**6. Fate of microplastics**

*Emerging Contaminants*

catching for researchers and environmentalists.

**5. Microplastics in freshwater ecosystem**

layer this may be due to preferential flow or animal movement. Even, mesoscale ocean dynamics have impact on distribution of plastic debris at sea surface within subtropical gyres [49]. Usually, sea platforms and marine trafficking are responsible for microplastics in far off Ocean, whereas microplastics in near shore originate mostly from waste water, runoffs, rivers etc. [50, 51]. However terrestrial environment also determines the concentration of microplastics as harbor and industries add huge amount of plastic debris either directly or indirectly which add up to the acumen concentration of microplastics in the ocean. The dire situation of disturbance in aquatic ecosystem is becoming huge day by day as these not only affect flora but fauna as well; even coral beds are not far away from disturbance. This plastic debris also includes mesoplastics accumulation. Use and through plastic items are becoming huge threat to the aquatic organisms hence number of reports are increasing in this area of research which indicate the negative impact of microplastics and is alarming accumulation rate in ecosystem which is also eye

To understand the impact of microplastics pollution in freshwater environment, various aspects are to be analyzed i.e. source, distribution, type and effect of microplastics. Source of freshwater pollution is usually synthetic textile, personal care products, industrial raw material, whereas the main source of microplastics in riverine system are wastewater discharge which may be industrial or household untreated waste water disposal. Microplastics are of serious concern because their accumulation potential increases with decreasing size [52]. It is also noted that, there may be change of composition of MP as they accumulate with waterborne contaminates which includes metals and persistent, bioaccumulative and toxic compounds this is possible due to larger surface-to-volume ratio. Studies by Engler [53] showed relationship between plastic debris and PBTs (e.g. PCBs and DDT) similarly a number of studies exist for polycyclic aromatic hydrocarbons [54–56]. Since the spectrum of contaminants is different between freshwater and marine system. In stagnant riverine system like ponds and lakes water pollution is more severe problems because of the irresponsible behavior of the inhabitants or by various tourism related activities which disturb the ecosystem due to accumulation of degradable or non- degradable waste. They float in the surface water and stay in the water sink into sediments of lake. For stagnant system rate of accumulation of microplastics is higher, since there is no efflux. Therefore, it can be concluded that there is a direct correlation between distance of contamination source and microplastics pollution levels in sediments [57]. Various studies confirmed the presence of microplastics in drinking water system which makes it a serious issue [58]. Research about river system and watersheds can provide the knowledge to the people to understand the alarming situation of microplastics accumulation in freshwater system [59]. Further the flow of river plays significant role in removal of plastic fragments. It is also observed that after precipitation high amount of MP is observed in sediments and running water [60]. Eventually, freshwater system also contributes to the pollutant content of marine ecosystems because ultimately riverine merge with the ocean resulting merger of mineral, sediments, soil content as well as pollutants. Hence the fact that freshwater system act as strong source of microplastics to marine ecosystem cannot be neglected. Although distribution of microplastics in freshwater

system is not uniform, it depends on nearby source of waste water disposal.

It is observed that the condemnation in water is observed higher in riverine near industrial area as compared to the residential area. However waste water treatment

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The threat of microplastics is rapidly increasing, and as the global plastic production projected to reach an accumulative 25 billion tons by 2050, things are going to be worse [63]. Although these plastic materials are key factors for innovation and development of various fields such as healthcare, energy generation, aerospace, automotive industries, construction, electronics, packaging, textile and many others [64]. However, instead of recycling or incineration or utilizing any other way of removing unused or discarded plastic from environment, these plastic wastes enters the environment from year to year and it is accumulated in Marine, freshwater and terrestrial ecosystem worldwide, even from densely populated countries like India and China to cold desert like Antarctica. And this became a matter of concern for scientists across the world. The reliance on plastic for huge number of consumer products, many of them being single-use, results in continuous entry into environment.

No doubt, with due course of time via biotic and abiotic degradation pathway, plastic loose its mechanical integrity but it may take several years to degrade completely. With gradual degradation this immortal plastic emits smaller size particle in environment i.e. macroplastics, mesoplastics and microplastics. Plastic particles <5 mm size are considered Microplastic, although there are efforts to redefine them as <1 mm in size, as recommended by [65]. However minimum size of Microplastics has not yet been specified and it depends on the sampling and processing as well as on the applied method for Microplastics identification.
