聚氯乙烯管在氯老化下塑膠微粒釋出與表面變化之關聯性研究

Abstract

飲用水配水系統中的塑膠管材已被確認為飲用水中塑膠微粒的重要潛在來源。消毒劑如餘氯可氧化塑膠聚合物，造成表面裂紋與孔洞生成，進而加速塑膠微粒的釋放。然而，塑膠管材表面變形與塑膠微粒釋放之間的定量關係至今仍缺乏明確的實證資料。 本研究以聚氯乙烯（PVC）水管為對象，探討在自由餘氯暴露下塑膠微粒的釋放行為，並分析其與表面形貌及化學結構變化之間的關聯性。實驗模擬氯化老化條件，以 0、0.5、5、50 與 100 mg Cl₂/L 五種氯濃度進行為期 60 天的老化模擬實驗。表面形貌變化透過數位顯微鏡、雷射掃描共軛焦顯微鏡與掃描式電子顯微鏡觀察，評估表面變形區域擴張、表面粗糙度變化與孔洞形成等指標；化學與元素變化則分別採用衰減全反射傅立葉轉換紅外光光譜儀與能量散射 X 射線光譜儀進行分析。塑膠微粒的定量採用尼羅紅染劑結合螢光顯微鏡與 ImageJ 軟體進行辨識與統計。 研究結果顯示，PVC 表面變形區域以及塑膠微粒的釋放皆隨氯濃度升高而增加，且兩者之間在增加量與速率上皆呈現高度線性相關性。釋放出的塑膠微粒中，絕大多數粒徑小於 10 μm。表面化學分析結果指出，在經過60天老化後，老化氯濃度越高，碳氧官能基（C=O）的吸收強度越明顯上升，而甲烷基（-CH₂）吸收訊號則呈下降趨勢；元素組成分析則顯示表面碳與氯的原子比例幾乎不變，顯示氧化作用主要發生於 C–H 鍵，而非 C–Cl 鍵，並可能進一步導致塑膠微粒的釋放。

Plastic pipes in drinking water distribution systems have been identified as an important source for microplastics (MPs) in drinking water. Disinfectants such as free chlorine can oxidize the plastic polymer, leading to cracking and pore formation that accelerate MPs release. However, quantitative evidences on the relationship between the deformation of plastic pipe surfaces and MPs release remains limited. This study investigates the release of MPs from PVC pipes in the presence of free chlorine and explores the correlation between surface morphological/chemical changes and MPs release. A 60-day aging experiment was conducted using chlorine concentrations of 0, 0.5, 5, 50, and 100 mg Cl₂/L to simulate chlorination aging of PVC pipes. Surface morphological changes were monitored using the digital microscopy, laser scanning confocal microscopy and scanning electron microscopy to assess the expansion of deformation area, changes in surface roughness and formation of pore structures. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and energy-dispersive X-ray spectroscopy (EDS) were employed to analyze chemical and elemental changes. MPs were quantified using Nile Red stain method coupled fluorescence microscopy and ImageJ. The results showed a strong linear correlation between the deformed area expansion and MPs release. Most of the released MPs were smaller than 10 μm. ATR- FTIR analysis revealed increasing carbonyl peak intensity with higher chlorine exposure, while EDS results showed stable surface C/Cl atomic ratios, suggesting that oxidation primarily occurred at C–H bonds rather than C–Cl bonds, which may have contributed to MPs release.