LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
algae, macrophytes [Elodea canadensis,Lemna minor], macroinvertebrates
[Daphnia magna, Paratanytarsus parthenogenica], and fish [Lepomis
macrochirus]). Flow rate in the proportional diluter delivered approximately
8 replacement volumes per day. Additionally, at each cycle of the diluter,
1.5 mL of a Daphnia food suspension diluted with a culture of Selenastrum
was added to each chamber. Following an initial 3 day acclimation period to
analytically confirm test concentrations, 4 glass periphyton slides (5 x 5 cm),
8 vegetative shoots of Elodea, 10 early instar Daphnia, 25 midge eggs and 5
pre-weighred juvenile bluegills (2.5-5.0 cm length) were added to each
aquarium. Fish were screened from access to the macroinvertebrates by a 60
mesh stainless steel screen and were fed a daily supplement of frozen brine
shrimp. In Phase II, the aquaria were supplied with LAS in sewage effluent
to simulate more closely the situation in an actual receiving stream. Sewage
effluent was generated in a continuous activated sludge (CAS) unit and was
adjusted to maintain 50 percent LAS degradation. Effluent from the CAS
unit was then supplied to the test chambers at continuous dilutions of 3.75,
7.5, 15, and 30 percent sewage concentrations to simulate sewage dilutions
existing in natural receiving waters. Test duration was 28 days. Effects
monitored included population and community effects. Nominal
concentrations were confirmed with MBAS analysis.
Results: Dissolved oxygen concentrations ranged between 7.0 and 9.0 mg/L during
Phase I. Dissolved oxygen concentrations in Phase II ranged between 3.1
and 7.3 mg/L, with the lowest readings consistently observed in the aquaria
receiving the 30% sewage concentrations, as would be expected.
Temperature was maintained at 2°C, mean pH was 8.1 ± 0.2 in Phase I and
7.5 ± 0.3 in Phase II. MBAS analysis confirmed the nominal concentrations.
No significant effects on microbial community structure occurred in Phase I,
with biomass levels in the high dose (4.0 mg/L) comparable to or greater than
the biomass levels in the controls. Similarly, no significant effects on
microbial community structure were observed in Phase II. The function of
microbial communities in Phase I was affected at the high dose (4.0 mg/L),
as evidenced by significant depression in the rates of both glucose and LAS
degradation. No effects on microbial function were observed in Phase II. No
dose response correlation in overall productivity was evident for the
periphyton (aufwuchs) community in Phase I. In Phase II, the introduction of
the sewage effluent produced a generally higher turbidity level and the higher
organic concentrations were conducive to the growth of thick sheets of
bacterial and fungal communities. Very little direct periphytic plant growth
was observed. The stimulatory effect of the increasingly higher sewage
concentration is evident in the progressively higher aufwuchs production
observed between 3.75 and 30% effluent. No effects on Elodea production
were observed in Phase I. However, in Phase II, Elodea and Lemna plant
growth was inhibited at all concentrations except 3.75% by the increased
bacterial and fungal periphyton growth as periphytic sheaths tended to cover
the leaves and vegetative tips of the macrophytes. Evaluation of the Daphnia
magna data from Phase I is confounded by unexpected poor control survival,
although productivity appeared to be lower in the 1.0, 2.0 and 4.0 mg/L
concentrations than at 0.5 mg/L. In Phase II, all Daphnia died in the 30%
sewage concentration but production reached much greater numbers in the
other concentrations than they did in Phase I. The midge species had an
apparent reduction in numbers at 4.0 mg/L compared to the controls in Phase
I. In Phase II, erratic growth in the controls and all exposures led to no
meaningful midge survival at the end of Phase II. Bluegill fish growth at the
end of Phase I was reduced at the 2.0 and 4.0 mg/L concentrations but not at
0.5 or 1.0 mg/L. In Phase II, fish in all wastewater dilution concentrations
from 3.75 to 30% grew less than the controls. The following table
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