Role of Chlorine Dioxide in N-Nitrosodimethylamine Formation from Oxidation of Model Amines.
N-Nitrosodimethylamine (NDMA) is an emerging disinfection byproduct, and we show that use of chlorine dioxide (ClO2) has the potential to increase NDMA formation in waters containing precursors with hydrazine moieties. NDMA formation was measured after oxidation of 13 amines by monochloramine and ClO2 and pretreatment with ClO2 followed by postmonochloramination. Daminozide, a plant growth regulator, was found to yield 5.01 ± 0.96% NDMA upon reaction with ClO2, although no NDMA was recorded during chloramination. The reaction rate was estimated to be ∼0.0085 s(-1), and on the basis of our identification by mass spectrometry of the intermediates, the reaction likely proceeds via the hydrolytic release of unsymmetrical dimethylhydrazine (UDMH), with the hydrazine structure a key intermediate in NDMA formation. The presence of UDMH was confirmed by gas chromatography-mass spectrometry analysis. For 10 of the 13 compounds, ClO2 preoxidation reduced NDMA yields compared with monochloramination alone, which is explained by our measured release of dimethylamine. This work shows potential preoxidation strategies to control NDMA formation may not impact all organic precursors uniformly, so differences might be source specific depending upon the occurrence of different precursors in source waters. For example, daminozide is a plant regulator, so drinking water that is heavily influenced by upstream agricultural runoff could be at risk.
SYSU-HKUST Research Center for Innovative Environmental Technology, School of Environmental Science and Engineering, Sun Yat-sen University , Guangzhou 510275, China.
Wenhui
W
Gan
Department of Civil and Environmental Engineering, Imperial College London , London SW7 2AZ, United Kingdom.
Tom
T
Bond
SYSU-HKUST Research Center for Innovative Environmental Technology, School of Environmental Science and Engineering, Sun Yat-sen University , Guangzhou 510275, China.
Xin
X
Yang
School of Sustainable Engineering and the Built Environment, Arizona State University , Tempe, Arizona 85287-3005, United States.
Paul
P
Westerhoff
D000588:Amines / Q000737:chemistry; D002700:Chloramines / Q000737:chemistry; D017606:Chlorine Compounds / Q000737:chemistry*; D004123:Dimethylamines / Q000032:analysis / Q000737:chemistry; D004127:Dimethylhydrazines / Q000032:analysis / Q000737:chemistry; D004128:Dimethylnitrosamine / Q000737:chemistry*; D004203:Disinfection / Q000379:methods; D060766:Drinking Water / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
D000588:Amines; D002700:Chloramines; D017606:Chlorine Compounds; D004123:Dimethylamines; D004127:Dimethylhydrazines; D060766:Drinking Water; D010087:Oxides; C025109:chlorine dioxide; C034516:dimethylamine; C030816:chloramine; D004128:Dimethylnitrosamine