聚氯乙烯管釋出塑膠微粒潛勢之研究 : 以外部光、內部氯和外部光加內部氯老化試驗

Abstract

塑膠微粒廣泛存在於各種環境介質，會對環境和人體健康造成影響。淨水廠中的塑膠元件和配水系統中的塑膠管被認為是自來水中塑膠微粒的潛在來源，其中配水系統及家戶内線系统中使用的塑膠管，以聚氯乙烯 (PVC) 管為最大宗。本研究之目的是探討PVC管在外部光老化、內部氯老化和外部光老化加內部氯老化後，管內釋出塑膠微粒的情況，並以靜態和循環沖刷兩種不同條件下來觀察塑膠微粒的釋出。實驗結果顯示，外部光老化並未對PVC管內塑膠微粒的釋出產生影響。在內部氯老化和外部光老化加內部氯老化下，隨著老化時間增加，管內塑膠微粒的釋出量顯著增加，最高的釋出量在老化81天後分別為5233和5722 #/L，然兩者並無顯著差異，顯示管內塑膠微粒的釋出主要是因為內部氯老化造成的。在循環沖刷實驗中，除了外部光老化，其他兩種老化方式隨著老化時間的增加，塑膠微粒的釋出量也增加，同時釋出的塑膠微粒數量也比靜態老化的多。然而，考慮總沖刷的水體積，其釋出的塑膠微粒濃度低於靜態老化。羰基指數 (Carbonyl index, CI) 和掃描式電子顯的結果顯示， CI隨著老化時間增加而增加，但與塑膠微粒的釋出量之間沒有顯著的關聯性，但表面形成的孔洞數量和塑膠微粒的釋出量則呈現正相關。

Microplastics are widely present in various environmental matrixes, potentially threating the ecological and human health. Plastic components in the water treatment plant and plastic pipes used in the distribution systems are recognized as potential sources of microplastics. Polyvinyl chloride (PVC) pipe is the most widely used plastic pipe in the distribution system. In this study, the effects of external photoaging, internal chlorine aging, and combined aging processes on the release of microplastics from the interior of PVC pipes in stagnant and flowing water were investigated. The results indicated that external photoaging did not significantly affect the release of microplastics from the interior of PVC pipes. After chlorine aging and combined aging, the release of microplastics increased significantly with the increasing aging period, in which the highest releases of microplastics were 5233 and 5722 #/L, respectively. There was no significant difference in microplastic released between chlorine aging and combined aging, suggesting that chlorine aging was primarily responsible for microplastics release from the interior of the pipes. Under flowing conditions, except for external photoaging, the release of microplastics increased with the increasing aging period, resulting in higher counts of released microplastics compared to those observed in stagnant water. However, due to the much higher total water volume flowing through the pipes, the concentrations of microplastics were lower compared to those in stagnant conditions. Carbonyl index (CI) and scanning electron microscopy (SEM) were employed to examine the interior surface changes of PVC pipes. Although CI increased with the increasing aging period, there was no significant correlation with the release of microplastics in stagnant water. SEM images revealed an increase in pore formation on the inner surfaces of PVC pipes with prolonged aging period after chlorine aging and combined aging. Positive correlations between the number of pores and the release of microplastics were found for chlorine aging and combined aging.