The levels of twelve elements most of which are either considered essential to plant growth or have been detected in air filter
samples in an air pollution survey, have been monitored in three transverse sections of trees, two elms (ring porous trees)
and one cedar (a conifer). Two dimensional distributions of these elements around the tree rings of the section and radially
from ring to ring, have been obtained to see if tree rings can be analysed for use as a record of historical pollution.