Combination of 3D Fluorescence/PARAFAC and UV-Vis Absorption for the Characterization of Agricultural Soils from Morocco.

The present study, combining UV-Visible absorption and 3D fluorescence supported by PARAFAC chemometric analysis, focused on the characterization of soil water extractable organic matter (WEOM) in the zone of Doukkala located near the Atlantic coast of Morocco. The extracts, in water, of a set of 30 samples covering the four main types of agricultural soils in the region (commonly labeled Tirs, Faid, Hamri and R'mel) were investigated. [Formula: see text] and [Formula: see text] absorbance ratios [Formula: see text] and [Formula: see text] spectral slopes, along with their ratios[Formula: see text], as well as the fluorescence [Formula: see text] and humification [Formula: see text] indices were calculated and interpreted. In the four soil types, these parameters revealed, on the one hand, organic materials of terrigenous origin with some biological component, and showed, on the other hand, that these materials are in similar stages of humification with an important humic character. In all the soils investigated, 3D fluorescence crossed with PARAFAC chemometrics highlighted the absence of any protein component and revealed the prevalence of the fulvic acids fraction in the organic matter humic material.

Relevance of using the non-reactive geochemical signature in sediment core to estimate historical tributary contributions.

Fluvial suspended particulate matter (SPM) fluxes transport large amounts of contaminants that can affect water quality and river ecosystems. To better manage these inputs in river systems, it is essential to identify SPM and sediment sources. Many studies have applied a fingerprinting method based on using metals integrated into a numerical mixing model to estimate source contributions in a watershed. Most fingerprinting studies use contemporary SPM to trace historical inputs, whereas their metal concentrations were modified over time due to anthropogenic inputs. Moreover, total concentrations of these properties are subject to change due to diagenetic processes occurring in stored sediments. The aim of this study was to assess the relevance of using the non-reactive fraction of metals (i.e. metals and metalloids) in fingerprinting studies to estimate the historical contributions of SPM tributary inputs in a sediment core. To assess metal concentrations in the 'conservative' (i.e. non-reactive) fraction, SPM (samples of sources) and sediment core layers (targeted sediments) were subjected to total mineralization and soft extraction, and the non-reactive fraction was obtained by calculating the difference between the two extractions. This approach was applied on a sediment core from the Upper Rhône River (France), using geochemical signature in contemporary SPM of three major tributaries. We showed that the non-reactive fraction retains a higher number of metals in the range test for the deepest layers, which are characterized by significant anthropogenic inputs. Through apportionment modelling using Monte Carlo simulation, we demonstrated that the tributary contributions computed using the non-reactive fraction are more consistent with historical flood and water flow data and have lower uncertainties than with the total fraction. Working with the non-reactive fraction made it possible to decipher historical inputs of SPM using contemporary SPM samples. This approach enables robust identification of sub-catchment areas liable to provide large quantities of SPM. The non-reactive fraction can be used in a variety of environmental conditions and at various spatial and temporal scales to provide a robust quantification of sediment sources.

Impact of dam flushing operations on sediment dynamics and quality in the upper Rhône River, France.

The Rhône River (France) has been used for energy production for decades and 21 dams have been built. To avoid problems due to sediment storage, dam flushing operations are periodically organized. The impacts of such operations on suspended particulate matter (SPM) dynamics (resuspension and fluxes) and quality (physico-chemical characteristics and contamination), were investigated during a flushing operation performed in June 2012 on 3 major dams from the Upper Rhône River. The concentrations of major hydrophobic organic contaminants (polychlorinated biphenyls, polycyclic aromatic hydrocarbons - PAHs, bis(2-ethylhexyl)phthalate [DEHP] and 4-n-nonylphenol), trace metal elements, particulate organic carbon (POC) and particle size distribution were measured on SPM samples collected during this event as well as on those obtained from 2011 to 2016 at a permanent monitoring station (150 km downstream). This allows to compare the SPM and contaminant concentrations and fluxes during the 2012 dam flushing operations with those during flood events and baseflow regime. At equal water discharge, mean SPM concentrations during flushing were on average 6-8 times higher than during flood events recorded from 2011 to 2016. While of short duration (19 days), the flushing operations led to the resuspension of SPM and contributed to a third of the mean annual SPM flux. The SPM contamination was generally lower during flushing than during baseflow or flood, probably due to the fact that flushing transports SPM only issued from resuspended sediment, with no autochtonous particles nor eroded soil. The only exception are PAHs and DEHP with higher concentrations during flushing, which must be issued from the resuspension of legacy-contaminated sediments stored behind the dams before the implementation of emission regulations. During flushing, the variations of POC and contaminant concentrations are also mostly driven by particle size. Finally, we propose a list of recommendations for the design of an adequate monitoring network to evaluate the impact of dam flushing operations on large river systems.

