LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
2) Tattersfield, L.J, Mitchell, C.G., Holt, M., Girling, A.G., Pearson, N., and
Ham, L. 1996. Linear alkylbenzene (LAS): Fate and effects in outdoor
artificial streams and pools – An extended study. Internal report. Shell
Research and Technology Centre, Thornton. Document No. TNER.96.005.
Reliability: 4 Not assignable due to restrictive test design and inconsistencies in the data
(c)
Type: Aquatic [ ]; Field [ ]; Soil [X]; Other [ ]
Results: LAS had no effect on heterotrophic respiration in the sludge compartment but
stimulated activity and metabolic quotient (microbial activity per unit of
biomass) in the surrounding soil. Basil respiration (BR) was significantly
stimulated up to 60 days in the 0-10 mm compartment, but only after 60 and
82 days in the 10-30 mm compartment. No significant stimulation in BR was
observed at 30-60 mm. Substrate-induced respiration stimulation was
variable and restricted only to soil in the 0-10 mm compartment. Autotrophic
ammonia oxidation was initially inhibited in the LAS-spiked sludge, which
led to dramatic but transient increases of NH4 + availability in the sludge and
surrounding soil, subsequently stimulating soil ammonia oxidizers. As
judged from a bioluminescence toxicity assay, however, LAS or other sludge
components never accumulated to toxic levels in the soil and the LAS
tolerance of the indigenous microbes further remained unchanged following
LAS exposure. Bioluminescence was slightly, but not significantly, reduced
in the 0-10 mm compartment at the first sampling, but not thereafter and not
in the 10-30 or 30-60 mm compartments. LAS effects on the microbial
populations largely occurred during the first two months and were confined
to soil closer than 30 mm from LAS-spiked sludge.
Test Substance: C10-13 LAS, sodium salt; average alkyl chain length C11.6
Method: Well-defined bands of sewage sludge spiked with 0 (control), 7.1, or 31.3 g
LAS/kg dry weight were applied to loamy sand soil in an agricultural field in
Lundgaard, Denmark using a random block design. To each block, three
sludge bands (one per LAS treatment) were carefully applied such that the
bands were eventually applied at a specific soil depth of approximately 6 to
10 cm and covered by soil. All treatments were replicated five times. A few
days after sludge application, the entire experimental site was sown with oats
in order to make experimental conditions as realistic as possible. Sampling
for microbial parameters was done on a weekly to monthly basis for the first
100 days, with the last samples being taken approximately one year after the
start of the experiment. A rectangular corer providing a 40 mm wide cross
section of the sludge bands and the surrounding soil was sectioned into four
compartments representing various distances (0-10, 10-30, 30-60 mm) from
the sludge. At each sampling date, two replicate cores from each sludge band
were sampled and the corresponding samples from the two cores were
pooled. Microbial parameters measured included basal respiration (BR),
substrate-induced respiration (SIR), potential ammonia oxidation (PAO), and
pollution-induced community tolerance. Bioluminescence toxicity tests were
also conducted and correlated with ammonia oxidation activity as a measure
of the physiological state of the cells. Two-way analysis of variance statistics
were used for each sampling date, followed by Dunnett’s test. Data were
transformed if necessary.
Remarks: Measured LAS concentrations were 0.069 (control), 7.1 and 31.3 g/kg dw
sludge. Results strongly suggest that disposed of LAS-contaminated sludge
will not produce a significant adverse effect on the function of the soil
microbial community under field conditions. Measured effects generally
lasted two months or less and were confined to soil closer than 30 mm from
the LAS-spiked sludge. No signs of long-term selection due to toxicity were
noted. According to the authors, the study should be considered a worst-case
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