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Tran, et al.

spatial dispersion of plastic waste in marine systems industrial, and domestic water demands across their
remains insufficiently understood, prompting further basins. However, they are increasingly subjected to
investigation into the complex interactions between anthropogenic pressures such as urban expansion,
riverine and oceanic processes. 11,14,15 In this context, deforestation, and agricultural runoff, which contribute
Thanh Hoa province – with its diverse and dynamic significantly to plastic waste discharge into aquatic
river networks – offers a representative case study systems. The convergence of these rivers into the
for examining plastic waste transport from inland coastal zone makes Thanh Hoa an ideal location for
waterways to coastal and offshore zones. 16 investigating land-to-sea plastic transport mechanisms.
The East Sea and its surrounding waters exhibit The combination of diverse riverine inputs and dynamic
complex plastic transport dynamics, primarily governed coastal hydrodynamics provides a representative setting
by atmospheric and ocean circulation patterns. 17-19 As a for analyzing the spatial and temporal variability of
semi-enclosed basin, the East Sea is strongly influenced plastic waste movement and accumulation. By focusing
by the Asian monsoon system, characterized by on this region, the study aims to capture the influence
northeasterly winds in winter and southwesterly winds of river discharge, ocean currents, and wind patterns
in summer. 20,21 These seasonal regimes generate distinct on plastic dispersion, thereby identifying potential
surface circulation patterns, with stronger vortices and accumulation zones and informing strategies for marine
wind speeds of 8 – 10 m/s in winter and weaker flows pollution mitigation.
averaging 4 – 5 m/s in summer. Wind forcing, combined
with geostrophic currents and tidal oscillations, produces 3. Research methods and data sources
wind-driven drift that significantly affects the dispersion
of floating plastic debris. 22-24 This drift is typically 3.1. Drift model selection
modeled as a fraction of wind speed – ranging from 1% OpenDrift is an open-source Lagrangian particle-
to 6% – with a coefficient of 2 – 3% commonly applied tracking framework developed by the Norwegian
29
for plastic particles, resulting in enhanced transport Meteorological Institute (MET Norway). It has been
during winter when wind intensity is greater. 21,25-27 widely applied in various environmental studies. For
Against this backdrop, the present study investigates example, it was used to model plastic drift from the
30
the transport trajectories and dispersion patterns of Mekong River, support search and rescue operations
plastic waste originating from three major rivers in in Korea, assess oil spill risks in Cuba and the Barents
31
Thanh Hoa province: the Ma, Lach Bang, and Len Sea, 32,33 and study microplastic dispersion in the
Rivers. Using the OpenDrift modeling framework – a Mediterranean Sea. 34,35 The model was selected for its
robust tool for simulating buoyant particle movement robustness, flexibility, and ability to integrate diverse
– we simulate plastic transport under varying seasonal environmental datasets such as ocean currents, wind
conditions. The model integrates key environmental fields, and river discharge. 29-31,36-38 In this study, five
drivers, including ocean currents, wind fields, river modules were configured to reflect the hydrodynamic
discharge, and flow velocity, to capture the complex conditions of the region. These modules simulate
hydrodynamic interactions influencing plastic key processes influencing plastic transport, and their
dispersion. This comprehensive approach enables the interrelationships are illustrated in Figure 2. This
identification of spatial and temporal variability in modeling approach enables a detailed analysis of
plastic transport, highlighting accumulation zones and seasonal variability and spatial patterns of plastic
potential pollution hotspots in marine environments. waste movement from riverine sources to marine
environments.
2. Study sites
3.1.1. Leeway module
The study area is located in the coastal zone of Thanh The Leeway module was used to simulate wind-induced
Hoa province, Vietnam, encompassing a 102 km arc- drift of floating plastic particles in aquatic environments.
shaped shoreline along the East Sea (Figure 1). This It accounts for key physical parameters such as wind
region receives freshwater input from three major resistance coefficients and the aerodynamic properties
rivers: the Ma, Lach Bang, and Len Rivers. Each river of different plastic types, which influence particle
exhibits distinct hydrological characteristics in terms responses to surface wind forces. The module calculates
of scale, flow regime, and seasonal variability. 16,28 the leeway drift velocity (V leeway ), representing the wind-
These rivers play a vital role in supporting agricultural, driven component of particle movement. This velocity

Volume 22 Issue 4 (2025) 76 doi: 10.36922/AJWEP025170129