Pseudo-first-order reaction of chemically and biologically formed green rusts with HgII and C15H15N3O2: effects of pH and stabilizing agents (phosphate, silicate, polyacrylic acid, and bacterial cells).

The kinetics of Hg(II) and methyl red (MR) reduction by hydroxycarbonate green rust (GR1) and by hydroxysulfate green rust (GR2) were studied in the presence of naturally occurring organic and inorganic ligands (phosphate, polyacrylic acid, bacterial cells, silicate). The reducing ability of biogenic hydroxycarbonate green rust (GR1bio), obtained after microbial reduction of lepidocrocite by Shewanella putrefaciens, was also investigated and compared to those of chemically synthesized GR1 and GR2 (GR1ab and GR2ab). Pseudo first-order rate constants (kobs) of Hg(II) reduction (at pH 7.0, 8.2, and 9.5) and MR reduction (at pH 7.0) were determined and were normalized to the structural Fe(II) content of GRs (kFeII) and to the estimated concentration of surface Fe(II) sites (kS). The kS values ranged from 0.3 L mmol(-1) min(-1) to 43 L mmol(-1) min(-1) for the Hg reduction, and from 0.007 L mmol(-1) min(-1) to 3.4 L mmol(-1) min(-1) for the MR reduction. No significant discrepancy between GRab and GRbio was observed in term of reactivity. However, the reduction kinetics of MR was generally slower than the Hg(II) reduction kinetics for all tested GRs. While a slight difference in Hg(II) reduction rate was noted whatever the pH values (7.0, 8.2, or 9.5), the reduction of MR was significantly affected in the presence of ligands. A decrease by a factor of 2-200, depending on the type of ligand used, was observed. These data give new insights into the reactivity of GRs in the presence of co-occurring organic and inorganic ligands, and have major implications in the characterization of contaminated systems as well as water treatment processes.

Non-adherence to standard treatment guidelines in a rural paediatric hospital in Sierra Leone.

SETTING: A rural paediatric hospital in Bo, Sierra Leone. OBJECTIVES: To assess the level of adherence to standard treatment guidelines among clinicians prescribing treatment for children admitted with a diagnosis of malaria and/or lower respiratory tract infection (LRTI), and determine the association between (non) adherence and hospital outcomes, given that non-rational use of medicines is a serious global problem. DESIGN: Secondary analysis of routine programme data. RESULTS: Data were collected for 865 children admitted with an entry diagnosis of malaria and 690 children with LRTI during the period January to April 2011; some patients were classified in both categories. Non-adherence to guidelines comprised use of non-standard drug regimens, dosage variations, non-standard frequency of administration and treatment duration. Cumulative non-adherence to guidelines for LRTI cases was 86%. For malaria, this involved 12% of patients. Potentially harmful non-adherence was significantly associated with an unfavourable hospital outcome, both for malaria and for LRTI cases. CONCLUSIONS: Overall non-adherence to standard treatment guidelines by clinicians in a routine hospital setting is very high and influences hospital outcomes. This study advocates for the implementation of routine measures to monitor and improve rational drug use and the quality of clinical care in such hospitals.

Non-Gaussian space-variant resolution modelling for list-mode reconstruction.

Partial volume effect is an important source of bias in PET images that can be lowered by accounting for the point spread function (PSF) of the scanner. We measured such a PSF in various points of a clinical PET scanner and modelled it as a product of matrices acting in image space, taking the asymmetrical, shift-varying and non-Gaussian character of the PSF into account (AMP modelling), and we integrated this accurate image space modelling into a conventional list-mode OSEM algorithm (EM-AMP reconstruction). We showed on the one hand that when a sufficiently high number of iterations are considered, the AMP modelling lead to better recovery coefficients at reduced background noise compared to reconstruction where no or only partial resolution modelling is performed, and on the other hand that for a small number of iterations, a Gaussian modelling gave the best recovery coefficients. Moreover, we have demonstrated that a deconvolution based on the AMP system response model leads to the same recovery coefficients as the corresponding EM-AMP reconstruction, but at the expense of an increased background noise.

Urban/peri-urban aerosol survey by determination of the concentration and isotopic composition of Pb collected by transplanted lichen Hypogymnia physodes.

In the northeastern part of France, around the city of Metz, lichens (Hypogymnia physodes) have been transplanted from a single reference site to five different sites: (i) the reference site itself, (ii and iii) two peri-urban sites, (iv) a site in the proximity of a highway, and (v) a final one close to an industrial site. The dynamics of two different system set-ups (one covered and one uncovered) were evaluated. Samples have been collected 14, 34, and 68 days after transplantation. Lead concentrations already accumulated in the thallus, and the corresponding Pb isotopic compositions have been measured by quadrupole-based ICP-mass spectrometry. A systematic difference between the two setups is found for Pb concentrations, with the higher concentrations measured in lichens from the uncovered devices. Lead concentrations in lichens from the covered devices were found to be lower than or equal to the original concentration. Also the Pb isotopic compositions show a systematic difference between the devices, with the Pb isotopic composition present in lichens from the uncovered device being more radiogenic. Substantial changes in the isotopic composition of Pb are recorded for lichens from the uncovered device (from about 1.15 up to 1.22 for the 206Pb/207Pb ratio), in some cases already after only 34 days of exposure. The increases in the Pb concentration and the 206pb/207Pb ratio and the differences between the devices are explained by hypothesizing that (i) different Pb sources give rise to a different size distribution of aerosol particles and (ii) in the lichens present in the covered setup, a part of the aerosol particles cannot be incorporated. Also the influence of the source of the aerosols to lichens after transplantation is evaluated and the potential influence of biological reactions is discussed.

Tracing source pollution in soils using cadmium and lead isotopes.

Tracing the source of heavy metals in the environment is of key importance for our understanding of their pollution and natural cycles in the surface Earth reservoirs. Up to now, most exclusively Pb isotopes were used to effectively trace metal pollution sources in the environment. Here we report systematic variations of Cd isotope ratios measured in polluted topsoils surrounding a Pb-Zn refinery plant in northern France. Fractionated Cd was measured in soil samples surrounding the refinery, and this fractionation can be attributed to the refining processes. Despite the Cd isotopic ratios being precisely measured, the obtained uncertainties are still large compared to the total isotopic variation. Nevertheless, for the first time, Cd isotopically fractionated by industrial processes may be traced in the environment. On the same samples, Pb isotope systematics suggested that materials actually used by the refinery were not the major source of Pb in soils, probably because refined ore origins changed over the 100 years of operation. On the other hand, Cd isotopes and concentrations measured in topsoils allowed identification of three main origins (industrial dust and slag and agriculture), assuming that all Cd ores are not fractionated, as suggested by terrestrial rocks so far analyzed, and calculation of their relative contributions for each sampling point. Understanding that this refinery context was an ideal situation for such a study, our results lead to the possibility of tracing sources of anthropogenic Cd and better constrain mixing processes, fluxes, transport, and phasing out of industrial input in nature.