Variations of trace element contents within single tree rings

X-ray fluorescence was used to measure variations in relative and absolute trace-element concentrations within single tree rings taken from a 32-year-old pine tree near a coalburning power plant. The Zn/Cu ratio was found to have a constant value, both along individual rings and between different rings. The Fe, Ca and 8 concentrations varied in a single tree ring and depended on the age of the tree. The results indicate that the variations in concentrations of elements along a single ring are caused by heterogeneous tree tissue structure.