Removal efficiencies and kinetic rate constants of xenobiotics by ozonation in tertiary treatment.

This study gives a full overview of the chemical oxidation by ozone of selected xenobiotics usually present in effluents of conventional wastewater treatment plants. A qualitative and quantitative overview of literature data was made, and describes the ozonation efficiency and processes for the elimination of 12 xenobiotics (pesticides and pharmaceuticals). A database was built, compiling literature results of experimental ozonation assays in laboratory and real-scale conditions. Special attention was paid to selecting the data and compiling reliable results on removal efficiencies and kinetic parameters. An original study was performed in a semi-batch reactor applying ozone on secondary effluent spiked beforehand with a cocktail of 12 xenobiotics. The results of this study were compared with the literature data to evaluate the influence of the kinetic competition of xenobiotics in spiked wastewater in the determination of kinetic rate constants. These 12 xenobiotics were classified into three groups (high-/medium-/low-oxidizable) according to the ranges of their direct kinetic rate constants (kO3). A best effective ozone dose between 0.2 and 0.4 gO3 gDOC-1 is proposed for the elimination of xenobiotics. The predominant elimination pathway between direct and indirect oxidation was identified for each xenobiotic.

Rethinking micropollutant removal assessment methods for wastewater treatment plants - how to get more robust data?

This paper covers the pitfalls, recommendations and a new methodology for assessing micropollutant removal efficiencies in wastewater treatment plants. The proposed calculation rules take into account the limit of quantification and the analytical and sampling uncertainty of measured concentrations. We identified six cases for which a removal efficiency value is reliable and four other cases where result is highly variable (uncertain) due to very low or unquantified concentrations in effluent or when the influent-effluent concentrations differential is below the measurement uncertainty. The influence of the proposed calculation rules on removal efficiency values was scrutinized using actual results from a research project. The paper arrives at detailed recommendations for limiting the impact of other sources of uncertainty during sampling (sampling strategy, cleaning and field blank), chemical analyses (suspended solids and sludge) and data processing according to the targeted objectives.

Combination of sorption properties of polydimethylsiloxane and solid-phase extraction sorbents in a single composite material for the passive sampling of polar and apolar pesticides in water.

Passive sampling techniques have been developed as an alternative method for in situ integrative monitoring of trace levels of neutral pesticides in environmental waters. The objective of this work was to develop a new receiving phase for pesticides with a wide range of polarities in a single step. We describe the development of three new composite silicone rubbers, combining polydimethylsiloxane mechanical and sorption properties with solid-phase extraction sorbents, prepared as a receiving phase for passive sampling. A composite silicone rubber composed of polydimethylsiloxane/poly(divinylbenzene-co-N-vinylpyrrolidone) was selected by batch experiments for its high sorption properties for pesticides with octanol-water partition coefficients ranging from 2.3 to 5.5. We named this composite material "Polar/Apolar Composite Silicone Rubber". A structural study by scanning electron microscopy confirmed the homogeneous dispersion of the sorbent particles and the encapsulation of particles within the polydimethylsiloxane matrix. We also demonstrate that this composite material is resistant to common solvents used for the back-extraction of analytes and has a maximal resistance temperature of 350°C. Therefore, the characteristics of the "Polar/Apolar Composite Silicone Rubber" meet most of the criteria for use as a receiving phase for the passive sampling of pesticides.

