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<br />a volume of test solution equal to the volume
<br />of solution in the chamber.
<br />5.4 For the purposes of 8.2, 10.4.2, and
<br />10.8.2, the term "organochlorine pesticides" re-
<br />fers to aldrin, DDD, DDE, DDT, dieldrin,
<br />endrin, heptachlor, heptachlor epoxide, lin-
<br />dane, mirex, and toxaphene. The term "organic
<br />chlorine" refers to chlorine that would be de-
<br />tected if, when samples are prepared for gas
<br />chromatographic analysis for polychlorinated
<br />biphenyls (PCBs) and the organochlorine pes-
<br />ticides listed above, a halide detector is used
<br />instead of an electron capture detector to mea-
<br />sure compounds that elute from just before
<br />lindane to just after mirex on the gas chro-
<br />matograph being used. Organic chlorine does
<br />not refer only to chlorine associated with or-
<br />ganochlorine pesticides and PCBs; it refers to
<br />all chlorine that elutes within the specified
<br />period.
<br />5.5 For definitions of other terms used in
<br />this practice, refer to Defmitions D 1129 (33).
<br />For an explanation of units and symbols, refer
<br />to Standard E 380.
<br />
<br />6. Apparatus
<br />6.1 Facilities-The facilities should include
<br />tanks for holding and acclimating test orga-
<br />nisms, and a constant-temperature area or re-
<br />circulating water bath for the test chambers.
<br />Holding tanks should operate on a flow-
<br />through basis, except that static or renewal
<br />systems can be used for most small organisms.
<br />For static tests a dilution-water tank, which
<br />may be used to prepare reconstituted water, is
<br />often elevated so dilution water can flow by
<br />gravity into holding and acclimation tanks and
<br />test chambers. For flow-through tests, an ele-
<br />vated headbox is often desirable so dilution
<br />water can flow by gravity into holding and
<br />acclimation tanks and the exposure system.
<br />Strainers and air traps should be included in
<br />the water-supply system. Holding, acclimation,
<br />and dilution-water tanks and headboxes should
<br />be equipped for temperature control and aera-
<br />tion. Air used for aeration must be free of oil
<br />and fumes; filters to remove oil and water are
<br />desirable. During holding, acclimation, and
<br />testing, test organisms should be shielded from
<br />disturbances. The test facility must be well
<br />ventilated and free of fumes. A l6-h light and
<br />8-h dark photoperiod should be provided. A 15
<br />to 30-min transition period between light and
<br />
<br />~~r~
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<br />E 729
<br />
<br />dark may be desirable (3).
<br />6.2 Special Requirements-Some organisms
<br />require special conditions during holding, ac-
<br />climation, and testing. For example, burrowing
<br />mayfly nymphs should be provided a substrate
<br />suitable for burrowing (4); immature stream
<br />insects should always be in a current (5); and
<br />crabs, shrimp, and bottom-dwelling fish should
<br />be provided a silica-sand substrate. Since can-
<br />nibalism can occur among many species of
<br />decapod crustaceans, the claws of crabs and
<br />crayfish should be banded, or the individuals
<br />should be physically isolated by such means as
<br />screened compartments.
<br />6.3 Construction Materials-Construction
<br />materials and commercially purchased equip-
<br />ment that may contact stock solutions, test
<br />solutions, or any water into which test orga-
<br />nisms will be placed should not contain any
<br />substance that can be leached or dissolved by
<br />aqueous solutions. In addition, materials and
<br />equipment that contact stock solutions or test
<br />solutions should be chosen to minimize sorp-
<br />tion of toxicants from water. Glass, Type 316
<br />stainless steel, or fluoroplastics must be used
<br />whenever possible in order to minimize leach-
<br />ing, dissolution, and sorption. Concrete and
<br />rigid (unplasticized) plastics may be used for
<br />holding and acclimation tanks and in the water-
<br />supply system, but they must be conditioned
<br />before use. Cast iron pipe may be used in
<br />freshwater supply systems, but colloidal iron
<br />will be added to the dilution water and strainers
<br />will be needed to remove rust particles. Natural
<br />rubber, copper, brass, galvanized metal, and
<br />lead must not come in contact with dilution
<br />water, stock solutions, or test solutions before
<br />or during exposure of test organisms.
<br />6.4 Metering System:
<br />6.4.1 The metering system must be designed
<br />to accommodate the type and concentration of
<br />toxicant to be tested and the necessary flow
<br />rate of test solution. The system must repro-.
<br />ducibly supply (11.9.2.2) the necessary toxicant
<br />concentrations (9.2). A wide variety of metering
<br />systems have used different combinations of
<br />syringes, "dipping birds," siphons, pumps, sat-
<br />urators, solenoids, valves, etc., to control the
<br />concentration of toxicant in, and the flow rate
<br />of, test solution (6). Proportional diluters (7)
<br />use an intermittent-flow design and various
<br />devices for metering toxicant (8). Continuous-
<br />flow metering systems are also available, as are
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