The effect of brown coal derived preparation on bioavailability of heavy metals contaminated soils
Alina Maciejewska , Jolanta Kwiatkowska-Malina
AbstractContaminants such as heavy metals, radionuclides, organic pollutants and their mixtures are threatening ecosystems and human health by their impact on water and food quality. Therefore, decontamination of soils and/or reduction of contaminants bioavailability and phytotoxity are priority topics in environmental legislation. The release of trace metals in biologically available forms, as a result of human activity, may impair or alter both natural and man-made ecosystems. Heavy metals in soils may be present in several forms regarding their degree of solubility, as: (i) dissolved, (ii) exchangeable, (iii) structural components of the lattices in soils and (iv) insolubly precipitated with other soil components. The adsorption and desorption of heavy metals can be associated with soil properties, including: pH, organic matter cont ent, cation exchange capacity (CEC), oxidation-reduction status (Eh), as well as the contents of: clay minerals, calcium carbonate, Fe and Mn oxides. Among them, soil pH and organic matter content were found to play the most important role in bioavailability, due to their strong effects on solubility and speciation of heavy metals in soil. To reduce the risks associated with introduction of heavy metals in the food-chain and their leaching to surface and groundwater, it is very important to know the interaction between metal ions, soil organic matter, plants and water bodies. In this st udy we assumed that the organic matter present in the brown coal-derived preparation called “Rekulter” after its addition to soil, would decrease the uptake of heavy metals by plants, by forming complex compounds and making the metals immobile. The formation of chelats will cause an exclusion of heavy metals at the stage of their transfer from soil to plants. The experiment was carried out on Haplic Luvisols formed from loamy sand (WRB), in field pots sank into the ground. The “Rekulter” was added to the soil in the amounts of: 180, 360 and 720 g per pot, which is equivalent to: 5, 1 0 and 20 tons .of organic carbon per ha, respectively. Not amended soil was used as a control. The soil was mixed up with the liquid form of salts: cadmium as Cd(NO3)2, lead as Pb(CH3COO)2 and zinc as ZnSO4, which led to the following contents of heavy metals: Zn = 90.0; Pb = 60.4; Cd = 0.80 (mg.kg-1 of soil), as examined by mineralization in 2M HNO3. Biovailable forms of heavy metals were determined in EDTA whereas content of Pb, Zn and Cd in the soil samples - using ICP-AES. Single application of the Rekulter at increasing doses resulted in decreased solubility (mobility) of heavy metals in soil, and consequently their bioavailability. The contents of Zn, Pb, Cd in 2M HNO3 in soil 4 years after the “Rekulter” application have not changed significantly. The content of soluble (EDTA) Zn, Pb , Cd fractions in soil depended on the quantity of organic matter added into soil. Sorption of heavy metals by soil increased with the increased doses of the Rekulter and was the highest at a dose of 720 g per pot. The highest reduction of bioavailability was observed for Cd. The Brown coal preparation can, thus be regarded as an efficient source of organic matter in soil to reduce the bioavailability, and consequently phyotoxicity of heavy metals, as well as their uptake by plants and/or leaching to surface or ground water.
|Publication size in sheets||0.5|
|Book||Abstract Proceedings of the 6th International Congress of European Society for Soil Coservation, Innovative Strategies and Policies for Soil Conservation, 2011, National Agricultural Research Foundation, ISBN 978-960-88296-9-5, 277 p.|
|Keywords in English||brown coal preparation, hevy metals, phytotoxicity, bioavailability, water quality, food chain|
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