No abstract

Microplastics are regarded as vectors of hazardous contaminants due to their ability to adsorb xenobiotic chemicals. This has led to increased interest in the risk of previously neglected microplastic contaminants in the aquatic environment. Here, we assessed the possibility of transferring chemical contaminants to microplastics by evaluating the adsorption performance of (in)organic pollutants on various types of microplastics (polystyrene, PS; polyethylene terephthalate, PET; high-density polyethylene, HDPE; and low-density polyethylene, LDPE;). Considering the toxicity and polarity of each pollutant, dyes (BB9 and RR120) and heavy metals (Cd(II), Pb(II), As(III), and As(V)) were selected for the adsorption experiments. Dye was found to be adsorbed through physical adsorption. The adsorption capacity of microplastics for RR120 and BB9 was the highest for HDPE-1 and LDPE-1, respectively. Additionally, the smaller the size of the microplastics, the higher the adsorbed amounts. The main adsorption mechanism of heavy metals was found to be through physical and chemical adsorption. And adsorption mechanism of dye depends on physical adsorption. Thus, the adsorption of microplastic contaminants was affected more by the condition than by the type of microplastics.

Since microplastics are considered harmful to the human body, studies on their samplings, pretreatments and analyses environmental media, such as water, are continuously being conducted. However, a standard sampling and pretreatment method must be established, particularly because microplastics of a few micrometers in size are easily affected by external contamination. In this study, a microplastic sampling device was designed and developed to obtain a high recovery rate of microplastics and prevent plastics contamination during all processes. For the evaluation of the developed device, microplastic reference materials were produced and used, and computational fluid dynamics (CFD) analysis was performed. This device has not only been applied to the relatively large previously studied microplastics (100 µm) but also to microplastics of approximately 20 µm that are vulnerable to contamination. A recovery rate of 94.2% was obtained using this device, and the particles were separated by filtration through a three-stage cassette. In conclusion, we propose a method to increase the accuracy and reproducibility of results for microplastic contamination in the environment. This method is able to consistently obtain and manage microplastics data, which are often difficult to compare using various existing methods.

Following the alarming reports of microplastic pollution in the marine environment, increased attention has been given to microplastics in other environmental media. Despite the attention, there is limited information on the effects of microplastics distribution in freshwater systems. Further, because the size of microplastics varies widely in the environment, the commonly used sampling devices are not suitable for selectively extracting microplastics without causing cross-contamination. Thus, we developed a suitable device for microplastics of size 5–20 µm and studied microplastics distribution in freshwater at various depths by considering various types of microplastics and aqueous systems. Lake and river, two major water sources in South Korea, were selected for the study of microplastics distribution in water system. The microplastics distribution characteristics in both water systems showed that polypropylene and polyethylene were the most abundant across all depths because of their production volume. Plastic types with higher density were found only at the lower layers, and polystyrene was found in the upper layers because of the environmental effects on its buoyancy caused pore diameter and surface area. The lake and river had higher microplastics distribution in the lower layer and upper layer, respectively. This was because the flow rate in river was higher than that of lake. The higher flow rate reduced the settling velocity in river. Thus, hydrodynamic stability influences the vertical distribution and concentrations of microplastics in the water systems. These results are expected to be used for understanding the behavioral characteristics of microplastics in water systems and to manage water sources.

Following the alarming reports of microplastic pollution in the marine environment, increased attention has been given to microplastics in other environmental media. Despite the attention, there is limited information on the effects of microplastic distribution in freshwater systems. Further, because the size of microplastics varies widely in the environment, the commonly used sampling devices are not suitable for selectively extracting microplastics without causing cross-contamination. Thus, we developed a suitable device for microplastics of size 5–20 µm and studied microplastic distribution in freshwater at various depths by considering various types of microplastics and aqueous systems. Two large water systems, a lake and a river, were chosen to study microplastic distribution. The microplastic distribution characteristics in both water systems showed that polypropylene and polyethylene were the most abundant across all depths because of their production volume. Plastic types with higher density were found only at the lower layers, and polystyrene was found in the upper layers because of the environmental effects on its pore diameter and surface area. The Lake and River had higher microplasticdistribution in the lower layer and upper layer, respectively. This was because the flow rate in River was higher than that of Lake. The higher flow rate reduced the settling velocity in River. Thus, hydrodynamic stability influences the vertical distribution and concentrations of microplastics in the water systems. These results contribute to the understanding and control of microplastics.