Effects of leaching from alkaline red mud on soil biota: modelling the conditions after the Hungarian red mud disaster

Abstract

A soil column experiment was set up to investigate the effect of red mud from Ajka (Hungary) on a typical soil profile from the concerned area. The chemical changes caused by the leachate of the red mud and the effects of these changes on living organisms were assessed. Ecotoxicological tests with Vibrio fischeri, Sinapis alba and Folsomia candida were performed and the number of aerobic heterotrophic microorganisms was determined. The total, plant available, exchangeable and water soluble fractions of Na, Mo, Cu, and Cr increased in the soil mostly due to their leaching from the red mud layer and partly to the increase of the pH and DOC concentration. The chemical changes had significant effects on the test organisms only in the 0 -30 cm soil layer except for F. candida that had a lower survival rate also in the 30 -50 cm soil layer. There were no severe toxic effects detected on the test organisms. Furthermore in case of the aerobic heterotrophic cell number and S. alba germination a stimulating effect was revealed. However, the red mud itself was toxic, therefore the performed ecotoxicology tests have justified the removal of red mud from the soil surface after the disaster.

Influence of red mud on soil microbial communities: Application and comprehensive evaluation of the Biolog EcoPlate approach as a tool in soil microbiological studies

“…This finding substantiated the recommended remediation option in the area: excavation of the RM flooded soil together with the overlain RM layer and storing of the excavated red mud and soil mixture (RMSM) in Ajka behind the red mud storage area. Rékási et al, 2013 showed similar results in a soil column experiment using 10 cm Ajka RM overlaying soil from Ajka: the CFU increased in the overlain soil until the 2 nd month, but it decreased by the 4 th month. Klebercz et al, 2012 measured 10-100 times elevation of CFU in the contaminated sediment of the rivers affected by the Ajka RM spill compared to reference samples.…”

Environmental Toxicity Assessment of the Spilled Ajka Red Mud in Soil Microcosms for Its Potential Utilisation as Soil Ameliorant

“…The Mo and Na contents in the aqua regia digest of the untreated soil (S) were significantly higher than in the reference soil (R) ( Table 1). This may be due to leaching of these metals into the soil from the red mud deposit on the soil surface (S), as observed also by Rékási et al [30], in a column experiment modelling the leaching into the soil of metals from a 10 cm red mud layer.…”

“…Rékási et al [30] observed an increase only in the water soluble Cu, Cr and Na concentrations and in the plantavailable (NH4-acetate + EDTA soluble) Cu, Pb, Na and Mo concentrations. The total amount of Zn in the reference soil (R) was higher than in the untreated soil (S), but this might be due to local differences in parent material.…”

“…According to the experiments performed by Rékási et al [30], the bioluminescence inhibition did not change significantly after the red mud treatment of the soils, but the untreated alkaline red mud was toxic to Aliivibrio fischeri. The Sinapis alba root length is shown in Fig.…”

“…The aim of our experiment was to predict the red mud amount that poses no risk on the mid-term to the environment when mixed into the soil in view of its potential utilisation as soil ameliorant in the future. Studying of the midterm effect of red mud mixed into soil is novel as compared to other studies conducted so far [28,25,30]. These studies have focused on the relatively short term effect of red mud on the soil surface, while the effect of mixing red mud into the soil was studied only by Ruyters et al [31].…”