A Baseline Study On The Occurrence And Distribution of Microplastics In The Highly Polluted Metropolitan River Cooum, Chennai, India.

The current research aimed to determine the distribution of micro plastics in surface sediments and water from Chennai's Cooum River. The ber dominates the Cooum River's surface sediments and water, followed by beads and fragments. Both the sediment and the water contain a high concentration of <1mm size micro plastics. The distribution counts of micro plastics in the Cooum River are signicantly low compare to those found in the St. River Lawrence and Amazon river brazil. The distribution of micro plastics in riverine environments is strongly inuenced by waste water discharge from domestic and industrial sources, as well as waste dumping near riverbanks. Table: 1 Data from the current and compared.


Introduction
Due to its low cost, durability, and versatility, the invention of plastic revolutionized the entire globe.
Plastics are engineered polymers that are used in a wide range of human applications and have become an indispensable element of our daily life (Hammer et al., 2012). Since the early part of use, the contamination of our environment by micro plastic has also begun. Studies on plastic pollution in the marine environment began in the late 1970s (Carpenter and Smith, 1972); since then, research on plastic contamination has increased, with major studies focusing on aquatic environments such as lakes, rivers, and deep-sea sediments (Carpenter and Smith, 1972 Plastics which are less than 5mm are termed a micro plastic (Thompson et al., 2009;NOAA 2015) categorized into primary and secondary based on their origin. Primary micro plastics are intently manufactured in the size of less than 5mm have a varied use in the eld of medicine, textile and cosmetic industry (Fendall and Sewell, 2009;Eriksen et al., 2013;Bergmann, et al., 2015).
Secondary micro plastics are produced as a result of the degradation of larger plastics (Thompson et al., 2009), and both types enter the ecosystem solely through domestic and industrial discharge. Due to prolonged exposure to sunlight and climate, micro plastic bres originating from land-based activities disintegrated quickly (Cooper and Corcoran, 2010). Plastics' low recycling rate contributes signi cantly to the emergence of micro plastics. Micro plastics pose a risk to the aquatic environment because of their long residence duration, the possibility of biota ingesting them, and the emission of harmful components during degradation.
Microplastics enter the food chain of higher organisms through phytoplankton in both the marine and fresh water environments (Moore et al. 2002). Micro plastic has made its way into soils, groundwater via percolation, rivers via discharge, and sh and molluscan tissues due to its tiny size

Study Area
Cooum is a non-perennial river that originates at a dam in Kesavaram, which is about 48 kilometers west of Chennai. During the monsoon season, the excess water from the cooum tank is the primary source of water in that river. Agriculture dominated the banks of the Cooum in its upper reaches, but as it neared the Vanagram, the river began to be polluted by the discharge of domestic and industrial waste and the ow of the river is almost nil in the city limits. It ows through Kanchipuram, Thiruvallur, and Chennai districts for approximately 68 kilometers before entering the sea, Bay of Bengal.

