Iodine budget in forest soils: Influence of environmental conditions and soil physicochemical properties

International audienceDue to its longevity, radioisotope 129I is a health concern following potential releases in the environment which raises questions about residence and exposure times relevant for risk assessments. We deter¬mined 127I concentrations (as a surrogate for 129I) in a series of French forest soils (i.e. litters, humus and mineral soils) under different vegetation and climate conditions in order to identify the major processes affecting its accumulation and persistence in the soil column. The input fluxes linked to rainfall, throughfall and litterfall were also characterized. Main results obtained showed that: (i) rainfall iodine concentrations probably influenced those of litterfall through absorption by leaves/needles returning to the ground; (ii) throughfall was the major iodine input to soils (mean = 83%), compared to litterfall (mean = 17%); (iii) humus represented a temporary storage of iodine from atmospheric and biomass deposits; (iv) iodine concentrations in soils depended on both the iodine inputs and the soil's ability to retain iodine due to its organic matter, total iron and aluminium concentrations; (v) these soil properties were the main factors influencing the accumulation of iodine in the soil column, resulting in residence times of 419-1756 years; and (vi) the leaching of iodine-containing organic matter dissolved in soil solution may be an important source of labile organic iodine for groundwater and streams

Characterization of biogas and biomethane trace compounds: A critical review of advances in in situ sampling and preconcentration techniques

International audienceWorldwide, the valorization of biogas, landfill gas and biomethane is gaining momentum as circular economies and energy transitions are triggered. Nevertheless, to sustainably integrate those gases into today's energy mix, their quality must be controlled regarding their major, minor and trace constituents to preserve the integrity of infrastructures wherein they are burned, transported or stored. Field gas sampling is the first and most critical step in the analytical chain to characterize the composition of such gases. A large array of gas sampling techniques is available, yet choosing the most suitable technique is complex, especially when targeting trace compounds (<ng·Nm−3 to mg·Nm−3) which often require a preconcentration step to be detectable. Sampled trace compounds must be kept stable (no loss, degradation or contamination can occur) during the storage phase between sampling and analysis, and all materials in the sampling chain that contact the gas potentially influence this stability. This paper aims to review the available gas sampling and preconcentration techniques for determining trace compounds in biogas, landfill gas and biomethane. Techniques reviewed include 1) whole gas sampling methods (gas sampling bags, gas cylinders, canisters) and 2) gas sampling methods with preconcentration on solid media (sorbent tubes for physisorption or chemisorption, amalgamation, solid phase microextraction); preconcentration in liquid media (absorption in impingers); and cryogenic preconcentration. These techniques are reviewed for the sampling of nonmetal(loid) volatile organic trace compounds (aliphatic, aromatic, halogenated and oxygenated species; organic silicon compounds (siloxanes, silanes), and (in)organic sulfur compounds) as well as for volatile (in)organic metal(loid) compounds. The suitability of all presented sampling and preconcentration methods for given families of trace compounds regarding storage stability issues, is discussed as well as considerations regarding the ease of field implementation, advantages and disadvantages. This review highlights the intricate complexity of sampling trace compounds in biogas, landfill gas and biomethane. The different trace compounds indeed display extremely diverse physicochemical properties (volatility, polarity, reactivity …) which results in different stabilities in given sampling units so that no sampling method along can trap and recover all families of trace compounds. The review finishes with a list of recommendations to select proper sampling units, materials and parameters and to apply suitable sample transport and storage conditions to safeguard the integrity of samples. © 2022 Elsevier B.V

Etude de la décontamination électrocinétique de l'aluminium d'une boue de laiterie

Le succès du procédé de décontamination électrocinétique des métaux d'une boue dépend du choix des conditions expérimentales : courant ou tension applique, pH, réactifs ajoutés, débit du flux électro-osmotique, etc. Des conditions bien adaptées doivent permettre notamment de minimiser les phénomènes d'adsorption, d'augmenter la solubilité pour éviter la précipitation du métal dans la boue. Ces précautions, entre autres, facilitent la récupération cathodique du métal. Dans cette étude de décontamination électrocinétique de l'aluminium d'une boue provenant d'eaux résiduaires de laiterie, il a été décidé de garder un débit électro-osmotique et un potentiel constants successivement à 10 ml/h et 15 V (1 V/cm), et de faire circuler dans le réacteur un milieu basique (NaOH 0,1 M) des deux côtés des compartiments anodique et cathodique. Ce choix de pH extrême a permis d'évaluer l'électromigration de l'espèce complexe mononucléaire de l'aluminium et non de l'aluminium monomère (Al3+) qui est largement prédominant en milieu acide (pH = 4,6). Les résultats obtenus ont montré l'efficacité de cette technique d'électromigration pour récupérer l'aluminium complexe Al(OH)52-. En effet, à pH supérieur à 10, mesuré dans les compartiments électrolytiques, l'aluminium redevient soluble et la récupération de ce métal atteint 72 %

ISIDORE, a Probe for In Situ Trace Metal Speciation Based on the Donnan Membrane Technique and Electrochemical Detection Part 2: Cd and Pb Measurements during the Accumulation Time of the Donnan Membrane Technique

