The Saigon River, coursing through Ho Chi Minh City, is a vital yet alarmingly polluted waterway. It ranks among the top 50 rivers globally contributing to plastic pollution. This study delves into the complex mechanisms governing the transport of floating plastic within a tidal system, such as the Saigon River. Our methodology adopts a multifaceted approach, combining visual observations, on-site measurements, and a comparison with existing literature data and methodologies. The factors influencing plastic transport in the studied river stretch are several and complex, ranging from the seasonal fluctuations in rainfall and tidal patterns to the role played by water hyacinths, acting as effective catchments for plastic litter, thus shaping the trajectory of these materials. Furthermore, we investigate the different types of plastic that flow on the river surface. At the end of our research, we develop an early-stage conceptual model. This model serves as a framework that could help understanding plastic transport within the Saigon River and emphasizing the interplay of numerous influencing factors. Our findings underscore the necessity for comprehensive investigations into plastic transport in the Saigon River. By addressing these knowledge gaps, we can develop more effective strategies to mitigate plastic pollution.

This study investigates pollutant dispersion from residential wood burning in a neighborhood in Utrecht, Netherlands, employing the Dutch Atmospheric Large-Eddy Simulation (DALES) model under various atmospheric conditions. Residential wood combustion is a major source of urban air pollution, especially during winter months. This research aims to quantify the distribution and distance traveled by pollutants from their release source. By using DALES, detailed analyses of atmospheric variables and pollutant concentration fields are conducted, providing valuable insights into how atmospheric stability influences pollutant spread. The results show that atmospheric stability significantly affects pollutant dispersion. Higher pollutant concentrations were generally observed near the surface under stable and very stable conditions as compared to neutral conditions, due to restricted vertical motions that limit the vertical dispersion of pollutants. Additionally, under stable conditions, pollutant concentrations remained elevated farther from the source, affecting residents who do not live close to the emission source. The study also compared the performance of DALES with commonly used Gaussian plume models (GPMs) to evaluate their performance in urban environments and under different atmospheric conditions. Three schemes that provide the dispersion parameters for the GPMs are tested to determine their accuracy in representing the DALES results. The comparison reveals that, while GPMs offer a general overview of pollutant distribution, they often fail to accurately capture concentration decay rates or the spatial extent of the plume. The study concludes that further research should investigate the impact of atmospheric stability on air pollutant dispersion in urban environments. It also highlights the limitations of Gaussian Plume Models (GPMs), which often simplify processes occurring in the boundary layer. In urban settings, where the urban geometry plays a significant role in pollutant dispersion, DALES proves to be more effective than GPMs, which cannot accurately capture the effects of buildings on the plume.