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[en] Highlights: • Development of an analytical model for assessing the well-mixing length of a tracer in a duct airflow. • Validation on data from in situ experiments. • Model simplification for proposing correlations more suitable for the industrial issue. - Abstract: The aim of this study is to propose an analytical model for assessing the well-mixing length of a tracer in a ventilation duct. The first part of the article is devoted to describe an experimental bench developed for validating the proposed model. This bench allows to follow the evolution of a tracer injected at a source point in the center of a duct by using an original optical measurement technique. In a second part, an analytical model for the spatial evolution of a tracer concentration in a circular duct is developed, taking into account an eddy viscosity model. The difficulty for applying this model to industrial cases led us to propose a simplified version that can be used for a non-dimensional distance greater than 20 diameters. The latter was then inverted in order to access to two criteria: the coefficient of variation in the duct section and the difference between the local measured concentration and the expected homogeneous concentration. Each one has its interest depending on whether a global information on the duct section or a local information (on the axis for example) at a given distance is required.
[en] Previous research has documented that total mercury concentrations ([THg]) are lower in anadromous Arctic charr than in non-anadromous conspecifics, but the two life-history forms have rarely been studied together. Here, data from nine pairs of closely-located anadromous and non-anadromous Arctic charr populations were used to explore the impact of biological and life-history factors on individual [THg] across a range of latitudes (49–81° N) in eastern Canada. Unadjusted mean [THg] ranged from 20 to 114 ng/g wet weight (ww) in anadromous populations, and was significantly higher in non-anadromous populations, ranging from 111 to 227 ng/g ww. Within-population variations in [THg] were best explained by fish age, and were often positively related to fork-length and δ15N-inferred trophic level. Differences in [THg] were not related to differences in length-at-age (i.e., average somatic growth rate) among populations of either life-history type. Mercury concentrations were not related to site latitude in either the anadromous or non-anadromous fish. We conclude that the difference in Arctic charr [THg] with life-history type could not be explained by differences in fish age, fork-length, trophic position, or length-at-age, and discuss possible factors contributing to low mercury concentrations in anadromous, relative to freshwater, fish. - Highlights: ► Total mercury concentrations ([THg]) were measured in 9 co-located anadromous and non-anadromous Arctic charr populations. ► Mean [THg] in non-anadromous populations exceeded mean [THg] in spatially paired anadromous populations. ► Among-individual variation in [THg] was best explained by fish age. ► The lower [THg] in anadromous fish could not be explained by differences in age, fork-length, trophic level, or growth rate. ► Variations in Arctic charr [THg] were independent of latitude (49–81° N) in eastern Canada
[en] Limited information exists on the exposure of benzophenone (BP)-type UV filters (i.e., sunscreen compounds) in children, adults, and pregnant women in China. In this study, we determined the concentrations of five BP derivatives, BP-1, BP-2, BP-3, BP-8, and 4OH-BP in urine (n = 101) as well as paired specimens of blood and urine (n = 24 pairs) collected from adults; in matched maternal and fetal cord blood (n = 20 pairs) collected from pregnant women; and in blood collected from children (n = 10). 4OH-BP, BP-1, and BP-3 were found in 61%, 57%, and 25%, respectively, of the urine samples analyzed. 4OH-BP was found in all blood samples; BP-3 was found more frequently in the blood of adults (83%), followed, in decreasing order, by pregnant women (35%) and children (30%). Among all adults, urinary BP-3 concentrations were significantly (p < 0.001) positively correlated with urinary BP-1 concentrations. Nevertheless, no significant correlations were found between urinary concentrations of BP-3 (or BP-1) and 4OH-BP. Our results suggest that human exposure to BP-3 and BP-1 is related, whereas 4OH-BP originates from a discrete source. Females had higher urinary concentrations of BP-3, BP-1 and 4OH-BP than males. The distribution profiles of BP-1 and its parent compound (i.e., BP-3) in urine decreased with increasing age of donors (p < 0.05). The ratio of concentrations of BP-3 between blood and urine was 0.21 in adults, which was significantly lower than that for 4OH-BP (0.36). The concentration ratio of BPs between cord blood and maternal blood was higher for 4OH-BP (0.61) than that for BP-3 (0.48), which suggested greater trans-placental transfer potential of 4OH-BP. This is the first study to document the occurrence of BPs in paired urine and blood, and in matched maternal and fetal cord blood. Highlights: • Benzophenone (BP) concentrations are determined in paired blood and urine for the first time. • BP-3 and 4OH-BP partition preferentially into urine. • Cord to maternal blood ratios of BP-3 and 4OH-BP were 0.48 and 0.61, respectively. • Exposure to BPs was significantly associated with sex