The Donnan membrane technique (DMT), in which a synthetic or natural solution (the “donor”) is separated from a ligand-free solution (the “acceptor”) by a cation-exchange membrane, is a recognized technique for measuring the concentration of a free metal ion in situ, with coupling to electrochemical detection allowing for the quantification of the free metal ion directly on site. However, the use of the DMT requires waiting for the free metal ion equilibrium between the donor and the acceptor solution. In this paper, we investigated the possibility of using the kinetic information and showed that non-equilibrium experimental calibrations of Cd and Pb with the ISIDORE probe could be used to measure free metal concentrations under conditions of membrane-controlled diffusion transport. The application of this dynamic approach made it possible to successfully determine the concentration of free Cd in synthetic and natural river samples. Furthermore, it was found that the determination of free Cd from the slope was not affected by the Ca concentration ratio between the acceptor and donor solution, as opposed to the traditional approach based on Donnan equilibrium. This ISIDORE probe appears to be a promising tool for determining free metal ions in natural samples

Assessment of erosion and sedimentation dynamic in a combined sewer network using online turbidity monitoring

cited By 1International audienceEroded sewer sediments are a significant source of organic matter discharge by combined sewer overflows. Many authors have studied the erosion and sedimentation processes at the scale of a section of sewer pipe and over short time periods. The objective of this study was to assess these processes at the scale of an entire sewer network and over 1 month, to understand whether phenomena observed on a small scale of space and time are still valid on a larger scale. To achieve this objective the continuous monitoring of turbidity was used. First, the study of successive rain events allows observation of the reduction of the available sediment and highlights the widely different erosion resistance for the different sediment layers. Secondly, calculation of daily chemical oxygen demand (COD) fluxes during the entire month was performed showing that sediment storage in the sewer pipe after a rain period is important and stops after 5 days. Nevertheless, during rainfall events, the eroded fluxes are more important than the whole sewer sediment accumulated during a dry weather period. This means that the COD fluxes promoted by runoff are substantial. This work confirms, with online monitoring, most of the conclusions from other studies on a smaller scale

Continuous Monitoring of Turbidity and Conductivity in Wastewater Networks : An Easy Tool to Assess the Pollution Load discharged into receiving water

Continuous monitoring of the sanitation network of the urban catchment of Pau (southwest France) has been performed since March 2012 using rain gauges, flowmeters, as well as turbidity and conductivity probes. Good correlations were obtained between turbidity, total suspended solids (TSS) and chemical oxygen demand (COD) on the one hand, and conductivity and total nitrogen on the other hand. This allowed an instantaneous and continuous estimation of pollutant concentrations and fluxes since that date. In the present paper we focused on the results of October 2012, which was characterized by alternating periods of dry and rainy events. Turbidity and conductivity raw data show different trends during the study period depending on the parameter and the rain events. A turbidity peak is observed at the beginning of each rain event but its amplitude varies with the intensity of the rain and the length of the preceding dry weather period. Conversely, conductivity decrease during each rain event implying, that rain water acts as a dilution factor. The behaviour of COD and total nitrogen differ markedly due to their partitioning between the dissolved (total nitrogen) and particulate phases (COD). Daily pollutant fluxes allow a global comprehension and monitoring of the sewer system. Important COD fluxes during a rain event preceded by a long dry weather period highlight the importance of erosion of sedimentary deposits in the sewerage network. During these events, important fluxes are discharged into receiving water leading to the question of the impact on aquatic life. Generally, these results highlight the potential of online monitoring to better understand the behaviour of the sewer network on long or short time scales. This could be a useful tool to manage wastewater treatment.Un suivi en continu du système d’assainissement de la Communauté d’Agglomération de Pau est mené depuis le mois de mars 2012 grâce à l’utilisation de pluviographes, de débitmètres, de turbidimètres et conductimètres. Des corrélations fiables ont été obtenues entre la turbidité, les matières en suspension (MES) et la demande chimique en oxygène (DCO) d’une part et entre la conductivité et l’azote total (TN) d’autre part. Ces mesures permettent une estimation instantanée et continue des flux de polluants transitant dans le réseau d’assainissement. L’article présente les résultats obtenus au mois d’octobre 2012 qui est caractérisé par une alternance de périodes de temps sec et d’événements pluvieux. Les données de turbidité et de conductivité montrent des tendances différentes pour un même type d’événement. Une augmentation de turbidité est observée au début de chaque épisode pluvieux, celle-ci variant en fonction de l’intensité des précipitations et de la durée de temps sec qui précède l’événement. À l’inverse, la conductivité diminue lors de chaque événement pluvieux en réponse à la dilution des eaux usées par l’eau de pluie. Le comportement différent de la DCO et de TN au cours d’un épisode pluvieux est dû à leurs répartitions différentes entre les phases dissoutes (TN) et particulaires (DCO). Les flux importants de DCO mesurés durant un événement de pluie précédé d’une longue période de temps sec mettent en évidence l’importance des phénomènes de sédimentation et d’érosion dans le réseau d’assainissement. Au cours de ces événements, les flux polluants rejetés vers le milieu récepteur peuvent être alors conséquents. Cela pose la question de leur impact sur la vie aquatique. Ces résultats montrent le potentiel de la mesure en continu pour une meilleure compréhension des systèmes d’assainissement. Cet outil pourrait être utile pour optimiser la gestion des eaux usées urbaines

Evaluation of a combined fractionation and speciation approach for study of size-based distribution of organotin species on environmental colloids

International audienc

Effect of water composition on aluminium, calcium and organic carbon extraction in tea infusions

Tea infusion is the second world wide consumed beverage. In this study, total aluminium and calcium concentrations, total organic carbon and total polyphenol content were determined and compared with respect to the origin of tea leaves, their particle size (broken or whole leaves) and also the mineral composition of four waters. It appeared that the higher the mineral content, the lower the extraction yield of aluminium, total organic carbon and total polyphenols. This could be due to calcium uptake by leaves. Calcium present in mineral waters could be complexed with pectins present in cell walls thus leading to a decrease in the element extraction