Integrating Field Data and Numerical Modeling to Assess Microplastic Distribution in the Aquatic Environment of Ha Long Bay, Vietnam

This study aimed to investigate the microplastic distribution in the aquatic environment and sediments, and integrate field data and numerical modeling to simulate the spreading of microplastics to gain valuable insights into microplastic accumulation and infiltration into the sea.The study showed that the microplastic density in seawater was ranging from 0.01 to 0.69 particles/m3; the color of microplastics were white/transparent with 41.3%, blue 22.3% and yellow/orange 21.3%; the morphology of microplastics were thin, spherical and fibrous filaments, accounted for 96.9%, of which the size from 1-5mm accounted for 87.9%; the main types of microplastics were HDPE and PS accounting for 47.4% and 18.8%, respectively.The amount of microplastics found in the sedimentation was rather low, up to 12 particles/kilogram, was mostly found in the coast and in rivers.The spreading of microplastic modeling indicated that the high microplastic concentration areas were primarily located in the coastal regions of Ha Long and Cam Pha cities; and the microplastic generated from the inland did not affect Ha Long Bay due to the geomorphological structure with numerous islands that limited the dispersion of microplastics into the offshore.The zones with the highest microplastic concentrations coincide with areas of intensive human activity, including cruise tourism, coastal services, maritime transport, coal mining, and coastal industrial zones.Hence, the waste capture in estuaries and coastal areas and the limitation of single-use plastic products on cruise ships are needed to avoid microplastic movement to the sea.