1 Introduction

Plastics have been widely used in recent decades because of their low cost, lightweight, corrosion and high-temperature resistances, and electrical insulation properties. With the daily use of plastic consumer goods, plastic and microplastic (MP) pollution has spread in soils and rivers worldwide. The impact on lakes, marine ecological environments, and human health has attracted increasing attention (Lin et al. 2022). As the storage of inland water resources, lakes provide resources for irrigation, shipping, power generation, runoff regulation, and tourism development for human beings. MPs enter lakes and cause extensive pollution (Bajkiewicz-Grabowska et al. 2020). Importantly, 80% of all MPs in the ocean originate from land-based and freshwater systems (Rochman 2018). As small catchments of freshwater systems with long residence times and weak disturbances, lakes are highly susceptible to the runoff-induced deposition of MPs at the bottom (Dong et al. 2020). Currently, the common types of MPs in lakes include polyethene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polyethene terephthalate (PET) (Wagner et al. 2014). In terms of shape, MPs also include chips, pellets, fibres, films, and foams (Baldwin et al. 2016). As they are difficult to degrade in natural environments, MPs have become new pollutants of great concern (Tang et al. 2021).

We use bibliometric methods to understand the development process of MPs; MPs were first defined in 2004 and have developed over 18 years (Thompson et al. 2004). However, lake MPs were first studied in 2013 (Eriksen et al. 2013), nearly 10 years after the study of MPs in the sea. Thus, the sources and distribution of MPs in lakes and their hazards are still controversial research topics. Dusaucy et al. (2021) summarized the abundance, shape, size, and colour of MPs in lakes worldwide, and analyzed and assessed the main possible sources of MPs and the contribution of the different sources. Yang et al. (2022) compared the differences in lake MPs across continents and countries globally, linking their distribution to development levels and economic structures, and finally summarized and analyzed the relevant policies in each country.

Reviews of MPs in lakes are limited, with the main studies focusing on typical areas or areas with typical characteristics, such as urban, alpine, and glacial lakes (Shi et al. 2022). Moreover, comprehensive and systematic elaboration on the sources and distribution of MPs in lakes is lacking. Although Yin et al. (2019) proposed a certain linear relationship between distance from cities and MPs, they focused on 20 lakes in Changsha and not on a global scale. In this study, we selected 66 global lakes for linear analysis of MPs in water and distance from residential areas, population density and other literature data, and analyzed the factors affecting MPs from various aspects such as population and lake characteristics. MPs are classified into two categories, primary and secondary, according to their sources (Halfar et al. 2021). Primary MPs mainly originate from toiletries, cleaning, and medical products and industrial production processes, and then enter aquatic systems through the discharge of domestic wastewater. The content of MPs in cleaning products and cosmetics in our freshwater environment is low, and large amounts of MPs in domestic wastewater are also removed during treatment at wastewater treatment plants (WWTPs) (Anagnosti et al. 2021). Secondary MP sources are much more extensive, including fishing nets abandoned in lakes or rivers and abandoned plastic sheds (Horton et al. 2017). Therefore, secondary MPs account for the majority of MPs in the current water environment and are considered the main pollutants in the water environment due to their smaller particle size. Influenced by water depth, flow velocity, particle type and density, the morphological types of MPs in the water column of lakes at different depths, etc. differ significantly (Lenaker et al. 2019), and similar findings were illustrated by the sediments of Chinese lakes (Feng et al. 2022).

Focusing on the progress of research on lake MPs, this study analyzed the development history, cutting-edge technologies, and future research trends of lake MPs. Using the CiteSpace bibliometric method, we systematically summarized the pollution status and challenges of MPs, analyzed the source and impact of MPs in 89 lakes globally, and the relationship between MP abundance, lake characteristics and human activities. Additionally, this study examined the toxicity and risk of MP exposure in the water environment and explored the focus and prospect of future theoretical research on MPs in lakes.

2 Research trend of MPs in lakes

Bibliometric analysis of MP-related studies in lakes was conducted by searching the Web of Science (WOS) core database from 2013-2022 using the search term “lake microplastics”. Word frequency and timeline development trend analyses were conducted to analyze lake MP source and distribution characteristics as well as the progress of environmental risk research, research hot spots, and future key research directions. A search for “microplastic” in the WOS core database yielded 1343 relevant articles, and a search for “lake microplastic” yielded 401 relevant articles with an exponential increase in annual publications (Fig. S1). Notably, the research on lake MPs was less than one-third of the total volume of publications in the field of MP research, which was dominated by marine environment studies (keywords: “marine environment” and “sea”). According to “lake microplastic” cloud analysis (Fig. S2a), 110, 70, 58, and 25 articles used “lake”, “great lake”, “river”, and “evaluation” as keywords, respectively. Further, this cloud analysis was combined with a cluster analysis on the keyword “lake MP” (Fig. S2b). The results were classified according to keyword frequencies using “China”, “North Sea”, “reservoir”, “Yellow Sea”, “mesoplastic”, “filtration rate”, “storage”, “microfibers”, and “ecosystem services”; research area hot spots included “China”, “North Sea”, and “Yellow Sea”, illustrating the increasing impact of MPs pollution in the area. Thus, the following research topics have become very popular among researchers: Mesoplastic and microfibers are the most extant types of plastics in the environment; from plastics to MP fibres; and illustrating the changing trends of research. The search results using keywords “conservatoire” and “storage” indicate that reservoirs are an important source of domestic water for humans, while the research on MP is also noteworthy. The white circle on the outer circle of the node in Fig. S2b denotes mutation words or words that appeared for the first time in the year. Meanwhile, the size of the circle indicates the number of research articles; that is, the circles represent research hot spots. The impact of MPs on ecosystems has become a research priority since 2015, as can be seen from the size of the circles with the keywords “impact” and “risk assessment”. There is a limited number of related articles, with only 25 and three studies having the keywords “impact” and “risk assessment”, respectively.

