Calibration of an Energy Dispersive X-Ray Fluorescence facility for the analysis of environmental samples

Aim of this work is the calibration of an Energy Dispersive X-Ray Fluorescence facility for the analysis of solid environmental samples such as soil, ashes produced in coal-fired power plants and sediments. The main components of the facility are: a 50W (4-50kV, 0-1mA) OXFORD X-ray tube with Mo target and a CANBERRA Super-SiLi x-ray detector with 160eV resolution @ 5.9keV. For the x-ray spectra collection an AMPTEK pocket MCA connected to a PC is used. The x-ray spectra are analyzed with the in-house developed computer code SPUNAL. For the sample preparation a 20t hydraulic press is used to compress the materials under analysis mixed with a binder additive, inside 40mm diameter aluminum cups. A thorough investigation has been performed for the determination of the best source-target-detector geometry and the ultimate irradiation conditions - in terms of high voltage, current and filtering - for the detection of the various elements of interest. For the efficiency calibration of the facility several Certified Reference materials were used from NIST (Montana soil nr. 2710, 2711, San Joaquin soil nr. 2709, Coal fly ash 1633b) and from IAEA (Soil nr. 7, Lake sediment nr.1). For each different type of material a response factor (ppm/cps) was determined for each element that was detected. Repeatability and reproducibility experiments were conducted for each Reference material. The calibration allowed for the quantitative determination of the following elements: Ca, Ti, V, Mn, Fe, Cu, Zn, Pb, Rb, Sr, Ba, Cs. Furthermore, Arsenic may be indirectly determined taking into consideration the interference of its KΞ± x-rays with the LΞ± x-rays of Pb. For most elements the detection limit is about 100ppm.

The facility is used for the determination of the elemental concentration of soil and sediment samples from industrial areas of the Attica district, as well as ash samples from lignite and biomass fired power plants.