Surfactants in the environment

The use of surfactants is increasing at a rate in excess of the population growth because of generally improved living conditions and processed material availability in the less industrially developed Third World countries. Hand in hand with increased surfactant use go the problems of surfactant disposal. As the more developed nations have learned by painful and expensive experience, the ability of an ecosystem to absorb and degrade waste products such as surfactants can significantly affect the potential usefulness of a given material. 

Of particular importance are the effects of surfactants on groundwater and waste treatment operations. Although it may be technologically possible to remove all detectable residual surfactants physically or chemically from effluent streams, the economic costs would undoubtedly be totally unacceptable. When possible, the preferred way to address the problem is to allow nature to take its course and solve the problem by natural biodegradation mechanisms. 

Because of their special characteristics, soaps will continue to be important surfactant products. Although increased industrialization in the third world will undoubtedly lead to greater use of synthetic alternatives, population growth alone can be expected to maintain the current levels of soap consumption worldwide. 

While the big six surfactants will almost certainly continue to dominate the surfactant market, there will always arise the need for new and improved surfactant products. A few potentially fruitful areas of research include 

Multifunctional surfactants (e.g., detergent and fabric softener in a single structure) 

Surfactants with good chemical and thermal stability 

Polymeric materials that show good surfactant activity and produce viscosity enhancement 

---

Scott MJ, Jones M (2000) The biodegradation of surfactants in the environment. Biochim Biophys Acta 1508 235-251... 

Fig. 1.17. Fate of surfactants in the environment after discharge into sewers.

The determination of cationic surfactants in the environment by GC and GC-MS is very scarce, as described above, but this is not the case for several compounds related to cationic surfactants. Thus, long chain tertiary amines that are amenable to direct analysis by GC have been... 

Numerous applications have been shown to exist that overcome the general problems of lack of volatility and instability at higher temperatures that principally hamper direct analysis of surfactants by GC methods. Thus, a whole suite of derivatisation techniques are available for the gas chromatographist to successfully determine anionic, non-ionic and cationic surfactants in the environment. This enables the analyst to combine the high-resolution chromatography that capillary GC offers with sophisticated detection methods such as mass spectrometry. In particular, for the further elucidation of the complex mixtures, which is typical for the composition of many of the commercial surfactant formulations, the high resolving power of GC will be necessary. 

As mentioned before, the presence of surfactants in anaerobic compartments cannot be separated from their physico-chemical characteristics and in fact surfactants which degrade extensively in the laboratory under anaerobic conditions, e.g. soap, are also found in considerable concentrations in anaerobic compartments. Due to their hydrophobic character surfactants are strongly sorbed to sludges and therefore a large amount of the load of these compounds into a sewage treatment plant (reportedly 20-50%) is associated with suspended solids [43,44]. The relevance of the presence of surfactants in the environment should be assessed, therefore, on the basis of their potential impact on the structure and function of the various compartments. In most cases, ionic surfactants are present as insoluble salts and therefore their potential impact is negligible as reflected in the lack of known negative impacts. 

This chapter presents a summary of the available information regarding the toxicity of surfactants in the aquatic environment and also the new data with special emphasis on the marine environment, the use of microalgae and early life-stages of fish in toxicity assays. In the last few years, one aspect related to the impact of biodegradation products of surfactants in the environment has acquired a significant relevance—the estrogenic effect—and this subject is treated in depth in Chapter 7.3 of this book. 

However, methods for predicting environmentally relevant properties of surfactants applicable for all surfactant classes are presently not available. Due to the absence of validated estimation methods, this chapter s goal is to supply information necessary to understanding the behavior of surfactants in the environment and to provide data on the relevant properties of surfactants. 

The data presented here may be helpful in modeling the environmental fate of surfactants. A recent modeling study for LAS (Mackay et al., 1996) has indicated that, due to negligible gas-water exchange, LAS interphase transfer via the gas phase will not occur. Instead, the aqueous phase is the central compartment for environmental fate of surfactants. Besides biodegradation, which reduces the amount of surfactants in the environment, sorption determines the partitioning of the surfactants between the aqueous and the solid phase. 

Klumpp, E., and M.J. Schwuger. 1997. Physicochemical interactions of surfactants and contaminants in soil. In M.J. Schick and F.M. Fowkes, Eds., Surfactants in the Environment, Surfactant Science Series Vol. 63, pp. 39-64. Marcel Dekker, New York. 

Gonzalez, S., D. Barcelo, and M. Petrovic. 2007. Advanced bquid chromatography-mass spectrometry (LC-MS) methods applied to wastewater removal and the fate of surfactants in the environment. Trends Anal. Chem. 26 116-124. 

Giesy, J. P, Kannan, K. Perfluorochemical surfactants in the environment. Environmental Science and Technology, 36 147A-152A. (2002). 

Linear alkylbenzenesulphonates (LAS). Surfactants in the environment have resulted in foaming in a number of rivers. Of the... 

Applications of FAB have been succesfully performed in the characterization of a wide range of compounds (dyes, surfactants, polymers...) but little attention has been devoted to the capabilities of this technique to solve environmental concerns, such as organic pollutants identification in water. The widespread use of surfactants in the environment has required the emplo yment of both sensitive and specific methods for their determination at trace levels. GC/MS and HPLC procedures has been used for the determination of anionic (LAB s) and non ionic surfactants (NPEO) in water (1-4). Levsen et al (5) identified cationic and anionic sirrfactants in surface water by combined field desorption/ collisionally activated decomposition mass spectrometry (FD/CAD), whereas FAB mass spectrometry has been used for the characterization of pine industrial surfactants (6-8). 

Nonspecific analytical methods, such as colorimetry and titrimetry, for determination of summary parameters were the earliest attempts to analyze surfactants in the environment. The main disadvantage of these methods is that, apart from surfactants, other interfering organic compounds from the environmental matrices are recorded too, resulting in systematic errors. Nevertheless, colorimetric and titrimetric methods are stiU widely used for determination of anionic, nonionic, and cationic surfactants because of their easy handling and the need for relatively simple apparatus. 

Scamehom. J.F. Christian, S.D. Harwell, J.H. Sabatini, D.A. Surfactants in the Environment. In New Horizons An AOCS/CSMA Detergent Industry Conference Coffey, R.T.. Ed AOCS Press Champaign, IL, 1996 79-96. 

Giesy JP and Kannan K (2002) Perfluorochemical surfactants in the environment. Environ Sci Technol 36(7)... 

Improvement of surfactant analysis will enhance the possibilities for the observation of surfactants in the environment, e.g., enable early detection of possible accumulation or differentiation of the components of complex mixtures. Novel surfactant systems with interesting properties and applications were presented which will be environmentally important in the fumre or can be used favorably in remediation techniques. 

The presence of fluorinated surfactants in the environment is of concern in air and in water or wastewater. 

---