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International audience; Indicators signaling Arsenic (As) stress through physiology of microalgae using non-destructive methods like variable fluorescence are rare but requisite. This study reports stress markers indicating arsenic (As) toxicity (in two concentrations 11.25 µg/L and 22.5 µg/L compared to a control) exposed to a microalga (Diacronema lutheri), using fast repetition rate fluorometry (FRRf). Growth and physiological parameters such as cell density, chl a and the maximum quantum yield Fv/Fm showed coherence and impeded after the exponential phase (day 9 - day 12) in As treatments compared to the control (p < 0.05). On contrary photo-physiological constants were elevated showing higher optical (aLHII) and functional [Sigma (σPSII)] absorption cross-section for the As treatments (p < 0.05) further implying the lack of biomass production yet an increase in light absorption. In addition, As exposure increased the energy dissipation by heat (NPQ-NSV) showing a strong relationship with the de-epoxidation ratio (DR) involving photoprotective pigments. Total As bioaccumulation by D. lutheri showed a strong affinity with Fe adsorption throughout the algal growth curve. This study suggests some prompt photo-physiological proxies signaling As contamination and endorsing its usefulness in risk assessments, given the high toxicity and ubiquitous presence of As in the ecosystem.

The innovation of this study was to assess which types of AC derived from three selected date stones (Species: Phoenix dactylifera; types: Ajwa, Anbari, Khudri) showed better performance for the adsorption of organochlorine pesticides from contaminated water (outflow water from WWTP and agricultural effluent). In the bed column, the first experiments demonstrated that AC prepared from Ajwa date stones has a high efficiency to eliminate OCPs from an aqueous solution that 10 g of adsorbent was treated with 12 L of contaminated water. Therefore, the effects of the adsorbent mass of the material prepared from Ajwa date stones and flow rate of organochlorine pesticides onto prepared activated carbon were studied; the optimum adsorption capacity for all studied organochlorine pesticides from the water having a natural pH has reached 70–100%, using a 50 g of adsorbent in the particle size range of 0.75–100 mm, a flow rate of 2.5 mL/min, and an inlet concentration 57 µg/L. Finally, this AC proved its effectiveness to control water pollution by OCPs for agricultural and WWTPs effluents.

International audience

International audience; Background: The latest generation of liquid chromatograph coupled to high-resolution quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) now competes with quadrupole tandem spectrometers (LC-MS-MS) in terms of sensitivity and speed. In addition, it is possible to obtain additional information retrospectively on the organic composition of the analyzed soil. Due to the exponential increase of the storage capacities of computer hard drives and the speed of electronic processing of computer data, it is all the more possible to recover all of the data generated during the analysis of a soil extract.Objective: The LC-QTOF-MS currently has an essential and primordial advantage; which is the entire transmission of the ions produced in the ionization source towards the mass spectrometer. This original feature opens the way to a probable full exploration of the organic composition of the soils.Methods: A new method for the analysis of pesticides in agricultural soils by using liquid chromatography coupled with a high-resolution quadrupole time-of-flight mass spectrometer (LC-QTOF-MS) has been developed.Results: Twenty-four pesticides including herbicides, insecticides or fungicides have been studied. The linearity of the external calibration of the pesticides obtained from levels of concentration ranging from 0.010 to 400 μg/L gives satisfactory results with the correlation coefficients higher than 0.99. The quantification limits of the equipment range from 0.010 to 1.250 μg/L and correspond to the lowest standard in the calibration range for which the residual deviation is less than 60%. An experimental design has been used to optimize the parameters of pressurized-liquid extraction (PLE) of pesticides in soils. The optimized conditions have been found by using methanol as extraction solvent at a temperature of 80°C, a pressure of 150 Bars and 2 extraction cycles of 5 minutes. The mean recoveries of pesticides (Mean) are higher than 72% with a relative standard deviation (RSD) less than 21%. These results demonstrate the good efficiency of PLE for the extraction of pesticides in agricultural soils of different nature. The LC-QTOF-MS is a sensitive, linear and robust instrument for the quantification of pesticides in unpurified soils extracts by external calibration. This analytical tool is not subjected to matrix effects of soil extracts.

