Modelling of impact of presence/absence of suspended particulate organic matter from river and sea and effluent wastewater on fluorescence signal in the coastal area of Gapeau River.

Organic matter has an important role in biogeochemistry in aquatic environments. This study investigated impact of suspended particulate organic matter (SPOM) on fluorescence signal of mixtures of three water types (river water RW, sea water SW, effluent wastewater WW) using fluorescence (excitation-emission matrix, EEM) spectroscopy and parallel factor analysis (PARAFAC) and multilinear regression. Four irradiation experiments (Expt-1, Expt-2, Expt-3, and Expt-4) were conducted during different times of the year ( two in autumn, one in winter, and one in spring season). Samples were exposed to natural sunlight on laboratory rooftop in University of Toulon, France, with another set of samples kept in dark as control samples. Three component (C1, C2, C3) model was validated by split-half and Concordia from the whole EEM dataset of all irradiation experiments. No protein-like fluorophores was found. The study revealed the effect of SPOM presence/absence on fluorescence signal of DOM and on resulting parameters of multilinear regression MLR model and kinetic constant of these MLR parameters. Kinetic constant (k) for all MLR coefficients was in order of greatness as Expt-1 (SPOM of WW only in mixtures) > Expt-3 (SPOM of SW only in mixtures) > Expt-2 (SPOM of RW only in mixtures)> Expt-4 (SPOM of RW + SW + WW in mixtures) indicating that SPOM of WW is the most resistant to photodegradation. For dark control samples, only relative standard deviation RSD could be calculated from dataset. RSD values for C3 were the highest indicating its chaotic variations, and the lowest RSD values were found for both C1 and C2 for all experiments. Statistical differences has been found between control and irradiated experiments. These models developed in this study can be used to predict fluorescence signal of anthropogenic effluent DOM during its transport in river systems to coastal zone.

Rapid on site assessment of a compost chemical stability parameter by UV and fluorescence spectroscopy coupled with mathematical treatment.

Sewage sludges are problematic due to the constant increase of urban population. The high level of organic matter in sludges can be valorized by co-composting with green waste. Many chemical changes occur in the compost maturation process, resulting on stabilized organic matter by humification which is recoverable as soil amendment. In this way, the knowledge of organic matter stability and maturity of compost is essential. However, estimation of chemical parameters allowing the management of compost quality usually need complex time consuming laboratory measurements. Indeed, there is not yet rapid, simple and robust method for their on site assessment at the moment. Among usual parameters used to monitor compost evolution, the C/N ratio is a fundamental chemical parameter. The aim of this work is the estimation of the C/N ratio using a Partial Least Squares regression based on UV and fluorescence spectroscopic data and pH from compost water extracts at various steps of composting process and measured on site. A mathematical linear model is established based on selected data (pH, spectroscopic indices) resulting on average relative error for C/N estimation of 5.26% (range between 0.5% min. and 9.5% max.). This tool leads to a rapid and simple on site estimation of the compost stabilization, allowing qualification of the end-product resulting on a global spectroscopic index of stability.

Characterization of the fate and changes of post-irradiance fluorescence signal of filtered anthropogenic effluent dissolved organic matter from wastewater treatment plant in the coastal zone of Gapeau river.

Anthropogenic effluent dissolved organic matter (DOM) plays an important role in coastal zone pollution. The objectives of the present study were to characterize the fluorescence signal of anthropogenic effluent DOM from wastewater treatment plant and to evaluate the effect of solar irradiation on the fluorescence signal in the coastal zone. Solar irradiation experiments were conducted to evaluate the effect photochemical degradation using excitation-emission matrix (EEM) method combined with parallel factor analysis (PARAFAC). Results showed high fluorescence of DOM before irradiation and the intensity tends to decrease after 4th and 15th day of irradiation. Rapid photochemical degradation of humic-like fluorophores and appearance of a post-irradiance dominant anthropogenic effluent DOM fluorophores were also observed after irradiation. Our experiments showed a sharp reduction in fluorescence intensity which occurred after 4th day of solar irradiation and the fluorescence signal did not disappeared after 15th day indicating the formation of a specific signal due to solar irradiation. PARAFAC model divided the bulk EEM spectra into three individual fluorescent components with C1 "terrestrial humic-like" and C2 "humic-like of longer wavelength" and C3 is a noisy component with two emission maxima. Multilinear regression of PARAFAC components contribution with mixing composition was most suitable according to the equation C*i = AWWi,0 + AWWi,1.fSW + AWWi,2.fRW, where C*i is the normalized contribution of PARAFAC component number i in a given irradiation day; AWWi,0, AWWi,1, AWWi,2 are the multilinear regression coefficients and contain implicitly the effect of fWW; and WW, SW, and RW are treated wastewater, sea water, and river water respectively. The values of AWWi,0, AWWi,1, and AWWi,2 fitted second-order kinetics with irradiation process with kinetic constant of 9.68, - 987.35, and - 977.67 respectively for C1 equation and the same trend for C2 and no values for C3 due to its noisy character indicating the rapid degradation with increase of fSW and fRW and the predominance of the residual fluorescence coming from fWW which is the content fraction of anthropogenic effluent DOM because AWWi,0 was 100 times less sensitive to photobleaching. A suitable model for predicting the fluorescence EEMs as a function of mixing composition was developed.

