EVALUATION OF BLACK SPRUCE (PICEA-MARIANA) AS A BIOINDICATOR OF ALUMINUM CONTAMINATION

The aim of this work is to evaluate black spruce (Picea mariana) as an indicator of environmental aluminum contamination. The territory stud ied extends to a radius of 100 km around the Alcan aluminum refinery i n Jonquiere, Quebec, Canada. Samples of wood were taken from the trunk s of trees at 26 sites at distances of 5, 10, 20, 30, 40, 50 and 100 k m from the refinery. Five trees were sampled at each site. Each sample was cut into 25 pieces corresponding to 50 yr growth. These were anal yzed for aluminum by neutron activation. Soil samples taken near the b ases of the trees were also analyzed and significant variations in exc hangeable aluminum were observed as a function of direction from the r efinery and distance. The pH of organic and mineral horizons show no s ignificant difference. Exchangeable aluminum increased with soil acidi ty. The most contaminated sites showed important correlations (r2 = 0. 73) between exchangeable aluminum in soil and aluminum in bark. We obs erved greater aluminum concentrations in tree rings corresponding to t he last 20 yr, especially at sites directly exposed to environmental c ontamination along prevailing winds. In conclusion, black spruce appea rs to be a better spatial than chronological indicator of aluminum con tamination.