Pilot for Validation of Online Pretreatments for Analyses of Organics by Gas Chromatography-Mass Spectrometry: Application to Space Research.

The search for complex organic molecules in extraterrestrial environments, including important biomolecules such as amino and fatty acids, will require a space compatible sample handling system to enable their detection by gas chromatography-mass spectrometry (GC-MS). For the future Mars exploratory mission Exomars 2018 aimed at organic molecules detection, a dedicated laboratory pilot, called Device for Pretreatment of Sample (DPS), reproducing representative space operating conditions has been developed. After its optimization, it aimed at validating under development protocols and interpreting forthcoming in situ resulting data. The DPS, dedicated to organic compounds' analysis, is discussed in terms of its technical features. The derivatization is carried out on a 50-100 mg mineral sample in a 4 mL reactor coupled with a GC-MS injector to simulate on line in situ derivatization-volatilization-transfer steps. Three derivatization reactions have been carried out with N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA) as silylating reagent, N,N-dimethylformamide dimethylacetal (DMF-DMA) and tetramethylammonium hydroxide (TMAH) as methylating agents. The performances are illustrated by comparison of conventional and in situ silylation, developed for space research applications, using terrestrial mineral matrix and Mars analog materials enriched with 25 nmol of each targeted organic molecule. The work presented in this rationale has established that the use of derivatization reactions widens the scope of targeted molecules but also clearly points out mineral matrix effect. Decreasing mineral influence on pretreatment will be the next scientific challenge in in situ analysis.

Storage and source of polycyclic aromatic hydrocarbons in sediments downstream of a major coal district in France.

During the 20th century, the local economy of the Upper Loire Basin (ULB) was essentially based on industrial coal mining extraction. One of the major French coal districts with associated urban/industrial activities and numerous coking/gas plants were developed in the Ondaine-Furan subbasins, two tributaries of the upper Loire main stream. To determine the compositional assemblage, the level and the potential sources of contamination, the historical sedimentary chronicle of the 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) has been investigated. PAH concentrations were determined using gas chromatography/mass spectrometry (GC/MS) in a dated core, sampled in the Villerest flood-control reservoir located downstream of the Ondaine-Furan corridor (OFC). The most contaminated sediments were deposited prior to 1983 (Σ16PAHs ca. 4429-13,348 ng/g) and during flood events (Σ16PAHs ca. 6380 ng/g - 1996 flood; 5360 ng/g - 2003 flood; 6075 ng/g - 2008 flood), especially in medium and high molecular weight PAHs. Among them, typical pyrogenic PAHs such as FLT, PYR, BbF and BaP were prevalent in most of the core samples. In addition, some PAHs last decade data is available from the Loire Bretagne Water Agency and were analyzed using high-performance liquid chromatography with postcolumn fluorescence derivatization (HPLC/FLD). These results confirm that the most highly contaminated sediments were found downstream of OFC (Σ16PAHs ca. 2264-7460 ng/g). According to the observed molecular distribution, PAHs are originated largely from high-temperature pyrolytic processes. Major sources of pyrogenic PAHs have been emphasized by calculation of specific ratios and by comparison to reported data. Atmospheric deposition of urban and industrial areas, wood combustion and degraded coal tar derived from former factories of coking/gas plants seem to be the major pyrogenic sources. Specifically, particular solid transport conditions that can occur during major flood events lead us to emphasize weathering of former contamination sources, such as more preserved coal tar.

Mineralogy and metals speciation in Mo rich mineral sludges generated at a metal recycling plant.

