Effects of laboratory biotic aging on the characteristics of biochar and its water-soluble organic products

• Published in: Journal of hazardous materials 2020-01, Vol.382, p.121071, Article 121071
• Main Authors: Quan, Guixiang, Fan, Qinya, Zimmerman, Andrew R., Sun, Jianxiong, Cui, Liqiang, Wang, Hailong, Gao, Bin, Yan, Jinlong
• Format: Article
• Language: English
• Subjects: Biochar; Biotic incubation aging; Dissolved organic matter (DOM); Excitation-emission matrix; Humification
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2019.121071

•Biochar had a positive influence on microbial population size.•Aged biochar surfaces showed increases in oxygen-containing functional groups.•Biologically-aged biochars were less stable than the abiotically-aged one.•Fulvic & humic acid-like components were main water-soluble matters of aged biochar. Effects of biotic aging on the characteristics of biochar and its water-soluble organic products were determined through a one-year laboratory incubation study. Biochar had a positive influence on microbial population size. Without microbial addition, biochars showed little change, except for an obvious increase in oxygen content from 3.2% to 6.3% after one year. By contrast, the carbon (C) content of the biologically-aged biochars continually decreased throughout the incubation at two humidity levels, suggesting that microbes consumed biochar C or encouraged organic matter solubilization. Fourier Transform Infrared Spectroscopy (FTIR) analysis indicated that all aged biochar surfaces showed increases in oxygen-containing functional groups and TG-DTG analysis showed that biologically-aged biochars were less stable than the corresponding abiotically-aged one. The release of dissolved organic matters from biologically-aged biochar logarithmically increasing with time, corresponded with of the pattern of microbe production, suggesting microbial involvement in solubilizing biochar. Combined three-dimensional excitation-emission matrix (3DEEM) and parallel factor (PARAFAC) analyses revealed that fulvic and humic acid-like components were the main water-soluble products of biologically-aged biochar, and these became increasingly rich in O-containing functional groups, i.e. humified, over time. These results highlight the importance of microbes in chemically transforming biochar and the dissolved products of biochar during aging.