Influence of Suspended Solids on the
Acute Toxicity of Endrin to
Fathead Minnows
WILLIAM A. BRUNGS, Aquatic Biologist
Aquatic Biology Activities
Basic and Applied Sciences Program
Cincinnati water Research Laboratory
Federal Water Pollution Control Administration
Cincinnati, Ohio
GEORGE W. BAILEY, Soil Physical Chemist
Southeastern Water Laboratory
Athens, Georgia
INTRODUCTION
The most frequent attempts to understand the relationship between suspended
solids and aquatic life have considered the direct deleterious effects of these solids
on the organisms (1,2,3,4,5,6,7,8,9). Such consideration is important and necessary in the study of water quality requirements, but it does not determine
whether turbidity needs to be considered when it occurs at concentrations that are
not in themselves directly adverse. Most studies concerned with the toxicity of
soluble materials to aquatic organisms, especially fish, have been conducted with
experimental waters that usually contain tittle or no suspended solids. Exceptions
to this are studies on the effect of suspended solids on black fly control with DDT
(10), and rotenone toxicity to fathead minnows (11). Ferguson et al. (12) conducted static fish-toxicity tests after adding endrin to a turbid water. They also
determined that several chlorinated hydrocarbons adsorbed on bottom sediments as
a result of runoff from cotton fields were not released in lethal amounts into standing water.
Wallen et al (13) determined the toxicity of 86 pure chemicals to mosquito
fish in turbid waters, but had no control (non-turbid) tests for comparison. Since
most waters that receive toxic wastes have some suspended solids, the interrelationship of suspended solids and toxicity must necessarily be further investigated.
This relationship appears potentially as important as pH, dissolved oxygen, nard-
ness, and other environmental variables that are commonly studied in relation to
toxic materials. Its ecological significance could be as important as the effect of
suspended solids on the distribution of radioactive wastes in aquatic environments
(14,15). The study reported here is a start in attempting to understand the effects,
if any, of natural levels of suspended solids on the toxicity of various dissolved
compounds to fish.
METHODS
We conducted duplicate 96-hr tests under continuous-flow conditions utilizing a natural water and fathead minnows. The experimental materials used were
montmorillonite clay, Brookston silty clay loam, and activated carbon. The clay
and soil were fractionated to remove particles larger than two microns (u) so that
pettling of these materials in the testing apparatus would be reduced.   AH results
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