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The deprotonation of NOM originating from the Rio Negro river basin can be quantified based on measurements of the effects of pH on its absorbance spectra, which contain multiple bands with maxima located at ca. 240, 280, 315 and >350 nm. The emergence of these features is associated with the engagement of phenolic, carboxylic and other chromophores. Correlations between the accumulation of charge in NOM molecules measured by potentiometric titrations and evolution of their differential absorbance spectra show that for wavelengths 300 nm the absorbance of NOM is sensitive to the deprotonation in the entire range of electrostatic charges, with notable differences between fulvic acids and colloidal fractions of NOM.

A kinetic model capable of simulating by-products formation in bromide-containing waters during disinfection processes is presented in this paper. The model is based on two parallel sequences of incorporation and oxidation reactions induced by bromine or chlorine reacting with NOM. Each sequence starts from a different type of NOM functionality that has its own set of specific reaction rate. Decay reactions of NOM and halogenated intermediates are assumed to follow a first order kinetic, while DBP generation reactions are simulated introducing so-called splitting coefficients. This approach allows obtaining explicit expressions for DBP species. Model’s results are compared with experimental data obtained for coastal seawater samples. Comparison of the data confirm the model’s ability to predict DBPs formation with high precision

Formation of disinfection by-products (DBPs) in chlorinated coastal (CS) and deep ocean (sampled at a 1500-m depth) seawater (DO) was explored using conventional chromatographic methods and differential absorbance spectroscopy. It was determined that trihalomethanes (THMs) predominated by bromoform, haloacetonitriles and haloacetic acids (HAA) form in chlorinated seawater. The yield of identified DBPs, especially THMs, was higher in CS, while in DO seawater the relative contribution of HAAs was almost four times higher than that of THMs. The fraction of consumed chlorine incorporated into the identified DBPs in DO natural organic matter (NOM) was much lower than that for coastal marine NOM, which was also more active in forming brominated DBPs. The kinetics of seawater chlorination was relatively rapid, and high levels of DBPs were released within the first 20–30 min of reaction. The kinetics of THMs and HAAs release could be approximated using a logarithmic function of reaction time. Absorbance measurements showed that chlorination caused the absorbance of DO and CS to decrease at wavelengths >250 nm. The features of the differential absorbance spectra of chlorinated seawater were close to those reported for drinking water, but their intensity was lower. The concentrations of CHBr3, CHBr2Cl and CHBrCl2 formed in CS and DO chlorinated at varying chlorine doses and reaction times were well correlated with the corresponding — ΔA272 and/or — ΔA405 values. (The differential absorbance at 405 nm can be measured in the presence of residual chlorine). These results show that differential absorbance provides a number of sensitive surrogate parameters that can be used to monitor and quantify the formation of halogen-containing DBPs in seawater.

Results of a pioneering study, concerning the development of a new technique far on-line monitoring of copper concentration in drinking water, are presented and discussed. The technique is based on the use of a surrogate parameter, represented by the electrochemical potential, to measure the amount of copper released in drinking water because of corrosion. The most representative findings, resulting from laboratory and field studies, are described, highlighting the potentiality of the proposed technique. Experimental data are used to verify the relationship between the electrochemical potential and the copper concentration derived from a mathematical model, shortly presented, which describes the corrosion process taking place during water stagnation in contact with a metal surface.

Il lavoro presenta I risultati di una ricerca sperimentale condotta per investigare le possibilità di utilizzo di misure spettrofotometriche per il monitoraggio dei sottoprodotti della disinfezione di acque destinate a scopo potabile, nel caso di impiego di cloro ed ozono. Dopo una rapida disamina dei sottoprodotti normalmente individuati nei processi di disinfezione e dei presunti meccanismi di formazione degli stessi, viene mostrata l’esistenza di forti correlazioni tra l’assorbanza differenziale di luce ultravioletta e la concentrazione delle singole specie di composti alogenati volatili, nel caso della clorazione, nonché dei principali composti ossidati, in particolare delle aldeidi totali, nel caso dell’ozonizzazione. Viene altresì mostrato come tali correlazioni siano legate alla fenomenologia dei processi in gioco, tanto da poter considerare la misura dell’assorbanza differenziale quale parametro surrogato per conoscere la concentrazione delle diverse specie di sottoprodotti.