[en] Arsenic (As) is extremely toxic to living organisms at high concentration. In aquatic systems, As exists in different chemical forms. The two major inorganic As (iAs) species are AsV, which is thermodynamically stable in oxic waters, and AsIII, which is predominant in anoxic conditions. Photosynthetic microorganisms (e.g., phytoplankton and cyanobacteria) take up AsV, biotransform it to AsIII, then biomethylate it to methylarsenic (MetAs) forms. Although AsIII is more toxic than AsV, AsIII is much more easily excreted from the cells than AsV. Therefore, majority of researchers consider the reduction of AsV to AsIII as a detoxification process. The biomethylation process results in the conversion of toxic iAs to the less toxic pentavalent MetAs forms (monomethylarsonate; MMAV, dimethylarsonate; DMAV, and trimethylarsenic oxide; TMAOV) and trimethylarsine (TMAOIII). However, biomethylation by microorganisms also produces monomethylarsenite (MMAIII) and dimethylarsenite (DMAIII), which are more toxic than iAs, as a result of biomethylation by the microorganisms, demonstrates the need to reconsider to what extent As biomethylation contributes to a detoxification process. In this review, we focused on the discussion of whether the biotransformation of As species in microorganisms is really a detoxification process with recent data
[en] Highlights: Efficient dimerization of protonated ellipticine (EH+) is found in water. The long-lived fluorescence decay component of EH+ in H2O is due to dimer emission. Dimerization is enthalpically driven and entropically disfavored process. Dimer formation must be taken into account even at μM EH+ concentrations. Absorption and fluorescence spectroscopic measurements, as well as isothermal calorimetric titrations showed that the biexponential decay kinetics of protonated ellipticine (EH+) fluorescence in water originates from dimerization. Due to the high equilibrium constant for the association of two EH+ and the intense fluorescence of the dimer, deviation from the exponential emission intensity decay commences below micromolar concentrations. Dimerization must be taken into account when EH+ concentration is determined by spectrophotometry, and when EH+ binding to substrates are studied. The molar absorption coefficients of the monomer and dimer were determined.
[en] Concentrations of cadmium and lead were measured in liver and kidneys of Mallard (n = 60) and Coot (n = 50). Free living birds were collected by hunters in years 2006–2008 in the area of fishponds near Zator in southern Poland. Age group was determined according to the appearance of the plumage (Mallards) and iris color (Coot). Concentrations of metals were measured with ET-AA spectrometer. Among all birds specimens with negligible (n = 5) and high concentrations (Mallards n = 18 and Coots n = 17) of cadmium and lead were chosen for further analysis. Histopathological alterations were observed, ranging from circulatory disturbances, retrogressive changes, inflammations to leukocytic infiltration in liver and kidney. They dominated among birds with the highest concentrations of metals. The control group of birds was characterized by a very small number of mentioned lesions. Probably the higher cadmium and lead concentrations in tissues are co-factors in the development of lesions. - Highlights: ► High levels of Cd and Pb were found in liver and kidneys of Mallard and Coot. ► Lower concentrations were found in young birds. ► Amount of metals exceeded the safety threshold established for edible poultry. ► Histopathological alterations were found in studied tissues. ► Lesions in birds with the highest concentrations of metals were numerous
[en] Effects of low-level cadmium (Cd) exposure during early life on fetal growth remain unclear. Our aim was to evaluate whether Cd exposure in maternal urine and umbilical cord blood was associated with birth size parameters. A birth cohort study including 1073 mother-newborn pairs was conducted from 2009 to 2010 in an agricultural population in China. Cd concentrations were analyzed in both cord blood and maternal urine. Generalized linear models were performed to determine associations between maternal and neonatal exposure to Cd and birth indicators, including birth weight, length, head circumference and ponderal index. The median (25th to 75th percentile) value of Cd concentration in maternal urine and umbilical cord blood was 0.19 (0.08, 1.00) μg/L and 0.40 (< LOD ~ 0.62) μg/L, respectively. After adjusting for potential confounders, Cd concentration in cord blood was significantly negatively associated with ponderal index at birth [β = − 0.06 g/cm3, 95% confidence interval (CI): − 0.11, − 0.02; p < 0.01]. Considering sex difference, significant reduction in ponderal index was only observed in males (β = − 0.06 g/cm3, 95%CI: − 0.11, − 0.02; p < 0.01), but not in females (β = − 0.03 g/cm3, 95%CI: − 0.07, 0.01; p = 0.18) (p for interaction term = 0.24). Additionally, no significant associations were observed between maternal urinary Cd levels and birth outcomes. Our findings suggest that adverse effects of neonatal exposure to Cd on fetal growth are of considerable public health importance. - Highlights: • Cd concentrations were determined in both umbilical cord blood and maternal urine. • Associations between Cd exposure and birth outcomes were explored in 1073 mother-newborn pairs. • Cord blood Cd concentrations were negatively associated with ponderal index of neonates. • Adverse effects of Cd exposure on birth outcomes differed by neonatal sex.
