科研之友
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摘要
Nitriles and amides are two classes of nitrogenous disinfection byproducts (DBPs) associated with chloramination that are more cytotoxic and genotoxic than regulated DBPs. Monochloramine reacts with acetaldehyde, a common ozone and free chlorine disinfection byproduct, to form 1-(chloroamino)ethanol. Equilibrium (K-1) and forward and reverse rate (k(1),k(-1)) constants for the reaction between initial reactants and 1-(chloroamino)ethanol were determined between 2 and 30 degrees C. Activation energies for k(1) and k(-1) were 3.04 and 45.2 kJ.mol(-1), respectively, and enthalpy change for K-1 was -42.1 kJ.mol(-1). In parallel reactions, 1-(chloroamino)ethanol (1) slowly dehydrated (k(2)) to (chloroimino)ethane that further decomposed to acetonitrile and (2) was oxidized (k(3)) by monochloramine to produce N-chloroacetamide. Both reactions were acid/base catalyzed, and rate constants were characterized at 10, 18, and 25 degrees C. Modeling for drinking water distribution system conditions showed that N-chloroacetamide and acetonitrile concentrations were 5-9 times higher at pH 9.0 compared to 7.8. Furthermore, acetonitrile concentration was found to form 7-10 times higher than Nchloroacetamide under typical monochloramine and acetaldehyde concentrations. N-chloroacetamide cytotoxicity (LC50 = 1.78 X 10(-3) M) was comparable to dichloroacetarnide and trichloroacetamide, but less potent than N,2-dichloroacetamide and chloroacetamide. While N-chloroacetamide was not found to be genotoxic, N,2-dichloroacetamide genotoxic potency (5.19 x 10(-3) M) was on the same order of magnitude as chloroacetamide and trichloroacetamide.
- 出版日期2015-8-18
