GEOGRAPHY

Progress has been made in the study of microplastic transport process in the southern Qinghai-Tibet Plateau


Microplastics, a potential indicator of the geological epoch of the Anthropocene, are a typical pollutant brought entirely by human activities. At present, there is a relative lack of research on the exposure of terrestrial wildlife to microplastics and the transport mode of microplastics in remote areas, especially for the Qinghai-Tibet Plateau with unique geographical unit characteristics and climatic conditions, although studies have confirmed that it has been contaminated by microplastics, the transport mechanism of microplastics on the Qinghai-Tibet Plateau is still relatively vague.

The Institute of Earth Environment, Chinese Academy of Sciences investigated in detail the microplastics in the lithosphere (soil) and biosphere (feces of Equus Kiang) in the southern Qinghai-Tibet Plateau, and evaluated the degree of microplastic hazards and microplastic transport process of the Tibetan wild ass, a national first-class protected animal, and found that the feeding and migration process of terrestrial wild animals is a unique microplastic transport mechanism in the Qinghai-Tibet Plateau. This work has resulted in the following results. (1) The median abundance of MPs in feces and soil of Tibetan wild donkey reached 102 and 4.01 particles/g dry weight (MPs particle size range of 20-500 μm), respectively, and 29 MPs types were identified in feces, while 26 species were in soil, and the morphology was dominated by ~50 μm slender fiber particles. (2) The feeding behavior of Tibetan wild asses causes MPs to be bioenriched (enrichment coefficient of ~25) and transmitted along the terrestrial food chain, which may become a “new” source of MPS pollution when migrating to other remote areas of the plateau. Taking a group of 20 Tibetan wild donkeys as an example, the potential transmission flux of MPs in the Tibetan wild donkey group is 1736 particles·m-2·a-1, and the migration behavior of the Tibetan wild donkey group may promote the spread of microplastics to the depths of the plateau. (3) Since the southern part of the Qinghai-Tibet Plateau is adjacent to the human settlements of South Asia and East Asia, a large number of MPs are transmitted through the atmosphere over long distances, which is an important way for MPs to enter the southern part of the Qinghai-Tibet Plateau. Atmospheric MPs sink to the surface of the Qinghai-Tibet Plateau or are intercepted by vegetation; It is then ingested by terrestrial wild animals and accumulates in the body, and then migrates to other locations and excretes the ingested MPs; Finally, the MPs in the feces are resuspended under the action of wind to become the source of transmission, that is, the propagation process of “atmospheric deposition-vegetation-feces-atmosphere” from the source to the sink to the source, thereby expanding the transmission range. This may be one of the special “source-sink-source” transmission modes of microplastics on the Qinghai-Tibet Plateau.

The study is crucial to exploring microplastic pollution and its impact on the ecological environment on the Tibetan Plateau, providing scientists with new insights into the ecological hazards of microplastic pollution on the Tibetan Plateau and Earth system feedback from terrestrial ecosystems. In addition, the concept of Anthropocene geochronology emphasizes the long-term and significant impact of human activities on the planet. Microplastics, as potential indicators, represent typical pollutants brought about by human activities. By in-depth study of the spread and impact of microplastics on the Qinghai-Tibet Plateau, we can better explore the impact of human activities on the environment and provide a scientific basis for the formulation of effective conservation measures.

The research was published in Environmental Science & Technology. The research work was supported by the National Natural Science Foundation of China, the Strategic Leading Science and Technology Project of the Chinese Academy of Sciences, the Second Qinghai-Tibet Plateau Comprehensive Scientific Expedition and the Youth Innovation Promotion Association of the Chinese Academy of Sciences. (Source: Institute of Earth Environment, Chinese Academy of Sciences)

Related paper information:https://doi.org/10.1021/acs.est.3c00582

Figure 1. Schematic diagram of the propagation process of microplastics in the Qinghai-Tibet Plateau

Figure 2.  Distribution of microplastic abundance at topsoil (black circle) and feces (red circle) sampling sites in the southern Qinghai-Tibet Plateau. Units: particles/g dry weight(d.w.). The schematic diagram contains the propagation paths of the westerly and Indian monsoons.

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