WWRC 87-02
Evaluation of Ambient Toxicity Tests for Detecting Groundwater Pollution Entering Streams and Rivers: Final Report
Abstract
Groundwater pollution is an emerging environmental concern in the
Rocky Mountain region. In this two-year study, we evaluated the utility of
two sublethal toxicity tests for detecting migration of contaminated ground
water into streams and rivers.
During Year 1, we tested groundwater or surface-water samples from
five locations at each of two study sites; 1) the Laramie River as it
flowed past a former railroad tie treating plant south of Laramie, Wyoming,
from June 1985 to October 1985; and 2) Crow Creek as it flowed past an oil
refinery in Cheyenne, Wyoming, from June 1985 to April 1986. During Year
2, we tested groundwater and surface-water samples only at the Crow Creek
site, from June to September 1986. Each water sample was tested for its
effects on survival and reproduction of Ceriodaphnia dubia (an aquatic
invertebrate) and survival and growth of fathead minnow (Pimephales
promelas) larvae. Chemical analyses of water samples included routine
water chemistry parameters, major inorganic ions, II trace elements,
dissolved organic carbon, reverse-phase HPLC gradients, and GC-MS analyses
of organics.
At the Laramie River, toxic ground water underlaid sediments adjacent
to the tie treating plant. However, migration of ground water into the
Laramie River did not adversely affect fathead minnows and Ceriodaphnia.
Some groundwater and surface-water samples from Crow Creek also were toxic.
The oil refinery's effluent appeared to cause much of the adverse effects
in surface water downstream from that discharge. Adverse effects upstream
from the refinery discharge may have been caused by contaminated ground
water or storm sewer runoff.
Results of this study indicate that (1) ambient toxicity tests can be used
in alkaline surface waters of the western U.S.; (2) they are sensitive enough
to detect migration of contaminated ground water into surface waters; (3) they
may be more sensitive in some cases than routine, inexpensive chemical analyses
for detecting the presence of contaminants; (4) toxicity of contaminated ground
water and an industrial discharge varied considerably during the two-year
study; and (5) toxicity of interstitial ground water did not always correspond
with toxicity of the overlying surface water or downstream surface water.
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