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International audience

International audience

The quality and quantity of natural organic matter (NOM) has been observed to evolve which poses challenges to water treatment facilities. Even though NOM may not be toxic itself, its presence in water has aesthetic effects, enhances biological growth in distribution networks, binds with pollutants and controls the bioavailability of trace metals. Even though NOM has heterogeneous functional groups, the predominant ones are the carboxyl and the phenolic groups, which have high affinities for metals depending on the pH. The properties of both the NOM and the trace elements influence the binding kinetics and preferences. Ca2+ prefers to bind with the carboxylic groups especially at a low pH while Zn2+ prefers the amine groups though practically, most cations bind to several functions groups. The nature of the chemical environment (neighboring ligands) the ligand finds itself equally influences its preference for a cation. The presence of NOM, cations or a complex of NOM-cations may have significant impact on the efficiency of water processes such as coagulation, adsorption, ion exchange resin and membrane filtration. In coagulation, the complexation between the coagulant salts and NOM helps to remove NOM from solution. This positive influence can further be enhanced by the addition of Ca2+. A negative influence is however, observed in lime-softening method as NOM complexes with Ca2+. A negative influence is also seen in membrane filtration where divalent cations partially neutralize the carboxyl functional groups of NOM thereby reducing the repulsion effect on NOM and increasing membrane fouling. The formation of disinfection by-products could either be increased or reduced during chlorination, the speciation of products formed is modified with generally the enhancement of haloacetic acid formation observed in presence of metal cations. This current work, presents in details the interactions of cations and NOM in the environment, the preference of cations for each functional group and the possible competition between cations for binding sites, as well as the possible impacts of the presence of cations, NOM, or their complex on water treatment processes.

Soil contamination by heavy metals (HM) and persistent organic pollutant such as organochlorine pesticides (OCPs) is a worldwide global concern. These pollutants are introduced to the soil through human activities, including mining, smelting, industry, and agriculture. They alter soil properties and affect all living beings. The present work is focused on the contamination level of OCPs and HMs in soils, originated from six villages located in an agricultural area northern Lebanon-Akkar. Determination of OCPs was established by accelerated solvent extraction followed by GC–MS analysis, and investigation of heavy metals was performed by total extraction occupied with ICP-AES. OCPs were found at high levels. Concentrations of DDTs, HCHs and cyclodiene insecticides were as following 29.4, 10.1 and 37.3 ng/g. A high concentration of OCPs was found in the cultivated area and a huge difference was observed between the same region and tillage land. Furthermore, a variation of concentration was determined also among depth and soil category. The predominance of DDE has been presented and a historical application of dicofol has been identified by 2,4′DDT/4,4′DDT and DDE + DDD/DDTs values. An unbroken and recent use of HCHs, chlordane, and heptachlor has been manifested based on the values of α-HCH/γ-HCH, Cis/trans-chlordane and heptachlor/heptachlor epoxide ratios, respectively. Nickel was mostly metal-detected at all sites; and a moderate pollution by cd (Enrichment factor > 25) has been provided probably due to the use of pesticides comprising a certain trace of this metal during agricultural practices. As a conclusion, the soil of Akkar is not only contaminated by pesticides but also with heavy metals which necessitates an effort to protect people living around this region from their risk.

According to its high production and value, Akkar is considered as the second agricultural region in Lebanon. Groundwater constitutes the principal source of water in Akkar including drinking water of local inhabitants in Akkar. As such, the contamination of groundwater by organic pollutants can impact directly the population health. In this study, we evaluated the contamination status of groundwater in this region. Three classes of pesticides including 19 organochlorine (OC) pesticides, 8 organophosphorus (OP) pesticides, and 6 organonitrogen (ON) pesticides were monitored in 15 groundwater samples collected from different villages on the Akkar plain. Samples were extracted by using solid phase extraction (SPE) and analyzed by gas chromatography coupled with mass spectrometry (GC-MS). The results showed high contamination of Akkar groundwater by OCs with levels that can reach 58.9 μg/L. They were detected in the majority of the sample and represent 95–100% of ∑pesticides. Our results showed the recent use of these molecules with an average level of 0.3 and 0.39 μg/L for ∑HCHs and DDTs, respectively. Their concentrations were higher than those observed in the same region in 2014 and other regions elsewhere. OPs were also detected at high levels and among them, methylparathion was the predominant OP detected (44.6 μg/L). For ONs, lower levels were measured in all samples with a mean value of 5.6 μg/L. As a conclusion of this work, groundwater on the plain of Akkar was remarkably contaminated by the studied pesticides; indefinitely, more efforts should be taken to manage the pesticide use in this region, assess, and reduce their effects on human health. In the future, the application of organic farming can be a great solution to the groundwater contamination problem.

