Response of weeping willows to linear alkylbenzene sulfonate

Linear alkylbenzene sulfonate (LAS) is the most commonly used anionic surfactant in laundry detergents and cleaning agents. LAS compounds are found in surface waters and soils. The short-term acute toxicity of LAS to weeping willows (Salix babylonica L.) was investigated. Willow cuttings were grown in hydroponic solution spiked with LAS at 24.0 ± 1 °C for 192 h. The normalized relative transpiration of plants was used to determine toxicity. Severe reduction of the transpiration was only found for high doses of LAS (greater-or-equal, slanted240 mg l−1). Chlorophyll contents in leaves of treated plants varied with the dose of LAS, but there was no significant linear correlation. The activities of the enzymes superoxide dismutases (SOD), catalase (CAT), and peroxidase (POD) were quantified at the end of experiments. At higher concentrations of LAS (greater-or-equal, slanted240 mg l−1), the activities of SOD and CAT were decreased. The correlation between the dose of LAS and the POD activity in leaf cells was the highest of all enzyme assays (R2 = 0.5). EC50 values for a 50% inhibition of the transpiration of the trees were estimated to 374 mg l−1 (72 h) and 166 mg l−1 (192 h). Results from this experiment indicated that phytotoxic effects of LAS on willow trees are not expected for normal environmental conditions.