Experiments with Alento River water (a drinking water source in the province of Salerno, Italy) showed that considerable amounts of disinfection by-products, primarily chloroform and haloacetic acids, form in that water upon chlorination. The total yield of haloacetic acids was almost twice as high as that of chloroform. Chlorination also caused significant changes in the intensity of NOM fluorescence and the position of the emission band. To quantify the latter, the wavelength that corresponds to the position of the emission band at its half-intensity (λ0.5) was employed. Chlorination caused the λ0.5 values to decrease, while the THMs and HAAs concentrations were linearly correlated with the corresponding λ0.5 values. The strength of correlations between DBP concentrations and λ0.5 values indicates that the latter parameter can be employed in studies of DBP formation in drinking water.

Vengono riportati i risultati di una ricerca sperimentale finalizzata a monitorare la formazione dei sottoprodotti della disinfezione in acque superficiali trattate con clorammine. Le concentrazioni e la tipologia delle singole specie individuate vengono analizzate per comprendere i possibili meccanismi cinetici di produzione dei diversi composti. I risultati ottenuti per acque di provenienza diversa caratterizzate da uno stesso valore di concentrazione di carbonio organico, vengono confrontati e discussi. Le modifiche indotte dal disinfettante sulla sostanza organica naturale in forma disciolta vengono seguite attraverso l’esame delle misure di assorbanza e fluorescenza.

International audience; Interactions between Natural Organic Matter (NOM) and mineral surfaces modify the properties of both reacting phases. It also alters the behaviour of metal ions such as radionuclides in the environment. Here, we focus on the influence of the interactions between humic substances, major NOM components, and some minerals of soils (metal oxides and clays) on the speciation of europium (III), chosen for its analogy with trivalent actinides. To understand the binding of metal ions, proton binding must first be considered. Potentiometric titrations of both organic matter and mineral suspensions are realized before and after their interactions, to study variations of their reactivity. To be closer to environmental conditions (i.e. low DOC concentrations), a new approach must be considered to characterize organic matter reactivity. Spectrophotometric titrations and UV-vis spectra of NOM [1] are used to estimate changes in reactivity with the help of differential absorbance spectra variations of the solution as function of pH. The correlation between the two methods of characterization of NOM is quite good, and it is used to determine the changes of the organic matter properties after adsorption onto the mineral surfaces, in order to better describe the binding of radionuclides in a ternary system. The speciation of Eu(III) in presence of NOM or oxide surface is also studied by time resolved laser fluorescence spectroscopy (TRLFS). [1] Dryer, Korshin & Fabbricino (2008) Environ. Sci. Technol. 42, 6644-6649.

Chlorination of coastal (CS) and deep ocean (DO) seawater was accompanied by a prominent decrease (of up to 70%) of the intensity of its emission which was measured using a 315 nm excitation wavelength. Deconvolution of the emission spectra of CS and DO seawater showed that these spectra comprised three Gauss-shaped bands. The intensities of two of these bands decreased rapidly as the halogenation proceeded. For both DO and CS seawater, two stages of changes of their fluorescence were observed. The first stage in which the relative changes of the fluorescence intensity (ΔF/F) were between zero to 0.30 and 0.40 was not accompanied by the release of individual disinfection byproduct (DBP) species. For ΔF/F values above the corresponding thresholds, the relative changes of fluorescence intensity were well correlated with the concentrations of individual DBP species such as trihalomethanes and haloacetonitriles. R2 values for CHBr3, CHBr2Cl and CHBrCl2 formed in DO seawater were 0.83, 0.80 and 0.68, respectively while for CS seawater, the corresponding R2 values were 0.91, 0.93 and 0.92. The presented data demonstrate that the intrinsic chemistry of DBP formation and dissolved organic matter (DOM) halogenation in seawater can be well quantified based on the examination of changes of its fluorescence. This approach can also be employed for practical monitoring of changes of properties of marine DOM and generation of DBPs in desalination, marine aquaculture and other processes.

This study compared the binding of europium by soil and aquatic natural organic matter (NOM) exemplified by Pahokee Peat humic acid (PPHA) and Northern Reservoir NOM, respectively. NOM/Eu3+ interactions were measured based on the differential absorbance approach. The experimental results show that the binding of Eu3+ by humic acid isolated from agricultural soil results in several features of the differential spectra that are distinct from those observed for aquatic NOM. These features may be associated with the presence in soil NOM of functional groups similar to gallic acid. The binding of Eu3+ by NOM was modeled using a phenomenological approach that accounted for the involvement of dissimilar metal-binding functionalities. This study also introduced the concept of integrated differential absorbance; the use of that parameter allowed achieving a close fit between the experimental and model data. This study presents an alternative approach to ascertain mechanisms of, and differences in the interactions of europium with model compounds and natural organic matter with the provenance from soil and surface water.

