RESPONSE OF BLUE SPRUCE (PICEA-PUNGENS) TO MANGANESE POLLUTION FROM MMT

The use of methylcyclopentadienyl manganese tricarbonyl (MMT) in unleaded gasoline has become a source of manganese (Mn) contamination to which urban ecosystems are exposed. The potential of coniferous trees as spatial and chronological indicators of Mn pollutation was investigated. Manganese concentrations in xylem from blue spruce (Picea pungens) growing near (high-exposure site) and far (low-exposure site) from a road were measured as a function of the year of wood formation. Exchangeable Mn content, which is the soil fraction most readily available for uptake by trees, was also measured in the soils of both sectors. The results of the soil analysis show that exchangeable Mn concentrations are about 10 times higher in soils exposed to contamination (p < 0.0005), in comparison with the concentrations found in soils weakly exposed. However, the Mn concentrations in the trees near the road were not significantly different from those in the reference trees (p > 0.05). Therefore, it appears that blue spruce is not sensitive to soil Mn contamination arising from the use of MMT in gasoline.