Lead migration in smelter-impacted deciduous and coniferous organic soil horizons based on a long-term in-situ implantation and laboratory column experiments

Abstract

Lead (Pb) contamination of forest soils constitute a serious threat against soil organisms and wildlife and the transport of previously deposited Pb from surface soils is of high environmental relevance. We studied the migration of Pb in highly contaminated deciduous and coniferous soils in a smelting area. A mixture of fermented/humified (F+H) deciduous and coniferous soil horizons highly contaminated by Pb smelting operations were implanted to the same horizon types in an area of low Pb atmospheric input for 6months. The implantation was accompanied with mechanical turbation, which caused changes in the soil parameters, i.e., CEC (cation exchange capacity), Corg. (organic carbon) or pH. The target soil horizons F+H (and partly A) were enriched with Pb, compared to background concentrations. The retention of Pb in smelter-impacted coniferous forest soil horizons L (raw litter), F+H, A (organo-mineral) and C (mineral) was studied using a column experiment.As a result of the Pb addition with a specific isotope composition (American galena) it was found that with the exception of the L horizon, all of the added Pb was completely retained in soil horizons. The isotope composition of Pb in eluate from the L horizon was represented by linear mixing between the original and added Pb sources. The majority of Pb would be eluted from the L horizon after less than 5years (using linear approximation).