Microplastics and their impact on the environment and humans have become more and more of an issue in recent years. Until now, the focus has mainly been on water and soil, but now the fine plastic particles have also been detected in cloud droplets.
Microplastics are everywhere
The sources of microplastics are manifold: they are often used intentionally in cosmetics and hygiene products, otherwise they are created as part of the aging process of plastics – whether plastic packaging, functional clothing or simply tire abrasion from millions of vehicles (actually one of the biggest polluters). Through mechanical, thermal and UV exposure, the primary microplastic (still somewhat coarser pieces) breaks down into ever finer particles – until it finally becomes nanoplastic. In recent decades, it has been distributed almost everywhere by rain, wind and wastewater. It is found in seawater and therefore also in the sea salt extracted from it, in fish and other organisms, even in the snow of the Arctic. We ingest it with our food and drinks. It is stirred up by the wind and we breathe it in. However, it is probably distributed much further into the atmosphere than expected. Above all, it also seems to act as a condensation nucleus.
This aspect is still relatively new and was recently investigated by researchers at Shandong University in Qindao. This study was published in Environmental Science & Technology Letters (link to original article). The working group chose Tài Shān, a 1545-metre-high mountain in eastern China, for the study. They used Teflon threads to collect water from cloud droplets and analyzed it. Microplastics of various sizes were found in 24 of 28 samples; on average, one liter contained 463 particles. They consisted of many different types of plastic (including polyethylene terephthalate, polypropylene, polyethylene, polystyrene and polyamide), and most of the particles were smaller than 100 micrometers (sizes between 8 and 1542 μm, 60% smaller than 100 μm).
Fig. 1: The Tài Shan mountain in China; Source: Wikipedia
In the laboratory, the ageing of the particles was investigated under various conditions. Under atmospheric conditions (oxygen, UV radiation, water and major temperature fluctuations) it was different from that in the sea or soil, for example. In the first case, the particles exhibited a rougher surface, which can be attributed to photochemical ageing. This improved the adsorption capacity for potentially toxic metals such as mercury and lead. In combination, these fine particles appear to act as condensation nuclei, which in turn modifies cloud formation. And this in turn influences the weather and climate (via the radiation balance and precipitation). This behavior must now be investigated in more detail.
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