Mechanism Of Formation Of Humic Substances By Different Natural Biological Evolution Materials

Humic substances(HS)are heterogeneous polymer compounds formed by humification,which have a commonality or "specificity" different from the chemical composition and structural characteristics of their precursors.So what is the mechanism for this "specificity" formation? Is it due to the humification process? This involves the roots of HS biochemistry which must be studied and answered in depth.Plant residues,microbial biomass,and clayminerals are the main parent materials and influencing factors for HS formation.In order to find out the special commonality of the formation of humic-like substances(HLS)through a wide range of typical raw materials,to answer the question of the mechanism of HS "specificity" formation,and further explore the differences in the formation of HLS and the reasons for its formation.According to the law of biological evolution,this study selects six kinds of typical natural biomaterials from low to high,from simple to complex,which are prokaryotic autotro phic(cyanobacteria),eukaryotic heterotrophic(mushroom),fungi and algae symbiosis(lichen),bryophytes,ferns,seed plants(alfalfa),and the addition of clay minerals(montmorillonite)and microorganisms(soil extract)to simulate the humification process and explore the specific commonalities and differences in the formation of HS.At the same time,we used the highest seed plants(alfalfa)of the six types of materials to conduct the control variable studies to explore whether montmorillonite can promote the humification process of materials.The research includes total organic carbon(TOC),humic-like composition,elemental composition of humic-like acid(HLA),infrared spectroscopy and differential thermal analysis.The results showed that the total organic carbon of the six natural biological evolution materials was much larger than that of the soil.The relative carbon content of the alkali soluble-acid insoluble components(ASAI)in the material was smaller than that of HA,and the condensation degree,aromaticity and thermal stability were much smaller than that of soil HA.During the simulated culture humification process,the TOC residual rate of the culture products of the six natural biomaterials showed a decreasing trend.The order of TOC and PQ values,(O+S)/C and H/C values of mushrooms,mosses,fiddlehead and alfalfa to the soil is the same as its evolutionary sequence.In the process of simulating culture humification,the addition of montmorilloniterapidly decomposes the white alfalfa TOC,promotes the formation of HLA a nd accelerates the humification process of white alfalfa,but reducing the degree of condensation of HLA,montmorillonite can not increase the degree of aromatization of HLA as speculated or reported in the literature,the structure is complicated,but the HLA structure is more simplified.The addition of soil extr act made the HLA accumulation of alfalfa increased and the structure of HLA became more complex when treated with montmorillonite.Therefore,ASAI of t he material is substantially different from HA,far less complex than HA,and HA does have specificity.The extracts of culture products of the six kinds of materials were still quite different from those of soil HS,but the difference wa s gradually reduced with the increase of culture time,indicating that the forma tion of soil HS specificity was due to the humification process.The lower and simpler the material is,the closer HLS is to soil HS.It also shows that the formation of soil HS specificity is due to humification process.Montmorillonite accelerates the process of humification,but simplifies the structure of HLA,and the difference with soil HA becomes larger,and it is not closer to true HS.In this experiment,the formation of HS was explored by comparing the extracts of natural biological evolution materials and culture products,which provided a scientific basis for the formation and origin of HS.