LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
2.2.4 Stability in Soil
Several measurements of LAS in sludge-amended soil from both laboratory and field studies have
been reported. Figge and Schoberl (1989) conducted a laboratory study using 14 C LAS (mixture not
defined), and thus measuring ultimate biodegradation, showing LAS mineralization rates in soil
corresponding to half lives (t0.5) of 13-26 days. Knaebel et al. (1990) observed more rapid
mineralization (half lives of 1.1-3.7 days) of C13 LAS in 10 soil types. Ward and Larson (1989)
observed similar rates of mineralization (half lives of 15.8 to 25.7 days) as Figge and Schoberl
using pure C10 to C14 LAS homologues and two different soil types. In the most recent laboratory
study, Elsgaard et al. (2001b) showed more than 73% primary biodegradation for nominal LAS
concentrations of 8 to 62 mg/kg and a 15% depletion for nominal concentrations of 488 mg/kg after
two weeks in soil spiked with aqueous LAS and LAS-spiked sewage sludge.
Field investigations in the U.K. in which the annual sludge spreading averaged 6 ton/ha (Holt et
al.,1989; Waters et al., 1989) demonstrated LAS removal (primary biodegradation) corresponding
to half lives in the range of 7-22 days. At a landfilling operation in Spain in which very high levels
of sludge were blended with soil (15% sludge, 85% soil), an LAS half live of 19.3 days was
observed (de Ferrer et al., 1997). At sludge application rates within those currently recommended in
Europe (equal or below 5 ton/ha/y), a field study estimated t0.5 values, due to primary
biodegradation, in the range of 3-7 days (Küchler and Schnaak,1997). Mortensen et al. (2001) also
reported data for degradation of LAS in sludge-amended soil under realistic field conditions. LAS
was not taken up by plants and its degradation in soil increased by the presence of crop plants with
concentration decreasing from 27 mg/kg (dry soil) to 0.7-1.4 mg/kg (dry soil) at harvesting time
after 30 days (t0.5