Effect of pyrolysis temperature on the composition of DOM in manure-derived biochar.

Dissolved organic matter (DOM) plays an important role in the migration and transformation of nutrients and pollutants. Recently, DOM derived from biochar has the potential to determine the application of biochar and has attracted much researcher's attention. However, the effects of pyrolysis temperature on the composition evolution of DOM in manure-derived biochar are still unclear. In this study, DOM solutions extracted from a series of biochars derived from three kinds of manure (chicken, swine and dairy) at six pyrolysis temperature (200-700 °C) were analyzed using UV-Visible, Fourier transform infrared and fluorescence spectroscopy, aiming to investigate the effects of pyrolysis temperature on the composition evolution of DOM. The results showed that, with the increased of pyrolysis temperature, the dissolved organic matter (DOC) content sharply declined to reach stable. High DOC content was obtained at low pyrolysis temperature. Moreover, the DOM mainly contained humic acid-like and protein-like substances. With the pyrolysis temperature increased, the protein-like substances firstly decreased and then increased, while there was an opposite trend for the humic acid-like substances. Moreover, functional groups evolution of DOM depended on the pyrolysis temperature and manure type, evidenced by the Fourier transform infrared spectroscopy with two-dimensional correlation analysis. This study highlights the importance of optical analysis and may provide valuable information regarding the characteristics evolution of biochar-derived DOM.