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Using Optical Brighteners as Proxies for Probing Waste in Surface Water
YEAR: 2023

Optical brighteners—or fluorescent whitening compounds (FWCs)—absorb light
in the ultraviolet and violet region of the electromagnetic spectrum, and reemit light by a process
known as fluorescence in a lower-energy region of the spectrum, namely in the blue region
(typically 420-470 nm). These additives are often used to enhance the appearance of the coloring
of fabrics and papers, causing a “whitening” effect; they make intrinsically yellow or orange
materials look less so, by compensating the deficit in blue and purple light reflected by the material,
with the blue and purple optical emission of the fluorophore [1-9]. Because these are synthetic
compounds and, consequently, not naturally occurring, they make excellent markers for detecting
leakage of wastewater into surface water as they are introduced into sewage from the detergents
used in clothes washing. We propose to characterize commercially available optical brighteners
that are used predominantly in laundry detergents to determine the uniqueness of their spectral
signatures and to ensure that there is no spectral overlap with spectral signatures from other waste
or from naturally occurring substances. We also propose to determine the lifetimes of the optical
brighteners in the presence of oxygen, light, microbes, and surface water as such environments
may contribute to their partial decomposition, rendering them potentially useless as analytical
probes yet still deleterious from a public health perspective. Funding for this proposal will, in
addition to ensuring the outcomes noted above, also continue the training of promising
undergraduate students, enable the submission of a larger federally-funded grant proposal, and
potentially permit the patenting and licensing of new detection technology (with which we have
experience, as noted on our vita and as indicated by our RD100 award).