Spectrophotometric characterization of human impacted surface waters in the Moselle watershed

A review on fluorescence spectroscopic analysis of water and wastewater

In recent years, the application of fluorescence spectroscopy has been widely recognized in water environment studies. The sensitiveness, simplicity, and efficiency of fluorescence spectroscopy are proved to be a promising tool for effective monitoring of water and wastewater. The fluorescence excitation-emission matrix (EEMs) and synchronous fluorescence spectra have been widely used analysis techniques of fluorescence measurement. The presence of organic matter in water and wastewater defines the degree and type of pollution in water. The application of fluorescence spectroscopy to characterize dissolved organic matter (DOM) has made the water quality assessment simple and easy. With the recent advances in this technology, components of DOM are identified by employing parallel factor analysis (PARAFAC), a mathematical trilinear data modeling with EEMs. The majority of wastewater studies indicated that the fluorescence peak of EX/EM at 275 nm/340 nm is referred to tryptophan region (Peak T1). However, some researchers identified another fluorescence peak in the region of EX/EM at 225-237 nm/340-381 nm, which described the tryptophan region and labeled it as Peak T2. Generally, peak T is a protein-like component in the water sample, where T1 and T2 signals were derived from the <0.20μm fraction of pollution. Therefore, a more advanced approach, such as an online fluorescence spectrofluorometer, can be used for the online monitoring of water. The results of various waters studied by fluorescence spectroscopy indicate that changes in peak T intensity could be used for real-time wastewater quality assessment and process control of wastewater treatment works. Finally, due to its effective use in water quality assessment, the fluorescence technique is proved to be a surrogate online monitoring tool and early warning equipment.

Spectrophotometric characterization of dissolved organic matter in a rural watershed: the Madon River (N-E France)

In the last 20 years, increasing dissolved organic carbon (DOC) concentrations have been observed in several rivers and lakes in Europe. This increase has reduced the quality of the aquatic environment. In this study, UV-vis spectroscopy and synchronous fluorescence spectroscopy with a difference of 50 nm between the excitation and emission (SF50) were used to characterize the DOC in a rural river (Madon River). The specific absorbance index at 254 nm (SUVA254) which is related to the aromaticity of DOC was extracted from UV-vis spectra, whose maximum of the second derivative (occurring near 225 nm) is related to nitrates. SF50 spectra which are characterized by well-defined peaks indicated large spatial and temporal variations. Two methods were used to analyze and compare these spectra. The first method was based on the decomposition of the SF50 spectra into four Gauss functions: B1 (related to tryptophan-like fluorescence), B2 and B3 (related to humic substances), and B4 (related to chlorophyll-like substances). The second method was principal components analysis (PCA), which results yielded three principal components that accounted for 95% of the variance. Although PCA enables the consideration of the spectra without making assumptions regarding the number of fluorophores, the results from the decomposition in Gauss function were easier to interpret.

Photodegradation-based detection of fluorescent whitening agents in a mountain river

Fluorescent whitening agents (FWAs) are highly soluble and poorly biodegradable ingredients used in laundry detergents and in industries (paper, textile, plastic manufacturing). They are likely to pass through biological wastewater treatment systems. The presence of FWAs in a mountain river was detected by monitoring the decay of synchronous fluorescence intensity at λ(ex)=360 nm after exposing samples to ultraviolet (UV) light (365 nm), for mimicking sunlight, for 15 min. The method was first validated on four commercial FWAs (DAS-1, FB28, DMA-X and CBS-X) in different water matrices (deionized water and pristine river water in the presence of humic acid and dyes). A 40% decay was observed after 15 min for the least photosensitive FWA (CBS-X). A field application was then performed on samples collected along a mountain river in which impacts of FWAs from domestic sources (laundry greywater) and industrial sources (paper and textile mills) were suspected. Variations of fluorescence decay at λ(ex)=360 nm could be explained by these potential sources of pollution. It is suggested that the fluorescence decay at λ(ex)=280 nm also be considered as an indicator, as some FWAs can exhibit fluorescence at that excitation wavelength.