Effect of neutralising substances on the total content of trace elements in soil contaminated with zinc

Trace elements are particularly important not only for plants but also for soil organisms. However, excessive concentrations of trace elements can be toxic to organisms, in which they can cause various disorders. Application of mineral and organic substances increases the soil sorption capacity and reduces the uptake of heavy metals by plants. A study was undertaken to determine the content of trace elements in zinc-polluted soil after an application of some neutralising substances. Soil was polluted with zinc in doses of 0, 150, 300 and 600 mg kg-1 of soil. To reduce the negative impact of zinc, the substrate was amended with compost (3%), bentonite (2%) and zeolite (2% relative to the soil mass). Soil pollution with Zn and application of neutralising substances significantly affected the soil content of trace elements. In the series without neutralising substances, the increasing soil pollution with Zn caused an increase in the content of this metal and Pb, but a decrease in the content of Ni, Cu and Cd, compared with the control treatment (without Zn). Bentonite and compost reduced the content of Zn and Pb, particularly in the treatments most severely polluted with Zn. All the tested substances caused a decrease in the soil content of Ni, Cu and Co compared with the series without neutralising substances. Zeolite had the strongest effect on the content of Cu and Co, whereas compost affected most strongly the content of Ni in soil. Application of bentonite and zeolite contributed to an increase in the soil content of Cr and Fe, but the effect of bentonite was significantly stronger than that of zeolite. Moreover, zeolite resulted in a small significant rise in the soil content of Pb compared with the control.