assessing the potential impact of the antisapstain chemicals ddac ...

4.6 ASSESSING THE POTENTIAL IMPACT OF THE ANTISAPSTAIN CHEMICALS DDAC AND IPBC
the analytical techniques used to date may not be effective at analyzing these target chemicals in these
complex mixtures of wood particles, clays and surfactants (Boethling and Lynch 1992; BC Research 1991).
Until the analytical difficulties are overcome and further controlled experiments are conducted, it is impossible
to assess whether the lack of analytical recovery is also indicative of biological unavailability.
Since the sampled effluent from the NP1 mill did not contain sufficient DDAC or IPBC for detection in the
mixing zone, the effluent was spiked with NP1 to assess the chemicals’ behaviour in a dilution series
mimicking a mixing zone. NP1 was added to the effluent to produce concentrations of 1400 μg/L DDAC
and 100 μg/L IPBC (assuming no DDAC or IPBC was in the original effluent). The river water used in this
test was marginally lower in suspended sediment content (126 mg/L) than the river water used in the F2
study (142 mg/L). The results are shown in Table 4 (see end of chapter) and in Figure 3. A little more than
10 per cent of the spiked IPBC was not recovered from the effluent or subsequent dilutions with river water
and slightly greater amounts were not recovered in decanted fractions. Almost 30 per cent of the spiked
DDAC was not recovered from the effluent and recoveries in mixtures became progressively less as the
percentage of river water increased. As the TSS content of the effluent was a relatively low 32 mg/L, much
of the calculated loss in the 100 per cent effluent could be due to an already mentioned analytical limitation.
SEDIMENT TOXICITY TESTS
WITH DDAC
Sediment toxicity bioassays were conducted
with DDAC to assess the chemical’s
bioavailability and toxicity to
aquatic organisms. The tests were conducted
using a bulk sediment sample
from the upper Fraser Basin, to which
DDAC was added. To investigate the
route of DDAC exposure from contaminated
sediment to organisms, the
following tests were employed:
Hyalella azteca was used to assess toxicity
to benthic invertebrates;
Daphnia magna was used to determine
if DDAC in the sediment was
bioavailable and toxic to organisms in
the overlying water; and a solid phase
Microtox® test was used to determine
if the chemical was available to organisms
directly from the sediment.
Acute and chronic toxicity of DDAC in
spiked sediment was tested with the
freshwater amphipod, Hyalella azteca.
The 14-day LC 50 was 1,100 μg/g
Figure 3. The effect of river water on DDAC and IPBC recovery from
NP1 mill stormwater effluent spiked with 1400 μg/L DDAC and
100 μg/L IPBC.
DDAC with a steep dose-response (Fig. 4). The NOEL (no-observable-effect level) was 750 μg/g and the
LOEL was 1,000 μg/g. Our acute toxicity results are similar to those observed by TRS in a 28-day sediment
toxicity study with Chironomis tentans (TRS 1997).
A concurrent 14-day bioassay was conducted with D. magna neonates exposed to the same spiked sediment.
Based on sediment concentrations, the 14-day LC 50 was 2,250 μg/g, with a NOEL value of 1,500
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