Revisiting organic waste-source-dependent molecular-weight governing the characterization within humic acids liking to humic-reducing microorganisms in composting process.

Abstract

Humic acids (HAs) coupled with humic-reducing microorganisms (HRMs) can facilitate contaminants reduction. Molecular-weight (MW) of HA governs the chemical and HRMs behavior. However, MW of HAs with chemical characteristics linking to HRMs in different wastes composting have never been investigated. Results from the HPSEC-UV analysis showed that composting significantly increased weight-average molecular weight (Mw) of HA with a broad range from 675Da to 27983Da, and governing heterogeneous chemical characteristics. In proteinaceous composts, MW<4000Da of HAs were greatly related to alkyl and carbonyl, while MW>20000Da of HAs were presented by oxygen-nitrogenous functional groups, methyl, and alkyl groups. For cellulosic composts, MW<1500Da and 4000-10000Da of HAs were characterized by aliphatic ethers and aromatic groups. MW>20000Da of HAs were constructed by phenols, methoxy and nitrogen functional groups. In lignocellulosic composts, MW>20000Da of HAs were only characterized by aromatic groups. Furthermore, seven groups of HRMs adapted to the heterogeneous chemical characteristics within HAs ranked by MW were recognized. Consequently, the possible routes that composting properties response to the connections of HRMs-chemical structures-MW of HAs in proteinaceous, cellulosic and lignocellulosic composts were constructed, respectively. Our results can help to develop the fine classification-oriented approach for recycling utilization of organic wastes.