The Euro-Mediterranean Consortium of Institutes of Higher Education and Industry (C3ESI) is made up of universities and colleges of engineering.

International audience

Dispersion of mercury pollution from the point pollution source in the semi-enclosed coastal area – Kastela bay, Eastern Adriatic coast N. Mikac1, D. Barisic1, N.Cukrov1, S. Kozar1, G. Kniewald1, B. Ouddane2 1 Division for Marine and Environmental Research, Rudjer Boskovic Institute, Zagreb, Croatia 2 Université des Sciences et Technologies de Lille, UMR CNRS 8110 (PBDS), Equipe Chimie Analytique et Marine Bat C8, 59655 Villeneuve d’Ascq Cedex, France The greatest environmental problem of local pollution by mercury in Croatia has occurred in Kaštela Bay following 40 years activity (1950-1990) of the chlor-alkali plant located on the northeastern coast of the Bay. It was estimated that about 50 tons of mercury has been introduced into the bay. Elevated mercury concentrations in sediments and bioaccumulation of total and methyl mercury in marine organisms of this area were demonstrated. The most recent study (2002) still showed very high concentrations of total mercury (up to 70 mg/kg) in sediments in front of the factory and favorable conditions for mercury methylation (up to 50 μg/kg of MeHg). High concentration of mercury in sediments in the different parts of the bay indicated that mercury is efficiently transported from the pollution source. In this work attempt was made to quantify dispersion of mercury from the point pollution source over the whole bay and the export of mercury from the bay into the coastal area. More than 80 sediment cores (up to 100 cm long) were sampled over the entire surface of the bay. Cores were sliced into 5 or 10 cm layers and concentration of total mercury, as well as level of radionuclides (natural U and its decay series products and artificial 137Cs) were determined in sediment sub-samples. It was recently shown that the sediments in front of the factory are also contaminated by uranium originating from the coal burning products of the thermoelectric factory unit. Therefore, comparing distributions of these two pollutants may help to elucidate the mechanism of transport of mercury from the pollution source. Data showed that generally the first 15 cm of the sediment over the whole bay are contaminated by mercury and that, in most of the sites, this contamination is still evident at depths greater than 50 cm. Principal pathways of mercury transport by sediment and its quantification will be discussed in the paper.

The use of dilute HCl for the selective extraction of mercury from suboxic and anoxic sediments has been evaluated. The effect of acid concentration (1-6 M HCl) on the extraction of Hg and on the recovery of aqueous Hg preextraction spikes from sediments containing various amounts of AVS has been studied. The results obtained by using 1 M HCl as extractant (~90 % of added Hg was recovered in the solid phase after extraction) indicated that acid-soluble Hg may react with H2S released from AVS phases (e.g. FeS, MnS) and precipitate in the form of HgS. The modeling of Hg speciation in HCl solutions in the presence of sulfide predicted the HgS(s) precipitation in 1 M HCl, observed experimentally. The precipitation of HgS(s) was found to be considerably lower when greater (2-6 M) HCl concentrations were used for Hg extraction. The modeling calculations confirmed that the extent of HgS(s) formation in the solution was controlled by the applied HCl concentration. The difference between HCl-soluble Hg fraction in an estuarine sediment core extracted by 1 M (1-5 % of Hgtot) and 6 M (50-60 % of Hgtot) HCl was consistent with the model experiments. These results suggest that the use of 1 M HCl extraction procedures must be questioned for methodological artifacts and that 6 M HCl could advantageously replace 1 M HCl for extracting Hg in the presence of AVS.