Role of non-fluorescent chromophores in inner filter effect correction and PARAFAC decomposition.

Numerous studies have shown the impact of inner filter effect (IFE) on the fluorescence signal. IFE reduces the fluorescence intensity and distorts the fluorescence peak shape and position, through the absorption of the emitted radiation by the sample components. In this study, we aimed to understand the role of a non-fluorescing chromophore in IFE correction and PARAFAC decomposition. Solutions of three fluorophores, tryptophan, fluorescein and quinine sulfate, and an absorbing compound, green ink, have been prepared using the controlled dilution approach (CDA). PARAFAC identified three components associated with quinine sulfate, fluorescein and an IFE artifact, which was caused by a shift in peak position. Results showed that the absorption of the chromophore played an important role in component determination. We observed that CDA-PARAFAC was able to correct the quinine sulfate and fluorescein signals, and to suppress the IFE artifact component. However, the method was not effective in removing the IFE impact at high concentrations. The results have significant implications on the analysis of samples that contain complex mixtures of fluorophores and chromophores, such as colored natural organic matter or nutrients, like NO32-.

Interdisciplinary Round-Robin Test on Molecular Spectroscopy of the U(VI) Acetate System.

A comprehensive molecular analysis of a simple aqueous complexing system-U(VI) acetate-selected to be independently investigated by various spectroscopic (vibrational, luminescence, X-ray absorption, and nuclear magnetic resonance spectroscopy) and quantum chemical methods was achieved by an international round-robin test (RRT). Twenty laboratories from six different countries with a focus on actinide or geochemical research participated and contributed to this scientific endeavor. The outcomes of this RRT were considered on two levels of complexity: first, within each technical discipline, conformities as well as discrepancies of the results and their sources were evaluated. The raw data from the different experimental approaches were found to be generally consistent. In particular, for complex setups such as accelerator-based X-ray absorption spectroscopy, the agreement between the raw data was high. By contrast, luminescence spectroscopic data turned out to be strongly related to the chosen acquisition parameters. Second, the potentials and limitations of coupling various spectroscopic and theoretical approaches for the comprehensive study of actinide molecular complexes were assessed. Previous spectroscopic data from the literature were revised and the benchmark data on the U(VI) acetate system provided an unambiguous molecular interpretation based on the correlation of spectroscopic and theoretical results. The multimethodologic approach and the conclusions drawn address not only important aspects of actinide spectroscopy but particularly general aspects of modern molecular analytical chemistry.

Fluorescence spectroscopy to study dissolved organic matter interactions with agrochemicals applied in Swiss vineyards.

UV/Vis fluorescence spectroscopy was used to study the possible interactions of dissolved organic matter (DOM) with the herbicide glyphosate and copper-based fungicide used in vineyards. The study focused on the role of DOM in the transport of these micropollutants from parcels to surface waters (river, lake). Soil solution and river water samples were collected in the Lavaux vineyard area, western Switzerland. Their fluorescence excitation emission matrices (EEM) were decomposed using parallel factor (PARAFAC) analysis, and compared to their content in glyphosate and copper. PARAFAC analysis of EEM of both types of samples showed the contribution of protein-like and humic-like fluorophores. In soil water samples, complexes between fulvic-like and humic-like fluorophores of DOM, copper, and glyphosate were likely formed. In surface water, DOM-copper and glyphosate-copper interactions were observed, but not between glyphosate and DOM.

Identification and quantification of known polycyclic aromatic hydrocarbons and pesticides in complex mixtures using fluorescence excitation-emission matrices and parallel factor analysis.

Polycyclic aromatic hydrocarbons (PAHs) and pesticides are among the most widespread organic contaminants in aquatic environments. Because of their aromatic structure, PAHs and pesticides have intrinsic fluorescence properties in the ultraviolet/blue spectral range. In this study, excitation-emission matrix (EEM) fluorescence spectroscopy and parallel factor (PARAFAC) analysis were used to characterise and discriminate fluorescence signatures of nine PAHs and three pesticides at the µg L(-1) level in the presence of humic substances (0.1-10 mgCL(-1)). These contaminants displayed a diversity of fluorescence signatures regarding spectral position (λEx: 220-335 nm, λEm: 310-414 nm), Stokes shift (39-169 nm) and number of peaks (1-8), with detection limits ranging from 0.02 to 1.29µgL(-1). The EEM/PARAFAC method applied to mixtures of PAHs with humic substances validated a seven-component model that included one humic-like fluorophore and six PAH-like fluorophores. The EEM/PARAFAC method applied to mixtures of pesticides with humic substances validated a six-component model that included one humic-like fluorophore and three pesticide-like fluorophores. The EEM/PARAFAC method adequately quantified most of the contaminants for humic substance concentrations not exceeding 2.5 mg CL(-1). The application of this method to natural (marine) samples was demonstrated through (1) the match between the Ex and Em spectra of PARAFAC components and the Ex and Em spectra of standard PAHs, and (2) the good linear correlations between the fluorescence intensities of PARAFAC components and the PAH concentrations determined by GC-MS.