Airborne nanoplastics: surface chemistry and cloud-crystallisation properties

不幸的是，由于人类活动，污染环境的微米和亚微米塑料颗粒的数量正在增加。已经表明，微塑料对环境有不利影响，但人们对它们对云中冰的形成(改变地球的辐射特性)的影响知之甚少。此外，我们对结冰现象的理论理解还相当差。因此，模型不能准确地预测基质是否会促进液态水中冰核的形成。因此，需要进行实验研究，以评估一种塑料物种是否会促进云中冰晶的形成。为此，采用低温球磨法制备了微塑料，并通过筛分对其进行了粒度分离。利用XPS、光学显微镜和红外光谱等表征技术对其尺寸和表面官能度进行了研究。通过对塑料样品在超纯水中的悬浮液进行液滴冻结实验，研究了实验室制备的微塑料的成冰性能。为此，冰箱--一种新型的开放式液滴系统--被用来在湿度可控的大气中以恒定的速度冷却悬浮液滴。根据塑料的化学和物理特性，微米和纳米塑料可能会对液滴的冻结温度产生显著影响。这项研究将对大气科学和冰物理领域都具有重要意义。

The amount of micro and sub-micro-sized plastic particles polluting the environment is, unfortunately, increasing due to human activity. It has been shown that microplastics have an adverse effect on the environment, but little is known about their influence on the formation of ice in clouds (which alters the radiative properties of the Earth). Moreover, our theoretical understanding of the phenomenon of ice formation is fairly poor. As a result, models cannot be used accurately to predict whether a substrate will promote the formation of an ice nucleus within a body of liquid water. Therefore, experimental investigations are needed to assess whether a plastic species will promote the formation of ice crystals in clouds. For this purpose, microplastics are synthesized using cryogenic ball milling and separated in size by sieving. Their sizes and surface functionalities were investigated using characterization techniques such as XPS, optical microscopy, and IR spectroscopy. The ice nucleating properties of the laboratory-made microplastics are investigated by performing droplet freezing experiments with suspensions of the plastic samples in ultrapure water. For this, the IceBox, a novel open droplet system, was used to cool suspension droplets at a constant rate in an atmosphere with controlled humidity. Depending on the plastic's chemical and physical characteristics, the micro and nano plastics could have a notable effect on the temperature of freezing of the droplets. This research will be of importance to both the field of atmospheric science and ice physics.