Entrainment and Enrichment of Microplastics in Ice Formation Processes: Implications for the Transport of Microplastics in Cold Regions

Abstract

Sea ice can serve as a temporary sink for microplastics (MPs), and thus, it too can function as a secondary source of and transport medium for MPs. This study aimed to explore the effect of various MP properties and environmental characteristics on the entrainment and enrichment of MPs in ice under varying turbulence conditions. It was found that high rotation speed in freshwater distinctively enhanced the entrainment of hydrophobic MPs in ice, this being attributable to the combined effects of frazil ice and air bubbles. The hydrophobic nature of these MPs caused them to be attracted to the water/air or water/ice interface. However, in saline water, high turbulence inhibited the entrainment of all of the MP types under study. The ice crystals formed a loose structure in saline water instead of congealing, and this allowed the exchange of MPs between ice and water, leading to the rapid expulsion of MPs from the ice. The enrichment factors of all the MPs under study increased in calm saline water compared to in calm freshwater. The results revealed that the entrainment and enrichment of MPs in ice can be critical pathways affecting their fate in cold regions.

Human Exposure to Ambient Atmospheric Microplastics in a Megacity: Spatiotemporal Variation and Associated Microorganism-Related Health Risk

“…75 During rainy periods, AMPs that were not easy to deposit would be transported by rainwater frequently, enhancing the deposition rate and the polymer type number of collected AMPs. 76,77 In dry periods, dry deposition became the primary mode of AMP deposition, 74 with external AMPs transported from other regions contributing to the polymer types. 45 However, this transport can be disrupted by rainfall, which could explain the negative correlation between the AMP polymer type number and RF.…”

“…45 However, this transport can be disrupted by rainfall, which could explain the negative correlation between the AMP polymer type number and RF. 75,76 High WS is unfavorable for local accumulation of AMPs, resulting in its negative correlation with AMP abundance and polymer types during rainy periods. 66 During dry periods, dry deposition was influenced by multiple factors like human activities and transportation distance, possibly obscuring the impact of WS.…”

Role of Aquatic Dissolved Organic Matter in the Entrainment of Microplastics under Freezing Conditions

“…After carefully separating the ice and residual water into separate beakers, they were sealed and left at room temperature overnight before taking measurements. The procedure of the ice formation experiment was modified from our previous study by Chen et al 12 The MP concentration in ice and water was measured with a LISST-200X (Sequoia Scientific, USA) using laser diffraction principles. The volume of melt ice (V ice ) was determined using a 50 mL graduated cylinder, and the volume of residual water after the ice formation experiments (V water ) was calculated.…”

“…For example, buoyant MPs are more likely to become entrapped in sea ice as it forms from the water’s surface . Additionally, the entrainment of MPs in ice can be affected by other factors such as turbulence, salinity, the hydrophobicity of the polymer, and the size of the particles. , …”

“…11 Additionally, the entrainment of MPs in ice can be affected by other factors such as turbulence, salinity, the hydrophobicity of the polymer, and the size of the particles. 12,13 The behavior of MPs is highly dependent on their physicochemical properties and surface characteristics, which can be significantly impacted by aging and the presence of organic matter on their surfaces. Aquatic dissolved organic matter (DOM) includes various functional groups that can provide diverse sites for the adsorption of environmental contaminants, including MPs.…”