Space-resolved determination of the mineral nutrient content in tree-rings by X-ray fluorescence

X-ray fluorescence spectroscopy (XRF) offers rapid, multi-elemental, low cost and non-destructive elemental analysis. Different studies have used this technique to investigate distribution and concentration of essential and deleterious elements in vegetation. Special emphasis has been recently placed on the key aspects concerning sampling processes, laboratory protocols and calibration methods for quantitative analysis. The aim of the present study was to develop a quantitative methodology to determine the nutrient content in Pinus taeda tree-rings by XRF. Using a 1 mm X-ray excitation beam from a Rh X-ray tube at 30 kV and 600 μA, and dwell time of 20 s, we present calibration curves for P, S, K, Ca, Mn and Fe based on multi-elemental standard addition using wood matrix of 17-year-old Pinus taeda trees. Satisfactory recoveries of our XRF approach for Ca, P, Mn, S and K (<115%), and tolerable for Fe (123%) were obtained compared to inductively coupled plasma optical emission spectrometry results. The non-destructive and quantitative XRF method allows assessing annual element concentrations of P. taeda trees, in order to provide tools for monitoring the nutrient dynamic in an experimental plantation. Furthermore, a method for elemental quantification based on multi-elemental standard addition using wood matrix is described as a useful procedure for future applications.