Active and legacy mining in an arid urban environment: challenges and perspectives for Copiapó, Northern Chile.

Urban expansion in areas of active and legacy mining imposes a sustainability challenge, especially in arid environments where cities compete for resources with agriculture and industry. The city of Copiapó, with 150,000 inhabitants in the Atacama Desert, reflects this challenge. More than 30 abandoned tailings from legacy mining are scattered throughout its urban and peri-urban area, which include an active copper smelter. Despite the public concern generated by the mining-related pollution, no geochemical information is currently available for Copiapó, particularly for metal concentration in environmental solid phases. A geochemical screening of soils (n = 42), street dusts (n = 71) and tailings (n = 68) was conducted in November 2014 and April 2015. Organic matter, pH and elemental composition measurements were taken. Notably, copper in soils (60-2120 mg/kg) and street dusts (110-10,200 mg/kg) consistently exceeded international guidelines for residential and industrial use, while a lower proportion of samples exceeded international guidelines for arsenic, zinc and lead. Metal enrichment occurred in residential, industrial and agricultural areas near tailings and the copper smelter. This first screening of metal contamination sets the basis for future risk assessments toward defining knowledge-based policies and urban planning. Challenges include developing: (1) adequate intervention guideline values; (2) appropriate geochemical background levels for key metals; (3) urban planning that considers contaminated areas; (4) cost-effective control strategies for abandoned tailings in water-scarce areas; and (5) scenarios and technologies for tailings reprocessing. Assessing urban geochemical risks is a critical endeavor for areas where extreme events triggered by climate change are likely, as the mud flooding that impacted Copiapó in late March 2015.

Dynamic Multiple Reaction Monitoring of amphipod Gammarus fossarum caeca expands molecular information for understanding the impact of contaminants.

Mass spectrometry in multiple reaction monitoring (MRM) mode is a powerful technique that can provide highly selective, multiplexed, and reproducible quantification of peptides derived from proteins. Ideal for the application of molecular biomarkers in biomonitoring surveys, MRM tools have been recently developed to quantify sets of pre-selected biomarkers in freshwater sentinel species. Still limited to the validation and application phase of biomarkers, dynamic MRM (dMRM) acquisition mode has increased the multiplexing capacity of mass spectrometers, expanding opportunities to explore proteome modulations in sentinel species. This study evaluated the feasibility to propose dMRM tools for investigating sentinel species proteomes at the organ level and demonstrated its potential for screening contaminant effects and discovering new protein biomarkers. As a proof of concept, a dMRM assay was developed to comprehensively capture the functional proteome of the caeca of Gammarus fossarum, a freshwater crustacean, commonly used as a sentinel species in environmental biomonitoring. The assay was then used to assess the effects of sub-lethal concentrations of cadmium, silver, and zinc on gammarid caeca. Results showed dose-response and specific metal effects on caecal proteomes, with a slight effect of zinc compared to the two non-essential metals. Functional analyses indicated that cadmium affected proteins involved in carbohydrate metabolism, digestive and immune processes, while silver affected proteins related to oxidative stress response, chaperonin complexes and fatty acid metabolism. Based on these metal-specific signatures, several proteins modulated in a dose-dependent manner were proposed as candidate biomarkers for tracking the level of these metals in freshwater ecosystems. Overall, this study highlights the potential of dMRM to decipher the specific modulations of proteome expression induced by contaminant exposure and pinpoints specific response signatures, offering new perspectives for the de novo identification and development of biomarkers in sentinel species.

Use of polar organic chemical integrative samplers to assess the effects of chronic pesticide exposure on biofilms.