In France, more than 250 million metric tons of sludges need to be treated each year. These sludges are either dumped on the landfills or reused as secondary resources in order to preserve natural resources. A large portions of these sludges are mineral sludges, originating from metal recycling plants. In order to estimate their metal recovery potential, these mineral sludges were characterized. Four types of mineral sludge samples were collected from a metal recycling plant (3 from the recycling plant storage areas (bulk storage, barrel storage and storage shed) and 1 from the collection basin). The sludges were characterized, wherein the Mo, Ni, Cr, Co, Zn and W content and speciation were quantified. The samples had pH values between 5.9 and 10.3 with organic matter contents varying between 6.3% (storage shed) and 29.5% (bulk storage) (loss on ignition at 500 °C). Based on their leaching properties, the four mineral sludge samples (in the case of Mo) and the bulk storage sludge (in the case of Ni and Zn) were classified as potentially hazardous regarding the EN 12457-1 and EN 12457-2 method. Mineralogical results reveal that both bulk storage and the storage shed give the highest contributions to the metal content of the collection basin sample. Sequential extraction of the collection basin samples indicated that Mo is bound to the oxidizable and residual fraction, while Ni, Cr and Co were bound to the residual fraction, and Zn to the soluble acid fraction, respectively. W tends to be equally distributed among all extracted fractions. A strong correlation existed between Mo and Co, as well as between Ni, Zn and Cr, respectively.

Investigation on the iron-uptake by natural biofilms.

Biofilms are natural communities of microorganisms living in aquatic ecosystems which play an important role in the biogeochemistry of many inorganic elements, including iron. The present work aimed to study the uptake of iron by natural river biofilms (produced in the laboratory) and to examine the relationships between biofilms and iron in water. For that, biofilms were formed from natural water samples collected at different times of the year. Total content and global localization of iron were determined by a combination of chemical analyses and microscopy, which indicated that iron was systematically distributed throughout the biofilm matrix. Depending on the level of iron uptake, iron was diffuse or present as hot spots, was primarily localized to the fraction ascribed to OM compounds (45-60%) or the residual fraction (∼14-40%). Additional experiments were conducted using iron-organic complexes with different affinities (log K) to study iron uptake according to the speciation. These experiments suggested the association between iron and organic ligands (i.e. depending on the affinity constant) influenced the uptake of iron, but did not control the biofilm affinity for iron, which appeared to be controlled by chemical-kinetic laws.

Impact of historical mining assessed in soils by kinetic extraction and lead isotopic ratios.

The aim of this study is to estimate the long-term behaviour of trace metals, in two soils differently impacted by past mining. Topsoils from two 1 km(2) zones in the forested Morvan massif (France) were sampled to assess the spatial distribution of Cd, Cu, Pb and Zn. The first zone had been contaminated by historical mining. As expected, it exhibits higher trace-metal levels and greater spatial heterogeneity than the second non-contaminated zone, supposed to represent the local background. One soil profile from each zone was investigated in detail to estimate metal behaviour, and hence, bioavailability. Kinetic extractions were performed using EDTA on three samples: the A horizon from both soil profiles and the B horizon from the contaminated soil. For all three samples, kinetic extractions can be modelled by two first-order reactions. Similar kinetic behaviour was observed for all metals, but more metal was extracted from the contaminated A horizon than from the B horizon. More surprising is the general predominance of the residual fraction over the "labile" and "less labile" pools. Past anthropogenic inputs may have percolated over time through the soil profiles because of acidic pH conditions. Stable organo-metallic complexes may also have been formed over time, reducing metal availability. These processes are not mutually exclusive. After kinetic extraction, the lead isotopic compositions of the samples exhibited different signatures, related to contamination history and intrinsic soil parameters. However, no variation in lead signature was observed during the extraction experiment, demonstrating that the "labile" and "less labile" lead pools do not differ in terms of origin. Even if trace metals resulting from past mining and metallurgy persist in soils long after these activities have ceased, kinetic extractions suggest that metals, at least for these particular forest soils, do not represent a threat for biota.

Impact of effluent organic matter on low-pressure membrane fouling in tertiary treatment.

This study aims at comparing low-pressure membrane fouling obtained with two different secondary effluents at bench and pilot-scale based on the determination of two fouling indices: the total fouling index (TFI) and the hydraulically irreversible fouling index (HIFI). The main objective was to investigate if simpler and less costly bench-scale experimentation can substitute for pilot-scale trials when assessing the fouling potential of secondary effluent in large scale membrane filtration plants producing recycled water. Absolute values for specific flux and total fouling index for the bench-scale system were higher than those determined from pilot-scale, nevertheless a statistically significant correlation (r(2) = 0.63, α = 0.1) was obtained for the total fouling index at both scales. On the contrary no such correlation was found for the hydraulically irreversible fouling index. Advanced water characterization tools such as excitation-emission matrix fluorescence spectroscopy (EEM) and liquid chromatography with organic carbon detection (LC-OCD) were used for the characterization of foulants. On the basis of statistical analysis, biopolymers and humic substances were found to be the major contribution to total fouling (r(2) = 0.95 and r(2) = 0.88, respectively). Adsorption of the low molecular weight neutral compounds to the membrane was attributed to hydraulically irreversible fouling (r(2) = 0.67).

