PROBING THE FORMATION OF INDIVIDUAL CHLORINATED AND BROMINATED DISINFECTION BY-PRODUCTS USING FLUORESCENCE INDICES

摘要

The discovery of disinfection by-products (DBPs) formed as result of halogenation of natural organic matter (NOM) and adverse health effects associated with DBPs has led to extensive efforts to determine their identities, model their formation and control their occurrence. Existing models of DBPs formation have been developed using statistical, limited mechanistic and surrogate parameters (e.g., differential UV, SUVA_(254)) based approaches. However due to the variety of individual DBP species, site-specificity of NOM, and pronounced effects of water chemistry parameters on DBP formation and speciation, development of a model that would take into account all these aspects is extremely challenging. Use of some of the surrogate parameters, notably differential absorbance at 272 nm, allows achieving more detailed and chemically-specific insights into the nature of DBP generation, but this method does not exhaust other options for in situ probing of NOM halogenation. For instance, NOM fluorescence has been shown to be affected by several NOM properties, notably its aromaticity and molecular weight and quantifiable fluorescence indices, such as the ratio of emission intensities at 500 and 450 nm, have been introduced to characterize NOM via its emission. It has also been shown that strong correlations exist between DBPs formation and shift of the wavelength that corresponds to 50% of the maximum intensity of fluorescence (λ_(0.5)).