The earliest studies on MPs were conducted in marine environments (Fig. S2c), with keywords including “marine environment”, “sea”, “coast”, and “ocean” (140, 51, 13 and 4 articles, respectively). As MPs became increasingly widespread, research focusing on different water environments was becoming more refined after 2014. Further, MP characteristics are influenced by the water quality conditions and have different characteristics in “lake”, “river”, and “freshwater” ecosystems, as well as with different “evaluation” methods (110, 58, 55 and 25 articles, respectively). In addition to surface waters, the degradation, accumulation, and migration mechanisms of MPs in sediments and fish species have attracted the interest of researchers; there were a total of 100 articles in 2015 that included the keywords “surface water”, 121 articles in 2015 that included “sediment”, and 34 articles in 2014 with the keyword “fish”. As research on MPs continues, the definition of MP characteristics has become more refined, with different types of studies on plastic particles, fragments, and fibres.

Combined with current development trends, this study extracted relevant data on 89 lakes worldwide (including 50 lakes in Asia, 22 in Europe, four in Africa, 10 in North America, one in South America, and two in Antarctica). The bibliometric analysis of different sources, distribution characteristics, and ecological and environmental effects of MPs in different lakes aimed to provide support for pollution research and treatment of lake MPs.

3 Sources of MPs

MP abundance in lakes is closely related to urbanization, human industrial activities, and wastewater impacts (Boucher and Friot 2017; Turner et al. 2019; Vaughan et al. 2017). We, therefore, classified lakes according to their origins into urban, suburban or rural, and remote alpine lakes.

3.1 Major sources of MPs in urban lakes

Sources of MPs in urban lakes mainly include WWTPs, urban landfills, and manufacturing activities (Fig. 1) (Xu et al. 2021b). The abundance of MPs in Honghu, China ranges from 1250–4650 n/m3 (near Honghu City in the northeast), where primary sources are municipal waste and sewage (Wang et al. 2018). The east coast of Lake Guaiba in Brazil is located in a dense urban area, comprising 70% of the sewage collection area and MP concentrations ranging from 36.9 ± 2.1–61.2 ± 6.1 n/m3; however, the west bank is not densely populated, with only 0.014% of the sewage collection and MP concentrations ranging from 11.9 ± 0.6–24.6 ± 1.2 n/m3 (Bertoldi et al. 2021). Similarly, tributaries of the Selenga River in Mongolia flow through cities such as Ulaanbaatar, Darkhan, Erdenet, and Sukhbaatar, which are industrially developed. Additionally, domestic waste from residential areas is transported to landfills. Hence, MPs and other pollutants migrate from the leachate into the environment and MP abundance along the coast ranges from 2 to 506 n/100 m2 (Battulga et al. 2019).

Fig. 1
figure 1

Main sources of microplastics (MPs) in lakes. a suburban and remote lakes and b urban lakes

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3.2 Major sources of MPs in suburban lakes

Fisheries, agricultural and other production activities are additional sources of MPs, with fishing lines and nets, and agricultural films as the main sources of these pollutants. Frequent fishing leads to the aging of several fishing equipment such as fishing nets, fishing lines, and ropes that enter the lake as waste. As the world’s largest inland fishery, 90% of MP fibres in Lake Victoria originate from abandoned fishing tools, of which 59.1% are white or transparent fibres, and the most dominant MP polymers are PE and PP, accounting for 54.2 and 23.3%, respectively (Egessa et al. 2020b). Higher concentrations of MPs have been found in the water body and sediments of Poyang Lake in China. The central region is close to the largest fishing port, with more than 10,000 fishing boats and 100,000 fishermen, resulting in the intensification of MP concentrations in the central region (Yuan et al. 2019). In addition to agriculture and tourism, the MPs of Lakes Bolsena and Chiusi in Italy are laterally imported from the coastline and terrestrial environment with the wind, rain, and tide (Fischer et al. 2016). Polyamide (PA) mainly originates from toothbrush manufacturing, fisheries, automobile, textile, and other industries (Cole et al. 2011). It is the main MP type of Anchar Lake in India (Neelavannan et al. 2022) and Vesijärvi Lake in Finland. Furthermore, 5 kg of PE cloth can generate six million microfibers (De Falco et al. 2019), therefore, even remote areas like Vesijärvi Lake can still receive plastic fibres (as high as 395.8 n/kg dw).