The responses of aquatic organisms to chronic exposure to environmental concentrations of toxicants, often found in mixtures, are poorly documented. Here passive sampler extracts were used in experimental contamination of laboratory channels, to investigate their effects on natural biofilm communities. A realistic mixture of pesticides extracted from Polar Organic Chemical Integrative Samplers was used to expose biofilms in laboratory channels to total pesticide concentrations averaging 0.5 ± 0.1 µg l⁻¹. The level of exposure was representative of field conditions in terms of relative proportions of the substances but the exposure concentration was not maintained (decreasing concentrations between contamination occasions). The impact on the structural as well as the functional characteristics of the autotrophic and heterotrophic components was determined, using biofilm grown in uncontaminated conditions (reference site) and in sites exposed to pesticides (contaminated site). The exposure imposed did not significantly modify the structure or functions of reference biofilms, nor did it modify tolerance as measured by mixture EC50 (EC50 mix). In contrast, the communities from the more contaminated downstream section lost tolerance following decreased dose exposure, but community composition remained fairly stable. Overall, these results indicate that low levels of contamination did not lead to strong changes in community structure, and 14-day changes in tolerance seemed to depend mainly on physiological adaptation, suggesting that other environmental factors or longer-lasting processes prevailed. This study reports the first attempt to use passive sampler extracts as a realistic composite contaminant for experimental exposure of biofilms, with promising perspectives in further ecotoxicology studies.

Polar organic chemical integrative sampler (POCIS): application for monitoring organic micropollutants in wastewater effluent and surface water.

In this paper, we discuss the advantages and drawbacks of POCIS (Polar Organic Chemical Integrative Sampler) for the evaluation of river water quality downstream of wastewater treatment plants. POCIS proved well adapted to sampling alkylphenols and several pharmaceuticals. Concentration factors and the decrease in limits of quantification, compared to grab water sample analyses, were significant except for hormones, ß-blockers and bronchodilators. Promising preliminary results obtained in situ on deuterated atenolol used as a performance reference compound need to be confirmed in-lab. This work confirms that POCIS is a valuable tool for monitoring hydrophilic organic molecules in river and wastewaters.

Enhanced database creation with in silico workflows for suspect screening of unknown tebuconazole transformation products in environmental samples by UHPLC-HRMS.

The search and identification of organic contaminants in agricultural watersheds has become a crucial effort to better characterize watershed contamination by pesticides. The past decade has brought a more holistic view of watershed contamination via the deployment of powerful analytical strategies such as non-target and suspect screening analysis that can search more contaminants and their transformation products. However, suspect screening analysis remains broadly confined to known molecules, primarily due to the lack of analytical standards and suspect databases for unknowns such as pesticide transformation products. Here we developed a novel workflow by cross-comparing the results of various in silico prediction tools against literature data to create an enhanced database for suspect screening of pesticide transformation products. This workflow was applied on tebuconazole, used here as a model pesticide, and resulted in a suspect screening database counting 291 transformation products. The chromatographic retention times and tandem mass spectra were predicted for each of these compounds using 6 models based on multilinear regression and more complex machine-learning algorithms. This comprehensive approach to the investigation and identification of tebuconazole transformation products was retrospectively applied on environmental samples and found 6 transformation products identified for the first time in river water samples.

Direct photodegradation of 36 organic micropollutants under simulated solar radiation: Comparison with free-water surface constructed wetland and influence of chemical structure.

Micropollutants such as pharmaceuticals and pesticides are still found in treated municipal effluent and are discharged into the natural environment. Natural direct photodegradation may be one pathway for removing these micropollutants in treatment processes such as free-water surface constructed wetlands (CW). This work was set out to evaluate the half-life (t1/2) of direct photodegradation of 36 micropollutants under controlled conditions of light exposure close to solar radiation. The results allowed to classify the micropollutants into three groups (fast, medium and slow). Seven micropollutants were classified in the fast group with t1/2 between 0.05 h and 0.79 h, 24 in the medium group with t1/2 between 5.3 h and 49.7 h, and five in the slow group with t1/2 between 56 h and 118 h. The t1/2 values obtained in laboratory were compared with those from a CW receiving treated wastewater. Correction factors were calculated to adjust the in situ data for the light intensity in laboratory and improved the correspondence especially for the micropollutants of the fast and medium groups. Finally, an innovative method based on statistical tests highlighted the chemical functions characteristic of micropollutants sensitive to photodegradation (OH-CË­O, CË­N-O-, =N-OH, -CH=N, -O-PË­O, -CË­C-) and with low sensitivity (-O-R, -Cl).

