Interaction between uranium and humic acid(Ⅰ):Adsorption behaviors of U(Ⅵ) in soil humic acids

The adsorption behaviors of uranium on three soil humic acids (HAs), which were extracted from soils of different depths at the same site, were investigated under various experimental conditions. The adsorption results showed that U(Ⅵ) in solutions can be adsorbed by the three soil HAs, with the order of FHA (HA from 5 m depth of soil) >SHA (HA from the surface) >THA (HA from 10 m depth of soil) for adsorption efficiency in each desirable condition, and the adsorption reached equilibrium in about 240 min. Although the maximum adsorption efficiency was achieved at a suitable uranium concentration (10 mg·L-1 U(Ⅵ) for SHA and THA, 20 mg·L-1 U(Ⅵ) for FHA), the adsorption could be described with Langmiur isotherm or Freundlich isotherm equation. The L/S (liquid/solid, mL/g) ratio and pH were important factors influencing the adsorption in our adsorption system besides uranium concentration. The adsorption efficiency decreased with the increase of the L/S ratio and pH at the pH range of 2.0-3.0 for SHA and THA or 2.5-6.0 for FHA. However, no significant difference in adsorption of U(Ⅵ) was observed at the experimental temperature. All the results implied that humic substances have different characteristics in samples even collected at the same site.

Study on Humic Acids of the Soil Applied with Corn Stalk by Spectroscopy Measurements

Spectroscopy measurements （Fourier transform infrared differential spectroscopy, Carbon-13 nuclear magnetic resonance spectrometry, Matrix-assisted laser resorption/ionization-time of flight mass spectrometry） were performed to study the humic acids of the soil applied with corn stalk. The results showed that after incorporation of corn stalks into the soil, the soil humic acid （HA） changed significantly in different stages. During first 60 days, new HAs were formed by polymerization and seems to be similar to that of initial HAs from composting corn stalk, some little molecular organic matters also reacted with soil HAs and turned into parts of soil HAs. After 60 days of the corn stalk residue incorporation, new HAs were formed by polymerization of decomposed lignin molecules, some methylenes transformed into methyls and methoxyls since the 90th day. Application of corn stalk led to the increase of aliphatic components in soil HAs, the decrease in aromatic components of soil HAs and the suppression in oxidation degree of soil HAs. The average molecular weight of soil HAs also declined because of application of corn stalk.

Extraction and Characterization of Humic Acids and Humin Fractions from a Black Soil of China

Twenty-three progressive extractions were performed to study individual humic acids (Has) and humin fractions from a typical black soil (Mollisol) in Heilongjiang Province, China using elemental analysis and spectroscopic techniques. After 23 HA extractions the residue was separated into high and low organic carbon humin fractions. HA yield was the highest for the first extraction and then gradually decreased with further extractions. Organic carbon (OC) of the humin fractions accounted for 58％ of total OC even after 23 successive HA extractions. In addition, the atomic C/H ratio decreased during the course of extraction while C/O increased; the E4/E6 ratio from the UV analysis decreased with further extraction while E2/Ea increased; the band assigned to aliphatic carbon (2 930 cm-1) in the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra gradually increased with progressive extraction; the calculated ratio of the sum of aromatic carbon peak heights to that of aliphatic carbon peak heights from DRIFTS spectra declined with extractions; and nuclear magnetic resonance (NMR) data suggested that HA aliphatic carbons increased with extractions while aromatic carbons decreased. Thus, hydrophobicity and aliphaticity of Has increased with extractions while polarity and aromaticity decreased. These data showed substantial chemical, structural, and molecular differences among the 23 Has and two humin fractions. Therefore, these results may help explain why soil and sediment humin fractions have high sorption capacity for organic contaminants.

Characteristics and distributions of humic acids in two soil profiles of the southwest China Karst area

Characteristics and distributions of humic acid(HA) and soil organic matter(SOM) in a yellow soil profile and a limestone soil profile of the southwest China Karst area were systematically investigated to reveal their evolutions in different soils of the study area. The results showed that characteristics and distribution of SOM along the two soil profiles were notably different. Total organic carbon(TOC) contents of soil samples decreased just slightly along the limestone soil profile but sharply along the yellow soil profile. TOCs of the limestone soils were significantly higher than those of the corresponding yellow soils, and C/N ratios of SOMs showed a similar variation trend to that of TOCs, indicating that SOM can be better conserved in the limestone soil than in the yellow soil. The soil humic acids were exhaustively extracted and further fractionated according to their apparent molecular weights using ultrafiltration techniques to explore underlying conservation mechanisms. The result showed that C/N ratios of HAs from different limestone soil layers were relatively stable and that large molecular HA fractions predominated the bulk HA of the top soil, indicating that HA in the limestone profile was protected while bio and chemical degradations were retarded. Combined with organic elements contents and mineral contents of two soils, weconcluded that high calcium contents in limestone soils may play a key role in SOM conservation by forming complexation compounds with HAs or/and enclosing SOMs with hypergene CaCO_3 precipitation.