3.3 Major sources of MPs in remote alpine lakes

MPs in remote and alpine lakes are mainly brought by surface runoff, atmospheric transport, and human hiking (Fig. 1) (Evangeliou et al. 2020; Geyer et al. 2017). As the largest inland lake in China, Qinghai Lake is far away from cities and has no industrial sources; nonetheless, its MP abundance is 18.09 ± 2.29 n/m3. The reason is that the lake is a famous tourist attraction with a tourist population 10 times higher than the local population, which introduces a large amount of disposable plastic waste. Unfortunately, these solid wastes are managed inefficiently, degrade into MPs in the soil, and eventually enter the water body (Xiong et al. 2018). Aerial transportation is an important pathway for MPs to spread to lakes in remote areas, such as high latitudes and altitudes, and glaciers, which are far away from residential areas as shown in Fig. 1 (Padha et al. 2022). González-Pleiter et al. (2020) found that some fine MP fibres settle in remote lakes, like an Arctic freshwater lake (located in the Svalbard Archipelago), following transportation via wind. High levels of MP pollution have also been found in Hovsgol Lake, which is located in a remote area of Mongolia. In addition to its small area and the long residence time that particles experience, the accumulation of MPs occurs easily. The prevailing southwest wind also leads to higher MP abundance on the west than on the east coast (Free et al. 2014). Therefore, wind is a transport agent for exposed MPs on the ground. These transported particles are dispersed further to reach oceanic, land-based, and freshwater systems through dry and wet atmospheric sediments (Evangeliou et al. 2020; Wang et al. 2021a). In addition to the wind, the precipitation process is also an important transmission pathway for secondary MPs. In Italian subalpine lakes (Lakes Maggiore, Garda, and Iseo) and the Funi Glacier, rainfall and snow reportedly play the same role in the transmission of MPs (Ambrosini et al. 2019; Sighicelli et al. 2018). Although the population density of lake basins in remote areas is low, the abundance of secondary MPs is still influenced by human activities. In Sassolo Lake, a remote Swiss lake with an altitude of 2074 m, MPs enter the lake via wind transportation, which is mainly related to human activities such as hiking, grazing, and diving (Negrete Velasco et al. 2020). In addition, the alpine Lake Dimon (Pastorino et al. 2021) and the Vatnajökull ice sheets in Iceland (Stefánsson et al. 2021) show evidence of the impact of human activities such as climbing and hiking. MPs fall from clothes and climbing equipment on tourists and enter lakes in high mountains or remote areas.

Secondary MPs have a wide range of sources. The main course is from the chemical and biological degradation of primary MPs into smaller fragments, by light, heat, and microorganisms, which then enter the water environment by runoff, rain, snow, and wind and thus most MPs in lakes are secondary sources.

4 Distribution characteristics of MPs

Considering the global distribution, the abundance of MPs is related to population density and human activities, and MPs have different distribution characteristics in different media. To facilitate analytical comparisons, the MP abundance units of 89 lakes worldwide were unified to n/m3 in water and n/kg dw in sediments (Yang et al. 2022). Additionally, the proportion of different types of MPs and the occurrence characteristics of different media such as lake ice/snow samples, water and sediments in winter were analyzed.

4.1 MPs in water

MPs in water are the most abundant type. The particle size will affect the migration and diffusion of MPs in water, with small-sized MPs being easily swallowed by aquatic organisms, thus endangering the biological health and water environment. The types of MPs in lake environments are complex, consisting of waste from human activities and fisheries, as well as man-made plastic waste entering by runoff, atmospheric transportation, and other means. These MPs include almost all the plastic types, with PP and PE making up the highest percentage (72.67% of the total), followed by PET (18.03%), and PS (3.19%) (Fig. 2). There are also gaps in the spreading of different types of plastics by different sources (Bond et al. 2018).

Fig. 2
figure 2

Distribution of MP types in (a) water and (b) sediment

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Lakes Maggiore, Iseo, and Garda, the three major volcanic lakes in Italy, are mainly fishery and agriculture-based, and all contain MPs consisting of >40% PE, whereas Lake Como in Italy, where tourism is the main source of MP pollution, PE comes second with the first being PP, accounting for 44.4% (Binelli et al. 2020; Sighicelli et al. 2018). PET and PVC are the main types of MPs in Lake Ox-Bow, Nigeria (Oni et al. 2020). There are three plastic companies located several kilometers from the lake, which mainly produce beverage bottles. In addition, the plastic type in Lake Ox-Bow is also associated with the dry and rainy seasons, where surface water during the dry season contains 72.6% of PET, followed by PVC, which accounts for 10.9%, whereas during the wet season, the highest percentage of PVC is 81.5%. This phenomenon may be explained by the fact that the MP pollution source in the dry season is mainly industrial, and during the rainy season, rain flushes and erodes water pipes carrying along more PET (Oni et al. 2020). PET fiber is predominant in arctic freshwater lakes, with the possible reason that fiber is more readily transported into high-latitude lakes through the atmosphere (González-Pleiter et al. 2020).

