市售自來水管材配件之溶鉛潛勢評估

Abstract

一般住戶端之自來水管材及配件如給水用管、管接配件(如水管接頭、止水閥門等)及水龍頭，普遍由不鏽鋼、銅、黃銅合金及塑膠製成。雖然鉛管在世界各國已被禁用，但由於鉛的穩定性和可塑性佳，仍被廣泛添加於常用之自來水管材及配件中，可能造成飲用水鉛污染。此研究的目的在了解臺灣市售的常用管材及配件在自來水中鉛溶出的濃度，並利用具有螯合金屬離子特性的乙二胺四乙酸溶液 (pH 4, EDTA = 100 mg/L) 及自來水來測定這些管材及配件的鉛溶出潛勢，最後利用掃描式電子顯微鏡-能量色散X射線光譜 (SEM-EDX) 對管件內部表面進行元素定性定量分析並探討其和鉛溶出之關聯性。實驗結果顯示鉛普遍存在於管材的濕表面及管件本身，兩者含鉛量與管件鉛溶出皆具正相關。就管件材料溶鉛量而言，由高至低為黃銅 >> 不鏽鋼 ~ 銅 ~ 聚氯乙烯。住戶端用水之內線設備屬私人財產，由用戶自行維護，含鉛量較高的管件 (鉛佔管件濕表面部分及管件總重量的重量百分比) 與自來水長時間接觸會增加自來水鉛污染的風險。

Commonly used premise plumbing materials such as pipes, valves, fittings and faucets are made of various materials, including stainless steel, copper, brass and plastic. Lead pipe has been banned for conveying drinking water in new constructions in many countries since the 1980s. Due to its flexibility and malleability, however, lead is still commonly used as an additive in these materials and may potentially leach into drinking water. The objective of this study is to investigate the likelihood of lead leaching from commonly used premise plumbing materials into drinking water. The maximum lead leaching potential for each pluming material was operationally determined using high strength acidic EDTA solutions (pH 4, EDTA = 100 mg/L). Lead leaching from each plumbing material was also evaluated using reconstituted tap water. Surface lead weight percentage obtained using SEM-EDX and lead weight percentages of the material body obtained using strong acid digestion were found to positively correlate with lead release. In general, lead release was found to follow the following order in terms of different materials: brass >> stainless steel ~ copper ~ PVC. In addition, lead release was found to positively correlate with the weight percentage of lead on the inner surfaces and in the whole body of the materials.