Tree tolerance to heavy metals

 

Summary

Tree survival, growth and physiological function can be affected detrimentally by many contaminants. The upper critical concentration at which such effects take place varies for both tree species and contaminant. However, our research together with other published data clearly show that trees can survive contaminant levels far greater than those laid down in current guidelines:

• High concentrations of potentially toxic elements (PTEs) affect root growth.  Roots typically accumulate significantly higher amounts of metals than the above-ground biomass.
   
• Lead, arsenic, cobalt, chromium, mercury, and tin remain mainly in the root system whilst copper, nickel, and selenium have an intermediate mobility.
   
• In contrast, cadmium and zinc are readily translocated within the tree and become concentrated in the above-ground biomass.

Research overview

Our research is focusing on determining optimum species choice for planting in metal contaminated soils. We have developed models of metal (lead, copper, cadmium, zinc) tolerance for a range of tree species and are currently field testing whether these models are robust enough to make predictions of species suitability at a site specific level.