Influence of tidal current on microplastic dynamics in Chao Phraya river estuarine ecosystem

Abstract

Microplastics (MPs) can be found almost everywhere in marine ecosystems. That is one of the issues of concern around the world, including in Thailand. Estuary ecosystems are also among the most disturbed. By the estuary ecosystem affected by both rivers and oceans, such as the mouth of the Chao Phraya River in Thailand. Due to the change in tide, it is necessary to study the effects of tidal currents on the depth of MPs. Water samples were collected at approximately 60 water levels in 24 hours. Samples and three water quality indicators were collected at Pak Nam Chao Phraya. The number, shape and color of the MPs are then counted and analyzed under a microscope. When polymers were counted and analyzed with µ-FTIR for size and type. An average of 4.0±3.8 pieces/L was found in the experimental samples. And from all the samples, it was found that the most shape of MPs was fragment (shape), blue (color), at 16-100 µm (size) from the sample and Polytetrafluoroethylene (type) is the most polymer of MPs. For MPs detected during high and low tide. The average MPs were 3.4±3.3 and 4.0±4.2 pieces/L, respectively. In addition, fragment shape, blue color, 16-100 µm and PTFE polymer were the dominant plastic during high and low tide. It was found that tidal changes directly affect salinity and the effects of microplastic also found that MPs in the Chao Phraya Estuary are very high ecological risk.

Currently, microplastics are found everywhere in the environment. However, research around the world is not known about the deposition rates of MPs in marine and coastal environments. In this study, the Chao Phraya River Estuary was selected as the research area to study the deposition rate and characteristics of microplastics on surface sediments and analyze the tidal current that might affect the accumulation. The results show that the highest deposition rate of microplastics (1,401 pieces/m2/hour) during 6:00-13:00 when the tide changes from the highest to the lowest. While the lowest deposition rate of microplastics was 533 pieces/m2/hour. Which occurs during the rising tide from the lowest-high tide 14:00-17:00. Microplastics, 16-100 µm was dominated throughout the tidal cycle. Fragment and fiber shapes were the most abundant microplastic shapes in all samples. In addition, polyamide (PA) was the main polymer type of microplastics that precipitated in surface sediments. And for 24 hours found 446±108 pieces/m2/hour of MPs at surface sediment. It was found that the most The MPs were 16-100 µm in size, fragment shape, black color, and polyamide (PA) as the main polymer. Monitoring the accumulation rate of microplastics in the aquatic environment and to better understand the factors of tidal currents in controlling the accumulation rate of microplastics.