This study utilized the methods of fluorescence quenching and differential absorbance to probe in situ the extent and the nature of the interactions between rare earth ions (REIs) and humic substances. Experiments were conducted with the standard Suwannee river humic acid (SRHA) in the presence of varying amount of lanthanum, europium and terbium. The data of differential absorbance showed that the mechanism of SRHA-metal complexation was largely the same for all the examined REIs. In all cases several discrete bands whose properties were discerned via numerical decomposition of the differential spectra absorbance were observed. Their nature was examined based on the comparison of the experimental data and those of NICA-Donnan modeling carried out for Eu3þ. The observed effects suggested that the changes of SRHA absorbance induced by REIs binding are likely to be caused by a bathochromic shift of the absorbance bands associated with such chromophores. The intensity of the Gaussian band with a maximum at 387 nm was observed to be proportional to the total concentration of SRHA-bound REIs. The data obtained in this study demonstrate the existence of complex yet quantifiable changes of the spectroscopic properties of humic species in the presence of REIs and their utility to quantify modes of interactions in such systems.

This study demonstrates that the deprotonation of dissolved organic matter (DOM) originating from a small creek characteristic for DOM-rich waters located in the Rio Negro basin can be quantified based on measurements of pH effects on its absorbance spectra. The method was ascertained by the data of Near-Edge X-Ray Absorbance Spectroscopy (NEXAFS), potentiometric titration to quantify the structural and compositional differences between the colloidal and hydrophobic fractions that contribute 91% of black-water creek DOM. Changes in the absorbance spectra of the DOM fractions caused by deprotonation quantified via numeric deconvolution which indicated the presence of six well-resolved Gaussian bands in the differential spectra. The emergence of these bands was determined to be associated with the engagement of carboxylic and phenolic functionalities and changes of inter-chromophore interactions in DOM molecules. Interpretation of the data based on the NICA-Donnan approach showed that behavior of DOM chromophores was consistent with results of potentiometric titrations. Similar trends were observed for changes of the spectral slope of the DOM absorbance spectra in the range of wavelengths 325e375 nm (DSlope325e375). The behavior of DSlope325e375 values was modeled based on the NICA-Donnan approach and correlated with potentiometrically-estimated charges

This study examined the behavior of corrosion potential (Ecorr) of iron exposed to drinking water during episodes of stagnation and flow. These measurements showed that during stagnation episodes, Ecorr values decrease prominently and consistently. This decrease is initially rapid but it becomes slower as the stagnation time increases. During flow episodes, the Ecorr values increase and reach a quasi-steady state. Experiments with varying concentrations of dissolved oxygen showed that the decrease of Ecorr values characteristic for stagnation is likely to be associated with the consumption of dissolved oxygen by the exposed metal. The corrosion potential of iron and its changes during stagnation were sensitive to the concentrations of sulfate and chloride ions. Measurements of iron release showed that both the absolute values of Ecorr measured prior to or after stagnation episodes were well correlated with the logarithms of concentrations of total iron. The slope of this dependence showed that the observed correlations between Ecorr values and Fe concentrations corresponded to the coupling between the oxidant consumption and changes of Fe redox status. These results demonstrate that in situ Ecorr measurements can be a sensitive method with which to ascertain effects of hydrodynamic conditions and short-term variations of water chemistry on metal release and corrosion in drinking water. This approach is valuable practically because Ecorr measurements are precise, can be carried out in situ with any desired time resolution, do not affect the state of exposed surface in any extent and can be carried out with readily available equipment.

The effects of pH changes on the absorbance spectra of fulvic acids, which constitute a major part of natural organic matter (NOM) were examined based primarily on the example of standard Suwannee River fulvic acid (SRFA). Differential absorbance spectra of SRFA generated at varying pH values were determined to be rich in features that are absent in the conventional spectra. Analysis of the differential absorbance revealed the existence of two predominant types of pH-active chromophores which produced features that emerged in the pH ranges associated with carboxylic and phenolic functional groups of fulvic acids. Comparison of the differential absorbance spectra of SRFA and those of the fraction of hydrophobic acids of South Platte River fulvic acid show the existence of differences indicative of fulvic acids's site-specificity. The evolution of the pH-differential spectra of fulvic acids was in accord with predictions made based on the NICA-Donnan theory. These results show that pH-differential absorbance spectroscopy can be used to quantify in situ the protonation and site-specificity of fulvic acids.