Abstract
Plastic has been an environmental pollutant far longer than claimed by the first reports surfacing in 1979, meaning some plastic materials have been decaying in nature for decades. Nevertheless, the threat posed to biota is not fully understood, especially from aged microplastic. The question considered in this study was whether the adverse effects of new plastic differ from those of old plastic material. Therefore, the morphological and physiological effects on Lepidium sativum with exposure to both new and aged polycarbonate were considered against a known stressor leaching from polycarbonate with time, bisphenol-A. Exposure to new and short-term aged polycarbonate (up to 80 days) elicited the most severe effects such as germination inhibition, reduced seedling growth, decreased chlorophyll concentrations, and increased catalase activity. These adverse effects in L. sativum associated with polycarbonate exposure were reduced as a function of the ageing time applied to the polycarbonate. The chemical substances that lend new polycarbonate material its toxicity were likely leached with time during the ageing process. Based on the results obtained, temperature and humidity based artificial ageing significantly reduced the phytotoxicity of the microplastic particles.
Highlights
Plastic pollution is not a new concern as the first evidence of its environmental distribution were given in 1979 via a study on pelagic tar and plastic in the ocean (Shaw and Mapes, 1979), as well as the description of patches of plastic waste in the ocean described back in 1986 (Day, 1986)
Bisphenol A (BPA), a building block of polycarbonate granulate (PC) previously reported to leach from the material (Carwile et al, 2009), was selected to elucidate the effects of substances possibly leaching from MP material on the germination and growth response of the garden cress, L. sativum after seven days
Even though the bisphenol A (BPA) concentration applied in this study (4166 μg BPA kg−1 soil) was much higher, the inhibition caused by new and 40-day aged PC was significantly higher, highlighting the synergistic effects of other toxic compounds leaching from the MP granules
Summary
Plastic pollution is not a new concern as the first evidence of its environmental distribution were given in 1979 via a study on pelagic tar and plastic in the ocean (Shaw and Mapes, 1979), as well as the description of patches of plastic waste in the ocean described back in 1986 (Day, 1986). The fate of MP toxicity with time is poorly understood and seeing as MP pollution has existed for as long as plastics have been in production and is steadily increasing, it is essential to establish the environmental effects of aged MP. It was hypothesised that the factor of time, or in the case of MP, ageing of the particles, will significantly influence the phytotoxicity due to the leaching of additives that possibly lend the toxic characteristics to MPs. The aim was to investigate possible adverse effects of artificially aged PC granulate (aged for varying periods) and bisphenol A (BPA) on seed germination, seedling growth, and physiological parameters such as pigment content and the antioxidative enzyme activity of catalase. Under environmental conditions, PCs degrade with time (Ram et al, 1985), and end up in nature and was selected as test material in the present study
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