Incorporation of metals into calcite in a deep anoxic granite aquifer

Understanding metal scavenging by calcite in deep aquifers in granite is of importance for deciphering and modeling hydrochemical fluctuations and water–rock interaction in the upper crust and for retention mechanisms associated with underground repositories for toxic wastes. Metal scavenging into calcite has generally been established in the laboratory or in natural environments that cannot be unreservedly applied to conditions in deep crystalline rocks, an environment of broad interest for nuclear waste repositories. Here, we report a microanalytical study of calcite precipitated over a period of 17 years from anoxic, low-temperature (14 °C), neutral (pH: 7.4–7.7), and brackish (Cl: 1700–7100 mg/L) groundwater flowing in fractures at >400 m depth in granite rock. This enabled assessment of the trace metal uptake by calcite under these deep-seated conditions. Aquatic speciation modeling was carried out to assess influence of metal complexation on the partitioning into calcite. The resulting environment-specific partition coefficients were for several divalent ions in line with values obtained in controlled laboratory experiments, whereas for several other ions they differed substantially. High absolute uptake of rare earth elements and U(IV) suggests that coprecipitation into calcite can be an important sink for these metals and analogousactinides in the vicinity of geological repositories

Cerium Sequestration in Fractures in the Upper Kilometer of Granitoids, SE, Sweden

This study seeks to define geochemical processes governing the accumulation and sequestration of Ce in granitoidic fractures down to >700 m depth, revealing past intrusions of oxygenated waters. The fracture coatings (secondary mineral precipitates in open fractures) gathered from the study area (Laxemar, SE Sweden) are characterized by high levels of Ce (Fig. 1b) compared to host rock cocentration (average: 86 ppm, n=65) and show a striking feature of distinct positive Ce anomalies (CeWN*=1.21-3.95, n=8) in the uppermost 20 m of the bedrock (Fig. 1a). Cerium and Mn X-ray absorption spectroscopy (XAS) of selected fracture coatings, together with existing data (e.g. fracture mineralogy and groundwater chemistry), indicate that: (1) Ce(IV) occurs down to c.a. 70 m depth and is exclusively associated with Mn oxides which occur as todorokite and triclinic birnessite as suggested by Mn EXAFS spectra; (2) Since Mn is largely speciated as Mn2+ in the present bedrock groundwaters, the Ce(IV)-bearing Mn oxides most probably resulted from oxidative weathering of wall rock and fracture coating minerals when oxygenated waters intruded into the bedrock (down to several hundred meters depth) during deglacation events (>13000 BP); (3) Unlike other samples, clear XAS features of a poorly-crystalline hexagonalbirnessite-like phase and larger proportion of aqueous Mn2+ were observed in the sample with strikingly positive Ce anomaly (CeWN* = 3.95) (Fig. 1b) at the depth of 0.87 m, suggesting an ongoing dynamic accumulatinon of Ce(IV), i.e. dissolution and reprecipiation of Mn oxides while Ce(IV)- enriched residue largely remained

Cerium Sequestration in Fractures in the Upper Kilometer of Granitoids, SE, Sweden

This study seeks to define geochemical processes governing the accumulation and sequestration of Ce in granitoidic fractures down to >700 m depth, revealing past intrusions of oxygenated waters. The fracture coatings (secondary mineral precipitates in open fractures) gathered from the study area (Laxemar, SE Sweden) are characterized by high levels of Ce (Fig. 1b) compared to host rock cocentration (average: 86 ppm, n=65) and show a striking feature of distinct positive Ce anomalies (CeWN*=1.21-3.95, n=8) in the uppermost 20 m of the bedrock (Fig. 1a). Cerium and Mn X-ray absorption spectroscopy (XAS) of selected fracture coatings, together with existing data (e.g. fracture mineralogy and groundwater chemistry), indicate that: (1) Ce(IV) occurs down to c.a. 70 m depth and is exclusively associated with Mn oxides which occur as todorokite and triclinic birnessite as suggested by Mn EXAFS spectra; (2) Since Mn is largely speciated as Mn2+ in the present bedrock groundwaters, the Ce(IV)-bearing Mn oxides most probably resulted from oxidative weathering of wall rock and fracture coating minerals when oxygenated waters intruded into the bedrock (down to several hundred meters depth) during deglacation events (>13000 BP); (3) Unlike other samples, clear XAS features of a poorly-crystalline hexagonalbirnessite-like phase and larger proportion of aqueous Mn2+ were observed in the sample with strikingly positive Ce anomaly (CeWN* = 3.95) (Fig. 1b) at the depth of 0.87 m, suggesting an ongoing dynamic accumulatinon of Ce(IV), i.e. dissolution and reprecipiation of Mn oxides while Ce(IV)- enriched residue largely remained

Comparison of behavior and vector efficiency of Anopheles gambiae and An. arabiensis (Diptera : Culicidae) in Barkedji, a Sahelian area of Senegal

et al. 1989 , Lindsay et al. 1993 , Toure et al. 1996 . With a long-term goal of using transgenic mosquitoes with reduced malaria vector competences for control, data are being collected on intra-and interspecific gene flow within the An. gambiae complex (Lanzar0 et al. 1995 Generally, An. arabiensis is considered to have an anthropo hilic rate, life expectancy, and vectoGillies and Coetzee 1987). Because of the methods of capture, the methods of identification of species rial capacity P ower than An. gambiae (Coluzzi 1984