[en] A snapshot sample of Arctic charr (Salvelinus alpinus) from Heintzelman Lake (81°42′N, 66°56′W), Ellesmere Island, Canada was used to elucidate the biological and life-history factors potentially influencing individual total mercury (THg) concentrations. Migratory history was significant, with anadromous fish having a lower mean THg concentration (64 μg/kg ww) than the non-anadromous Arctic charr (117 μg/kg ww). The increase in individual THg concentration with age was shown to be independent of length-at-age when large and small individuals within the same age groups were compared. Similarly, the diets of individual Arctic charr were comparable regardless of size, and there was no apparent ontogenetic shift in diet that could explain differences in length-at-age or THg concentration among fast- and slow-growing groups of fish (i.e., fish of the same age but differing sizes). Maturity state was also not related to THg concentration, but appears to be related to differences in length-at-age, with slow-growing fish allocating more energy to reproduction than fast-growing conspecifics. The differences in THg concentration among individual Arctic charr were best explained by fish age. We suggest that the increase in mercury concentration with age can be altered by a shift in diet (e.g., to piscivory) or habitat (e.g., anadromy), but is otherwise unaffected by changes in size or length-at-age. -- Highlights: ► Total mercury concentrations ([THg]) were measured in Arctic charr from a single lake in the Canadian high Arctic. ► Anadromous Arctic charr had a significantly lower mean [THg] (64 μg/kg ww) than the non-anadromous fish (117 μg/kg ww). ► Length-at-age (i.e., average somatic growth rate) was not related to mean [THg] when same-age groups were compared. ► Prey resource use, determined by δ13C and δ15N isotopes and gut contents, was similar among fast- and slow-growing fish. ► Maturity state was not related to [THg], but the slow-growing group had a greater proportion of current year spawners.
[en] Seven trees were felled in the Briansk region in 1997. The trees were sectioned for sampling, both at different heights and according to year rings, and samples were analysed for content of 137Cs. In general, the specific activity of 137Cs was much higher in the fresh parts of the tree (needles, leaves and twigs) than in the core wood. The year ring study showed that 137Cs had penetrated deeply in to the trunk, and no peak was detectable in the year ring corresponding to the Chernobyl accident in 1986. The specific activity in the trunk wood had a maximum at the height corresponding to the growth years at approximately 1986. Neutron activation analysis was used to analyse for stable Cs. The results showed that the relationship between concentrations of 137Cs and stable caesium is much higher in the newer parts of growing trees than in the older parts. Together with a tendency of inward migration this leads to a preliminary conclusion that the 137Cs activity will continue to accumulate in the core wood
[en] Polyhydroxyalkanoates (PHA) are biopolymers that can be an alternative against conventional plastics. The study reported herein evaluated the enrichment of a mixed microbial culture (MMC) operated under feast/famine regime and different pHs in a sequencing batch reactor (SBR) using acetate as sole carbon source to produce polyhydroxyalkanoates (PHAs). The enrichment step was evaluated at controlled pH of 7.5 and also without pH control (averaged value of 9.0). The acetate uptake rate (− qS) of both enrichments at the end of the experimental period exhibited similar behaviour being about 0.18 Cmol Ac Cmol X−1 h−1 and 0.19 Cmol Ac Cmol X−1 h−1 for SBR-A and SBR-B, respectively. However, the PHA-storing capacity of the biomass enriched without pH control was better, exhibiting a maximum PHA content of 36% (gPHA g−1 VSS) with a PHA production rate (qPHA) of 0.16 Cmol PHA Cmol X−1 h−1. Batch experiments were performed to evaluate PHA-storing capacity of the enriched culture at different pHs and nutrients concentrations. In the pH experiments (without nutrient limitation), it was found that in the absence of controlled pH, the enriched biomass exhibited a PHA content of 44% gPHA g−1 VSS with − qS and PHA to substrate yield (YPHA/Ac) of 0.57 Cmol Ac Cmol X−1 h−1 and 0.33 Cmol PHA Cmol Ac−1, respectively. Regarding the experiments at variable nutrients concentration (pH ranging 8.8 to 9.2), the results indicate that the PHA content in the enriched biomass is significantly higher being around 51% gPHA g−1 VSS under nitrogen limitation. This work demonstrated the feasibility of the enrichment of a MMC with PHA storage ability without pH control. Results also suggest that better PHAs contents and substrate uptake rates are obtained without controlling the pH in the accumulation step. Finally, this work also highlights the importance of understanding the role of nutrients concentration during the accumulation step. - Highlights: • Mixed microbial culture enrichment for PHA production was achieved without pH control under feast/famine regime. • Higher PHA productions were obtained at pH values ≥ 7.5. • A PHA content of 51% was obtained with N-limited conditions. • PHA content was more than three times higher for P-limited conditions than when it was in excess.