Decomposition of microplastics: Emission of harmful substances and greenhouse gases in the environment

Abstract

Few reports have been reported on the conditions of the decomposition of plastics in the environment and their threats, while the influence of the decomposition of plastics as a potential factor in increasing greenhouse gas emissions has not been investigated. Greenhouse gases from the decomposition of plastics have so far not been considered in the development of models that show the likely climate change in the future. The work described here examined the presence and possibility of emission of phthalic acid esters and greenhouse gases from various plastic materials in daily use in the aquatic environment. The article presents, inter alia, research on the influence of temperature (20, 60, and 90 °C), pH (3, 7, and 10), plastic material, time (1, 3, 5, 7, and 14 d), and ultraviolet radiation on the migration of components present in various types of plastics, such as poly(vinyl chloride) (with high and low content of plasticizers) and polypropylene. No significant effect of pH on the migration of the plasticizers from the polymer matrix was observed. In turn, the influence of temperature on the emission of these susceptibilities was determined by the type of polymer. The highest emission level of plasticizers made of poly(vinyl chloride) was recorded for 60 °C, while from polypropylene for 20 °C. Depending on environmental conditions, the degradation of microplastics leads to a reduction in the mass of the material and conversion to methane and carbon dioxide. Each material was degraded, which resulted in the observed migration of components and methane and carbon dioxide emissions from the analysed materials. The highest degree of bis(2-ethylhexyl) phthalate migration was observed for the material made of poly(vinyl chloride). The amount of greenhouse gas emissions depended on the insolation conditions, and the poly(vinyl chloride) material showed the highest emission of methane and carbon dioxide. The highest concentration of methane at the level of 94 ppm after 360 days was observed for poly(vinyl chloride) with a large amount of plasticizers without access to light.