The transformation of different dissolved organic matter subfractions and distribution of heavy metals during food waste and sugarcane leaves co-composting.

As a heterogeneous fraction, dissolved organic matter (DOM) in a compost is the most active because of its direct supply of energy sources for microbes. Also, the transfer and distribution of heavy metals in the DOM fraction attract many attentions of researchers. To this end, the dynamics of humic acids (HA), fulvic acids (FA), hydrophobic neutrals (HoN), and hydrophilic (Hi) fractions derived from DOM was investigated in this study, and the transformation of different DOM subfractions and distribution of heavy metals during food waste and sugarcane leaves co-composting were assessed by excitation-emission matrix fluorescence (EEM-FL) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. The results revealed that HA transformed from polycyclic aromatic humic acid-like to polycarboxylic humic acid-like and FA changed from soluble microbial products (SMP) to humic acid-like; Hi and HoN composed mainly of SMP substances; FA showed more abundant compositions, such as SMP, humic acid-like and tryptophan. Heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) were redistributed among different DOM subfractions in the thermophilic phase of composting. Compost DOM and its subfractions showed obvious effects on germination index (GI), biomass, root length, shoot length and healthy index of Chinese cabbage seedlings. These findings shed some novel lights into the dynamic composition and characteristics of DOM subfractions and their impacts on heavy metals distribution in a composting process.