The effects of soil sand contents on characteristics of humic acids along soil profiles

It is generally accepted that the compositions and properties of soil organic matter(SOM) are in?uenced by many factors. In order to reveal the effects of soil texture on characteristics and dynamics of SOM and its sub-fraction,humic acid(HA), along two soil pro?les, a yellow soil pro?le and a purplish soil pro?le, under the same climate and vegetation conditions were determined. Results indicate that the decomposition and humi?cation degrees of SOM and HA of the purplish soils are higher than those of the corresponding yellow soils indicated by A/O–A ratios of HAs, TOCs and HA yields of bulk soil samples, nevertheless, the development degree of the purplish soil is lower than that of the yellow soil. The variations of E_4/E_6 ratios of HAs along the soil pro?les indicate the overall molecular sizes of HAs decreased downward along the soil pro?les.A/O–A ratios of HAs decreased downward along both the soil pro?les indicate that humi?cation processes decrease downward along both the soil pro?les. Leaching of SOM shows signi?cant effects on the distribution and characteristics of HAs in the yellow soil pro?le but the purplish soil pro?le, which is consistent with the higher hydrophobicity of HAs in purplish soils, shows that the distribution characteristics of SOM along the soil pro?les are a complex result of the combination of soil texture and characteristics of SOM itself. The remarkably different sand contents are concluded tentatively as one of reasons to the different distributions and dynamics of HAs along the soil pro?les,however, to profoundly understand the evolution and transport of SOM along soil pro?les needs more researches.

Effects of Humic Acid and Solution Ph on Dispersion of Na-and Ca-Soil Clays

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Using humic acid for remediation of sandy soils contaminated by heavy metal

This paper presents the development of a new remediation technology for contaminated sandy soil using humic acid (HA). Distribution of amount of Cr (VI) in the aqueous or solid system containing humic acid and sandy soil, was studied using batch experiments, es-pecially for effects of reaction time, pH, concentrations, temperature and irradiation on the reduction of Cr (VI), and the optimum reaction conditions. The results indicated a significant increase of the adsorption of Cr (VI) because of the complexion reaction between HA and Cr (VI) that occurred under acidic condition. The reaction mechanisms of HA with chromium on sand surfaces were certified. Thus it came to a conclusion that HA could be used effectively on remediation of Cr (VI)–contaminated soil and groundwater in a wide range of pH, with or without sunlight. These results suggest that the organic-inorganic complex—such as sandy soils coated with humic substances—is important as a metal reservoir in the environment.

Soil organic carbon contents, aggregate stability,and humic acid composition in different alpine grasslands in Qinghai-Tibet Plateau

Alpine grassland soils on Qinghai-Tibet Plateau store approximately 33.5 Pg of organic carbon(C) at 0–0.75 m depth and play an important role in the global carbon cycle.We investigated soil organic C(SOC),water-soluble organic C(WSOC),easily oxidizable organic C(EOC),humic C fractions,aggregate-associated C,aggregate stability,and humic acid(HA) composition along an east-west transect across Qinghai-Tibet Plateau,and explored their spatial patterns and controlling factors.The contents of SOC,WSOC,EOC,humic C fractions and aggregate-associated C,the proportions of macroaggregates(2-0.25) and micro-aggregates(0.25-0.053 mm),and the aggregate stability indices all increased in the order alpine desert < alpine steppe < alpine meadow.The alkyl C,O-alkyl C,and aliphatic C/aromatic C ratio of HA increased as alpine desert < alpine meadow < alpine steppe,and the trends were reverse for the aromatic C and HB/HI ratio.Mean annual precipitation and aboveground biomass weresignificantly correlated with the contents of SOC and its fractions,the proportions of macro- and microaggregates,and the aggregate stability indices along this transect.Among all these C fractions,SOC content and aggregate stability were more closely associated with humic C and silt and clay sized C in comparison with WSOC,EOC,and macro- and microaggregate C.The results suggested that alpine meadow soils containing higher SOC exhibited high soil aggregation and aggregate stability.Mean annual precipitation should be the main climate factor controlling the spatial patterns of SOC,soil aggregation,and aggregate stability in this region.The resistant and stable C fractions rather than labile C fractions are the major determinant of SOC stocks and aggregate stability.

