Fluorescent dissolved organic matter components as surrogates for disinfection byproduct formation in drinking water: a critical review

Disinfection byproduct (DBP) formation, prediction, and minimization are critical challenges facing the drinking water treatment industry worldwide where chemical disinfection is required to inactivate pathogenic microorganisms. Fluorescence excitation–emission matrices-parallel factor analysis (EEM-PARAFAC) is used to characterize and quantify fluorescent dissolved organic matter (FDOM) components in aquatic systems and may offer considerable promise as a low-cost optical surrogate for DBP formation in treated drinking waters. However, the global utility of this approach for quantification and prediction of specific DBP classes or species has not been widely explored to date. Hence, this critical review aims to elucidate recurring empirical relationships between common environmental fluorophores (identified by PARAFAC) and DBP concentrations produced during water disinfection. From 45 selected peer-reviewed articles, 218 statistically significant linear relationships (R2 ≥ 0.5) with one or more DBP classes or species were established. Trihalomethanes (THMs) and haloacetic acids (HAAs), as key regulated classes, were extensively investigated and exhibited strong, recurrent relationships with ubiquitous humic/fulvic-like FDOM components, highlighting their potential as surrogates for carbonaceous DBP formation. Conversely, observed relationships between nitrogenous DBP classes, such as haloacetonitriles (HANs), halonitromethanes (HNMs), and N-nitrosamines (NAs), and PARAFAC fluorophores were more ambiguous, but preferential relationships with protein-like components in the case of algal/microbial FDOM sources were noted. This review highlights the challenges of transposing site-specific or FDOM source-specific empirical relationships between PARAFAC component and DBP formation potential to a global model

Dissipation des pesticides à l'interface eau-sédiment : apports de l'analyse isotopique composé-spécifique

River contamination by pesticides on a global scale impacts biodiversity and the production of drinking water. The water – sediment interface in these environments plays a key role in the dissipation of pesticides, although its functioning remains poorly understood. This thesis targeted degradation processes at this interface by developing Compound-Specific Isotope Analysis (CSIA) for a panel of pesticides, from the laboratory scale to rivers. The results made it possible to identify the specific carbon and nitrogen isotopic enrichment factors for different degradation processes (photolysis, biodegradation) in order to interpret the isotope signatures in rivers. The key role of river runoff on the persistence and degradation of pesticides has been identified. Ways to improve the CSIA are proposed to more systematically assess the persistence of pesticides in rivers.La contamination des rivières par les pesticides à l’échelle de la planète impacte la biodiversité et la production d’eau potable. L’interface eau–sédiment des rivières joue un rôle clé dans la dissipation des pesticides mais son fonctionnement reste méconnu. Cette thèse a ciblé les processus de dégradation à cette interface en développant l’analyse isotopique composé-spécifique (AICS) d’un panel de pesticides, de l’échelle du laboratoire jusqu'aux rivières. Les résultats ont permis d’identifier les facteurs d’enrichissement isotopiques en carbone et azote spécifiques pour différents processus de dégradation (photolyse, biodégradation) pour interpréter des signatures isotopiques en rivière. Le rôle clé des écoulements en rivière sur la persistance et la dégradation des pesticides a été identifié. Des pistes d’amélioration de l’AICS sont proposées pour évaluer plus systématiquement la persistance des pesticides dans les rivières

Characterizing the habitat requirements of the Common Redstart (Phoenicurus phoenicurus) in moderately urbanized areas

The clash of checklists

Phase Transfer and Biodegradation of Pesticides in Water–Sediment Systems Explored by Compound-Specific Isotope Analysis and Conceptual Modeling

International audienc

Direct and indirect photodegradation of atrazine and S-metolachlor in agriculturally impacted surface water and associated C and N isotope fractionation

Knowledge of direct and indirect photodegradation of pesticides and associated isotope fractionation can help to assess pesticide degradation in surface waters. Here, we investigated carbon (C) and nitrogen (N) isotope fractionation during direct and indirect photodegradation of the herbicides atrazine and S-metolachlor in synthetic water, mimicking agriculturally impacted surface waters containing nitrates (20 mg L–1) and dissolved organic matter (DOM, 5.4 mgC L–1). Atrazine and S-metolachlor were quickly photodegraded by both direct and indirect pathways (half-lives <5 and <7 days, respectively). DOM slowed down photodegradation while nitrates increased degradation rates. The analysis of transformation products showed that oxidation mediated by hydroxyl radicals (HO•) predominates during indirect photodegradation. UV light (254 nm) caused significant C and N isotope fractionation, yielding isotope enrichment factors ε_C = 2.7 ± 0.3 and 0.8 ± 0.1‰, and ε_N = 2.4 ± 0.3 and –2.6 ± 0.7‰ for atrazine and S-metolachlor, respectively. In contrast, photodegradation under simulated sunlight led to negligible C and slight N isotope fractionation, indicating the influence of the radiation wavelength on the direct photodegradation-induced isotope fractionation. Altogether, this study highlights the relevance of using simulated sunlight to evaluate photodegradation pathways in the environment and the potential of CSIA to distinghuish photodegradation from other dissipation pathways in surface waters

