Hydrophobicity-dependent electron transfer capacities of dissolved organic matter derived from chicken manure compost

The electron transfer capacities (ETC) of dissolved organic matter (DOM) are related to their hydrophobicity. However, the underlying mechanism is poorly understood. The DOM was extracted from chicken manure compost, and fractionated into four fractions based on hydrophobicity, i.e., hydrophobic acid (HOA), hydrophobic base (HOB), hydrophilic matter (HIM) and acid insoluble matter (AIM) fractions. The composition, structure and ETC of the four fractions were measured using spectral technology and electrochemical methods. The results showed that the HOA and AIM fractions consisted mainly of fulvic- and humic-like substances, the HOB fraction comprised mainly organic nitrogen compounds, and the HIM was mainly composed of carbohydrates and protein-like matter. The electron donating capacities (EDC) and electron accepting capacities (EAC) of the four fractions were in the range of 616.90-5224.66 and 7.30-191.20 μmoL/g(C), respectively, The HOB fraction exhibited the highest EDC among the four fractions, followed by the HOA, AIM and HIM fractions. The EAC of the four fractions was characterized by the order of AIM, HOB, HOA and HIM. The tryptophan- and humic-like substances and organic nitrogen compounds accounted for the EDC, whereas the carboxyl group on aromatic substance responsible for the EAC.