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doi:10.3808/jei.202500546
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Study on the Migration and Distribution Characteristics of Microplastics in the Pearl River Estuary under Changing Environmental Conditions

G. P. He1, H. Wan2 *, R. Li3, Y. P. Cai1,2, and Z. F. Yang1,2

  1. Guangdong Basic Research Center of Excellence for Ecological Security and Green Development, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
  2. Research Centre of Ecology & Environment for Coastal Area and Deep Sea, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China
  3. State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China

*Corresponding author. Tel.: +8618628052184. E-mail address: wanhang@gmlab.ac.cn (H. Wan).

Abstract


Estuaries, such as the Pearl River Estuary (PRE), play a crucial role in hydrological exchange and material transport, serving as key zones for the discharge and accumulation of microplastics (MPs). Recent reports indicated that the PRE released approximately 66 tons of MPs annually into the South China Sea. While previous studies have examined the distribution of MPs in the PRE, the dynamic migration processes of MPs in the estuary, especially under changing environmental conditions, remain inadequately understood. To elucidate the migration and distribution characteristics of MPs under changing environmental conditions in PRE, the study established a MPs transport model integrated with the hydrodynamic module and Lagrangian particle tracking module. The established model accounted for the dynamic effects of runoff, sea level rise, and wind conditions, allowing for a more comprehensive simulation of MPs migration. The results demonstrated a high level of agreement between simulated and observed data, with R2 values exceeding 0.95. The PRE exhibited marked seasonal variability in MPs distribution, with Shenzhen Bay (SZB) emerging as a persistent accumulation hotspot. This phenomenon stemmed from the synergistic effects of unique hydrodynamic constraints (flow velocities < 0.2 m/s) and intense anthropogenic pressures. Compared to adjacent regions, these conditions created a convergence-dominant regime that amplified MPs retention efficiency by 2.0 ~ 4.0 folds. Eight cases were designed to estimate the impacts of runoff, sea level rise, wind speed changes, and their interactions on the transport and distribution of MPs in the PRE in 2050 and 2070. These researches could highlight the complex interplay between hydrodynamic processes and climate change, underscoring the importance of considering multiple environmental factors when assessing MPs pollution in estuarine regions.

Keywords: microplastics, changing environmental conditions, particle tracking, sea level rise, hydrodynamic constraints


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