Influence of pea and wheat growth on Pb, Cd, and Zn mobility and soil biological status in a polluted amended soil

In this paper we evaluated the effects of various amendments, notably zeolite, red mud (a by-product of
aluminium manufacturing) and lime on decreasing the bioavailability and phytotoxicity of Pb, Cd and Zn
present in a contaminated acidic soil (pH=4.2). Pisum sativum and Triticum vulgare were grown in a
glasshouse experiment on untreated-polluted (control) and amended soils and their yield and metal uptake
determined. The influence of plants on the total concentration and mobility of Pb, Cd, and Zn, and on several
soil microbiological and biochemical parameters was also evaluated and compared to unplanted (control and
amended) soils on which we have previously reported.
All the amendments enhanced plant yields significantly. Red mud and lime decreased Zn, Pb and Cd
availability to plants, whilst zeolite was efficient only at blocking Pb. Red mud in particular decreased heavy
metal uptake of pea and wheat by 60–34% (Pb), 79–80% (Cd), and 93–64% (Zn) respectively when compared
to the control plants.
After plant growth, Cd and Zn solubility in theamended soilswas significantly higher than in respective unplanted
soils. Likewise, the number of fast-growing heterotrophic bacteria and fungi was higher after pea and wheat
compared to bare soil, and thiswas irrespective of the treatment applied. These data togetherwith Biolog-derived
parameters (AWCD and richness) and enzyme activities (dehydrogenase, urease and â-glucosidase) also
suggested that pea rhizodeposits, in the different soils, were either more abundant or more readily-available to
soil bacterial communities compared to wheat rhizodeposits.