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I <br />38 JOSEPH B. HUNN AND ROSALIE A. SCHNICK <br />Table 4.6. Recommended quantities, containers, preservation techniques, and holding times for sediment <br />samples to be analyzed for selected variables (modified from Tetra Tech 1986). <br /> <br /> <br />Variable <br />Minimum sample <br />size (g)a <br /> <br />Containerb <br /> <br />Preservation Maximum <br />holding time <br />(d = day; m = month) <br />Particle size 100-150 P,G Cool, 4° C 6 and <br />Total solids 50 P,G Freeze 6 and <br />Total volatile solids 50 P,G Freeze 6 and <br />Total organic carbon 25 P,G Freeze 6 and <br />Oil and grease 100 G only Cool, 4° C, HCl; 28 dd <br /> Freeze 6 and <br />Total sulfides 50 P,G Cool, 4° C, 7 dd <br /> IN zinc acetate <br />Total nitrogen 25 P,G Freeze 6 and <br />Biochemical oxygen demand 50 P,G Cool, 4° C 7 d <br />Chemical oxygen demand 50 P,G Cool, 4° C 7 d <br />a Recommended field sample sizes for one laboratory analysis. If additional laboratory analyses are required (e.g., replicates), the <br />field sample size should be adjusted accordingly. <br />bp = polyethylene, G = glass. <br />'Larger samples are required for <br />d sandy sediments than for muddy ones. <br />This is a suggested holding time. No U.S. Environmental Protection Agency criteria exist for the preservation of samples or quan- <br />tities needed for determination of this variable. <br />able containers. The caps should be lined with Teflon <br />sheeting (metal analysis) or aluminum foil (organic <br />analysis). All jars, lids, sheeting, or foil should first <br />be washed with a nonphosphate, laboratory-grade <br />detergent, and triple rinsed with tap water. They <br />should then be rinsed with reagent grade nitric acid <br />(1:1) and tap water, followed by a rinse with 1:1 <br />hydrochloric acid (reagent grade), and a triple rinse <br />with distilled water. The containers and materials <br />should then be rinsed with acetone, followed by <br />pesticide grade hexane, and dried in a contaminant- <br />free area. Commercially prepared containers are <br />available. Clean jars should be stored in the sample <br />kit with lined caps screwed on the jars. <br />When widemouthed glass jars are used, the jars <br />should be filled almost to the top with sediment, <br />topped off with water from the site, and sealed with <br />a Teflon-lined cap or aluminum foil beneath the lid. <br />After appropriate labeling, the samples should be <br />stored at 4° C. If samples are to be held for long- <br />term storage, jars should be only two-thirds full, <br />including the cover water. Samples should then be <br />immediately frozen and stored on dry ice for trans- <br />port. For short-term storage (less than 7 days), they <br />should be refrigerated at 4° C; for long-term <br />storage, they should be frozen and kept frozen until <br />analyzed. <br />Invertebrate Samples <br />Samples of benthic invertebrates can be used to <br />determine the extent of the kill and to document <br />recovery after the kill. Samples should be taken in <br />the same areas in which water and sediment samples <br />were taken. If sufficient invertebrates, especially <br />unionid mussels, are available, tissue can be used for <br />residue analyses. Tissue samples should be frozen <br />in a suitable clean container and properly tagged and <br />labeled. <br />In most investigations, benthic invertebrate sam- <br />ples are not needed for toxicant residue analyses. <br />If information on residues in the benthos is desired, <br />a sample of at least 100 g is required for analyses. <br />Generally, large invertebrates such as crayfish or <br />unionid mussels suffice as samples for analytical pur- <br />poses. Samples should be frozen in the same type <br />of prepared containers as those used for sediments, <br />and stored at -20' C until they are analyzed. <br />It is usually difficult to collect enough zooplankton <br />for residue analysis. Generally, a record of its <br />