Trace metal levels in tree barks as indicators of atmospheric pollution

Barks of six species of trees were sampled at thirty-nine different locations in Ibadan, Nigeria and were analysed for the trace metals lead, cadmium, cobalt, copper, zinc, manganese, and iron. Lead levels in barks from areas with relatively high traffic density were generally higher than lead levels in barks from areas with low traffic density. The lead level recorded in the high traffic density areas, 40–140 μg/g, is low compared to values reported for barks of trees along busy roads in developed countries. For the other metals, no correlation with traffic density was observed.