Vol. 12, No.1 (December 2010) – Preface
Focus on Marine Environment and Sediments Leads to New Advances in Understanding of LAS and LAB
Initial reports demonstrating anaerobic biodegradation of LAS were published in vol. 6, No. 1 of The CLER Review (October, 2000). In this issue, P. A. Lara-Martin and others (“Anaerobic Degradation Pathway of Linear Alkylbenzene Sulfonates (LAS) in Sulfate-Reducing Marine Sediments”) demonstrate the crucial initial steps in the LAS anaerobic biodegradation pathway. With the demonstration that the pathway is similar to that for other compounds (ethylbenzene, n-hexane) known to undergo anaerobic biodegradation, there can be no doubt that LAS also undergoes anaerobic biodegradation.
- A. Mauffret and others (“Colonized Beads as Inoculum for Marine Biodegradability Assessment: Application to Linear Alkylbenzene Sulfonate”) report that the rate of LAS mineralization in seawater was greatly increased by adding glass beads that were pre-exposed to LAS in seawater and thus colonized by the full consortium of bacteria that are required to mineralize LAS. The lesson from this study is that the slow rate of mineralization of LAS in seawater is simply due to the low probability of encountering the full consortium of bacteria required for LAS mineralization. Most previously published reports had noted only initial (primary) biodegradation. This is the first report to demonstrate substantial LAS mineralization in seawater, an important observation because mineralization, not just primary biodegradation, is the current standard for environmental acceptability.
- R. P. Eganhouse and others (“Susceptibility of Synthetic Long-Chain Alkylbenzenes to Degradation in Reducing Marine Sediments”) had been studying LAB and other compounds as markers for man-made (anthropogenic) wastes in marine environment (anaerobic sediments) for over 25 years when they noticed a surprising development. The LAB concentrations, unlike all of the other compounds they were observing, were not conserved over the long time periods they were studying. In fact they were decreasing over time, suggesting a slow but steady rate of anaerobic biodegradation. In this study, they were able to return to the same marine sediment site (off the coast of California, USA) that they had previously studied in 1993 and collect new sediment samples to show that, while the concentrations of other compounds were unchanged, LAB levels had declined 50-60% over 11 years, demonstrating significant anaerobic biodegradation of LAB in marine sediments. This is the first unambiguous demonstration of significant anaerobic biodegradation of LAB, and it occurs in marine sediments.
- A series of three papers by A. Rico-Rico (“Effect of Sediment Properties on the Sorption of C12-2-LAS in Marine and Estuarine Sediments,” “Equilibrium Partitioning Theory to Predict the Sediment Toxicity of the Anionic Surfactant C12-2-LAS to Corophium volutator,” and “Predicting Sediment Sorption Coefficients for Linear Alkylbenzenesulfonate Congeners from Polyacrylate-Water Partition Coefficients at Different Salinities”) discuss the interactions of LAS with sediments. The first paper focuses on understanding how the absorption of an LAS model compound to sediments is determined by the components of the sediments (clay, organic, iron and aluminum content) and the salinity of the water. The second paper demonstrates that the toxicity of an LAS model compound to a sediment-dwelling organism is determined by the LAS concentration in water; the concentration bound to sediment is inactive. The third paper uses a model system to predict sediment absorption properties of LAS under a wide variety of environmental conditions. Together these papers provide a comprehensive update to our understanding of the complex interactions of LAS with sediment.
Finally, I would like to take the opportunity to recommend a paper that we could not include in The CLER Review. The paper is “The Missing Link in Linear Alkybenzenesulfonate Surfactant Degradation: 4-Sulfonacetophenone as a Transient Intermediate in the Degradation of 3-(4-Sulfophenyl)Butyrate by Comamonas testosteroni KF-1 (D. Schleheck et al., Appl. Environ. Microbiol., vol. 76, pp. 196-202, 2010).
This paper provides the first complete biodegradation pathway for an LAS biodegradation intermediate, a remarkable achievement in LAS science. We are pleased to point out that one of the co-authors of the paper is none other than A.M. Cook of the University of Konstanz, Germany, whose papers have appeared in two previous issues of The CLER Review (vol. 5, No. 1, p. 63; vol. 6, No. 1., p. 46).
Unfortunately, we were not able to include this paper because the journal in which it was published has a strict policy against reprinting entire articles. This is particularly disappointing because the policy extends to all of the publications of the American Society for Microbiology (ASM), one of the scientific associations of which I have been a member for years and the only one of which I am aware that has this restrictive policy. Since CLER of course pays copyright fees, there really is no justification for ASM not to allow articles to be reprinted – this is an unnecessary and counter-productive restriction on the high quality scientific information published in the ASM journals.
But don’t hold that against the Schleheck et al. paper – it is a really terrific study and well worth searching out.
John Heinze, Ph.D.