Comparison of behavior and vector efficiency of Anopheles gambiae and An. arabiensis (Diptera : Culicidae) in Barkedji, a Sahelian area of Senegal

The ecology, population dynamics, and malaria vector efficiency of #Anopheles gambiae and #An. arabiensis were studied for 2 yr in a Sahelian village of Senegal. Anophelines were captured at human bait and resting indoors by pyrethrum spray. Mosquitoes belonging to the #An. gambiae complex were identified by polymerase chain reaction. Of 26,973 females, #An. arabiensis represented 79% of the mosquitoes captured and remained in the study area longer than #An. gambiae after the rains terminated. There were no differences in nocturnal biting cycles or endophagous rates between #An. gambiae and #An. arabiensis$. Based on an enzyme-linked immunosorbent assay test of bloodmeals, the anthropophilic rate of these 2 vectors were both approximately 60$ and #An. arabiensis varied temporally. Despite similar behavior, the #Plasmodium falciparum circumsporozoite protein (CSP) rates were different between #An. gambiae$(4.1$ (1.3%). #P. malariae and #P. ovale only represented 4% of the total #Plasmodium identified in mosquitoes. Transmission was seasonal, occurring mainly during 4 mo. The CSP entomological inoculation rates were 128 bites per human per year for the 1st yr and 100 for the 2nd yr. Because of the combination of a high human biting rate and a low CSP rate, #An. arabiensis accounted for 63% of transmission. Possible origin of differences in CSP rate between #An. gambiae and #An. arabiensis is discussed in relation to the parity rate, blood feeding frequency, and the hypothesis of genetic factors. (Résumé d'auteur

Excess risk of urinary tract cancers in patients receiving thiopurines for inflammatory bowel disease: a prospective observational cohort study

IF 6.32International audienceBackgroundThe risk of urinary tract cancers, including kidney and bladder cancers, was increased in transplant recipients receiving thiopurines.AimTo assess the risk of urinary tract cancers in patients with inflammatory bowel disease (IBD) receiving thiopurines in the CESAME observational cohort.MethodsBetween May 2004 and June 2005, 19 486 patients with IBD, 30.1% of whom were receiving thiopurines, were enrolled. Median follow‐up was 35 months (IQR: 29–40).ResultsTen and six patients developed respectively kidney and bladder cancer. The incidence rates of urinary tract cancer were 0.48/1000 patient‐years in patients receiving thiopurines (95% CI: 0.21–0.95), 0.10/1000 patient‐years in patients who discontinued thiopurines (95% CI: 0.00–0.56) and 0.30/1000 patient‐years in patients never treated with thiopurines (95% CI: 0.12–0.62) at entry. The standardised incidence ratio of urinary tract cancer was 3.40 (95% CI: 1.47–6.71, P = 0.006) in patients receiving thiopurines, 0.64 (95% CI: 0.01–3.56, P = 0.92) in patients previously exposed to thiopurines and 1.17 (95% CI: 0.47–12.42, P = 0.78) in patients never treated with thiopurines. The multivariate‐adjusted hazard ratio (HR) of urinary tract cancer between patients receiving thiopurines and those not receiving thiopurines was 2.82 (95% CI: 1.04–7.68, P = 0.04). Other significant risk factors were male gender (HR: 3.98, 95% CI: 1.12–14.10, P = 0.03) and increasing age (HR after 65 years (ref <50): 13.26, 95% CI: 3.52–50.03, P = 0.0001).ConclusionPatients with IBD receiving thiopurines have an increased risk of urinary tract cancers. Clinically relevant excess risk is observed in older men

A Novel 8-Predictors Signature to Predict Complicated Disease Course in Pediatric-onset Crohn’s Disease: A Population-based Study

International audienceBackground The identification of patients at high risk of a disabling disease course would be invaluable in guiding initial therapy in Crohn’s disease (CD). Our objective was to evaluate a combination of clinical, serological, and genetic factors to predict complicated disease course in pediatric-onset CD. Methods Data for pediatric-onset CD patients, diagnosed before 17 years of age between 1988 and 2004 and followed more than 5 years, were extracted from the population-based EPIMAD registry. The main outcome was defined by the occurrence of complicated behavior (stricturing or penetrating) and/or intestinal resection within the 5 years following diagnosis. Lasso logistic regression models were used to build a predictive model based on clinical data at diagnosis, serological data (ASCA, pANCA, anti-OmpC, anti-Cbir1, anti-Fla2, anti-Flax), and 369 candidate single nucleotide polymorphisms. Results In total, 156 children with an inflammatory (B1) disease at diagnosis were included. Among them, 35% (n = 54) progressed to a complicated behavior or an intestinal resection within the 5 years following diagnosis. The best predictive model (PREDICT-EPIMAD) included the location at diagnosis, pANCA, and 6 single nucleotide polymorphisms. This model showed good discrimination and good calibration, with an area under the curve of 0.80 after correction for optimism bias (sensitivity, 79%, specificity, 74%, positive predictive value, 61%, negative predictive value, 87%). Decision curve analysis confirmed the clinical utility of the model. Conclusions A combination of clinical, serotypic, and genotypic variables can predict disease progression in this population-based pediatric-onset CD cohort. Independent validation is needed before it can be used in clinical practice