Dendroanalysis: a tool for biomonitoring environmental pollution?

Trees of temperate regions usually form visible annual growth rings, which can be dated accurately. It is therefore possible to collect wood samples o f different age and analyse their heavy metals content in order to get a ch ronological record of trace elements pollution in the tree's environment. T his method of retrospective biomonitoring was called dendroanalysis. A basi c assumption of dendroanalysis is the stability of the mineral distribution patterns, i.e. once the elements are stored, no significant mobility shoul d occur. Additionally, neighbouring trees growing in the same environment s hould show similar radial element patterns. While some studies presented go od correlations between radial distributions of heavy metals in tree rings and temporal records of pollution from industry or traffic, others failed i n using dendroanalysis as a chronological record of pollution. Probably som e elements can move at a certain rate in radial direction through the ray p arenchyma cells. In this way the radial element distributions are subsequen tly changed. Growth rates of tree rings can also influence the concentratio ns of elements in wood. During periods of slow growth higher concentrations of elements can be found in the wood. Therefore, radial distribution patte rns of heavy metals in tree rings should be used with caution as a tool for retrospective biomonitoring of environmental pollution. (C) 1999 Elsevier Science B.V. All rights reserved.