DTPA SOIL EXTRACTABLE AND PLANT HEAVY-METAL CONCENTRATIONS WITH SOIL-ADDED CD TREATMENTS

Seed of six plant species native to a heavy metal contaminated urban site in northwestern Indiana was collected and grown in soil from the urban site and similar soil collected from a relatively uncontaminated rural site. The rural soil was amended with CdCl2. Plant tissue and soils were analyzed for Cd, Zn, Pb and Cu. Soil extractable Cd concentrations increased with increasing soil-added Cd levels, a larger proportion of the added Cd becoming extractable as the soil addition level increases. Soil Cd additions also affected the levels of extractable Zn, Pb, and Cu. Soil extractable Cd levels were not, however, influenced by the plant species grown in the soil. Differences were noted between the two soils for extractable Cd concentrations, but were much smaller than the differences noted in plant Cd concentrations between the two soils. Plant Cd levels increased linearly with soil Cd addition levels. Composites had higher Cd concentrations than other herbs or grasses tested. Total Cd content of above-ground plant biomass also increased with soil Cd addition levels, but with a non-linear, upper limit type response. Rudbeckia hirta, a composite, had similar Cd concentrations in both top and root biomass, indicating that for this species Cd is not immobilized in the root systems as for other species. © 1979 Martinus Nijhoff, The Hague.