Lin Yi-Pin, Valentine Richard L
Department of Civil and Environmental and Engineering, University of Iowa, Iowa City, Iowa 52242-1527, USA.
Environ Sci Technol. 2008 Feb 1;42(3):760-5. doi: 10.1021/es071984w.
PbO2 has been identified as an important scale in some distribution systems that historically use lead service lines and free chlorine for maintaining a disinfectant residual. The stability of this highly insoluble scale with respect to its reductive dissolution may play an important role in lead release into drinking water. In this study, we investigated the release of lead from a commercially available PbO2 in the presence of natural organic matter (NOM) using a hydrophobic acid extracted from the Iowa River. Experiments were conducted using synthetic solutions with different NOM concentrations, solution pH, and NOM samples with different levels of prechlorination. It was found that release of lead from PbO2 occurred both in solutions with and without NOM, and the extent of lead release increased with increasing NOM concentration and decreasing pH value. Furthermore, the released lead was Pb(II) and not particulate PbO2 conclusively showing that reductive dissolution occurred. Prechlorination of NOM reduced the rate of lead release. Our results indicate that PbO2 can be reduced both by water and NOM. Characterization of final solid phases by scanning electron microscopy and X-ray photoelectron spectroscopy are also presented.
在一些历史上使用铅质供水管道并通过自由氯来维持消毒剂余量的配水系统中，二氧化铅已被认定为一种重要的水垢。这种极难溶解的水垢在其还原溶解方面的稳定性，可能在铅向饮用水中的释放过程中起到重要作用。在本研究中，我们使用从衣阿华河提取的一种疏水性酸，研究了在天然有机物（NOM）存在的情况下，市售二氧化铅中铅的释放情况。实验使用了具有不同NOM浓度、溶液pH值的合成溶液，以及经过不同程度预氯化处理的NOM样品。结果发现，在有和没有NOM的溶液中都会发生二氧化铅中铅的释放，并且铅的释放程度随着NOM浓度的增加和pH值的降低而增大。此外，释放出的铅是二价铅（Pb(II)）而非颗粒状二氧化铅，这确凿地表明发生了还原溶解。NOM的预氯化处理降低了铅的释放速率。我们的结果表明，水和NOM都能使二氧化铅发生还原。还介绍了通过扫描电子显微镜和X射线光电子能谱对最终固相的表征情况。
