The recovery of aerosol-sized microplastics in highly refractory vegetal matrices for identification by automated Raman microspectroscopy.

Ombrotrophic peatlands are fed uniquely by atmospheric inputs and therefore have much potential as temporal archives of atmospheric microplastic (MP) deposition, yet the recovery and detection of MP within an almost purely organic matrix is challenging. This study presents a novel peat digestion protocol using sodium hypochlorite (NaClO) as a reagent for biogenic matrix removal. NaClO is more efficient than hydrogen peroxide (H2O2). By using purged air-assisted digestion, NaClO (50 vol%) reached 99% matrix digestion compared with 28% and 75% by H2O2 (30 vol%) and Fenton's reagent, respectively. At a concentration of 50 vol% NaClO did however chemically disintegrate small amounts (<10 mass %) of polyethylene terephthalate (PET) and polyamide (PA) fragments in the millimeter size range. Observation of PA6 in natural peat samples, while not found in the procedural blanks, questions whether PA is fully disintegrated by NaClO. The protocol was applied to three commercial sphagnum moss test samples, in which MP particles in the range of 0.8-65.4 µm were detected by Raman microspectroscopy. The MP mass% was determined at 0.012% corresponding to 129 thousand MP particles/g, of which 62% were smaller than 5 µm and 80% were smaller than 10 µm, yet were accountable for only 0.4% (500 ng) and 3.2% (4 µg) of the total mass of MP, respectively. These findings underline the importance of the identification of particles Ø < 5 µm when investigating atmospheric MP deposition. The MP counts were corrected for MP recovery loss and procedural blank contamination. MP spike recovery following the full protocol was estimated at 60%. The protocol offers an efficient way of isolating and pre-concentrating most aerosol sized MPs in large quantities of refractory vegetal matrices and enables the automated µRaman scanning of thousands of particles at a spatial resolution on the order of 1 µm.

Strong temporal and spatial variation of dissolved Cu isotope composition in acid mine drainage under contrasted hydrological conditions.

Copper export and mobility in acid mine drainage are difficult to understand with conventional approaches. Within this context, Cu isotopes could be a powerful tool and here we have examined the relative abundance of dissolved (<0.22 µm) Cu isotopes (δ65Cu) in the Meca River which is an outlet of the Tharsis mine, one of the largest abandoned mines of the Iberian Pyrite Belt, Spain. We followed the chemical and isotopic composition of the upstream and downstream points of the catchment during a 24-h diel cycle. Additional δ65Cu values were obtained from the tributary stream, suspended matter (>0.22 µm) and bed sediments samples. Our goals were to 1) assess Cu sources variability at the upstream point under contrasted hydrological conditions and 2) investigate the conservative vs. non conservative Cu behavior along a stream. Average δ65Cu values varied from -0.47 to -0.08‰ (n = 9) upstream and from -0.63 to -0.31‰ downstream (n = 7) demonstrating that Cu isotopes are heterogeneous over the diel cycle and along the Meca River. During dry conditions, at the upstream point of the Meca River the Cu isotopic composition was heavier which is in agreement with the preferential release of heavy isotopes during the oxidative dissolution of primary sulfides. The more negative values obtained during high water flow are explained by the contribution of soil and waste deposit weathering. Finally, a comparison of upstream vs. downstream Cu isotope composition is consistent with a conservative behavior of Cu, and isotope mass balance calculations estimate that 87% of dissolved Cu detected downstream originate from the Tharsis mine outlet. These interpretations were supported by thermodynamic modelling and sediment characterization data (X-ray diffraction, Raman Spectroscopy). Overall, based on contrasted hydrological conditions (dry vs flooded), and taking the advantage of isotope insensitivity to dilution, the present work demonstrates the efficiency of using the Cu isotopes approach for tracing sources and processes in the AMD regions.

Laser-induced fluorescence spectroscopy of the (0, 0) Schumann-Runge band of O(2).

We report laser-induced fluorescence recording and identification of the R and P branches (J = 1-21) of the (0, 0) Schumann-Runge band of molecular oxygen, excited near 202 nm by a tunable pulsed laser beam (3-MW/cm(2) maximum intensity). The intensity of the excitation spectrum varies linearly with the density of the laser power. In the conditions of the experiment, the detection limit of ground-state O(2) molecules deduced from the R(5) line is ~10(15) cm(-3).

The radiographic signs of arthritis: a computer teaching module.

This article describes the steps involved in production of a computer teaching module on the radiographic diagnosis of arthritis. The module was part of a research project aimed at producing seven computer teaching modules. Several staff radiologists and residents were involved, as well as a consultant on medical education. A generic shell program was used as a frame for all seven modules. The author of each module then filled in the empty pages of the shell with the appropriate text and images, along with additional short program scripts. The module on the radiographic diagnosis of arthritis described and illustrated the basic radiographic signs of arthritis. Practice cases were also included, and interactive and hypermedia features were implemented. The modules were then evaluated by means of task list tests and interviews. The experience was judged to have been successful, although the amount of time spent by some authors was much more than expected.