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The oxidation of hydrogen-terminated porous silicon surfaces produced by electrochemical etching has been studied using transmission FTIR spectroscopy. The surface is passivated to oxidation by surface hydrogen below about 523 K. Above this temperature as hydrogen depletion occurs by H2 evolution, Si surface dangling bond sites, capable of O2 dissociation, are involved in initiating the first stage of oxidation. Two reactions are observed. The first, O insertion into Si−Si back-bonds, leads to −O y SiH x surface species which exhibit frequency shifts to the blue compared to parent SiH x stretching modes. In addition, Si−O−Si modes are also observed to form. The second reaction involves oxygen atom insertion into Si−H bonds to produce isolated Si−OH surface species.

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The artificial sweetener sucralose has recently been shown to be a widespread of contaminant of wastewater, surface water, and groundwater. In order to understand its occurrence in drinking water systems, water samples from 19 United States (U.S.) drinking water treatment plants (DWTPs) serving more than 28 million people were analyzed for sucralose using liquid chromatography tandem mass spectrometry (LC-MS/MS). Sucralose was found to be present in source water of 15 out of 19 DWTPs (47-2900 ng/L), finished water of 13 out of 17 DWTPs (49-2400 ng/L) and distribution system water of 8 out of the 12 DWTPs (48-2400 ng/L) tested. Sucralose was only found to be present in source waters with known wastewater influence and/or recreational usage, and displayed low removal (12% average) in the DWTPs where finished water was sampled. Further, in the subset of DWTPs with distribution system water sampled, the compound was found to persist regardless of the presence of residual chlorine or chloramines. In order to understand intra-DWTP consistency, sucralose was monitored at one drinking water treatment plant over an 11 month period from March 2010 through January 2011, and averaged 440 ng/L in the source water and 350 ng/L in the finished water. The results of this study confirm that sucralose will function well as an indicator compound for anthropogenic influence on source, finished drinking and distribution system (i.e., tap) water, as well as an indicator compound for the presence of other recalcitrant compounds in finished drinking water in the U.S.

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