BIOAVAILABILITY OF HEAVY-METALS AND ABUNDANCE OF ARBUSCULAR MYCORRHIZA IN A SOIL POLLUTED BY ATMOSPHERIC DEPOSITION FROM A SMELTER

The bioavailability of heavy metals (Cd, Zn, Pb, Cu) and the abundance of arbuscular mycorrhiza (AM) were studied in two agricultural fields close to a Pb-Zn smelter and three fields outside the pollution zone all cultivated with maize (Zea mays L.). Metal extractability with eth ylenediaminetetraacetic acid (EDTA)NH4OAc and Ca(NO3)(2), plant metal uptake, and mycorrhizal parameters (spore number, root colonization) w ere assessed at two growth stages (six-leaf and maturity). Despite reg ular liming, the availability of Cd, Zn, and Pb was markedly higher in the two metal-polluted fields than in the three uncontaminated fields . However, the AM abundance was not correlated with metal availability . Root colonization and spore numbers in the metal polluted fields wer e relatively high, though at plant maturity the former was significant ly lower than in one of the uncontaminated fields. The very low AM abu ndance in the two other unpolluted fields was related to other factors , particular soil and plant P status and soil pH. AM root colonization did not substantially prevent plant metal accumulation, since the met al concentrations in maize grown on the polluted fields strongly excee ded normal values, and for Cd and Pb reached the limits of toxicity fo r animal feed.