Sorption of linear alkylbenzene sulfonate to soil components and effects on microbial iron reduction.
When sewage sludge is applied to arable land, linear alkylbenzene sulfonate (LAS) is released into the environment. In soils, LAS has been shown to impede microbial processes, such as bacterial iron reduction. The aim of the present study was to quantify LAS adsorption and desorption to agricultural soils and iron oxides and relate this to the inhibition of microbial iron reduction. Two agricultural soils were used, namely, Askov (coarse sandy loam soil) and Lundgaard (coarse sandy soil). In both soils, LAS inhibited microbial iron reduction even at low LAS concentrations with 10% effect concentrations of 6 to 7 and 26 to 32 mg LAS/kg dry-weight soil for Lundgaard and Askov soil, respectively. The sorption isotherms showed that sorption of LAS to iron oxides was 10 to 100 times stronger than sorption to the agricultural soils. Also, it appeared that at low LAS concentrations (< 10 mg/kg dry-wt soil), Lundgaard soil adsorbed approximately 10 times more LAS than Askov soil. Thus, the inhibitory effect of LAS on microbial iron reduction was highest in the Lundgaard soil, which exhibited both the strongest sorption and the lowest desorption of the two soils. A possible hypothesis to explain this correlation was that LAS toxicity toward bacterial iron reduction was, at least partly, caused by LAS adsorbed to iron oxides, which could interfere with transfer of electrons between the bacteria and their respiratory electron acceptor.
Kristiansen
Inge Broberg
IB
Department of Earth Sciences, University of Aarhus, Ny Munkegade 520, DK-8000 Aarhus C, Denmark. inge.broberg@geo.au.dk
de Jonge
Hubert
H
Nørnberg
Per
P
Mather-Christensen
Ole
O
Elsgaard
Lars
L
D000327:Adsorption; D000383:Agriculture; D017738:Alkanesulfonic Acids / Q000737:chemistry* / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005290:Ferric Compounds / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D012987:Soil / Q000032:analysis*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000633:toxicity*; D014867:Water / Q000737:chemistry
D017738:Alkanesulfonic Acids; D005290:Ferric Compounds; D012987:Soil; D012989:Soil Pollutants; C030641:alkylbenzyl sulfonic acid; D014867:Water; C000499:ferric oxide