Application of different alkaline materials as polluted soil amendments: A comparative assessment of their impact on trace element mobility and microbial functions

• Published in: Ecotoxicology and environmental safety Vol. 227; p. 112927
• Main Authors: Álvarez-Ayuso, E., Abad-Valle, P.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 20-12-2021; Elsevier
• Subjects: Aluminum salt slags; Calcite; Coal combustion fly ashes; Polluted soil stabilization; Soil enzymatic activities; Zeolite NaP1; Aluminum salt slags; Soil enzymatic activities; Polluted soil stabilization; Coal combustion fly ashes; Calcite; Zeolite NaP1
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2021.112927

Treatment with chemical amendments is among the best techniques to remediate soils highly polluted with trace elements. The use of waste-derived products has several advantages in this regard, mainly in terms of reducing process costs and conserving natural resources. In this study, the performance of the synthetic zeolite NaP1 derived from coal combustion fly ash (SZ) and the by-product generated from the processing of aluminum salt slags (BP) was evaluated with this aim in comparison to calcite (CC). For this purpose, mine soils polluted with Zn, Cd, and Pb were amended under controlled laboratory conditions with different doses (0%, 1%, 2%, 5%, and 10%) of SZ, BP, or CC, and their impact on trace element mobility and microbial functions was evaluated. Specifically, the mobile and mobilizable trace element pools, basal soil respiration, and different enzyme activities were analyzed. Both SZ and BP performed better than CC in the immobilization of trace elements, reaching, respectively, mobility decreases up to 89–94% and 66–87% when applied at a dose of 10%. These amendments reduced the mobile trace element pool by precipitating them as acid-soluble precipitates and/or retaining them in the reducible fraction of soils. The alkaline nature of these materials and the concomitant increase in soil pH caused by their application mainly accounted for this behavior. Additionally, soil microbial functionality improved after amendment, especially in the case of SZ, as shown by dehydrogenase and alkaline phosphatase activities, which significantly increased (p < 0.05) up to 536% and 48%, respectively. Therefore, applying SZ or BP as soil amendments can significantly decrease the mobile trace element contents of heavily polluted soils without negatively affecting soil quality, thus facilitating plant growth to revegetate and reclaim degraded spaces.
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•Synthetic zeolite NaP1 from coal combustion fly ashes (SZ) as polluted soil amendment.•By-product from the processing of aluminum salt slags (BP) as polluted soil amendment.•SZ and BP performed better than calcite (CC) in the immobilization of trace elements.•Zn, Cd and Pb mobility decreases up to 89–94 or 66–87% were reached by 10% SZ or BP.•SZ and BP use had positive or no negative impact on polluted soil enzyme activities.