Reaction of DMS and HOBr as a Sink for Marine DMS and an Inhibitor of Bromoform Formation

Recently, we suggested that hypobromous acid (HOBr) is a sink for the marine volatile organic sulfur compound dimethyl sulfide (DMS). However, HOBr is also known to react with reactive moieties of dissolved organic matter (DOM) such as phenolic compounds to form bromoform (CHBr3) and other brominated compounds. The reaction between HOBr and DMS may thus compete with the reaction between HOBr and DOM. To study this potential competition, kinetic batch and diffusion-reactor experiments with DMS, HOBr, and DOM were performed. Based on the reaction kinetics, we modeled concentrations of DMS, HOBr, and CHBr3 during typical algal bloom fluxes of DMS and HOBr (10-13 to 10-9 M s-1). For an intermediate to high HOBr flux (≥10-11 M s-1) and a DMS flux ≤10-11 M s-1, the model shows that the DMS degradation by HOBr was higher than for photochemical oxidation, biological consumption, and sea-air gas exchange combined. For HOBr fluxes ≤10-11 M s-1 and a DMS flux of 10-11 M s-1, our model shows that CHBr3 decreases by 86% compared to a lower DMS flux of 10-12 M s-1. Therefore, the reaction between HOBr and DMS likely not only presents a sink for DMS but also may lead to suppressed CHBr3 formation.ISSN:0013-936XISSN:1520-585

Direct and indirect photodegradation of atrazine and S -metolachlor in agriculturally impacted surface water and associated C and N isotope fractionation

International audienceKnowledge of direct and indirect photodegradation of pesticides and associated isotope fractionation can help to assess pesticide degradation in surface waters

Pollutant Dissipation at the Sediment‐Water Interface: A Robust Discrete Continuum Numerical Model and Recirculating Laboratory Experiments

International audiencePollutant exchange in the hyporheic zone is a major process controlling its degradation in river systems. Knowledge of mass transfer processes at the sediment-water interface (SWI) remains scarce. Accurate predictive modeling of flow driving pollutant fluxes at the SWI is currently limited. We examined mass exchange at the SWI by combining laboratory tracer experiments and the development of a flow reactive transport (FRT) model. NaCl and Foron Blue 291 tracers were used as surrogates of conservative and moderately sorptive organic pollutants, respectively. Tracer experiments in the bench-scale river channel reproduced the influence of overlying water velocities, the source of the pollutant, and its sorption capacity on pollutant exchange. A methodological framework to calibrate the FRT model against experiments was developed. Good agreement between the experimental and numerical results confirmed the robustness of the experimental setup and numerical model. The pollutant origin, either from the sediment or the overlying water, did not affect the pollutant exchange rates. The exchange rates were quasi-proportional to the overlying water velocity. The sediment bed caused retention of more than half of the initially injected mass of Foron Blue 291. The moderately sorptive tracer partitioning retarded the equilibrium up to six times compared with the conservative tracer NaCl. Numerical tests, including both overlying and vertical velocities, showed that the latter is the main factor controlling pollutant exchange at the SWI. Altogether, the model allows capturing interactions between pollutant transport and partitioning to the rivers sediment, paving the way for systematic investigations of pollutant behavior in rivers

A Comparison of the Sorption Reactivity of Bacteriogenic and Mycogenic Mn Oxide Nanoparticles

Biogenic MnO₂ minerals affect metal fate and transport in natural and engineered systems by strongly sorbing metals ions. The ability to produce MnO₂ is widely dispersed in the microbial tree of life, leading to potential differences in the minerals produced by different organisms. In this study, we compare the structure and reactivity of biogenic Mn oxides produced by the biofilm-forming bacterium <i>Pseudomonas putida</i> GB-1 and the white-rot fungus <i>Coprinellus</i> sp. The rate of Mn­(II) oxidation, and thus biomineral production, was 45 times lower for <i>Coprinellus</i> sp. (5.1 × 10^–2 mM d^–1) than for <i>P. putida</i> (2.32 mM d^–1). Both organisms produced predominantly Mn­(IV) oxides with hexagonal-sheet symmetry, low sheet stacking, small particle size, and Mn­(II/III) in the interlayer. However, we found that mycogenic MnO₂ could support a significantly lower quantity of Ni sorbed via inner-sphere coordination at vacancy sites than the bacteriogenic MnO₂: 0.09 versus 0.14 mol Ni mol^–1 Mn. In addition, 50–100% of the adsorbed Ni partitioned to the MnO₂, which accounts for less than 20% of the sorbent on a mass basis. The vacancy content, which appears to increase with the kinetics of MnO₂ precipitation, exerts significant control on biomineral reactivity