9637

• UCREFRP Catalog Number: 9637
• Author: American Society For Testing And Materials.
• Title: Standard Practice For Conducting Acute Toxicity Tests With Fishes, Microinvertebrates, And Amphibians.
• USFW Year: 1980.
• USFW - Doc Type: Philadelphia, PA.
• Copyright Material: YES

8.2.2 Natural Dilution Water-Natural di-
lution water should be uncontaminated and of
constant quality and should meet the require-
ments given in Table 5 to help ensure that test
organisms are not stressed during holding, ac-
climation, and testing and that test results are
not unnecessarily affected by water quality.
8.2.2.1 A freshwater natural dilution water
is considered to be of constant quality if the
monthly ranges of hardness, alkalinity, and
specific conductance are less than 10 % of their
respective averages, and if the monthly range
of pH is less than 0.4 unit. Freshwater natural
dilution water should be obtained from an
uncontaminated well or spring if possible or
from a surface water source.
8.2.2.2 A saltwater natural dilution water is
considered to be of constant quality if the
weekly range of salinity is less than 6 g/kg, and
if the monthly range of pH is less than 0.8 unit.
A specially designed system is usually necessary
to obtain salt water from a natural water source
(16).
8.3 Recommendations:
8.3.1 Soft reconstituted fresh water (Table 1)
should be used whenever possible when testing
freshwater animals, although some problems
have been encountered with daphnids in this
water. The other reconstituted fresh waters
(Tables 1 and 2) should be used for studying
the effects of water quality on results of toxicity
tests. However, the buffers used in Table 2 may
react chemically with some toxicants. When the
use of reconstituted water is impractical, such
as for most flow-through tests, a natural dilu-
tion water with a hardness of 40 to 48 mg/L as
CaC03 should be used when possible.
8.3.2 Natural or reconstituted (Table 3) salt
water of 34 g/kg (ppt, 0/00) salinity and pH
8.0 should be used whenever possible when
testing true marine stenohaline species, and 17
g/kg salinity and pH 7.7 with euryhaline spe-
cies. Other salinities may be used for studying
the effects of water quality on results of toxicity
tests. The initial salinity of reconstituted water
prepared according to Table 3 is 34:!: 0.5 g/kg,
and the desired test salinity is attained at time
of use by dilution with acceptable water (see
8.2.1). Problems have been encountered with
some animals in this water; some ofthese prob-
lems have been overcome by aging the recon-
stituted water for several weeks. Reconstituted

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water should not be used for shell deposition
tests because of the difficulty of providing ad-
equate amounts of acceptable food for the or-
gamsms.
8.3.3 A chlorinated water should never be
used because residual chlorine is quite toxic to
aquatic animals (15). A dechlorinated water
should only be used as a last resort because
removal of residual chlorine is often incom-
plete. In addition to residual chlorine, munici-
pal drinking water often contains unacceptably
high concentrations of copper, lead, zinc, and
fluoride; and quality is often rather variable.
When necessary, metals can usually be re-
moved with chelating resins. Sodium bisulfite
should be better for dechlorinating water than
sodium sulfite, and both are more reliable than
carbon filters, especially for removing chlora-
mines. If dechlorinated water is used as the
dilution water or in its preparation, at the be-
ginning of static tests and daily during flow-
through tests, it must be shown that in fresh
samples of the dilution water either (a) Acartia
tonsa, mysid shrimp, bivalve mollusc larvae, or
first-instar daphnids can survive for 48 h with-
out food, or (b) the concentration of residual
chlorine is less than 3 /lg/L.
NOTE- The limit of 3 ltg/litre is based on the
sensitivity of aquatic organisms (15). If this concen-
tration cannot be measured chemically, then only
alternative (a) can be used.
9. Toxicant

9.1 General-The toxicant should be reagent
grade (14) or better, unless a test on a formu-
lation or commercial product, or use-grade ma-
terial is specifically needed. If the identity and
concentration of major ingredients and impur-
ities are unknown, they should be determined.
The toxicant should be added to the dilution
water (in the metering system in flow-through
tests) without the use of any additives, except
water, if possible. If a stock solution is used, the
stability of the toxicant in the stock solution
should be determined. Minimum necessary
amounts of hydrochloric acid, nitric acid, po-
tassium hydroxide, sodium hydroxide, and sul-
furic acid may be used to solubilize basic and
acidic compounds in aqueous stock solutions,
but they may affect the pH of test solutions
appreciably. When possible, such use of acids
and bases should be avoided by use of more
soluble forms ofthe toxicant, for example, chlo-

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