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OpenDrift plastic waste in Thanh Hoa

data. Within the designated study area, plastic waste from winter to summer, marked by a gradual shift in
originating from riverine sources is introduced into the wind direction and increasing river flow. Simulations
model and subsequently advected through the marine were conducted for April 2022 and April 2024, each
environment under the combined influence of ocean lasting 1 month, to analyze interannual variability and
currents, wind forcing, wave dynamics, and vertical the emergence of new transport pathways; (iii) Scenario
mixing processes. The module dynamically tracks 3 simulates summer monsoon conditions, featuring
the trajectory and transformation of plastic particles, intensified southwest winds, elevated precipitation,
enabling comprehensive simulations of their transport and high river discharge. These factors enhance long-
pathways. In addition, the coastal interaction module distance dispersion and introduce additional plastic
was employed to resolve shoreline-related processes, waste from land-based sources via surface runoff.
including accumulation, retention, and redistribution The simulation covered July 2021 and July 2024;
of plastic debris. This integrated approach facilitated (iv) Scenario 4 reflects the transition from summer
a detailed understanding of plastic waste behavior to winter, characterized by declining river discharge
across both open ocean and coastal zones, supporting and shifting wind regimes. Conducted in September
assessments of environmental impact and mitigation 2021, this scenario provides insights into redistribution
strategies. mechanisms and the formation of new hotspots during
seasonal change.
3.2. Environmental scenarios and their influence on Collectively, these scenarios offer a comprehensive
plastic waste dispersion framework for understanding the spatiotemporal
Variations in environmental conditions – particularly dynamics of plastic waste in response to monsoonal
wave and wind regimes – play a pivotal role in shaping variability and coastal hydrodynamics.
the transport trajectories and dispersion patterns of
plastic debris in the marine environment. These dynamic 3.3. Data sources
forces not only influence the movement of particles but 3.3.1. Wave, wind, and ocean current data
also contribute to the formation of new accumulation To evaluate the dispersion of marine litter in the
zones or the redistribution of existing hotspots. 44,45 coastal waters of Thanh Hoa, this study employed
In the coastal region of Thanh Hoa, a long-term a combination of statistical analysis and numerical
climatological analysis spanning 30 years (1992 modeling. Specifically, long-term wave and wind regime
– 2022) reveals that both wave and wind regimes data were analyzed to define computational scenarios
exhibit bidirectional characteristics. Specifically, the and to construct the corresponding input datasets for the
wave regime is dominated by northeast and southeast simulation model.
directions, with average significant wave heights Central to the modeling framework is the integration
ranging from 0.7 to 1.2 m (Figure 3). Similarly, the of high-resolution oceanographic data. Ocean current
wind regime shows two principal directions – northeast velocity, temperature, and salinity are derived from
and southeast – as illustrated in the wind rose diagram the Regional Ocean Modeling System (ROMS) and
(Figure 4). satellite-based observations. The data sources include:
Based on these environmental patterns, four (i) ROMS: A widely recognized and rigorously validated
representative simulation scenarios were developed to ocean modeling system that synthesizes multiple
reflect distinct seasonal and transitional phases. Each oceanographic datasets to produce high-resolution
scenario integrates key environmental drivers – such simulations of ocean dynamics; and (ii) satellite-derived
as wind direction, river discharge, and temperature – data: Remote sensing products from the National
to evaluate their combined influence on plastic waste Oceanic and Atmospheric Administration and Moderate
behavior and distribution. Resolution Imaging Spectroradiometer were utilized to
To comprehensively assess seasonal variability, the calculate temperature and salinity parameters within the
scenarios are defined as follows: (i) Scenario 1 represents study area (project code: ĐTDL.CN.55/20).
winter conditions, dominated by the northeast monsoon. By combining these datasets with long-term wave,
This period is characterized by lower temperatures wind, and ocean current records specific to the Thanh
and reduced river discharge, which affect the vertical Hoa coastal region, a comprehensive set of input
movement and localized accumulation of plastic debris. conditions was constructed. These inputs correspond
The simulation spanned from January 1 to January 31, to four distinct seasonal and transitional scenarios, as
2021; (ii) Scenario 2 captures the transitional phase detailed in Table 1, and serve as the foundation for

Volume 22 Issue 4 (2025) 79 doi: 10.36922/AJWEP025170129