Predicting potential release of dissolved organic matter from biochars derived from agricultural residues using fluorescence and ultraviolet absorbance.

A combination of fluorescence excitation-emission (EEM) spectrophotometry with parallel factor analysis (PARAFAC) and UV-vis spectroscopy was used to assess dissolved organic matter (DOM) release by the wheat straw-derived biochar in various environmental conditions. The results showed that the concentration of dissolved organic carbon (DOC) extracted from the biochar ranged from 435 to 5000mgkg, and the high DOM release would occur under the high temperature and alkaline environmental conditions. Four humic acid-like substances (C1, C2, C4 and C5), one fulvic acid-like substance (C3) and one tryptophan-like substance (C6) were identified by PARAFAC model. The distribution of the PARAFAC components in DOM was distinctively different among various extracts, and mainly composed of humic acid-like and fulvic acid-like material (accounting 55-78% and 10-37%). The high temperature enhanced the high release of humic acid-like DOM from the biochar. Humification index (HIX) of DOM released from the biochar in various extracts at the temperature of 20°C (0.99-1.09) was lower than that at the temperature of 60°C (1.31-1.92). The results obtained in the present study would be beneficial to understand biochar's effects and processes in the possible environmental applications.