Selection of a density separation solution to study microplastics in tropical riverine sediment

Area of Science:

• Environmental Science
• Analytical Chemistry
• Ecotoxicology

Background:

• Microplastics (MPs) are pervasive environmental contaminants, posing risks to ecosystems.
• Accurate quantification of MPs in freshwater sediments is crucial for environmental assessment.
• Standardized methods for MP extraction from freshwater sediments are limited.

Purpose of the Study:

• To assess the recovery efficiency of four salt solutions (NaCl, NaI, CaCl2, ZnCl2) for microplastic isolation from freshwater sediment.
• To identify the most effective, cost-efficient, and environmentally sound method for microplastic extraction.
• To evaluate the selected method in real-world riverine sediment samples.

Main Methods:

• Density separation using NaCl, NaI, CaCl2, and ZnCl2 solutions.
• Spiking river sediment with known quantities of artificial microplastic particles (PS, PE, PVC, PET, PP, HDPE).
• Testing the optimized protocol on sediment samples from the Red River Delta, Vietnam.

Main Results:

• NaCl, NaI, and ZnCl2 solutions showed higher microplastic recovery rates (37-97%) compared to CaCl2 (28-83%).
• Lower-density microplastics (PE, HDPE, PP, PS) were recovered more efficiently (>87%) than denser polymers (PET, PVC: 37-88.8%).
• Sediments from urban rivers in the Red River Delta exhibited high microplastic pollution (26,000 MPs items·kg-1 DW).

Conclusions:

• Sodium chloride (NaCl) offers an effective, cost-efficient, and environmentally safer alternative for microplastic extraction from freshwater sediments.
• The developed NaCl-based protocol is suitable for large-scale microplastic monitoring programs, particularly in regions like Vietnam.
• Findings highlight significant microplastic contamination in urban riverine systems.