The influence of microplastics from ground tyres on the acute, subchronical toxicity and microbial respiration of soil

Abstract

As a rubber annular coat of rim wheels, tyres are inevitable parts of all vehicles in modern times. As to their composition, however, they represent a risk for the environment. During the use of tyres, tyre tread patterns become abraded, which results in its gradual wear and necessary re-placement. These micro and nano particles are then gradually extracted into the environment, namely soils and waters. Our research study was focused on the assessment of subchronical phytotoxicity (pot trial with a mixture of substrate and predetermined ratio of abrasion products lasting 28 days) and biological tests (testing phytotoxicity of leaches with predetermined ratio of abrasion products on Petri dishes). The biological tests were comprised two plant species—seeds of white mustard (Sinapis alba L.) and garden cress (Lepidium sativum L.). In the mixtures of substrate with determined shares of abrasion products (5%, 25%, 50% and 75%), respiration of CO2 was also established by means of soil microbial respiration (Solvita CO2-Burst). Substrates with 5% and 25% abrasion proportions showed increased biological activity as well as increased CO2-C emissions. The increasing share of abrasion products resulted in decreasing biological activity and decreasing CO2-C emissions. The results of subchronical phytotoxicity ranged from 62% to 94% with values below 90% indicating substrate phytotoxicity. The results of biological tests focused on the phytotoxicity of tested samples exhibiting values from 35% to 70% with respect to the germination index with values below 66% indicating the phytotoxicity of tyre abrasion products.