Methodology
Systematic sampling was carried out to collect the 15 surface sediments and water samples the Cooum River at one-kilometer intervals. The sampling locations were pre-xed using ARC-GIS 10.3, and the resulting kml data was superimposed on Google maps with use of LOCUS MAP (Free version 3.50.1) -Hiking GPS navigation and map software tracking the sampling locations. For accuracy, the coordinates were cross-checked with the GPS in the eld. The sediment samples were collected using a Van-Veen grab sampler. The sediment samples were packed in glass bottles (to avoid contamination) with a metal lid labeled with the sampling location. One liter of water samples were taken in pre-cleaned glass bottles with metal lids in the same area where the sediments were collected.
Wet sediment samples were oven dried at 60°C and sieved through 5mm mesh to remove coarser plastics while retaining ner ones. To remove organic matter and calcareous debris, sieved samples were coned and quartered, and 30g of sediments were treated with 30% hydrogen peroxide (H 2 O 2 ) and 2N HCL. The extraction procedure of micro plastic was followed as per (NOAA, 2015). The pre-treated riverine sediment samples were mixed with 50ml of zinc chloride solution (density of 1.55mg/cm3) and passed through 0.45 µm nitrocellulose membrane lter paper (Whatsman®) using a vacuum pump. The lter paper and vacuum pump assembly are used for the ltration procedure on the water samples. Each sediment and water sample undergoes the ltration procedure twice to ensure accuracy. The lter paper then be carefully placed in the perish dish (marked with sampling locations) and allowed to dry before being examined for micro plastic distribution using an optical stereo zoom microscope. To avoid contamination from an external source (air), all laboratory analyses were meticulously monitored. To avoid sample contamination, the glassware used for the analysis was rinsed with the distilled water and wiped with ethanol.
Under the NIKON SMZ25 optical stereo zoom microscope attached to the camera, the extracted micro plastic was sorted by color, size, and shape. A pie-chart depicts the concentration and distribution percentage of micro plastics. Microsoft Excel 2010 was used to create the graphical diagrams.

Result And Discussion
This study found total of 342 micro plastics in sediments and 89 micro plastics in the water samples. In sediments the maximum concentration of micro plastics of 37 counts was observed in the sampling location 4. In water samples the maximum concentration of 15 counts was observed in the sampling location 3. Table: 1 Data from the current study and data from other rivers throughout the world were compared.

Color
Micro plastics were separated into two groups as Colored and White for the color classi cation (Radhakrishnan et al., 2021). Almost 69 percent of the micro plastics in the sediments were colored, while the remaining 31 percent were colorless. In water samples, 68% of the micro plastics were colored, while 32% were colorless (Fig. 3c &3d). Colored micro plastics were abundant in both the sediment and the water at the sample site 4 31 & 12 counts (Fig: 3a &3b). This data shows that colored micro plastics dominate in the sediment and water of the Cooum River.
Size Thompson et al., (2004) explained the size of the micro plastics is greatly affected by the disintegration process (wave action, UV light, wind, etc.). The size distribution (Fig: 4c&4d) of micro plastics in Cooum River sediment and water is as follows: <1mm (56 %), 1-3mm (28 %) 3-5mm (16%) and < 1mm (45%), 1-3mm (25%), 3-5mm (30%). Plastics with a size of < 1mm predominated in both the sediment and the water of the Cooum River. The highest concentration of micro plastic with a size of 1mm is found in sample 4 of both water and sediments. Sample 9 has the highest concentration of micro plastics with a size range of 1-3mm in sediments, while sample 10 has the highest concentration in water. Sample 9 has the highest concentration of micro plastics ranging in size from 3-5mm in both sediment and water (Fig:   4a&4b).

Shape
Micro plastics are classi ed into four types: bers, fragments, lms, and pellets (Doyle et al., 2011). The sediments were dominated by bers (86%), followed by beads (6%), and fragments (8%). In Water, bers were the most prevalent in total distribution, accounting for (87%) of the total, followed by beads (8%), and fragments (5%) (Fig: 5c& 5d). Sample 4 had the highest concentration of bers and beads, while sample 3 had the highest concentration of fragments in sediments. Sample 4 has the highest concentration of bers in water, while sample 3 has the highest concentration of beads and the sample 14 has the highest concentration fragments (Fig: 5a&5b). Microplastics in the form of bres and fragments may be discharged indirectly from secondary sources as a result of the disintegration of larger plastic particles caused by photo catalytic breakdown, oxidation, and/or mechanical weathering (Andrady, 2011).

Conclusion
The research highlights the spatial distribution of micro plastics in surface sediments and water from Chennai's Cooum River. The distribution of micro plastics in the Cooum River is heavily in uenced by domestic waste dumping near the river's banks and the discharge of untreated waste water from industries. Enforcing strong policies on the use of plastics, increasing exposure about the negative impact of micro plastics on the environment, and recycling plastics could all help to solve this problem.