Using fractal geometry to determine phytotoxicity of landfill leachate on willow

Phytotoxicological tests were conducted during 6 weeks on the willow Salix amygdalina using six concentrations of landfill leachate. Plants were exposed to landfill leachate solutions using two regimes: (A) – the willow shoots were watered by leachate solution from the beginning of the test; (B) – the willow shoots were cultivated in pots with clean water during 4 weeks, then water was exchanged for leachate solutions. The tolerance of plants to prepared leachate concentration was determined by observations of morphological parameters of leaves including their fractal dimension. The lowest effective concentration (LOEC) was calculated. Results showed that in regime A, all measured parameters indicated similar response of plants to phytotoxic compounds in leachate. The LOEC was in the range 4.69–5.63% of leachate concentration. In regime B, only such parameters as leaf length and fractal dimension indicated a marked response (LOEC was much lower for other parameters, 0.8% and 1.84% respectively). Leaf length and, especially, fractal dimension are shown to be good indicators of plant response to toxicants in their environment.