One and multi-compartments toxico-kinetic modeling to understand metals' organotropism and fate in Gammarus fossarum.

The use of freshwater invertebrates for biomonitoring has been increasing for several decades, but little is known about relations between external exposure concentration of metals and their biodistribution among different tissues. One and multi-compartments toxicokinetic (TK) models are powerful tools to formalize and predict how a contaminant is bioaccumulated. The aim of this study is to develop modeling approaches to improve knowledge on dynamic of accumulation and fate of Cd and Hg in gammarid's organs. Gammarids were exposed to dissolved metals (11.1 ± 1.2 µg.L-1 of Cd or 0.27 ± 0.13 µg.L-1 of Hg) before a depuration phase. At each sampling days, their organs (caeca, cephalon, intestine and remaining tissues) were separated by dissection before analyses. Results allowed us to determine that i) G.fossarum takes up Cd as efficiently as the mussel M.galloprovincialis, but eliminates it more rapidly, ii) organs which accumulate and depurate the most, in terms of concentrations, are caeca and intestine for both metals; iii) the one-compartment TK models is the most relevant for Hg, while the multi-compartments TK model allows a better fit to Cd data, demonstrating dynamic transfer of Cd among organs.

Development and validation of an analytical method by LC-MS/MS for the quantification of estrogens in sewage sludge.

A sensitive method for the simultaneous analysis of five estrogens in sewage sludge was developed. The extraction and purification steps were optimized and the matrix effects were evaluated. The chromatographic gradient was optimized to limit matrix effects and the analysis step was performed by LC-MS/MS. The method consists of an ASE® extraction with a solvent mixture water/methanol 80/20 v/v at 100 °C followed by two consecutive purifications on Oasis HLB® and florisil cartridges. A thorough validation of the developed method was performed. Recoveries determined at two different spiking levels ranged between 86% and 126% depending on the molecule. Repeatability was evaluated on five replicates of the same sludge sample spiked at two different levels and measuring native estrogens in triplicates of 12 sludge samples. Relative standard deviations obtained a range of between 2% and 27%. Reproducibility was also studied by analyzing the same sludge on four different days: the relative standard deviation ranged between 14% and 20% for E1, ßE2 and E3. For αE2, poor reproducibility (68%) was observed but it was linked to the very low quantity of αE2 present in the sludge sample and not to the method performance. The specificity of the method was evaluated on various sludge samples spiked at different spiking levels showing that performances of the proposed method were not modified by matrix effects. Finally, sensitivity of the method was evaluated taking into account both instrumental sensitivity and matrices; the estimated limits of quantification were around 1 ng/g for E1, between 2 and 4 ng/g for αE2, ßE2, and E3 and around 5 ng/g for EE2.

Partitioning of copper at the confluences of Andean rivers.

The fate of copper (Cu) in rivers impacted by acid drainage remains poorly studied in waters with comparatively low Al and Fe concentrations. This work addresses the role of confluences in controlling the physical and chemical fate of Cu in a system with total molar ratio Cu/Al > 0.2 and Cu/Fe > 0.15. Two consecutive confluences were studied in the upper Mapocho watershed, a densely populated basin with intensive mining located in the Chilean Andes. The inflow had acidic conditions with seasonal variations and Cu up to 9 mg L-1. Lability measurements with diffusive gradient in thin films showed that Cu entered as a dissolved labile form. However, downstream from the confluences a higher pH shifted Cu toward nonlabile compounds and solid phases enriched with Cu. Measurements of x-ray absorption spectroscopy of freshly formed particles showed that composition was dominated by sorbed Cu and Cu(OH)2(s) precipitates, with a higher proportion of sorbed Cu downstream from confluences when pH < 5. Particle size distributions (PSD) measured in field showed that downstream from the confluences the total volume and average diameter of the suspended particles grew progressively, with estimated mean settling velocities increasing from 0.3 to 4.2 cm s-1. As a result, 7-30% of the influent Cu was removed from the river flow. These results highlight that shifts in chemical partition and PSDs in river confluences and the hydrodynamic environments at the river reach level control the mobility of Cu in systems with high Cu/Al and Cu/Fe.

