Red mud as acidic sandy soil ameliorant: a microcosm incubation study

Abstract

BACKGROUND: Red mud is increasingly considered a valuable by-product requiring development of new re-use technologies instead of deposition as waste. This paper reports the results of a microcosm study aiming to reveal the beneficial effects of the Ajka red mud, as soil ameliorant, on a specific acidic sandy soil in eastern Hungary. RESULTS:The red mud amount mixed into the sandy soil ranged between 0 and 50%. The experiment was monitored by an integrated methodology combining physical and chemical methods with biological and ecotoxicological measurements. The adverse effects of red mud were examined by ecotoxicity tests using test organisms from three trophic levels: Aliivibrio fischeri (luminescent bacterium), Sinapis alba (plant), Triticum aestivum (plant) and Tetrahymena pyriformis (unicellular animal). The results showed that red mud applied at 5% had positive effects on the degraded acidic sandy soil, significantly increasing soil pH, improving soil texture and water holding capacity. In addition, according to the ecotoxicological test results 5% w/w red mud had no significant adverse effects on the tested organisms as members of the soil ecosystem. CONCLUSION:The results demonstrated the beneficial effects of red mud as an ameliorant of acidic sandy soils under continental climatic conditions.

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

“…+ -N and NO3 --N) and humus-content slightly decreased (Ujaczki et al, 2016a). EC and pH showed negative correlation, while nitrogen forms showed positive correlation with AWCD in our experiment (Suppl Table 2), thus the changes in the chemical composition of the soil do not explain the AWCD increase at low RM doses.…”

“…Several case studies have demonstrated the applicability of red mud in soil amelioration and remediation, however, only a few have dealt with its effect on the soil biota, including the soil microorganisms (Lombi et al, 2002, Garau et al, 2007, Ujaczki et al, 2016a. In experiment "A" red mud (RM) at up to 20% had positive short term (3 months after treatment) effect on the microflora of an acidic sandy soil based on the AWCD values of the Biolog EcoPlate (Figure 1).…”

“…In experiment "A" red mud (RM) from Ajka (red mud, sampled in February 2011, 4 months after the accident from the top of a flooded grassland) was added at 0,5,10,20,30,40 and 50 w/w% to an acidic sandy soil (S) (sandy texture 87 w/w% sand) from Nyírlugos, Hungary in a microcosm experiment (Ujaczki et al, 2016a). The soil samples were placed into 2 kg pots, kept at room temperature and irrigated every 2 weeks.…”

“…Additionally, due to red mud mineralogy (iron and aluminium oxides, hydroxides) it can increase the phosphorus retention of sandy soils adsorbing phosphate (Summers et al, 1993, Summers andPech, 1997), thus reducing phosphate leaching and preventing eutrophication, and creating a phosphate pool that is available to plants and soil microorganisms. However, the alkalinity, the trace metal content and the naturally occurring radioactive material content of red mud may pose significant environmental risks (Akinci andArtir, 2008, Klauber et al, 2011), therefore its careful application is recommended in soil (Ruyters et al, 2011, Ujaczki et al, 2015, 2016a, Mayes et al, 2016.…”

“…Therefore, further studies are needed to better understand the influence of red mud not only on polluted soils but also in improving soil quality, given the scarcity of published research on this topic. Recently Ujaczki et al, 2016a have studied the effect of red mud (RM) as acidic sandy soil (S) ameliorant. Similarily Ujaczki et al, 2016b have studied in a field trial the potential application of red mud-soil mixture (RMSM) as additive to the surface layer of a landfill cover system made from low quality subsoil (LQS).…”