Structural differences between humic substances from natural sources and valorized organic waste (compost, biochars) – how does source material and humification conditions define their sturcture

Abstract

Humic substances (HS) are commonly defined as natural organic matter (NOM) occurring in soil, water and geological organic deposits Although derived from detritus of decaying organisms, HS from different locations can show considerable variations with respect to their chemical composition Structural differences which were revealed by well established and advanced analytical tools indicate that the quality of HS depends not only on the source material but also on the environmental conditions governing during the humification process Whereas, for example, in anaerobic and acid environments a preferential preservation of paraffinic structures is observed, interactions of NOM with the soil mineral phase support the biochemical recalcitrance of carbohydrates Considerable chemical differences are also expected for HS derived from biosolids, composts and biochars Being suggested as a cost-effective solution to reduce organic waste by its recycling as soil amendment, the acceptance of such products on the market depends not only on their positive impact on soil fertility but also on their environmental sustainability and the capability to maintain constant quality standards Those premises require a good understanding of the chemical properties the product and their fate after their amendment to soils Therefore, the goal of the present communication is to introduce new and established analytical tools such as pyrolysis GCMS, isotopic ratio MS and advanced one and two dimensional solid-state NMR spectroscopy as means for HS characterization and to relate the determined typical patterns of the organic matter composition of various HS from different origins to their source materials and the conditions during.