Aged biochar alters nitrogen pathways in bauxite-processing residue sand: Environmental impact and biogeochemical mechanisms. (April 2019)

• Record Type: Journal Article
• Authors: Rezaei Rashti, M.; Esfandbod, M.; Phillips, I.R.; Chen, C.R.
• Is Part Of: Environmental pollution. Volume 247(2019)
• Page Start: 438
• Page End: 446
• Publication Date: 2019-04
• Subjects: Bauxite-processing residue sand -- Aged acidic biochar -- Nitrogen loss -- Rehabilitation; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2019.01.034
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Low nitrogen (N) content and retention in bauxite-processing residue sand (BRS) disposal areas pose a great challenge to the establishment of sustainable vegetation cover in this highly alkaline environment. The budget and fate of applied N in BRS and its potential environmental impacts are largely unknown. We investigated the effect of combined application of biochars [aged acidic (AC) vs alkaline pine (PC)] and di-ammonium phosphate (DAP) fertiliser on ammonia (NH3 ) volatilisation, nitrous oxide (N2 O) emission and N retention in a 116-day glasshouse study. The application of AC to BRS decreased pH (≈0.5 units) in BRS, while PC biochar increased pH (≈0.3 units). The application of AC reduced NH3 volatilisation by ca. 80%, while PC by ca. 25%. On the other hand, the AC treatment increased N2 O emission by 5 folds. However, the N loss via N2 O emission in the AC treatment only accounted for ca. 0.4% of applied N. The reduction in BRS pH and increased retention of mineral N due to the presence of oxygen-containing (phenolic and carboxylic) functional groups in AC may be responsible for reduced NH3 volatilisation and increased N2 O emission. This study has highlighted the potential of biochar (particularly aged biochar) in improving N retention and minimising environmental impacts in highly alkaline environments. Graphical abstract: Image 1 Highlights: Effects of biochar and mineral fertiliser studied on nitrogen fate in bauxite residue. Aged acidic biochar decreased, while alkaline pine biochar increased pH of residue. Aged biochar showed high oxygen-containing functional groups and adsorption capacity. Added biochar decreased ammonia volatilisation while increased nitrous oxide emission. Aged biochar increased nitrogen retention, plant nitrogen concentration and uptake.