![]() ![]() Presence of HAs in soil solution also influences availability of important nonmetal elements: N, S and P. Moreover, HAs readily bind clay minerals to form complexes with different properties and stability. They interact with metal ions, hydroxides and oxides on the way of ion-exchange, surface-adsorption, chelation, coagulation, and peptization. Because of this feature, HAs demonstrate a great impact on soil-buffering capacity and especially the form, bioavailability and retention abilities of metals in soils. ![]() A large sorption capacity in the range of 300–1400 meq 100 g -1 makes HAs one of the most charged substances among naturally occurring polyelectrolytes (mineral parts of the soil have from 2 to 30 times lower sorption capacity). They are some of the most valuable components of the soil environment, mainly due to their significant reactivity. HAs are insoluble under acidic conditions but can be extracted using alkaline solutions. HAs are formed by humification, which generally involves biochemical processes of decay and transformation of plant and microbial remains. Their macromolecules are rich in aromatic units, aliphatic chains and functional groups and reveal flexibility and high sensitivity to chemical agents. Humic acids (HAs)-principal component of humic substances, belong to complex and heterogeneous mixtures of polydispersed dark brown to black organic substances. Granted to PB (Competing interests: The authors have declared that no competing interests exist. The project was financed from funds of National Science Centre on the base of decision number DEC- 2013/11/D/NZ9/02545. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.ĭata Availability: All relevant data are within the paper and its Supporting Information file.įunding: The studies were partly carried out within the framework of a research project. Received: FebruAccepted: ApPublished: April 14, 2016Ĭopyright: © 2016 Boguta, Sokołowska. PLoS ONE 11(4):Įditor: Leonardo Fraceto, São Paulo State University, BRAZIL Effect of pH, Zn Concentrations and Humic Acids Chemical Properties. ![]() To summarize, the above studies have showed significant impact of Zn concentration, pH and some properties of HAs on complexation reactions of humic acids with zinc.Ĭitation: Boguta P, Sokołowska Z (2016) Interactions of Zn(II) Ions with Humic Acids Isolated from Various Type of Soils. Such processes were noticed for HAs characterized by high oxidation degree and high oxygen functional group content where these were low, HAs displayed bidentate bridging or even bidentate chelation. Low Zn doses at pH 7 caused formation of unidentate complexes while higher Zn doses caused bidentate bridging. FTIR spectra at pH 5 revealed that the most-humified HAs tended to cause bidentate bridging coordination, while in the case of the least-humified HAs, Zn caused bidentate bridging coordination at low Zn additions and bidentate chelation at the highest Zn concentrations. The stability of complexes at α and β-areas at pH 7 decreased with a drop in HAs humification. At pH 5, stability decreased with C/N increase for α-areas and -COOH content increase for β-sites stability increased with humification decrease for γ-structures. The stability of complexes was higher at pH 7 and was the highest for γ-structures. The amount of metal complexed at pH5 and 7 by α and γ-structures increased with a decrease in humification and aromaticity of HAs, contrary to β-areas where complexation increased with increasing content of carboxylic groups. This trend was not observed for γ-sites (structures with linearly-condensed aromatic rings, unsaturated bonds and large molecular weight). Complexation at α-sites (low humified structures of low-molecular weight and aromatic polycondensation) and β-sites (weakly humified structures) was stronger at pH 7 than 5. ![]() The presence of a few areas of HAs structures responsible for Zn(II) complexing was revealed. The main aim of this study was the analysis of the interaction between humic acids (HAs) from different soils and Zn(II) ions at wide concentration ranges and at two different pHs, 5 and 7, by using fluorescence and FTIR spectroscopy, as well as potentiometric measurements. ![]()
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