Hydro-climatic drivers of land-based organic and inorganic particulate micropollutant fluxes: The regime of the largest river water inflow of the Mediterranean Sea.

Land-based micropollutants are the largest pollution source of the marine environment acting as the major large-scale chemical sink. Despite this, there are few comprehensive datasets for estimating micropollutant fluxes released to the sea from river mouths. Hence, their dynamics and drivers remain poorly understood. Here, we address this issue by continuous measurements throughout the Rhône River basin (∼100,000 km2) of 1) particulate micropollutant concentrations (persistant organic micropollutants: polychlorobiphenyls [PCBi] and polycyclic aromatic hydrocarbons [PAHs]; emerging compounds: glyphosate and aminomethylphosphonic acid [AMPA]; and trace metal elements [TME]), 2) suspended particulate matter [SPM], and 3) water discharge. From these data, we computed daily fluxes for a wide range of micropollutants (n = 29) over a long-term period (2008-2018). We argue that almost two-thirds of annual micropollutant fluxes are released to the Mediterranean Sea during three short-term periods over the year. The watershed hydro-climatic heterogeneity determines this dynamic by triggering seasonal floods. Unexpectedly, the large deficit of the inter-annual monthly micropollutant fluxes inputs (tributaries and the Upper Rhône River) compared to the output (Beaucaire station) claims for the presence of highly contaminated missing sources of micropollutants in the Rhône River watershed. Based on a SPM-flux-averaged micropollutant concentrations mass balance of the system and the estimates of the relative uncertainty of the missing sources concentration, we assessed their location within the Rhône River catchment. We assume that the potential missing sources of PAHs, PCBi and TME would be, respectively, the metropolitan areas, the alluvial margins of the Rhône River valley, and the unmonitored Cevenol tributaries.

Combining flux monitoring and data reconstruction to establish annual budgets of suspended particulate matter, mercury and PCB in the Rhône River from Lake Geneva to the Mediterranean Sea.

Long term and high resolution data on water discharge, suspended particulate matter (SPM) and contaminant concentrations in rivers are required for a better understanding of particulate transfers from the continental areas to the seas. The aim of this study was to provide a novel estimation of annual fluxes of SPM and related pollutants in the Rhône River from Lake Geneva to the Mediterranean Sea by combining high frequency or time-integrative monitoring and novel relations between SPM concentration (Cs) and water discharge (Q). At six stations of the Rhône Sediment Observatory (OSR), SPM fluxes were calculated over the 2000-2016 period by combining observational data and Cs-Q relations. Monthly average concentrations of mercury (Hg) and PCB 180 were obtained by analysis of SPM samples collected in time integrative particle traps between 2011 and 2016. These pollutants were selected because of the well documented contamination of the Rhône watershed by these substances. Inter-annual fluxes at the Rhône River outlet averaged 6.6 Mt. yr-1 for SPM, 572 kg yr-1 for Hg and 14 kg yr-1 for PCB 180. The Isère and Durance tributaries were found to be the main contributors of SPM fluxes. Annual SPM budgets were not balanced, suggesting deposition, remobilization of bottom sediments and/or contributions from non-monitored tributaries. The SPM sampled at the outlet was more contaminated than the combined SPM inputs from the monitored tributaries, suggesting that intermediate sources of contamination were not captured in the budget.

Experimental Warming Differentially Influences the Vulnerability of Phototrophic and Heterotrophic Periphytic Communities to Copper Toxicity.

