Applications of a 10 um spot size laboratory micro-XRF to environmental sciences

X-ray spectromicroscopy coupling micro-XRF and X-ray microscopy has been developed on synchrotron source more then ten years ago. At the laboratory scale such techniques were more confidential. Due to recent developments in terms of X-ray source and especially in terms of focalization (capillaries, Zone plates...) laboratory micro-XRF equipment have been commercialized in the last 4 or 5 years (Horiba-Jobin Yvon, EDAX, Shimadzu, COX...). Such laboratory instrument are not only limited to material science but they are known to be very efficient in geosciences and environmental science. In these last domains, the main issue is to assess the transfer of pollutant and/or to localise spatially some element(s) of interest. Elements are often present at low concentration and can not be detected by SEM-EDX. Otherwise,the studied samples are generally disordered, heterogeneous, and/or fragile but X-ray spectromicroscopy is a non destructive method and allows In the present work we will present and discuss the advantages and limitations of micro-XRF/microscope (XGT-5000, Horiba-Jobin-Yvon ) equipped with of a 10 µm spot size on different environmental applications.The X-ray beam is generated with a Rh X-ray tube at an acceleration voltage of 15 to 50 keV with a current adjustable up to 1 mA.The X-ray beam is focused with an X- ray guide tube, whose inner diameter is 10 µm, producing a finely focused and high-intensity X-ray beam. The latter is calibrated by measuring the absorption of a tungsten wire of 5 µm thickness, scanned through the beam. X-ray emission from the irradiated sample is detected with an Energy-Dispersive X-ray (EDX) spectrometer equipped with a liquid-nitrogen-cooled high-purity Si detector. The resolution of the detector is 145 eV at the Mn K(alpha) emission line. Furthermore, a scintillator enables transmission measurements. Many scientific topics benefit from the application of our micro-XRF. For example, the impact of waste reuse can be assessed by determining the transfer mechanism of metal pollutants. Recent results concerning by-products from steel industry indicate that vanadium is released from the initial matrix. Lab-installed m cro XRF helped to identify the mineral bearing phases of V. First results concerning the composition of marine sediments are very promising. For example, the ultra-high resolution analysis of a partly laminated sediment core from the Arabian Sea reveals element variabilities at the seasonal scale (100 µm scale).This helps to determine the extend and exact timing of individual phase transitions with respect to past climatic and oceanic changes. Micro-XRF can also be very helpful to identify and classify extra terrestrial material by analyzing e.g. Fe/Ni and Fe/Si ratio.This technique has been successfully applied to meteorites and m crometeorites. Indeed such materials are rare,fragile and very small (down to a few tens of µm in size for micrometeorites). One needs a non destructive technique. Moreover the surface is generally altered and SEM-EDX failed to discriminate samples. Lab-micro-XRF appears as a very interesting routine tool.