According to the global MP abundance analysis of the 89 lakes (Fig. 3, Table S1), we found that lake area, water depth, population number, and distance from the residential area had a weak positive correlation with lake MP abundance, so linear fitting analysis of each factor individually yielded MP concentrations that were inversely related to lake area (r = 0.32, P < 0.001) and water depth (r = 0.67, P < 0.001). Among them, lake area and water depth may affect the deposition of MPs in water; the smaller the lake area, the easier it is for pollutants to remain and accumulate in a lake. Further, compared with rivers and oceans, lakes have low turbulent flow and less fluctuation; thus, MPs are less likely to decompose and degrade, extending the pollution persistence in lake water (Barnes et al. 2009; Vaughan et al. 2017). Population and distance from residential areas are important parameters for characterizing the effects of anthropogenic activity on MP abundance. Among them, MP abundance was positively correlated with the population (r = 0.39, P < 0.001) and negatively correlated with residential area distance (r = 0.58, P < 0.001), indicating that anthropogenic activity is an important factor influencing MP abundance in lakes (Eriksen et al. 2013; Wang et al. 2017). Wang et al. (2017) reported that MPs concentrations greater than 5,000 n/m3 were found in lakes within Wuhan in central China, among which the highest MP abundances in Bei and Huanzi Lakes were 8,925 ± 1,591 n/m3 and 8,550 ± 989.9 n/m3, respectively, due to their location near densely populated areas, and were mainly derived from domestic waste decomposition. However, the concentrations of MPs in lakes far from the urban areas, such as the Hou, Wu, Yandong, Yanxi, and Zhushan Lakes, ranged from 1,660.0 ± 639.1 to 4,600 ± 1,804.2 n/m3. Similarly, Yuejin and Nianjia Lakes in Changsha City are located in the Martyrs Park, with more than 5 million tourists per year, and the MP abundance in both lakes was 7,050 ± 1,060.7 n/m3 and 5,600 ± 1,555.6 n/m3, respectively. However, Yang, Meixi, and Xianjia Lakes, which are located in Yuelu District and are surrounded by wetland parks and less populated university campuses, all had MP concentrations ranging from 2,425 ± 247.5 n/m3 to 5,063 ± 1,891.5 n/m3 (Yin et al. 2019). Red Hill Lake in India is the main reservoir leading to Chennai city, supplying water to nearly 10 million people, with an average MP concentration of 5.9 n/L in the water (Gopinath et al. 2020). The Simcoe Lake Basin in Canada is dominated by agricultural production, with a resident population of about 400,000, covering an area of 3400 km2. Compared with Lake Erie and Lake Ontario, which are close to densely populated urban areas, the pollution level of MPs in Simcoe Lake is much lower. The abundance of MPs in the water is only 0.34 n/m3.

Fig. 3
figure 3

The linear relationships between abundance and (a) lake area, (b) average depth, (c) population, and (d) distance from a residential area

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The biggest difference between urban and remote lakes is the population density of the surrounding area. The higher the population density, the higher the degree of human activity and the higher the abundance of MPs, with relatively complex plastic types. Therefore, the average MP abundance of urban lakes is 4078 n/m3, whereas that of remote lakes is 1302 n/m3, making the abundance of urban lakes twice that of remote lakes.

4.2 MPs in sediments

Sediments are an important medium for material and energy metabolism in lakes. MPs in sediments may have a longer pollution exposure period and a more complex geochemical cycle process, and this is one of the intriguing areas in MP research. The distribution of MPs in sediments is more concentrated compared to that in water (0.53–2188.7 n/kg dw) (Fig. S3).

Overall, the abundance of MPs in lake sediments remains mainly affected by human activities. From the perspective of global lakes, the abundance of MPs in sediments has limited influence on the lake area. The surface area of Lake Victoria, the largest freshwater lake in Africa, is 68,800 km2 (Egessa et al. 2020a), 34 times that of Vembanad Lake in India (Srinivasalu et al. 2021), but its MP abundances do not differ much from 6.53 and 7.9 n/kg dw, respectively, whereas Hampstead No.1 pond, an urban lake in Britain, has an area of only 0.015 km2, but has 539 n/kg dw MPs. Lakes with MP abundance above 1000 n/kg dw include Ox-Bow lake in Nigeria, Lake Tollense in Germany, and Lake Onego in Italy. These lakes are located in densely populated areas or areas with active human activities. MP abundances of four lakes (Siling Co, Geren Co, Wuru Co, and Mujiu Co Lakes) in remote areas of Qinghai Tibet Plateau in China are all low, at 4.84, 1.31, 3.66, and 0.53 n/kg dw, respectively (Zhang et al. 2016). In Dongting and Taihu Lakes in China with large population densities (Wang et al. 2018; Zhang et al. 2021), the abundance of MPs in sediments ranges from 400 to 1000 n/kg dw.

With continents, the abundance of MPs in lake sediments ranges from 0.53 to 856.66 n/kg dw in Asia; 39 to 352 n/kg dw in North America; 6.53 to 1585.2 n/kg dw in Africa; and 33 to 2188.7 n/kg dw in Europe. MPs were studied early in most developed European countries and their abundance in sediments was the highest (604.125 n/kg dw on average). In contrast, most Asian countries, which are developing countries, have an MP abundance of 218.84 n/kg dw on average, much lower than that in Europe, but higher than that in North America (134.63 n/kg dw). In addition to the different economic development conditions, it is more likely that insufficient data lead to inaccuracies between different continents (Ballent et al. 2016; Fischer et al. 2016).

4.3 MPs in ice/snow

There is limited data about MPs in ice/snow samples, and their distribution ranges from 0.11 to 593 n/L (Fig. S3). As an important freshwater resource in the world, glacial lakes have been polluted by MPs in the Arctic, Antarctica, Alps, and Mount Everest (Ambrosini et al. 2019; Bergmann et al. 2019; Kelly et al. 2020). Ice/snow MPs in high latitudes and glacial lakes are mainly derived from atmospheric transport. MPs in the air settle and collect in the ice/snow layers of lakes during freezing in winter. When snow and glaciers melt, ice/snow MPs are released into the lake water and sediments (Padha et al. 2022).

