## 1 Introduction
### Microplastics Research in Kazakhstan and Central Asia  
Although microplastics were officially recognized as an ecosystem pollutant at the global level in the early 2000s, they are of growing concern in Kazakhstan currently. MPs are practically not studied in Kazakhstan. The prerequisites for the beginning of the present study were a huge amount of plastic garbage found during previous field studies. With scientific investigations analyzing the degree of pollution by plastic of the world ocean, freshwater ecosystems and the environment as a whole [40; 41; 42; 43; 44; 45; 52], we raise for the first time the issues of micro- and macroplastic pollution of the environment in Kazakhstan, with the example of the freshwater Lake Markakol (48\({}^{\circ}\)45\({}^{\prime}\) N 85\({}^{\circ}\)45\({}^{\prime}\) E). The present study was carried out within the framework of a scientific project under grant funding from the Ministry of Science and Higher Education of the Republic of Kazakhstan (AP14870595) \"Monitoring of the state and assessment of the level of pollution by micro- and macroplastics in the aquatic environment of Lake Markakol\". A literature review demonstrates the relevance of plastic pollution [53; 54; 55; 56; 57; 58; 59; 60]. The detection of MPs in water and bottom sediment samples in landlocked countries of Central and East Asia indicates that even less densely populated countries are exposed to MP pollution. It is difficult to understand the severity of MP pollution in these countries because of the limited number of regional MP pollution analyses. Experts claim that among all landlocked countries in Asia, Mongolia has the most studies on MP pollution, while Turkmenistan, Afghanistan, Uzbekistan, Kyrgyzstan, Tajikistan and Kazakhstan have nearly none [61]. Unfortunately, references to studies on plastic in the aquatic environment in Kazakhstan are rather scarce. One of the first references to plastic debris in Kazakhstan was made by [PERSON]. (2017) in the publication \"How to save the Caspian seal (_Pusa caspica_)\". Here, the author noted the visual detection of plastic debris on the Kazakh shores of the Caspian Sea. In 2021, the same author emphasized the need to study the problem of plastic pollution and its impact on the biodiversity of water bodies in Kazakhstan [62; 63]. Interesting results were also obtained by a group of scientists led by [PERSON], who conducted an ecological assessment of MP pollution of solid domestic waste landfills in the Akmola region located in northern Kazakhstan. Thus, the results obtained during the study should serve as both prerequisite and fundamental data for the forthcoming numerical modeling of MP behavior in soil and water [64]. The results of another study on the tributaries of the Syrdarya River conducted by Uzbek colleagues also aroused interest [65]. Thus, according to these authors, they screened the MP content in the surface water and bottom sediments of the Karadaya and Chirchik rivers, the first-order tributaries of the Syrdarya River in Uzbekistan. The average amount of MPs in the Karadaya and Chirchik rivers was 4.28 \(\pm\) 0.09 and 0.95 \(\pm\) 0.36 items per m\({}^{3}\), and in the benthic sediments, it reached 244 \(\pm\) 28.9 and 333 \(\pm\) 11.5 items per kg of dry soil, respectively. The MP concentrations in the surface water and bottom sediments of the Karadaya River were significantly higher (\(p\) value \(<\)0.01) than those in the Chirchik River. Microfibers were the most widespread there; the proportion of MP fibers in the water of the Karadaya and Chirchik rivers was 89% and 95%, and in the rivers' bottom sediments, it was 86% and 84%, respectively [65]. The prevalence of microfibers may indicate the pathway of entry into the rivers through discharges of domestic wastewater treatment facilities. Polymer microparticles in surface water and bottom sediments of the Karadaya and Chirchik rivers were mainly represented by polyethylene terephthalate (PET), which accounts for half of all MPs found in the Karadaya River.