LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
Method: Sewage sludge was incorporated into a sandy soil to give a range of very low
to very high applications (0.4 to 90 mg/ha dry weight). LAS was added as
water solutions to this mixture. The soil was transferred to pots and sown
with barley, rape, or carrot and allowed to grow for 19, 85, and 30 days,
respectively in a greenhouse. Plant-free controls were also established.
Samples were collected of the soil and analyzed for total LAS and for
individual homologues.
GLP: Yes [ ] No [ ] ? [X]
Test substance: LAS C10-13, Approximate composition at start of study: C10 3%, C11 22%, C12
40%, C13 35%
Results: LAS was not taken up by plants and its degradation in soil increased by the
presence of crop plants with concentration decreasing in rape from 27
mg/kg (dry soil) to 0.7 - 1.4 mg/kg (dry soil) at harvesting after 30 days.
During degradation, the relative fraction of homologues C10, C11, and C12
decreased, while C13 increased.
Reference: Mortensen, G.K., Elsgaard, H., Ambus, P., Jensen, E.S., and Gron, C. 2001.
Influence of plant growth on degradation of linear alkylbenzene sulfonate in
sludge-amended soil. J. Environ. Qual. 30:1266-1270.
Reliability: 2 Valid with restrictions
(h)
Type of Measurement: Background [ ]; At contaminated site [ ]; Other [X]
Medium: Sludge modified soils
Method: LAS biodegradation and its kinetic parameters were studied in a land filling
operation using sludges (15%) blended with soil (85%) at a site in Spain.
Once the soil was blended with the sludges, grab samples were taken in three
different zones of the plot. All samples were blended every day in order to
have a daily composite sample. Immediately after sampling, all samples
were frozen and then sieved to a 2 mm particle size. The sampling was
conducted on 10 different days over a period of 62 days. LAS determination
in sludge-modified soils was carried out by HPLC-UV. Degradation was
determined based on LAS concentrations measured on the 10 sampling days.
Results: Average LAS concentrations on the 10 sampling days were 155, 55.6, 28.0,
30.2, 35.2, 28.2, 31.6, 35.1, 19.3 and 16.7 for days 0, 6, 15, 20, 27, 34, 41, 48,
55 and 62, respectively. The biodegradation level reached after 62 days was
89.2%. Assuming first order kinetics, the half-life is 19.3 days.
Remarks: LAS adsorbed or precipitated on anaerobic sludges is biodegraded during soil
amendment operations by commonly occurring micro organisms. The table
shows a shift in the percent homologue distribution on days 0 and 62,
demonstrating that higher molecular weight homologues exhibit stronger soil
adsorption.
% phenyl homologue Day 0 Day 62
C10 3.7 1.2
C11 29.4 18.7
C12 41.4 48.9
C13 25.5 31.2
Reference: de Ferrer, J., Moreno, A., Vaquero, M.T. and Comellas, L. 1997.
Monitoring of LAS in direct discharge situations. Tenside Surf. Det. 34:278-
283.
Reliability: 2 Valid with restrictions
3.2 MONITORING DATA (ENVIRONMENTAL)
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