Evaluation of Surface morphology and erosion in marine microplastics

Microplastics (MP: ۱mμ-۵mm) have received particular attention due to their number and wide range of their distribution in all water, soil, and air sources. These particles have physical and chemical damage risks because of the carcinogenic plasticizer chemicals and pollutants absorbed into the plastic surface so breathing and eating them can cause disturbances even at cell and tissue level. As a piece of a macro-plastic or a primary one, marine MPs are exposed to mechanical, biological, and chemical surface erosions as soon as entering the marine environment. Over time, the erosion changes their surface properties and effectively degrade them into smaller MPs and even nanoplastics. Researches on MPs' surface morphology are dependent on the expert’s skills and the high resolution and accurate images captured by the electron microscope. In the central laboratory of Shahid Beheshti University, after visual separation by an Olympus SZ۴۰ stereomicroscope, and plastic polymer approval by EDAX method (Energy Dispersive X-ray Spectroscopy), the Hitachi SU۳۵۰۰ electron microscope (Hitachi, Japan) was used to capture high-resolution images of surface detail, possible erosion, and sedimentation on the MP’s surface. SEM images showed some diverse morphologies including deposited or adhered biological or non-biological particles; indentation and protruding; shallow surface cracks and deep grooves; pits; breakages; and scaly appearances. The results showed that the intensity and type of surface erosion varied depend on the type and shape of the MPs i.e. irregular fragments, beads, and fibers. The highest deformation was observed in the surface of fragments. However, the minor erosion in fibers and beads indicate their slow degradation process and durability in the environment. It may lead to their higher stability and transfer rate in the food chain, make them available to a wide range of marine biota, and put human health in danger due to the consumption of seafood products.

کلیدواژه ها:

Pollution ، Plastics ، SEM ، Surface erosion