Effect of tidal current on the settling and accumulation of microplastics in the Chao Phraya River estuary, Thailand.

The deposition of MPs in a water column and surface sediment during a mixed spring tidal cycle of the Chao Phraya River estuary was investigated. The settling MPs during flood and ebb tides were collected by deploying traps at 3 m below the surface, while the settled MPs throughout the tidal cycle were collected by deploying traps at 1 m above the bottom. The settling rate of MPs was 2168 pieces/m ² /h during highest to low tide, and 639 pieces/m ² /h during high to lowest tide. The deposition rate of MPs after the end of the tidal cycle was 3172 pieces/m ² /day, while the accumulation rate of MPs in the surface sediment was 1515 pieces/m ² /day. The settling MPs tended to decrease inversely to the suspended solids and salinity. The major types of the deposited MPs were polyethylene (36 %) and polyamide (33 %), while that of the surface sediment was epoxy resin (80 %).
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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