Study On The Interaction Of Humic Substance With Iron And Phosphorus

Dissolved organic matter（DOM）,which plays an important role in the aquatic ecology can be widely found in soils,peat swamps,natural water bodies,sewage and lake sediments.DOM is the main provider of the energy needed by heterotrophic microorganisms,and the regulator and control factor of the pH of the water body.Besides,it is an important medium for the transfer and transformation of pollutants in the environment,which can interact with metal ions,and affect its migration and transformation,toxicity,and bioavailability.Humic substance（HS）is an important component of organic matters in rivers and lakes.With a complex structure,the hydroxyl and carboxyl groups contained in the HS easily interact with Fe,and Fe and P can produce Fe-P precipitation during the alternate process of anoxic to enriched conditions.Therefore,it is necessary to study the interaction between HS and iron and phosphorus to understand the migration,transformation and fate of organic carbon（OC）,iron and phosphorus.This paper first characterizes four kinds of humic substances from different sources:humic acids（HA）extracted from the surrounding soil of mountain lakes（Tiancai Lake and Haba Black Sea）,and fulvic acid（FA）of the Suwannee River and Nordic Lake bought from the International Humic Substances Society（IHSS）.The result of UV-Vis absorption spectra,three-dimensional fluorescence spectra,infrared spectroscopy and nuclear magnetic resonance show that the biological activity of these four organic matters are very low,but the microbial action and contribution rate of terrestrial sources are high.And the humification and aromatization of HA and FA are similar.It shows that there are more aromatic structures in humic acid.In fulvic acid,there are mainly UVC humic substances-like and UVA humic substances-like.Humic acid is rich in polyphenols.Humic acids are rich in benzene ring aromatics and their associated carboxyl and hydroxyl groups.The results provide a theoretical basis for studying the biogeochemical processes of organic matter.To study the interaction of four humic substances and Fe under different pH conditions,Fe³⁺with Different concentrations were added to the humic solutions.It is shown that humic substances and iron mainly have complexation and co-precipitation.Fe³⁺concentration,pH,and humic substances structure all have a great influence on the interaction between humic substances and iron.Due to the difference in Fe³⁺concentration,humic substances and iron mainly have complexation and co-precipitation.pH affects the complexation and co-precipitation of humic substances and iron.When PH is in the range of 5 to 7,the lower the pH,the more easily and completely the co-precipitations of humic substances and Fe will be.The humic acids containing polyphenols,benzene ring carboxylic acids,and benzene ring hydroxyls are more likely to interact with iron than fulvic acid.This conclusion provides a theoretical basis for revealing the influence of organic matter on the biogeochemical processes of metal ions.To study the co-precipitation of four humic substances and Fe,P under different pH conditions,a certain concentration of Fe³⁺and PO₄^3—were added to the humic substances solution.It was shown that both the pH and the structure of the humic substances will influence the interaction between humic substance and iron and phosphorus.Humic acids rich in polyphenol structure,benzene ring carboxyl group,benzene ring hydroxyl and other functional groups are more likely to co-precipitate with Fe and P than fulvic acid.Due to the competitive relation between humic substances and phosphor during the interaction of humic substances,iron,and phosphorus,phosphorus will reduce the participation of humus in the co-precipitation reaction.When pH is in the range of 5 to 7,the lower the pH,the more completely co-precipitation reaction between HS and iron and phosphorus will be.This conclusion provides a theoretical basis for the study of the effects of organic matter on the biogeochemical cycles of different forms of phosphorus in aquatic environments.