近年來，塑膠大量使用與衍生的塑膠汙染相關議題越來越受到重視，塑膠微粒(Microplastics, MPs)於環境中廣泛存在和其持久性可能對生態系統造成潛在風險，因此了解環境中MPs汙染至關重要。然而，現有MPs定量方法多費時或需使用昂貴儀器(如：FTIR、拉曼光譜儀和熱裂解GC/MS等)，相對便宜省時之顯微鏡搭配螢光染劑-尼羅紅(Nile red, NR)則易受環境有機質干擾，而高估其含量。本研究選擇以螢光染劑-尼羅紅方法搭配螢光顯微鏡進行MPs分析，旨在建立樣品前處理程序(包括乾燥、前氧化、浮選分離和後氧化)，再進行染色測定以減少有機物干擾，並於2021年7、8以及9月(濕季)及2021年4、12月以及2022年2月(乾季)採集六次台灣台南鹽水溪上游至下游表面水(n=27)及底泥樣品(n=33)，檢測其汙染豐富度、大小及外型分佈。
測試塑膠顆粒對於氧化的穩定性、密度分離回收率及尼羅紅染色的分析，從日常生活中獲得5種聚合物類型的塑膠，建立樣品前處理流程。以結果顯示使用30%H2O2將會使塑膠微粒尺寸縮小20%的現象發生，然而15%H2O2並不會有此現象發生。DI水(1 g/cm3)及氯化鈉溶液(1.2 g/cm3)無法有效分離比重較大的塑膠微粒，密度較大之氯化鋅溶液(1.5 g/cm3)能分離5種聚合物類型塑膠。NR染劑均可染色MPs，且聚合物類型並不影響螢光強度。
結果顯示針對底泥樣品經由15% H2O2、5 M ZnCl2及1.2% H2O2分別進行前氧化、浮選分離及後氧化程序，能將底泥中有機物含量從0.47%減少至0.19%，去除率為59.0%，每20 g乾重底泥樣品螢光訊號由14,359.7 item減少至86.3 item，減少率為99.4%，本研究確認使用此程序可有效減少有機物的干擾。利用此建立之流程應用於環境樣品中，結果顯示表面水之MPs豐富度為9-27 item/L，底泥之MPs豐富度為18-134.5 item/20g sediment dw。表面水及底泥中主要尺寸以小粒徑(10–100 μm) (表面水：80.6%、底泥：61.0%)、外型以纖維(表面水：44.77%、底泥：51.0%)及碎片(表面水：35.1%、底泥：32.7%)為主。在鹽水溪之空間分布顯示不論在表面水或是底泥樣品下游地區(表面水：21.6±5.5 item/L；底泥：79.2±28.4 items/20 g dw)豐富度大於上游(表面水：13.4±3.4item/L；底泥：26.7±9.1 items/20 g dw)。在鹽水溪之季節變化顯示在表面水或是底泥樣品濕季(表面水：18.1±6.7 item/L；底泥：56.3±26.6 items/20 g dw)豐富度皆大於乾季(表面水：12.8±4.5 item/L；底泥：54.6±24.2 items/20 g dw)。

In recent years, the issue of plastic pollution arising from the massive use of plastics has received increasing attention. The prevalence and persistence of microplastics (MPs) in the environment may pose potential risks to ecosystems, and therefore it is important to understand MPs concentration in the environment. However, the existing methods for quantification of MPs are time-consuming or require expensive instruments (e.g., FTIR, Raman spectroscopy, pyrolysis GC/MS, etc.), and the relatively inexpensive and time-saving microscope with the fluorescent dye stain (Nile red, NR), is easily interfered by natural organic matter and overestimates its contents. In this study, MPs were stained by NR dye and analyzed by fluorescence microscopy. A pretreatment procedure (including drying, pre-oxidation, flotation separation, and post-oxidation) was established for environmental sediment samples. During July, August, and September 2021 (wet season), April and December 2020, and February 2022 (dry season) surface water samples (n=27) and sediment samples (n=33) were collected from the upstream to downstream of the Yanshui (YS) river in Tainan, Taiwan investigated the abundance, size and shape distribution of MPs.
The oxidation stability, density separation recovery, and Nile red staining tested MPs five polymer types of plastics. The results showed that the use of 30% H2O2 in the MPs was 20% smaller than its original size, but 15% H2O2 hadn't this phenomenon. DI water (1 g/cm3) and sodium chloride solution (1.2 g/cm3) cannot effectively separate the MPs with larger specific gravity. In comparison, the denser zinc chloride solution (1.5 g/cm3) can separate five polymer types of plastic. NR dyes can stain MPs, and the type of polymer did not affect the fluorescence intensity.
The results showed that the organic matter content was reduced from 0.47% to 0.19% with a removal rate of 59.0%; The fluorescence signal per 20 g sediment sample was reduced from 14,359.7 items to 86.3 items with a reduced rate of 99.4% by the pre-oxidation, flotation separation, and post-oxidation processes with 15% H2O2, 5 M ZnCl2, and 1.2% H2O2, respectively. This procedure is effective in removing the interference of organic matter. The results showed that the MPs abundance was 9-27 items/L and 18-134.5 items/20g sediment in surface water and sediment, respectively. The size of MPs in surface water and sediment were dominated by small particles (10-100 μm) (surface water: 80.6%, sediment: 61.0%), the shape is mainly fiber (surface water: 44.77%, sediment: 51.0%) and debris (surface water: 35.1%, sediment: 32.7%). The spatial distribution showed that the abundance was greater in the downstream area (surface water: 21.6±5.5 item/L; sediment: 79.2±28.4 items/20g) than in the upstream area (surface water: 13.4±3.4 item/L; sediment: 26.7±9.1 items/20g) for both surface water and sediment samples in the YS river. The seasonal variation showed that the abundance of surface water and sediment samples in the wet season (surface water: 18.1±6.7 items/L; sediment: 56.3±26.6 items/20g) was higher than that in the dry season (surface water: 12.8±4.5 items/L; sediment: 54.6±24.2 items/20g) in YS river.

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