Understanding the fouling of UF/MF hollow fibres of biologically treated wastewaters using advanced EfOM characterization and statistical tools.

Five secondary effluents and a river water source were characterized using size exclusion chromatography (LC-OCD-UVD-OND) and emission-excitation matrix (EEM) fluorescence spectroscopy in order to identify the major effluent organic matter (EfOM) fractions responsible for membrane fouling. This study showed the feasibility of coupling fluorescence EEM and LC-OCD-UVD-OND to investigate the fouling potential as well as a means to differentiate natural organic matter (NOM) from EfOM. The secondary effluents and river water showed a significant difference in organic matter characteristics and fouling potential, highlighting the importance of biological processes and the feed water source on EfOM characteristics and fouling potential. On the basis of statistical analysis, protein-like substances were found to be highly correlated to the fouling potential of secondary effluents.

High pressure membrane foulants of seawater, brackish water and river water: origin assessed by sugar and bacteriohopanepolyol signatures.

The present work aimed to study the origin of foulant material recovered on membranes used in water treatment. Firstly, sugar signatures were assessed from the monosaccharide composition. As results were not conclusive, a statistical approach using discriminant analysis was applied to the sugar data set in order to predict the origin of the foulant material. Three groups of various origins (algal, microbial, continental dissolved organic matter) were used as sugar references for the prediction. The results of the computation showed that the origin of reverse osmosis (RO) seawater foulant material is influenced by both the location of the water sources and the season. RO brackish water and nanofiltration river water foulant materials had a terrestrial origin. Secondly, bacteriohopanepolyol signatures indicated that RO seawater foulant material had a marine signature, RO brackish water foulant material had both a marine and a terrestrial origin and the nanofiltration river water foulant material contained only a terrestrial signature.

Study of organic matter during coagulation and electrocoagulation processes: application to a stabilized landfill leachate.

Organic matter contained in leachates appears to be a relevant indicator of waste evolution. Among the physico-chemical treatments applied to stabilize leachates, coagulation-flocculation is considered a classical process and electrocoagulation can be developed. Electrocoagulation tests were carried out in a laboratory pilot using aluminium plates and compared to classical coagulation-flocculation with aluminium ions and to electrolysis alone. The leachate used in this study came from the landfill of Crezin (Limoges, France) and it presented low biodegradability and high concentration of macromolecules. To assess the efficiency of the chemical and electrochemical processes, we specifically studied Organic Matter (OM) by using two protocols: adsorption on XAD resins and fractionation by ultrafiltration. Biodegradable Dissolved Organic Carbon (BDOC) measurements were applied to the fractions extracted by XAD resins and were also used as an indicator of the efficiency of the treatments. Residual organic matter concentration was the same for the two processes but its composition appeared different after electrocoagulation: a higher percentage of small hydrophilic organic molecules which seemed to be less biodegradable than the initial organic matter was observed.

Modeling of 137Cs migration in soils using an 80-year soil archive: role of fertilizers and agricultural amendments.

An 80-year soil archive, the 42-plot experimental design at the INRA in Versailles (France), is used here to study long-term contamination by 137Cs atmospheric deposition and the fate of this radioisotope when associated with various agricultural practices: fallow land, KCl, NH4(NO3), superphosphate fertilizers, horse manure and lime amendments. The pertinence of a simple box model, where radiocaesium is supposed to move downward by convectional mechanisms, is checked using samples from control plots which had been neither amended, nor cultivated since 1928. This simple model presents the advantage of depending on only two parameters: alpha, a proportional factor allowing the historical atmospheric 137Cs fluxes to be reconstructed locally, and k, an annual loss coefficient from the plow horizon. Another pseudo-unknown is however necessary to run the model: the shape of historical 137Cs deposition, but this function can be easily computed by merging several curves previously established by other surveys. A loss of approximately 1.5% per year from the plow horizon, combined with appropriate fluxes, provides good concordance between simulated and measured values. In the 0-25cm horizon, the residence half time is found to be approximately 18yr (including both migration and radioactive decay). Migration rate constants are also calculated for some plots receiving continuous long-term agricultural treatments. Comparison with the control plots reveals significant influence of amendments on 137Cs mobility in these soils developed from a unique genoform.

