Fluorescence and Quenching Assessment (EEM-PARAFAC) of de Facto Potable Reuse in the Neuse River, North Carolina, United States

Abstract

The Neuse River, North Carolina, U.S., exemplifies a typical de facto potable reuse scenario, where drinking water sources are located downstream of treated wastewater effluent discharges. The study results imply that planned potable water reuse, whether in an indirect or direct potable reuse scenario, might provide better control over water quality than the status quo conditions. Using fluorescence excitation-emission matrix (EEM) measurements, anthropogenic influence of a wastewater treatment plant (WWTP) discharge was observed in samples near the location of drinking water treatment plant (WTP) intakes, eight or more miles downstream of the WWTP, implying that anthropogenic compounds were not fully removed or degraded by natural processes in this reach of the river. PARAllel FACtor (PARAFAC) analysis supported a two-component model of humic-like and nonhumic-like dissolved organic matter (DOM). A nonmodeled anthropogenic feature was also indicated. Significantly, the quenched fluorescence of humic-like DOM (static and/or dynamic quenching) by nonhumic-like DOM-previously demonstrated for probe molecules but first reported here in a natural/anthropogenic-influenced system-offers exciting insight into studies of humic/nonhumic interactions with important implications for pollutant fate and transport, sensing applications, and water treatment. A molecular spectroscopic explanation for dual fluorescing peaks in amino acids and humic substances is postulated.

Supramolecular Answers to the Organic Matter Controversy

“…Pre‐ and post‐extracted terrestrial and aquatic sources have been examined, and literature reports of EEM applications have multiplied exponentially. Excitation–emission matrix images and mathematical PARAFAC analyses are being used to monitor geochemical processing in soil via porewater, anthropogenic inputs to our water supply from wastewater effluent, and disinfection byproduct formation during drinking water treatment, among other applications (Markechova et al, 2013; Wells et al, 2017; Zhang and Liang, 2019). Excitation–emission matrix studies of natural and not so natural (i.e., built) environments are evidence that diagenetic “humic substances” have been observed by modern analytical techniques (Coble et al, 2014; Yang et al, 2015).…”

“…The EEM regions assigned to tyrosine‐like and tryptophan‐like fluorophores in amino acids and proteins are well known (Wells et al, 2017). Sutton and Sposito (2005) described humic substances as supramolecular associations of low‐molecular‐mass organic molecules including recognizable biomolecules.…”

“…This manuscript provides enhanced data analysis and interpretation of previously reported empirical data. Detailed experimental procedures for flow FFF (Wells, 2015), DLS measurements (Esfahani et al, 2015a), EEM fluorescence spectroscopy, and parallel factor (PARAFAC) data processing (Wells et al, 2017) are published elsewhere. These data are summarized in the supplemental material associated with this manuscript.…”

Molecular compositions and optical properties of dissolved brown carbon in biomass burning, coal combustion, and vehicle emission aerosols illuminated by excitation–emission matrix spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry analysis

“…Carbonaceous aerosols play an important role in the Earth's radiative balance. One such aerosol, black carbon (BC), absorbs significant amounts of light and exerts a warming effect, while organic carbon (OC) was initially thought to only scatter solar radiation (Wong et al, 2017;Mo et al, 2017;Saleh et al, 2014). However, recent studies show that there are certain types of OC that absorb radiation efficiently in the near-ultraviolet (UV) (300-400 nm) and visible ranges, which are called brown carbon (BrC).…”

Molecular compositions and optical properties of dissolved brown carbon in smoke particles illuminated by excitation-emission matrix spectroscopy and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis

“…Excitation-emission matrix (EEM) spectroscopy has been widely applied to identify the sources and chemical nature of chromophoric dissolved organic matter (CDOM) in aquatic environments since the 1990s (Shimabuku et al, 2017;Wells et al, 2017;Bhattacharya and Osburn, 2017;Coble, 1996), while few studies have focused on the fluorescence properties of chromophores in atmospheric environments.…”