ORISE Post-Doctoral Fellow at the U.S. Environmental Protection Agency , Cincinnati , Ohio 45268 , United States.
National Risk Management Research Laboratory , U.S. Environmental Protection Agency , 26 W. Martin Luther King Dr. , Cincinnati , Ohio 45268 , United States.
Environ Sci Technol. 2018 Mar 20;52(6):3365-3374. doi: 10.1021/acs.est.7b06010. Epub 2018 Feb 28.
Galvanic corrosion as a mechanism of toxic lead release into drinking water has been under scientific debate in the U.S. for over 30 years. Visual and mineralogical analysis of 28 lead pipe joints, excavated after 60+ years from eight U.S. water utilities, provided the first direct view of three distinct galvanic corrosion patterns in practice: (1) no evidence of galvanic corrosion; (2) galvanic corrosion with lead cathode; (3) galvanic corrosion with lead anode. Pattern 3 is consistent with empirical galvanic series (lead → brass → copper in order of increasing nobility) and poses the greatest risk of Pb exposure. Pattern 2 is consistent with galvanic battery reversion. The identification of copper-sulfate minerals (Pattern 2), and lead-sulfate and lead-chloride minerals (Pattern 3) in galvanic zones illustrated the migration of chloride and sulfate toward the anode. Geochemical modeling confirmed the required pH drop from the bulk water level to at least pH 3.0-4.0 (Pattern 2) and pH < 5.5 (Pattern 3) in order to form these minerals. Despite joints being over 60 years old, galvanic zones in Pattern 3 were active and possibly posed an important source of lead to drinking water. Importantly, Pattern 3 was not observed in samples from systems representing water qualities favoring PbO formation.
电化学腐蚀作为导致饮用水中有毒铅释放的一种机制，在美国已经引发了超过 30 年的科学争论。对从 8 家美国水务公司挖掘出的、使用 60 多年后的 28 个铅管接头进行的视觉和矿物学分析，首次直接观察到了三种不同的实际电化学腐蚀模式：（1）无电化学腐蚀证据；（2）存在铅阴极的电化学腐蚀；（3）存在铅阳极的电化学腐蚀。模式 3 与经验性的电化学序列（从铅到黄铜再到铜，按电正性递增的顺序排列）一致，是 Pb 暴露风险最大的模式。模式 2 与电化学电池反转一致。在电化学腐蚀区鉴定出的硫酸铜矿物（模式 2），以及硫酸铅和氯化铅矿物（模式 3），说明了氯离子和硫酸根离子向阳极的迁移。地球化学模型证实，为了形成这些矿物，需要将 pH 值从整体水平降低至至少 pH3.0-4.0（模式 2）和 pH<5.5（模式 3）。尽管接头已使用超过 60 年，但模式 3 的电化学腐蚀区仍处于活跃状态，可能是饮用水中铅的重要来源。重要的是，在代表有利于 PbO 形成的水质的系统样本中，未观察到模式 3。
