Institute of Environmental Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam.
Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam.
Environ Monit Assess. 2022 Jan 7;194(2):65. doi: 10.1007/s10661-021-09664-0.
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 and ZnCl) 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 and NaCl solutions resulted in higher recovery rates from 37 to 97% compared to the CaCl 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 solutions. However, the effective flotation of ZnCl 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 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.
微塑料（MPs）是指小尺寸（<5 毫米）的塑料颗粒，广泛存在于海洋、淡水、陆地和大气环境中。由于其广泛存在和持久性，MPs 被认为是一种新兴的环境关注污染物。从淡水中分离和定量 MPs 是一个具有挑战性和关键的问题。有必要确定 MPs 在环境中的归宿和来源，以减少其释放和不利影响。与海洋沉积物相比，从淡水沉积物中提取和估算 MPs 数量的标准化方法相对有限。本研究重点研究了四种常用盐溶液（NaCl、NaI、CaCl 和 ZnCl）在密度分离步骤中分离 MPs 时对淡水沉积物中 MPs 的回收率。将已知组合的人工 MPs 颗粒（PS、PE、PVC、PET、PP 和 HDPE）掺入标准河流沉积物中。与 CaCl 溶液（28-83%）相比，使用 NaI、ZnCl 和 NaCl 溶液提取导致回收率从 37%到 97%的提高，且回收率因聚合物类型而异。使用 NaCl、NaI 和 ZnCl 溶液可以更有效地回收低密度 MPs（PE、HDPE、PP 和 PS）（>87%），而较致密的聚合物（PET 和 PVC：37 至 88.8%）则效果较差。然而，ZnCl 和 NaI 溶液的有效浮选相对昂贵，对环境不安全，特别是在发展中国家的情况下。因此，考虑到效率、成本和环境标准，选择了 NaCl 溶液。然后，通过从红河三角洲的 9 个河流沉积物样品中提取 MPs 来测试该方案。与位于下游的沉积物相比，来自城市河流的沉积物受到 MPs 的高度污染（26,000 MPs 个·kg DW）。在这种情况下，使用 NaCl 溶液被证明是有效的，也可能用于越南的长期和大规模 MPs 监测计划。