Early diagenetic reactions occurring in the upper layers of sediment are important in the remobilisation of heavy metals. The mobilisation of sediment-bound metals during diagenesis could have two consequences: the release of dissolved metal from the sediment to the overlaying water, or change in the association of metal from one sediment phase to another. Many sediment-bound metals are affected by redox cycling of iron and manganese during early diagenesis. Recently has been suggested that mercury in sediment is also affected by early diagenesis and particularly associated with iron and manganese oxyhydroxides. Information about diagenetic behaviour of trace metals in sediments could be obtained by simultaneous analysis of elements of interest (Hg, Fe, Mn) in both solid and dissolved sediment phases, or alternatively, by partial extraction of the solid phase. Two kinds of partial extractions have been used to evaluate the association of mercury with oxide phases: extraction with hydroxilamine-acetic acid solution which extract Mn and Fe oxides and carbonates and extraction with diluted hydrochloric acid which extract Mn and Fe oxides and AVS-Fe (acid volatile sulphides). Both extractions could suffer from artefacts introduced during the extraction procedure. The extraction with a reducing hydroxilamine solution, which should be, in addition, performed at elevated temperature, can result in loss of mercury trough volatilisation. The extraction with dilute HCl can suffer from serious post extraction readsorption, when sulphides are present in sediments. Upon addition of acid, dissolved mercury can precipitate as HgS by reaction with H2S and may be readsorbed onto sulphide minerals, both reactions occurring even at very low pH values. Therefore, if extraction efficiency of mercury depends on the sulphide level in sediment (which normally increase with sediment depth), it would be difficult to make conclusions on the mercury association with oxides from such set of data. In this work the use of partial extraction with dilute HCl as a tool for the assessment of the mercury association with oxide sediment phases will be evaluated. The work will be performed by analysis of acid-extractable mercury in natural sediments containing different amounts of AVS. Also preextraction spikes will be used to assess the accuracy of mercury extraction and dependence of spikes recoveries on the sediment composition.

A new method for the analysis of pesticides in agricultural soils by using liquid chromatography coupled with a high-resolution quadrupole time-of-flight mass spectrometer (LC-QTOF-MS) has been developed. Twenty-four pesticides including herbicides, insecticides or fungicides have been studied. The linearity of the external calibration of the pesticides obtained from levels of concentration ranging from 0.010 to 400 µg/Lgives satisfactory results with the correlation coefficients higher than 0.99. The quantification limits of the equipment range from 0.010 to 1.250 µg/L and correspond to the lowest standard in the calibration range for which the residual deviation is less than 60%. An experimental design has been used to optimise the parameters of pressurised-liquid extraction (PLE) of pesticides in soils. The optimised conditions have been found by using methanol as extraction solvent at a temperature of 80°C, a pressure of 150 Bars and 2 extraction cycles of 5 minutes. The mean recoveries of pesticides (Mean) are higher than 72% with a relative standard deviation(RSD) less than 21%. These results demonstrate the good efficiency of PLE for the extraction of pesticides in agricultural soils of different nature. The LC-QTOF-MS is a sensitive, linear and robust instrument for the quantification of pesticides in unpurified soil extracts by external calibration. This analytical tool is not subjected to matrix effects of soil extracts.

A new method for the analysis of pesticides in agricultural soils by using liquid chromatography coupled with a high-resolution quadrupole time-of-flight mass spectrometer (LC-QTOF-MS) has been developed. Twenty-four pesticides including herbicides, insecticides or fungicides have been studied. The linearity of the external calibration of the pesticides obtained from levels of concentration ranging from 0.010 to 400 µg/Lgives satisfactory results with the correlation coefficients higher than 0.99. The quantification limits of the equipment range from 0.010 to 1.250 µg/L and correspond to the lowest standard in the calibration range for which the residual deviation is less than 60%. An experimental design has been used to optimise the parameters of pressurised-liquid extraction (PLE) of pesticides in soils. The optimised conditions have been found by using methanol as extraction solvent at a temperature of 80°C, a pressure of 150 Bars and 2 extraction cycles of 5 minutes. The mean recoveries of pesticides (Mean) are higher than 72% with a relative standard deviation(RSD) less than 21%. These results demonstrate the good efficiency of PLE for the extraction of pesticides in agricultural soils of different nature. The LC-QTOF-MS is a sensitive, linear and robust instrument for the quantification of pesticides in unpurified soil extracts by external calibration. This analytical tool is not subjected to matrix effects of soil extracts.

Conférence invité (présentation par visioconférence); International audience