Dendroanalysis: The study of trace and minor elements in trees.

The work described in this thesis attempts to determine the degree of retention of essential, non-essential and/or pollutant, trace and minor elements that are taken into a tree's system, in order to evaluate the usefulness of the elemental analysis of tree rings (dendroanalysis) as a means of investigating past environmental conditions. A list of elements that are of interest in such a study, is compiled. The concentrations of many of these elements in a wood matrix can be measured by using the multi-elemental analytical technique neutron activation, which is the method employed for the majority of analyses performed in this work. A brief outline of relevant tree physiology is given; and two sampling techniques, the irradiation conditions and the computer assisted analysis of results, are described. Preliminary results are obtained by determining the concentrations of up to eighteen elements in an elm and an oak tree from the Guildford area, and a cedar tree that had been situated in the suburbs of Reading. Ring by ring variations of many of the elemental concentrations are plotted out, with particular reference to the physiologically different areas in which the growth rings are situated. From these results, and others reported in this thesis, it appears that the natural biochemical processes in a tree can alter some of the original elemental concentrations of the tree rings. A three-dimensional analysis of a second elm from Guildford has been performed, and the results from the two Guildford elms and a third elm tree are compared to evaluate the effects of 'Dutch' elm disease, and an associated secondary infection, on the elemental analysis of elm trees. Four elm trees from Stoke-on-Trent (a city which has had high levels of atmospheric pollution in the past) are analysed and compared with the results from the first Guildford elm. Other methods that might be used for the elemental analysis of tree rings are also investigated, and some suggestions for future work in the field of dendroanalysis, are made