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

Identification et quantification de métabolites séléniés dans l urine humaine

La barrière entre l aspect bénéfique du sélénium (Se) et son aspect toxique est étroite. Afin de mieux contrôler les apports de cet élément dans l alimentation, de nombreux travaux s intéressent à la compréhension de son métabolisme. Cette thèse présente le développement et l optimisation de méthodes d analyse des espèces séléniées dissoutes et volatiles présentes dans l urine de sujets non supplémentés. Le couplage entre la chromatographie liquide et la spectrométrie de masse atomique précédé d un prétraitement de l échantillon par extraction sur phase solide a permis non seulement de confirmer la présence de métabolites séléniés précédemment détectés dans l urine de sujets supplémentés mais également, de mettre en évidence des composés inconnus. Un de ces composés a été identifié par spectrométrie de masse moléculaire. Les couplages entre la chromatographie gazeuse et les spectrométries de masse atomique et moléculaire, précédés d une micro-extraction sur phase solide ont été utilisés pour l analyse des formes volatiles de Se. Ces méthodes ont permis de confirmer la présence de composés séléniés et mixtes Se/S dans les urines de sujets non supplémentés et, de définir des conditions de stockage permettant de préserver la spéciation originelle dans l échantillon.The concentration range between beneficial and toxic effects for selenium (Se) is very narrow. In order to monitor selenium intake and to improve knowledge of Se metabolism, studies on selenium species ingested and excreted are performed. This report presents the development and the optimization of speciation analysis of dissolved and volatile Se species in urine of non supplemented subjects by coupling liquid chromatography or gas chromatography to inductively coupled plasma mass spectrometry. In the case of dissolved species, solid phase extraction of the sample as sample pretreatment allowed us to confirm the presence of known selenium compounds and to highlight unknown selenium species. One of these new species was further identified by molecular mass spectrometry. The analysis of volatile selenium compounds was performed by gas chromatography coupled to ICP-MS after sample extraction by SPME. This method led to the identification of some selenium and mixed selenium/sulphur species in urine from non supplemented subjects and allowed us to define suitable storage conditions to maintain original speciation.PAU-BU Sciences (644452103) / SudocSudocFranceF

Simultaneous determination of twelve inorganic and organic arsenic compounds by liquid chromatography-ultraviolet irradiation-hydride generation atomic fluorescence spectrometry

International audienceA coupling between column liquid chromatography (LC) and atomic fluorescence spectrometry was developed for arsenic speciation. After separation, the compounds are oxidised on-line by UV irradiation, volatilised by hydride-generation and carried to the detector by a stream of argon. A combination of anion-exchange and hydrophobic interactions in a single column (Dionex AS7) was found suitable for the simultaneous separation of organic and inorganic species. Twelve compounds (arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine, arsenocholine, trimethylarsine oxide, tetramethylarsonium ion and four arsenosugars) were separated using an acetate buffer and a nitric acid solution as mobile phases. Limits of detection are 4–22 pg. The technique was applied to three marine samples. Arsenobetaine was detected as the main species in all samples, with concentrations varying from 59 to 1947 ng(As) g−1 of fresh mass

Development of an on-line UV decomposition system for direct coupling of liquid chromatography to atomic-fluorescence spectrometry for selenium speciation analysis

International audienc

Selenate bioaccumulation and toxicity in Chlamydomonas reinhardtii: Influence of ambient sulphate ion concentration

International audienceThe aim of the present study was to investigate selenate toxicity in the unicellular green algae Chlamydomonas reinhardtii as a function of sulphate ion concentration and the relationship with intracellular bioaccumulation. The toxicity of selenate was evaluated by measuring the effect of different selenate concentrations on algal growth during a 96 h exposure period. A non-linear regression according to the Hill model was used to describe the dose-effect relationship and estimate the effect concentrations (EC) of selenate. EC50 values of 0.40 [0.24-0.52] μmol L-1 and of 3.10 [1.65-4.86] μmol L-1 of ambient selenate were obtained, at 8 and 80 μmol L-1 of sulphate ions in the medium, respectively. For non-toxic and low-level ambient selenate concentrations, bioaccumulation in presence of 80 μmol L-1 was one tenth that of 8 μmol L-1 of sulphate ions. When expressed as intracellular selenium burden, EC50 values determined at 8 and 80 μmol L-1 of sulphate ions were not significantly different (126 and 67 nmol Se·109 cells-1, respectively). In conclusion, toxicity appeared to be correlated to selenate bioaccumulation which suggests that toxicity must be linked to intracellular selenium accumulation that is directly dependent on ambient sulphate ions that may compete with selenate for transport sites. © 2009 Elsevier B.V. All rights reserved

Effects of tributyltin oxide on survival and osmoregulation of the shrimp Penaeus japonicus (crustacea, decapoda)

International audienceThe acute toxicity of tributyltin oxide (TBTO) was determined in larvae (nauplii, zoeae 1-3, mysis 1-3), post-larvae (PL stages) and juvenile shrimp (Penaeus japonicus Bate), in two media, seawater (SW) and diluted seawater (DSW; 1100 and 550 mosm kg-1 ≃37 and 19%). Survival, osmoregulatory capacity and Na+-K+ ATPase activity were measured. A gill and epipodite histopathological study was also conducted. The 24 and 48 h LC50s values for TBTO in SW ranged from 2.03 μg l-1 (1.7-2.4) and 0.88 μg l-1 (0.8- 1.0) for nauplii to 773 μg l-1 (344-1823) and 708 μg l-1 (361-1608) for juveniles. The 96 h LC50s values in SW ranged from 19.4 μg-1 (12.6- 27.3) for PL5 to 370 μg l-1 (202-662) for juveniles. The 96 h LC50s value was not affected by salinity in juveniles. Tolerance to TBTO tended therefore to increase with the development from larval to juvenile instars. In juveniles kept in SW and in DSW, acute TBTO-exposures decreased the osmoregulatory capacity (OC = difference between the hemolymph osmolality and the osmolality of the medium) of animals exposed to lethal and sublethal concentrations. Effects of TBTO exposure on hypo- and hyper-OC were time- and dose-dependent and the ability to osmoregulate was recovered after exposure of the shrimp to water free of TBTO for 48 120 h. These experiments confirmed OC as a valuable tool for monitoring the physiological state of peneid shrimp. Gill and epipodite Na+-K+ ATPase activities were not altered in SW and DSW after acute TBTO-exposures, either at sublethal or at lethal concentrations. Haemocytic congestion (thrombosis), multiple necrosis and nephrocyte hyperplasia were observed in gill lamellae of exposed shrimp. Multiple necrosis and lacunae in the epithelial monolayers were also observed in epipodites. At lethal concentrations, the interconnecting lacunae were reduced and/or replaced by proliferating tissues. Epithelial cells were peeling and oedema was observed. For both tissues, histopathological effects increased with the dose and they are probably the cause of impaired osmoregulation

Production and use of reference materials for environmental analyses: conclusions of a workshop

International audienceReference materials (RMs) play a vital role for the verification of the quality control of environmental analysis. The increasing requirements imposed to environmental control laboratories call for greater co-operation among RM producers and end-users to better define future production strategies. It is recognised that the present system is unlikely to be able to cope with the increasing demand for certified and non-certified RMs within the forthcoming years. These issues were discussed in the framework of a workshop funded by the M&T programme of the European Commission, which brought together RM producers, certification experts and end-users. This report summarises the round-table discussions and expert recommendations

Speciation analysis of organoarsenical compounds in biological matrices by coupling ion chromatography to atomic fluorescence spectrometry with on-line photooxidation and hydride generation

International audienc