DOM spectral characteristics of straw biochar and its interaction with Cu2+

Fluorescence quenching titration was used to explore the spectral characteristics of DOM in maize straw biochar (MSB), rice straw biochar (RSB) and peanut straw biochar (PSB), and their complexation mechanism with Cu2+. The results showed that the DOM in biochar had higher hydrophilicity and lower aromatability. RSB-DOM had relatively strong aromatability, higher molecular weight and lower DOM content. DOM of PSB had more oxygen-containing functional groups in the aromatic structure. Fulvic acid-like component C1and humic acid-like component C3 and C4 were found in MSB-DOM and RSB-DOM, and tryptophan-like component C5 in RSB-DOM. PSB-DOM was composed of two kinds of fulvic acid-like components C1 and C2 and humic acid-like component C4 with longer wavelength. DOM were dominated by fulvic acid-like components, accounting for 54.93~86.29%. The stability constant (logKM) of Cu2+ and humic acid-like component was higher than that of fulvic acid-like component, and the complexation capacity (f) of C4 was the strongest. The logKM and f values of humic acid-like component were as follows: PSB-DOM