Specific biotests to assess eco-toxicity of biodegradable polymers in soil

In the present investigation, the extent of biodegradation and potential eco-toxicological effects of synthetic biodegradable plastic materials were investigated under laboratory conditions. Different polymers in powder at the final concentration of 1% were added to the soil; the polymer treatments were: polyethylene (PE), polystyrene (PS), Ecoflex and cellulose. The monitoring of the mesoscale experiment consisted of soil sampling carried out after one days (T0) and 45 days (T1) from the experiment set up. Chemical, biochemical and biological parameters were used to evaluate the soil conditioning during the polymer biodegradation. Furthermore, two terrestrial plants, oat (Avena sativa) and red radish (Raphanus sativum), were used to evaluate the phytotoxicity of the polymers. For this purpose, after 35 days from the experiment set up, 100 seeds of each plant species were sown uniformly in each pot. The upper growth was checked at the end of experimentation (after 10 days of incubation). Polymers stimulated soil metabolic activity with time, thus indicating their possible biodegradability in soil. These effects were more evident in Radish treatments than in Avena, suggesting the higher sensitivity of radish to the polymers treatment. Because Radish growth was inhibited while Avena was stimulated, there is clear evidence that the easiest biodegradation of polymers in Radish treated soil has produced intermediate phytotoxic compounds.