Some lake ice/snow MPs remain directly related to human activities. Lake Vesijärvi in Finland is located near urban surroundings, where the abundance of MPs is 7.8 ± 1.2 n/L and 117.1 ± 18.4 n/L in ice and snow samples, respectively, with the main MP types in both samples being cellulose and wool, mainly originating from human activities as well as atmospheric transport effects in the surrounding Lahti City. Additionally, the MP abundance in the ice of this freshwater lake was significantly lower than that in snow samples, indicating that with the winter precipitation process, airborne MPs would be adsorbed and accumulated in surface snow (Scopetani et al. 2020). Some fine fibres accumulate in lake ice covers during winter freezing of lakes, with stratification. Detection of MPs in the upper (0–20 cm) and lower (60–80 cm) layers of ice samples in Baikal Lake, Russia, revealed that the abundance of MPs in the generally lower layer of ice (average: 65 n/L) was higher than that in the upper layer (average: 55 n/L). The possible reason for this analysis was that more than 80% of MP types were plastic fibres that would migrate from water into ice layers during freezing (Karnaukhov et al. 2022). Anchar Lake (Neelavannan et al. 2022) in India and Dimon Lake (Pastorino et al. 2021) in Italy are small in area and high in altitude, and their abundance of MPs in ice/snow samples is not high with the main source being atmospheric transport. Wang et al. (2021b) analyzed the distribution characteristics of MPs in the ice layers of Lakes Ulansuhai and Daihai, seasonally ice-covered lakes in China. Among them, the Lake Ulansuhai ice cover was divided into four layers, in which the MP percentages were 37, 17, 12, and 34% in the surface, middle, near-bottom, and bottom layers, respectively. Notably, the highest concentrations of MPs were found in the upper and the bottom ice layers, indicating a possible pooling effect of ice on MPs. Additionally, the average abundance of MPs in ice is 56.75–141 n/L, which is an order of magnitude higher than that in surface water (Wang et al. 2019). The abundance of MPs in the ice layer of Lake Daihai ranged from 283 to 1055 n/L and was 4–9 times higher than the abundance of MPs in water (Wang et al. 2021c), but their sources need to be further studied and clarified.

Areas to study MPs in winter lake ice caps are limited, but their distribution is significantly different from that in water, and their transport, as well as distribution mechanisms, are ideal for future research.

4.4 The vertical distribution of MPs

MP distribution varies in different lake media. Generally, MPs <1 mm have more than 70% abundance, because smaller MPs are more easily affected by hydraulic force and wind, spreading more widely in the environment, becoming the most abundant classification type in lake water bodies. MPs <0.5 mm occupy 52.49% of the lake water bodies. The bigger the particle size proportion in the water body, the larger the particle size and the smaller the proportion in the water column. In sediments, most lakes were found to have a large amount of MPs <0.5 mm; however, a few lakes had 1–5 mm MPs occupying more than 80% of the sediment. The deposition of MPs is influenced by various factors such as particle density and composition, as well as the energy of the transmission media (Corcoran et al. 2015). Larger MPs are more likely to be deposited at the bottom of lakes, thus the sediment has a higher proportion of 1–5 mm particle size. While the proportion of <0.5 mm is higher in surface ice and snow, the relatively even size distribution in aquatic organisms may be mainly due to the fact that organisms are more likely to accidentally eat small and medium-sized MPs visible to the naked eye, resulting in a higher proportion of 0.5–1 mm MPs in their bodies (Fig. 4).

Fig. 4
figure 4

Sizes of MPs in different media. (a) Ice/snow, (b) water, (c) sediment and (d) organism

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The vertical distribution of MP morphology varies significantly in different media, with fibres in snow and ice accounting for up to 84.21%, and with usually small and light MP morphology (Rebelein et al. 2021) more likely to float on the surface of lakes. Ice is more likely to adsorb hydrophobic materials with low-density and non-smooth surfaces during the freezing process (Kulinich et al. 2015). Capillary condensation occurs due to the contact of ice pores with rough-surfaced MPs, leading to a deterioration of the backward and forward contact angles, which in turn leads to an increase in the actual contact area between the ice and the surface. The second possible cause is the release of latent heat during the freezing process, which leads to an increase in liquid temperature compared to the surrounding air and substrate, resulting in a short-term local increase in the vapour pressure close to the liquid meniscus. The localized vapour supersaturation compared to the substrate temperature characteristic value leads to fly-off or capillary condensation of the supersaturated vapour around and under the frozen droplets (Emelyanenko et al. 2020). MPs form in water bodies include fragments, films, fibres, particles, and foam, existing mainly as fibres, followed by fragments and films (Fig. 5). Significant increase in the proportion of debris in sediment MPs is driven by rapid flow in tributaries and deposited as turbulence and bottom currents subside (Ballent et al. 2016). As a result, larger areas of debris MPs are more likely to be deposited at the bottom of the lakes (Fig. 5).

