Effects of biochar on transport and retention of phosphorus in porous media: Laboratory test and modeling

• Published in: Environmental pollution (1987) 2022-03, Vol.297, p.118788-118788, Article 118788
• Main Authors: Li, Yuelei, Zhao, Ying, Cheng, Kui, Yang, Fan
• Format: Article
• Language: English
• Subjects: Biochar; Charcoal; Osmolar Concentration; Phosphate transport; Phosphorus; Physicochemical factors; Porosity; Porous media; Silicon Dioxide
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2022.118788

Given the complexity of soil components, a detailed understanding of the effects of single factors on phosphorus transport and retention will play a key role in understanding the environmental effects of phosphorus. In this work, quartz sand columns (considering five factors: doping rate, pH, particle size, ionic strength and cation type), combined with a two-site nonequilibrium transport model (TSM), were used to investigate phosphate (P) transport behavior. The results show that changes in doping ratio (0.4%–1.6%) and pH (5–9) have a notable effect on the transport of P, while, particle size of quartz sand hardly impacts the transport. When biochar was added at 1.6%, the surface of biochar increased the P fixation rate by about 37% through direct interaction with phosphate and bridging action with metal ions. As the morphology of P changed under different pH conditions, a part of P was immobilized in the form of precipitation. The immobilization of P was further enhanced with the increase of ionic strength. Compared with the direct interaction of P with biochar in Na+ solution, Ca2+ and Mg2+ solutions are more likely to adsorb P. Meanwhile, the TSM model also fits the transport behavior well. This study provides a perspective for evaluating the environmental behavior of P in the porous media interaction with biochar. [Display omitted] •High proportion of biochar and ionic strength retard phosphorus breakthrough.•Acidic conditions is more favorable for phosphorus transport compared to alkaline conditions.•Interaction of biochar with different valence cations affects retention of phosphorus.•Sand size had no significant influence on breakthrough and retention of phosphorus.•Two-site model results matched phosphorus breakthrough data well.