Lara-Martín Pablo A, Gómez-Parra Abelardo, Köchling Thorsten, Sanz José Luis, González-Mazo Eduardo
Departamento de Química Física, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Campus Río San Pedro s/n, 11510 Puerto Real, Cádiz, Spain.
Environ Sci Technol. 2007 May 15;41(10):3580-6. doi: 10.1021/es062373r.
An accompanying article has demonstrated the anaerobic degradation of the surfactant linear alkylbenzene sulfonate (LAS) in microcosms filled with marine sediments through the generation of sulfophenylcarboxylic acids (SPCs). A detailed study shows that this process was uniform in the blanks (non-spiked natural sediments) for every LAS homologue during the complete course of the experiment. However, when sediments were spiked with commercial LAS and, therefore, enriched with short-chain homologues, degradation was enhanced for these homologues until their percentages were close to those for non-spiked sediments. The reason is that short-chain homologues are more bioavailable due to their higher solubility and lower sorption capacity. Thus, sorption on sediments was found to be increased with the length of the alkyl chain for LAS homologues, following a linear Freundlich isotherm, whereas the metabolites generated were predominant in solution due to their much higher polarity. Intermediate-chain SPC homologues (C7-C9 SPCs) were the most abundant during the experiment, but a significant increase in the concentration of shorter-chain SPC homologues (C4-C6 SPCs) was detected toward the end. In the case of isomers, the steric effect of the aromatic group implies that LAS primary degradation took place preferentially over external isomers. Therefore, the generation of external isomers of SPCs was predominant during the complete experiment although internal isomers of SPCs became more evident when the degradation process had advanced and external isomers of LAS became scarce. The identity of both types of SPC isomer was confirmed by tandem mass spectrometry. With respect to LAS coproducts, the relative percentage of iso-LAS increased during the complete experiment and removal percentages for dialkyl tetralinsulfonates (<30%) were typically lower that those for LAS (66-79%), although a similar behavior was observed for their homologues in both cases.
一篇随附文章表明，在充满海洋沉积物的微观世界中，通过生成磺基苯基羧酸（SPCs），表面活性剂直链烷基苯磺酸盐（LAS）可进行厌氧降解。一项详细研究表明，在整个实验过程中，对于每个LAS同系物，该过程在空白样（未添加LAS的天然沉积物）中是一致的。然而，当向沉积物中添加商业LAS并因此富含短链同系物时，这些同系物的降解会增强，直至其百分比接近未添加LAS的沉积物中的百分比。原因是短链同系物因其较高的溶解度和较低的吸附能力而具有更高的生物可利用性。因此，发现LAS同系物在沉积物上的吸附随烷基链长度的增加而增加，遵循线性弗罗因德利希等温线，而生成的代谢产物由于其极性高得多而主要存在于溶液中。实验过程中，中间链SPC同系物（C7 - C9 SPCs）最为丰富，但在实验末期检测到短链SPC同系物（C4 - C6 SPCs）的浓度显著增加。对于异构体，芳基的空间效应意味着LAS的初级降解优先于外部异构体发生。因此，在整个实验过程中，SPCs外部异构体的生成占主导地位，尽管当降解过程推进且LAS外部异构体变得稀少时，SPCs内部异构体变得更加明显。两种类型的SPC异构体的身份通过串联质谱法得以确认。关于LAS副产物，在整个实验过程中，异LAS的相对百分比增加，二烷基四氢萘磺酸盐的去除率（<30%）通常低于LAS的去除率（66 - 79%），尽管在这两种情况下其同系物表现出类似的行为。