Fig. 5
figure 5

Morphology of MPs in different media. (a) Ice/snow, (b) water, (c) sediment and (d) organism

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MP colours in water bodies include blue, red, brown, purple, black, white, and transparent. The majority of coloured MPs in the water column are usually from the coloured frosted particles in human personal care products, whereas the transparent and white ones are mostly from agricultural and fishery mulch, as well as fishing nets and lines (Fig. 6) (Xu et al. 2020). The coloured plastic particles indicate the influence of different human activities, and these are more likely to be accidentally consumed by aquatic organisms. The main possible reason for this is that MPs are exposed to the natural environment and subjected to UV light, wave and wind stress, mechanical wear and tear, thermal oxidation, and biodegradation, resulting in surface discolouration (Zhao et al. 2022). In contrast, black MPs may mainly originate from the release of rubber from road vehicle tires due to wear and tear (Xu et al. 2020) (Fig. 6).

Fig. 6
figure 6

Colour of MPs in different media. (a) Ice/snow, (b) water, (c) sediment and (d) organism

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5 Ecological effects of MPs

The environmental effects of MPs mainly include 1) toxic effects of flora and fauna in water caused by the MPs; 2) environmental effects resulting from additives in plastics released during MPs degradation; and 3) “microplastic carrier effect” due to MPs hydrophobic nature and high specific surface area.

5.1 Toxicity of MPs

MPs are mainly misfed by aquatic organisms or accompanied by food chain trophic grade stepwise enrichment, which can have toxic effects on aquatic animals and plants, and eventually humans. The average abundance of MPs in aquatic organisms in the current study was 8.24 n/ind (Fig. S3). Large-sized MPs in aquatic organisms are less abundant because small-sized MPs are easier to enter aquatic organisms’ bodies, and these are dominated by fibres and fragments. In addition, coloured MPs are more easily swallowed by water organisms. As illustrated by Figs. 4, 5 and 6, coloured and black MPs are dominant in the organisms, with almost no transparent and white MPs.

Almost all fish species in fishery-dominated lakes worldwide are contaminated to different degrees. Biginagwa et al. (2016) detected the presence of MPs in fish in Lake Victoria, the largest fishery source in Africa. Merga et al. (2020) studied the intake of MPs by four fish species in Ziway Lake in Ethiopia during wet and dry seasons and found that MP abundance in the organisms was generally higher in the wet than in the dry season. Galafassi et al. (2021) sampled bass (Perca fluviatilis) from Lakes Como, Garda, Maggiore, and Orta in Italy, and concluded that the number of MPs in fish bodies is strongly related to high anthropogenic activities since the abundance of MPs in fish in Lake Garda (5.59 ± 2.61 n/ind) was significantly higher than that in Lakes Como (1.24 ± 1.04 n/ind), Maggiore (1.24 ± 1.04 n/ind) and Orta (2.75 ± 2.29 n/ind). Freshwater fish in China are often cultured, and the MPs in living organisms are also generally high. Su et al. (2016) selected Corbicula fluminea, a clam from Taihu Lake, as a research object, and MPs were detected at 0.2–12.5 n/g. Jabeen et al. (2017) selected six other freshwater fish species from Taihu Lake (Table S2), and extracted MPs in their gastrointestinal tract (GIT) and their abundances were in the range of 1.8–2.5 n/ind on average. Gehu Lake, the connecting point between Taihu Lake and Yangtze River, is an important fish culturing site and a feeding and fattening habitat in the Taihu Lake Basin, where busy fishing activities lead to aged fishing nets entering the lake, and its MPs abundance on the surface water ranges between 1.51 and 22.22 n/L. Consequently, the MP abundance in fish bodies (10.7 n/ind) is closely related to that of surface water (Xu et al. 2021a). Yuan et al. (2019) found a high MP contamination level in wild Carassius auratus in Poyang Lake, with an abundance of 9.3 ± 5.4 n/ind. Xiong et al. (2018) sampled ten fish (Gymnocypris przewalskii) from Qinghai Lake and noted the presence of MPs in their digestive tract, with abundances of 2–15 n/ind. MP contamination level continues to increase ending up in human consumption (Blackburn and Green 2021).

Progress of toxicological research on MPs can be summarized by the MPs impacts on producers and consumers (Fig. 7) (Anbumani and Kakkar 2018), for the biotoxicity study of MPs in aquatic life and human health.

Fig. 7
figure 7

Impact of MPs on producers and consumers in the freshwater environment (GST: glutathione S-transferase, AchE: Acetylcholinesterase, SOD: superoxide dismutase, CAT: catalase)

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Lake ecosystem producers, mainly algae, are the food chain basis (Cardinale et al. 2011). MPs currently inhibit algal photosynthesis and growth mainly through their light shielding effect, increased turbidity of the medium, cell internalization processes, and adhesion to cell walls (Rani-Borges et al. 2021). Bhattacharya et al. (2010) conducted a study on carbon dioxide consumption by adding different concentrations of charged PS microbeads to the algal growth medium, confirming that PS adsorption on Chlorella blocks light from reaching the photosynthetic centre and may disrupt the entry of light through the cell wall into the cell interior. Sjollema et al. (2016) performed exposure experiments on microalgae using charged PS microbeads, and although the high concentration of MPs decreased the light intensity accepted by the microalgae, it did not have much effect on the MPs photosynthesis, confirming that uncharged PS microbeads had an inhibitory effect on microalgae growth, which of course had a correspondence with the size of MPs as well as the concentration, that is, the higher the MP concentration and the smaller the size, the stronger its inhibition on the growth of microalgae. Wu et al. (2019) used MPs of PP and PVC to probe their effects on chlorophyll and the photosynthetic activity of freshwater algae and found that both PP and PVC had different degrees of photosynthetic inhibition on algae. The greater inhibitory effect of PVC on photosynthesis was possibly related to the chloride ion contained in PVC, whereas higher concentrations of MPs caused clear inhibition effects of MPs on algal growth. Kalčíková et al. (2017) demonstrated that PE microbeads significantly prevent phytoplankton (Lemna minor) root growth through mechanical blocking. Different types of MPs (PS, PP, PE, PVC, PET) inhibited aquatic and terrestrial plant growth at different degrees (Ge et al. 2021).

