Journal Article

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

Hoang, Thi Quynh, Bui, Huyen Thuong, Tran, Thi Kim Chi, Le, Thi Phuong Quynh, Nguyen, Thuy Lien, Le, Phuong Thu, Trinh, van Tuyen, Phuong, Ngoc Nam, Vu, Thanh Mai, Duong, Thi Thuy, Ngo, Ha My, Nguyen, Thi Nhu Huong, Doan, Thi Oanh, da Le, Nhu, Ho, Tu Cuong, Strady, Emilie, Bui, Manh Ha

2022

Overview

Microplastics (MPs) are small (< 5 mm) plastic particles that are widely found in marine, freshwater, terrestrial and atmospheric environments. Due to their prevalence and persistence, MPs are considered an emerging contaminant of environmental concern. The separation and quantitation of MPs from freshwater sediments is a challenging and critical issue. It is necessary to identify the fate and sources of MPs in the environment, minimise their release and adverse effects. Compared to marine sediments, standardised methods for extracting and estimating the amount of MPs in freshwater sediments are relatively limited. The present study focuses on MP recovery efficiency of four commonly used salt solutions (NaCl, NaI, CaCl 2 and ZnCl 2 ) for isolating MPs during the density separation step from freshwater sediment. Known combinations of artificial MP particles (PS, PE, PVC, PET, PP and HDPE) were spiked into standard river sediment. Extraction using NaI, ZnCl 2 and NaCl solutions resulted in higher recovery rates from 37 to 97% compared to the CaCl 2 solution (28–83%) and varied between polymer types. Low-density MPs (PE, HDPE, PP and PS) were more effectively recovered (> 87%) than the denser polymers (PET and PVC: 37 to 88.8%) using NaCl, NaI and ZnCl 2 solutions. However, the effective flotation of ZnCl 2 and NaI solutions is relatively expensive and unsafe to the environment, especially in the context of developing countries. Therefore, considering the efficiency, cost and environmental criteria, NaCl solution was selected. The protocol was then tested by extracting MPs from nine riverine sediment samples from the Red River Delta. Sediments collected from urban rivers were highly polluted by MPs (26,000 MPs items·kg −1 DW) compared to sediments located downstream. Using a NaCl solution was found to be effective in this case study and might also be used in long-term and large-scale MP monitoring programmes in Vietnam.

• Publisher: Springer Science and Business Media LLC,Springer International Publishing,Springer Nature B.V,Springer
• Subject: [SDE] Environmental Sciences / Calcium chloride / case studies / Chloride / Contaminants / Density / Developing countries / Earth and Environmental Science / Ecology / Ecotoxicology / Environment / Environmental Management / Environmental Monitoring / Environmental perception / Environmental science / Environmental Sciences / Flotation / Fluvial sediments / Fresh water / Freshwater / Geologic Sediments / Inland water environment / LDCs / Marine sediments / Microplastics / Monitoring/Environmental Analysis / Plastic debris / Plastic pollution / Plastics / Polyethylene terephthalate / Polymers / Polystyrene resins / Polyvinyl chloride / Quantitation / Recovery / riparian areas / river deltas / River sediments / Rivers / Saline solutions / Sediment / Sediment samplers / Sediment samples / Sediments / Separation / Sodium / Sodium chloride / Tropical climate / Vietnam / Water Pollutants, Chemical / Water Pollutants, Chemical - analysis / Zinc chloride