Anthropogenic lead distribution in soils under arable land and permanent grassland estimated by Pb isotopic compositions.

The role of land use on fate of metals in soils is poorly understood. In this work, we studied the incorporation of lead in two neighboring soils with comparable pedogenesis but under long-term different agricultural management. Distributions of anthropogenic Pb were assessed from concentrations and isotopic compositions determined on bulk horizon samples, systematical 5-10 cm increment samples, and on 24-h EDTA extracts. Minor amounts of anthropogenic lead were detected until 1-m depth under permanent grassland, linked to high earthworm activity. In arable land, exogenous Pb predominantly accumulated at depths < 60 cm. Although the proximity between the two sites ensured comparable exposition regarding atmospheric Pb deposition, the isotopic compositions clearly showed the influence of an unidentified component for the cultivated soil. This work highlights the need for exhaustive information on historical human activities in such anthropized agrosystems when fate of metal pollution is considered.

Binding of fibrin monomer and heparin to thrombin in a ternary complex alters the environment of the thrombin catalytic site, reduces affinity for hirudin, and inhibits cleavage of fibrinogen.

Interaction of the blood clotting proteinase, thrombin, with fibrin monomer and heparin to form a thrombin.fibrin monomer.heparin ternary complex is accompanied by a change in thrombin catalytic specificity. Equilibrium binding interactions in the assembly of the ternary complex were characterized quantitatively using thrombin labeled at the active site with a fluorescent probe and related to changes in thrombin specificity toward exosite I-dependent binding of hirudin and cleavage of fibrinogen. Changes in the active site environment accompanying binding of heparin or fibrin to thrombin in binary complexes were reported by fluorescence enhancements which contributed additively to the perturbation accompanying formation of the ternary complex. Quantitative analysis of the interactions supports a preferentially ordered path of ternary complex assembly, in which initial binding of heparin to thrombin facilitates binding of fibrin monomer with an approximately 40-fold increased affinity. Binding of fibrin monomer in the ternary complex decreased the affinity of native thrombin for hirudin by >100-fold and inhibited cleavage of fibrinogen, but this inhibition was overcome when fibrin(ogen)-fibrin interactions occurred. These results support a ternary complex model in which heparin binding through exosite II of thrombin facilitates fibrin monomer binding via exosite I, with accompanying changes in thrombin catalytic specificity resulting from perturbations in the active site and reduced accessibility of exosite I to hirudin and fibrinogen.

Modeling of the electrostatic potential field of plastocyanin.

The DelPhi computer program is used to calculate the electrostatic potential field of the photosynthetic electron transport protein plastocyanin. Knowledge of the potential field is important for understanding the mechanisms by which plastocyanin interacts with other charged reagents. The program uses a macroscopic, continuum approach in which the protein and solvent are assigned different dielectric constants, the crystal structure of the protein defines the dielectric boundary, and the ionic strength of the solvent is taken into account. The potential field is determined by numerically solving the Poisson-Boltzmann equation. The field surrounding plastocyanin is characterized by a region of positive potential over the copper center active site, and a region of negative potential over the adjacent association site containing tyrosine 83. The shape and magnitude of the potential field shows a strong dependence on the ionic strength and pH of the solvent. The program is able to accurately predict the effect of the copper center oxidation state on the pKa of a tetranitromethane derivative of tyrosine 83 using an intrinsic protein dielectric constant of 2 to 4. Evidence is also presented that the glutamate 68 side chain is exposed to the solvent to a greater extent in the solution structure of plastocyanin than in the crystal structure.