0 4 -P, NOJ-N, N0 2 -N, NHJ-N) (See Lee et al.
1975 ).
Notes: (a) Dredge material that should be analyzed for nutrients would be sediment from areas near
fertilizer plants or in areas of heavy drainage from agricultural regions.
(b) The whole concept of the elutriate test is still under review, so that the actual procedures may be
altered considerably in the near future.
References
BREWER, P. G., D. W. SPENC'ER, AND C. L. SMITH . 1969. Determination of trace metals in seawater by atomic absorption
spectrophotometry. ASTM Spec. Tech. Publ. 443: 70-77.
BROOKS, R. P., B. J. PRESLEY, AND I. R. KAPLAN. 1967. APDC-MIBK extraction system for the determination of trace elements in saline
waters by atomic absorption spectrophotome try. Talanta 14: 809- 816.
LEE, G. F., M. D. PtWONI, J. M. LOPEZ, G. M. MARIANt, AND J. S. RI CHARDSON. 1975. Research study for the development of dredged
material disposal criteria. U.S. Waterw. Exp. Stn., Vicksburg, Miss., Res. Rep. 75-4: 386 p.
NIX, J., AND T. GOODWtN . 1970. The simultaneous extraction of iron, manganese, copper. cobalt, nickel, chromium, lead and zinc from
natural water for determination by atomic absorption spectroscopy. At. Absorpt. News!. 9: 119-122.
STRICKLAND. J. D. H., AND T. R. PARSONS. 1972. A practical handbook of seawater analysis. 2nd ed. Bull. Fish. Res. Board Can. 167:
310 p.
7.3 Chemical Oxygen Demand
I. Theory
Chemical oxygen demand is a measure of the oxygen equivalent to that portion of the organic matter
in the sediment that is susceptible to oxidation by strong chemical oxidants. Most types of organic matter
can be oxidized by refluxing with a mixture of chromic and sulphuric acids. This method has the
advantages of oxidizability, applicability to a wide variety of sam pies, and ease of manipulation.
II. Summary of Method (APHA et al. 1975)
A sample is combined with potassium dichromate and sulphuric acid and the mixture is refluxed. The
excess dichromate is titrated with ferrous ammonium sulphate. The amount of oxidizable organic matter
measured as oxygen equivalent is proportional to the potassium dichromate consumed.
III. Interferences
Straight-chain aliphatic and aromatic hydrocarbons and pyridine are not oxidized to any appreciable
extent. The straight-chain aliphatics are more readily oxidized by the addition of silver sulphate catalyst.
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