Aquatic ecosystems are generally subjected to multiple perturbations due to simultaneous or successive combinations of various natural and anthropogenic environmental pressures. To better assess and predict the resulting ecological consequences, increasing attention should be given to the accumulation of stresses on freshwater ecosystems and its effects on the vulnerability of aquatic organisms, including microbial communities, which play crucial functional roles. Here we used a microcosm study to assess the influence of an experimental warming on the vulnerability of phototrophic and heterotrophic periphytic communities to acute and chronic copper (Cu) toxicity. Natural periphytic communities were submitted for 4 weeks to three different temperatures (18, 23, and 28°C) in microcosms contaminated (at about 15 µg L-1) or not with Cu. The vulnerability of both phototrophic and heterotrophic microbial communities to subsequent acute Cu stress was then assessed by measuring their levels of sensitivity to Cu from bioassays targeting phototrophic (photosynthetic activity) and heterotrophic (ß-glucosidase and leucine aminopeptidase extracellular enzymatic activities) microbial functions. We postulated that both the increase in temperature and the chronic Cu exposure would modify microbial community structure, thus leading to changes in the capacity of phototrophic and heterotrophic communities to tolerate subsequent acute exposure to Cu. Our results demonstrated that the influence of temperature on the vulnerability of phototrophic and heterotrophic microbial communities to Cu toxicity can vary greatly according to function studied. These findings emphasize the importance of considering different functional compartments and different functional descriptors to better assess the vulnerability of periphyton to multiple stresses and predict the risks induced by multiple stressors for ecosystem balance and functioning.

Calibration of silicone rubber rods as passive samplers for pesticides at two different flow velocities: Modeling of sampling rates under water boundary layer and polymer control.

There is a need to determine time-weighted average concentrations of polar contaminants such as pesticides by passive sampling in environmental waters. Calibration data for silicone rubber-based passive samplers are lacking for this class of compounds. The calibration data, sampling rate (Rs ), and partition coefficient between silicone rubber and water (Ksw ) were precisely determined for 23 pesticides and 13 candidate performance reference compounds (PRCs) in a laboratory calibration system over 14 d for 2 water flow velocities, 5 and 20 cm s-1 . The results showed that an in situ exposure duration of 7 d left a silicone rubber rod passive sampler configuration in the linear or curvilinear uptake period for 19 of the pesticides studied. A change in the transport mechanism from polymer control to water boundary layer control was observed for pesticides with a log Ksw of approximately 3.3. The PRC candidates were not fully relevant to correct the impact of water flow velocity on Rs . We therefore propose an alternative method based on an overall resistance to mass transfer model to adjust Rs from laboratory experiments to in situ hydrodynamic conditions. We estimated diffusion coefficients (Ds ) and thickness of water boundary layer (δw ) as adjustable model parameters. Log Ds values ranged from -12.13 to -10.07 m2 s-1 . The estimated δw value showed a power function correlation with water flow velocity. Environ Toxicol Chem 2018;37:1208-1218. © 2017 SETAC.

Kinetic accumulation processes and models for 43 micropollutants in "pharmaceutical" POCIS.

The "pharmaceutical" polar organic integrative sampler (POCIS) is a passive sampler composed of an outer polyethersulfone (PES) membrane and an inner receiving Hydrophilic-Lipophilic Balance (HLB) phase. Target micropollutants can accumulate in the POCIS HLB phase following different uptake patterns. Two of the most common ones are a first-order kinetic uptake (Chemical Reaction Kinetic 1, CRK1 model), and a first-order kinetic uptake with an inflexion point (CRK2 model). From a previous study, we identified 30 and 13 micropollutants following CRK1 and CRK2 accumulation model in the POCIS HLB phase, respectively. We hypothesized that uptake in the outer PES membrane of POCIS may influence the uptake pathway. Thus, novel measurements of uptake in PES membrane were performed for these micropollutants to characterise kinetic accumulation in the membrane with and without the HLB phase. We determined, for the first time, the membrane-water distribution coefficient for 31 micropolluants. Moreover, the lag times for molecules to breakthrough the POCIS membrane increased with increasing hydrophobicity, defined by the octanol-water dissociation constant Dow. However, Dow alone was insufficient to predict whether uptake followed a CRK1 or CRK2 model in the POCIS HLB phase. Thus, we performed a factorial discriminant analysis considering several molecular physico-chemical properties, and the model of accumulation for the studied micropollutants can be predicted with >90% confidence. The most influent properties to predict the accumulation model were the log Dow and the polar surface area of the molecule (>70% confidence with just these two properties). Molecules exhibiting a CRK1 uptake model for the POCIS HLB phase tended to have log Dow>2.5 and polar surface area <50Ǻ2.