|M.Sc Student||Berger Natalia|
|Subject||Determination of Surfactants Concentration in Estuaries and|
Seawater and Assessment of their Effects on Corals
|Department||Department of Civil and Environmental Engineering||Supervisors||Professor Eran Friedler|
|Dr. Nurit Kress|
|Full Thesis text - in Hebrew|
Surfactants are one of the most environmentally relevant organic chemical groups due to their extensive use in industry and households as the active part of detergents. Surfactants can be toxic to aquatic organisms even at low concentrations. Since most surfactants are biodegradable, the concentrations expected in the environment are low and the classic determination methods are not applicable to environmental samples. Moreover, the complicated matrix of environmental samples, such as salt in seawater, hinders the analysis methods.
The goals of this research were to develop methods for quantitative determination of surfactants in environmental aqueous matrices, to apply the methods and measure the surfactants' concentrations in environmental samples and to assess possible effects of acute surfactants exposure on corals.
High performance liquid chromatography (HPLC) was chosen as the analytical tool to achieve the goals of this research. Methods were developed for the joint determination of the most common surfactants, belonging to two groups: the anionic- linear alkylbenzesulfonates (LAS) and alkylethoxylates (AES), and the nonionic- nonylphenol ethoxylates (NPE), octylphenol ethoxylates (OPE) and their biodegradation products nonylphenol (NP) and octylphenol (OP). The method development included pre-concentration and elimination of background interference by solid-phase extraction (SPE) and quantitative analysis by HPLC. All the methods were validated and the recovery, reproducibility and detection limit were determined.
The methods were applied on samples from the coastal Mediterranean and Red Seas and from river’s estuaries. In general, the highest concentrations of surfactants were detected in river mouths: the range of anionic surfactants' concentrations spanned from 5.87 μg/L to 1,318 μg/L and the nonionic surfactants' concentrations were in the range of 0.98 μg/L to 40.6 μg/L. In the Mediterranean Sea the range of anionic surfactants' concentrations was from 0.55 μg/L to 10.0 μg/L and the nonionic surfactants' concentrations were in the range of 0.36 μg/L to 2.76 μg/L. The lowest concentration were found in the seawater at the Gulf of Eilat: majority of the anionic surfactants' concentrations were below 1.5 μg/L and the concentration of nonionic surfactants were below 2 μg/L.
The effect of acute discharges with high concentrations of surfactants on the survival of corals was assessed in laboratory experiments. Short-term exposure (24 hours) to high concentrations (0.75-5 mg/L) of LAS and NPE caused a significant decrease in the survival of corals, depending on the species and concentrations and identity of the surfactant.