Agustí Marsal

Biodegradability and toxicity of sulphonate-based surfactants in aerobic and anaerobic aquatic environments.

Four types of commonly used sulphonate-based surfactants (alkane sulphonates, alpha-olefin sulphonates, sulphosuccinates and methyl ester sulphonates) were tested for their aerobic and anaerobic biodegradability as well as for their toxicity to Daphnia magna and Photobacterium phosphoreum to assess the effect of the surfactant structure on those properties. Aerobic biodegradation was evaluated by means of the CO2 headspace test and anaerobic biodegradation was assessed by a method based on the ECETOC test. All the surfactants tested were readily biodegraded under aerobic conditions. No clear effect of the surfactant structures on the toxicity to the aquatic organisms tested was found. The most significant differences in the surfactants studied were observed in their behaviour under anaerobic conditions. Alkane sulphonates, alpha-olefin sulphonates and methyl ester sulphonates were not mineralized in lab anaerobic digesters despite the fact that the last one showed a certain degree of primary degradation. Nevertheless, these surfactants did not significantly inhibit methanogenic activity at concentrations up to 15 g surfactant/kg dry sludge, a concentration that is much higher than the expected concentrations of these surfactants in real anaerobic digesters. Sulphosuccinates showed a high level of primary biodegradation in anaerobic conditions. However, linear alkyl sulphosuccinates were completely mineralized whereas branched alkyl sulphosuccinates achieved percentages of ultimate biodegradation < or =50%.

Fate and effects of amphoteric surfactants in the aquatic environment

Amphoteric surfactants form part of specialty surfactants available for formulators to improve or design new formulations in response to environmental, toxicity, safety and performance demands. Nevertheless, limited information on the ecological properties of amphoterics is available. In the present work, the aerobic and anaerobic biodegradability and the aquatic toxicity of different types of amphoteric surfactants (three alkyl betaines, one alkylamido betaine and three alkyl imidazoline derivatives) were studied. The amphoteric surfactants tested were readily biodegradable under aerobic conditions (CO2 headspace test) and alkylamido betaines and alkyl imidazoline derivatives were also easily biodegradable under anaerobic conditions (test based on the ECETOC method). Toxicity to Photobacterium phosphoreum and Daphnia magna increased with the fatty chain length of the surfactant. The EC50 toxicity values of the amphoterics tested were higher than 5 mg/L, and alkyl imidazoline derivatives, with EC50 values from 20 to > 200 mg/L, showed the lowest aquatic toxicity.

Determination of organochlorine pesticides in skins and leather by gas chromatography

The simultaneous determination of residues of lindane (gamma-HCH) and 10 other organochlorine pesticides (OCPs) in skins and leather was carried out by gas chromatography (GC) with electron-capture detection (ECD). GC with mass spectrometric detection was used to identity confirmation. Samples were extracted with hexane. The extracts were concentrated, and cleaned up on a Florisil column. Dibromooctafluorobiphenyl was added as internal standard. Hide fortifications of 0.5 an d5.0 ppm yielded average lindane recoveries of 98% and 96%, respectively. OCPs was determined in 57 samples of skins purchased from American, European and African countries in 1996-1997. OCPs were not detected in any of the American and European samples. Residues of lindane were found in 56% of African samples.