Consumers are at the heart of biogeochemical processes in lake ecosystems and mainly function in energy transfer, material exchange and information transfer, and their presence promotes circulation and development as well maintaining the stability of the whole ecosystem (Atkinson et al. 2017). The contact between MPs and consumers leads to energy metabolism disorders, liver physiological changes, and synergistic and/or antagonistic effects of other hydrophobic organic pollutants (Browne et al. 2008). Ogonowski et al.’s research (2016) on the bioactivity of Daphnia Magna exposed to MPs found that exposure to both primary and secondary MPs reduced the feeding and reproductive capacity of D. Magna and accumulated MPs in the digestive tract with increasing intestinal transit time. Lei et al. (2018) studied the biotoxicity effects of MPs on pelagic and benthic (sediment) aquatic animals in freshwater ecosystems. In sediment, nematode survival, body length, and reproduction were significantly inhibited, along with elevated GST enzyme levels. MPs’ effect on the survival rate of zebrafish in the water column was unclear, but the fish’s postmortem intestinal tissues all developed different degrees of damage, including villus rupture and intestinal epithelial cell division. Hu et al. (2020) showed that MPs’ toxic effect against Caenorhabditis elegans is mainly dependent on their size and concentration. Among PS particles with different sizes (0.1, 0.5, 1, 2, and 5 μm), 1 and 5 μm fragments affected growth and resulted in developmental inhibition. Whereas PS greater than 1 μg/L can cause intestinal damage, alter locomotor behaviour, and cause neurotoxicity and even lethality in C. elegans. Peda et al. (2016) found that MPs caused an intestinal disturbance in European sea bass (Dicentrarchus labrax), and severe histological changes were found in the distal intestine after PVC fragments were ingested for more than 90 days. Lu et al. (2016) performed MP exposure experiments on zebrafish and found that MPs accumulated in the gills and intestines of the fish and even entered into the liver of animals, causing liver inflammation and lipid accumulation in fish. Binelli et al. (2020) sampled zebrafish mussels in alpine lakes in Italy, through exposure to PS under laboratory conditions, evaluated the harmful effects of MPs on mussels in water, and ultimately found that PS significantly increased the activity of superoxide dismutase (SOD) and catalase (CAT) in mussels, which induced oxidative stress. Ding et al. (2018) also found that PS MPs would have an inhibitory effect on brain acetylcholinesterase (AChE) activity of tilapia (Oreochromis niloticus) with a maximum inhibition rate of 37.7%, indicating the potential neurotoxicity of MPs to freshwater fish.

MPs are harmful to both algae and fish in freshwater ecosystems, and the degree of injury depends on the particle size and dose of MPs. PS is commonly used to explore MPs’ harmful effects on living organisms in water at concentrations between 1 and 100 μg/L; significant damage is incurred with higher concentrations leading to biological death.

5.2 Combined pollution

5.2.1 Additives in plastics

The eco-environmental complex pollution of MPs can mainly be attributed to plastic additives accompanied by the breaking of solid plastics and leachates from landfill sites being released into soil and water as well as air, causing more serious and complex consequences for lake ecology (Teuten et al. 2009). Currently, many popular plastics are additives used in the market, such as stabilizers, plasticizers, flame retardants, or antioxidants, to improve the properties of plastic products and extend their service lives. The main components include nonyl phenol (NP), polybrominated diphenyl ethers (PBDEs), phthalates and bisphenol-A (BPA), among others (Hahladakis et al. 2018).

BPA can interact with estrogen receptors, leading to the occurrence of several endocrine diseases (Konieczna et al. 2015). Recent studies have also reported phthalates in domestic wastewater leaching from plastic originating from WWTPs (Bergé et al. 2014), which are a major source of MPs in urban lakes. The leaching of endocrine disruptors into humans disturbs the nervous system, affects reproduction, induces genetic aberrations, and adversely affects endocrine function and reproductive development. Thus, phthalates and BFRs are now listed as endocrine disruptors (EDCs) that damage human health (Campanale et al. 2020). Beiras et al. (2021) found that the original plastic polymers (PE, PVC, and PA) were not harmful in terms of short-term aquatic toxicity, while MPs with functional additives showed toxicity to microalgae (Tisochrysis lutea population growth), crustaceans (Acartia clausi larval survival), and echinoderms (Paracentrotus lividus sea-urchin embryo test) in the water column. Leached MPs are not only ingested by fish, causing hazards to aquatic life but also enter drinking water sources. Direct exposure can also occur via plasticized vinyl products (Hahladakis et al. 2018).

