Microplastic contamination of aquatic environments has become an increasingly alarming problem. These, defined as particles <5 mm, are mostly formed due to the cracking and embrittlement of larger plastic particles. Recent reports show that the increasing presence of microplastics in the environment could have significant deleterious consequences over the health of marine organisms, but also across the food chain. Herein, we have studied the effects of artificial seawater on polyethylene (PE)-based beads by exposing them up to eight weeks to saltwater in stirred batch reactors in the dark and examined the structural and morphological changes these endured. Electron microscopy observations showed that artificial seawater induces severe microcracking of the pellets' surfaces. Additionally, Fourier transform infrared spectroscopy (FTIR) analyses evidenced the formation of oxidized groups whenever these particles were exposed to water and an increase in organic matter content of the waters in which the pellets were kept was evidenced by Raman spectroscopy. There were also noticeable consequences in the thermal stability of the polyethylene pellets, as determined by thermogravimetric studies (TGA). Furthermore, the parallel exposure of polyethylene pellets to UV radiation yielded less pronounced effects, thus underscoring its lower preponderance in the degradation of this material. These results highlight the importance of determining the mechanisms of degradation of microplastics in marine settings and what the implications may be for the environment. Overall, the herein presented results show that a relatively short period of time of accelerated exposure can yield quantifiable chemical and physical impacts on the structural and morphological characteristics of PE pellets.

Environmental context: There is increasing concern from both the general public and the scientific community about microplastic-related pollution. Despite the alarming and well-documented accumulation of plastics in the marine environment, little attention has been paid to the sources, fate and effects of microplastics in terrestrial settings. We overview the prevalence of microplastics in soils, evaluate their impacts, and appraise the current difficulties in their determinations in terms of sampling, isolation and identification. There has been an increasing interest by both the general public and the scientific community in microplastic-related pollution. Owing to their physical and chemical characteristics, these highly ubiquitous contaminants may be ingested by numerous organisms at the base of food-webs. Furthermore, owing to their tendency to adsorb other chemical substances, such as persistent organic pollutants (POPs), these plastic particles can lead to bioaccumulation and bioamplification phenomena, which significantly increases their potential environmental effects. However, most of the current research available is focussed on the prevalence and effects of these materials in water, and, more precisely, in oceans. Although this is understandable, owing to the alarming accumulation of plastics in this environmental compartment, little attention has been paid to the sources, fate and effects of microplastics (MPs) in terrestrial settings. This is further complicated by the current lack of universally accepted methods for the assessment and identification of MPs, not only in liquid, but also in solid matrices. We overview the most current data regarding the presence and prevalence of MPs in soils and evaluate their recognised impacts and potential consequences. We also appraise the current sampling, isolation and identification methodologies and suggest methods that may contribute to the development of standard operating procedures (SOPs) for the sampling and characterisation of these pervasive pollutants in complex matrices, such as soils.