Laboratory of Environmental Toxicology and Aquatic Ecology, Coupure Links 653, B-9000 Ghent, Belgium.
Department of Green Chemistry and Technology, Graaf Karel de Goedelaan 5, 8500 Kortrijk, Belgium.
Environ Sci Technol. 2020 Jul 21;54(14):8668-8680. doi: 10.1021/acs.est.9b07378. Epub 2020 Jul 2.
Microplastics are ubiquitous pollutants within the marine environment, predominantly (>90%) accumulating in sediments worldwide. Despite the increasing global concern regarding these anthropogenic pollutants, research into the remediation of microplastics is lacking. Here, we examine those characteristics of microplastics that are essential to adequately evaluate potential remediation techniques such as sedimentation and (air) flotation techniques. We analyzed the sinking behavior of typical microplastics originating from real plastic waste samples and identified the best-available drag model to quantitatively describe their sinking behavior. Particle shape is confirmed to be an important parameter strongly affecting the sinking behavior of microplastics. Various common shape descriptors were experimentally evaluated on their ability to appropriately characterize frequently occurring particle shapes of typical microplastics such as spheres, films, and fibers. This study is the first in this field to include film particles in its experimental design, which were found to make up a considerable fraction of marine pollution and are shown to significantly affect the evaluation of shape-dependent drag models. Circularity χ and sphericity Φ are found to be appropriate shape descriptors in this context. We also investigated the effect of biofouling on the polarity of marine plastics and estimated its potential contribution to the settling motion of initially floating microplastics based on density-modification. It is found that biofouling alters the polarity of plastics significantly; this is from (near) hydrophobic (i.e., water contact angles from 70 to 100°) to strong hydrophilic (i.e., water contact angles from 30 to 40°) surfaces, rendering them more difficult to separate from sediment based on polarity as a primary separation factor. Thus, besides providing a better understanding of the fate and behavior of typical marine microplastics, these findings serve as a fundamental stepping-stone to the development of the first large-scale sediment remediation technique for microplastics to address the global microplastic accumulation issue.
微塑料是海洋环境中无处不在的污染物，在全球范围内主要（>90%）积累在沉积物中。尽管人们对这些人为污染物的关注度日益提高，但对微塑料的修复研究却很少。在这里，我们研究了微塑料的特性，这些特性对于充分评估潜在的修复技术（如沉降和（空气）浮选技术）至关重要。我们分析了来自真实塑料废物样本的典型微塑料的沉降行为，并确定了最佳可用阻力模型来定量描述它们的沉降行为。颗粒形状被确认为强烈影响微塑料沉降行为的重要参数。各种常见的形状描述符在实验中评估了它们适当描述典型微塑料（如球体、薄膜和纤维）常见颗粒形状的能力。这项研究是该领域中第一个将薄膜颗粒纳入其实验设计的研究，发现薄膜颗粒在海洋污染中占有相当大的比例，并且显著影响了基于形状的阻力模型的评估。圆形度 χ 和球度 Φ 被发现是这种情况下合适的形状描述符。我们还研究了生物污垢对海洋塑料极性的影响，并根据密度修正估计了其对初始漂浮微塑料沉降运动的潜在贡献。结果发现，生物污垢会显著改变塑料的极性；从（近）疏水性（即水接触角为 70 到 100°）到强亲水性（即水接触角为 30 到 40°）表面，使得它们更难以根据极性作为主要分离因素从沉积物中分离出来。因此，除了更好地了解典型海洋微塑料的命运和行为外，这些发现还为开发第一个大规模的微塑料沉积物修复技术奠定了基础，以解决全球微塑料积累问题。