5.2.2 Adsorption of MPs

MP adsorption is mainly due to its small particle size, large specific surface area, and strong hydrophobicity, which strengthen the molecular adsorption capacity for hydrophobic organic pollutants (Tang et al. 2021). In addition, the oxygen-containing groups, size, and charged minerals on the surface of MPs allow them to act as carriers for the transport of heavy metals in the environment (Liu et al. 2019b) (Fig. 8), complicating MP pollution toxicity further. MPs adsorption capacity is shown in Table S3. Among them, organic pollution substances can be adsorbed onto the surface of MPs through electrostatic, hydrophobic as well as noncovalent interactions and be absorbed by MPs through a partitioning effect (Fu et al. 2021; Hanun et al. 2021). At present, it has been confirmed that MPs exhibit adsorption behaviour toward various organic pollutants, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), Dichlorodiphenyltrichloroethane’s (DDTs), hexachlorocyclo-kines (HCHs), and polybrominated diphenyl ethers (PBDEs), among others (Santana-Viera et al. 2021). Therefore, MPs can act as carriers for organic pollutants, causing significant risks to the environment as well as organisms. By observing the concentration of PCBs in water as well as in aquatic life, it was found that the concentration of PCBs directly increased by an order of magnitude from water to shellfish to crustaceans as well as fish (Takeuchi et al. 2009). Thus, MPs would aggregate organic pollution materials into the food chain, affect aquatic life and even jeopardize human health (Engler 2012). In addition, EDCs and PBDEs have been shown to enter aquatic organisms via MPs adsorption and exhibit combined toxicity (Browne et al. 2013; Chua et al. 2014).

Fig. 8
figure 8

Adsorption mechanism of MPs on organic matter, heavy metals, and antibiotics

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In addition to organic pollutants, MPs enrich some trace elements in water (Binda et al. 2021). Brennecke et al. (2016) found that two MPs, PVC and PS, showed strong adsorption effects on copper and zinc, heavy metals leaked from antifouling coatings. Kim et al. (2017) found that D. Magna bodies accumulated more nickel in water with MPs compared to water without MPs. Trace heavy metals also cause certain environmental risks to water once they have undergone MP enrichment.

The unique bacterial environment in MP enables the enrichment of specific antibiotics (Liu et al. 2021). MPs adsorb organic or inorganic substances to provide nutrients with a relatively stable habitat for microorganisms, thus accelerating microbial dissemination as well as gene exchange (Shen et al. 2019). Liu et al. (2019a) found that MPs with ciprofloxacin (CIP) could be adsorbed by electrostatic action and its interaction was enhanced by π - π bonds. As the oxygen-containing functional groups of MPs increased after ageing, so did their capacity to adsorb CIP. Adsorption of antibiotic resistance genes (ARGs) by MPs will be transferred to aquatic animals, followed by aquatic product consumers, increasing the risk of drug resistance transfer, which in turn poses a threat to human health (Mughini-Gras et al. 2019; Zhou et al. 2020). In addition, Imran et al. (2019) also reported that MPs can act as common carriers of heavy metals and antibiotics, and human pathogenic bacteria will form biofilms on the surface of MPs, which can make pathogens develop multi-drug resistance under the influence of heavy metals.

Lake MPs may aggregate in the human body through physical contact such as drinking water, food products, and swimming in lakes. However, currently, the mechanisms by which these polluted substances in lakes contribute to human health problems remain unknown and represent an important future direction for research (Thiagarajan et al. 2021).

6 Conclusion and perspectives

In the study, we found that MP abundance and characteristics such as morphology and type are influenced by human activities, with MP abundance in urban lakes being generally twice higher than that in remote lakes. Urban lake MPs, originating from WWTPs and landfill sites, pharmaceutical and personal care products (PPCPs) and household supplies contain many plastic microbeads, which are mainly made of PP and PE (more than 70% of the total). Meanwhile, MPs in lake water are proportional to population size and inversely proportional to the distance from residential areas. Thus, we can minimize the generation of MP waste at the source and reduce environmental pollution by studying the different MP types and behaviour in the environment and tracing them to their source.

The vertical distribution of MPs in lakes was related to the shape and size of MPs. MP abundance in water (0.14–92,000 n/m3) is very widely distributed, and morphological types are also more abundant than in sediments. Importantly, debris and large particle size MPs (1–5 mm) settle easily into sediments, whereas plastic fibres easily migrate upward; MPs in ice covers of lakes during winter consist mainly of fibres. Coloured MPs are more likely to enter aquatic organisms, whereas black particles are more abundant in the ice layer. Currently, there are clear stratification characteristics in the vertical distribution of MPs in different media. However, detailed studies on the stratification characteristics of individual media are limited; thus, further analysis is required. In addition, the abundances of MPs in the upper and lower layers of ice cover are 20% higher than those in the middle layer, and existing studies illustrate that there are specific structures in the ice cap that lead to the adsorption and enrichment of certain particulate matter, without mentioning lake MPs. Additionally, more relevant studies on MPs in lakes during the ice melt period are required.

The toxic effects of MPs on animals and plants in water as well as sediments include growth inhibition, energy metabolism disorders, oxidative stress, the release of harmful additives, and combined effects with other contaminating substances. However, studies are mostly conducted under laboratory conditions to explore the effects of single MPs or pollutants on living organisms in the water. Therefore, examining the coupled effects of multiple pollutants in the real lake environment may be ideal for future research, and the toxicological mechanism of abundant MPs will be a key research topic.