Abstract:
Plastic pollutants act as the emerging contaminant with possible threats to aquatic
ecosystems. The present study attempts to assess microplastic (MP) content in surface
water and sediments of Madu-Ganga estuary which is one of the ecologically and
commercially important Ramsar wetlands in Sri Lanka. Manta net (380 μm) was
employed to collect surface water samples by towing net horizontally along water surface
for 10 m with 1.8 ms-1 of average flow rate, while Ekman grab was used for sampling
sediments from 4 study sites during October 2019 to January 2020. Wet Peroxide
Oxidation (WPO) protocol was applied after subjecting both water and sediment samples
to the wet sieving process. Fourier Transform Infrared Radiation (FTIR) analysis was
used to confirm polymer types of extracted MPs in samples. MPs in digested samples
were enumerated and categorized microscopically according to their size, shape, and
color. One Way Analysis of Variance (ANOVA) was applied to identify the differences
of MPs density with sampling location (p<0.05). According to the results, both surface
water and sediment layers had contaminated by MPs accumulation. Sampling location
had not significant (p>0.05) effect on the MP content of surface water and sediment
samples. Average MPs accumulation rate of surface water and sediment samples were
recorded as 40.06±1.84 items/m3
and 5.88±1.33 items/100g respectively. Whitetransparent, blue, black, and red were major color categories observed in MPs, while
white-transparent color was dominant MP type of water and sediment samples. Most of
the accumulated MPs were at the 0.50-1.00 mm of long-range. Fiber, sheet, and fragment
shape MPs were commonly found in water and sediment samples. According to FTIR
analysis, polypropylene (Characteristic absorption bands: 2950 cm−1
, 2915 cm− 1
, 2838
cm− 1
, 1455 cm− 1
, 1377 cm− 1
) was abundant polymer type in surface water, while
sediment contains polypropylene and polyvinyl chloride (Characteristic absorption bands:
1427 cm−1
, 1331 cm−1
, 1255 cm−1
,1099 cm−1
, 966 cm−1
). As per the preliminary survey,
two major anthropogenic activities: commercial fishery and tourism were identified as the
main point and non-point pollution sources in this ecosystem. In conclusion, this study
emphasizes the growing risk of plastic pollution and the urgent need for a sustainable
management plan to reduce plastic pollution in the Madu-Ganga estuary ecosystem.
Keywords: Plastic contamination, Microplastics, Coastal ecosystem, Surface water,
Benthic sediments, Anthropogenic factors