Effects of Nano-carbon Humic Acid Water-retaining Fertilizer on Citrus Growth and the Soil Bacterial Community in Citrus Field

[Objective] In order to reveal the effects of reducing the amount of novel nano-carbon humic acid water-retaining fertilizer(CSF) on soil microbial community structure and citrus growth. [Method]In this study,conventional fertilization was as the control(KC1) in Wanzhou citrus orchard of Three Gorges Reservoir area. CSF reductions by 0%(KC2),10%(KC3),20%(KC4),30%(KC5) and 40%(KC6) were used to analyze the changes of soil bacterial community structure,citrus yield and quality. [Result]The results showed that the observed species,Shannon index,Chao1 index and PDwholetree of KC6 were higher than those of KC1,and were the same as KC2. The abundance of Xanthomonadaceae was the highest in KC5. Compared with KC1,the Xanthomonadaceae in KC3,KC4 and KC6 was significantly decreased,and the levels of Nitrosomonadaceae and Pseudomonasaceae were higher than that of KC1 after the treatment of KC6. Sphingomonas in different reduction treatments was lower than that of KC1,but Burkholderia and Pseudomonas were significantly higher than those of KC1. It was found that the similarity among treatments was small after bacterial community similarity clustering analysis,and citrus yield increased somewhat after CSF fertilization reduction.When CSF fertilization reduced by 30%,citrus yield increased by 4. 50%. When CSF fertilization reduced by 40%,citrus yield decreased by4. 14%. After CSF fertilization,citrus quality did not change significantly in CSF conventional fertilization and reduction of 10% and 40%,while significantly decreased in 20% and 30% of fertilization reduction. [Conclusion] CSF fertilization reduction changed the diversity of soil bacterial community structure and the yield and quality of citrus.

Interaction between uranium and humic acid (Ⅱ): complexation, precipitation and migration behavior of U(Ⅵ) in the presence of humic substances

The complexation, precipitation, and migration behavior of uranium in the presence of humic acid (HA) or fulvic acid (FA) were investigated by cation exchange, ultrafiltration and dynamic experiment, respectively. The results showed that (i) complex equilibrium between the uranium and humic substances was achieved at approximately 72 h, (ii) the coordination number varied from 1:1 to 1:2 ( U(Ⅵ) : humic acid) as pH increased from 3 to 6; and (iii) , while the complex stability constant decreased when temperature increased, but increased with pH value. We found that the precipitation of uranyl could only be observed in presence of HA, and the precipitation was influenced by conditions, such as pH, uranium concentration, temperature, and the HA concentration. The maximum precipitation proportion up to 60% could be achieved in the condition of 40 mg/L HA solution at pH 6. We further observed that the migration behavior of uranium in soil in the presence of humic acid (HA) or fulvic acid (FA) was different from that in the presence of inorganic colloid, and the effect of humic substances (HS) was limited.

Evaluation of Humic Acid Application Methods for Yield and Yield Components of Mungbean

A triplicate field experiment laid out in randomized complete block design was conducted to evaluate different humic acid (HA) application methods at Agricultural Research Farm, of KPK Agricultural University, Peshawar. Three methods of HA application: seed priming, foliar spray and soil application were included in the experiment. Humic acid application methods significantly affected pods plant-1, grains pod-1, 1000 grain weights, and grain yield whereas biological yield was not significantly affected by HA application methods. Humic acid application at the rate of 3 kg&middotha-1 resulted in higher number of pods plant-1, thousand grain weights and grain yield, however it was statistically similar to the treatments where HA was soil applied at rate of 1 and 2 kg&middotha-1, seed priming with 0% (water soaked), 1%, 2% HA solution and foliar spray with 0.01%, 0.05% and 0.1% of HA solution. It is concluded that HA application in all the three methods significantly enhances grain yield and yield components of mungbean.

Determination of Formation Constants of Co^2＋,Ni^2＋,Cu^2＋and Zn^2＋ Complexes with Humic and Fulvic Acids by Potentionmetric Titration Method

The formation constants of Co^2+,Ni^2+,Cu^2+ and Zn^2+ complexes with humic acid(HA) and fulvic acid(FA) in red soil wrer determined by the potentiometric titration method.The constants as a function of composition of the complexation solutions were obtained by two graphical approaches respetively,The formation constants decreased with increasing concentration of metal in the solution,The results provide unambiguous evidence for the heterogeneity of the function groups of humic substances,the formation constants of FA were much smaller than those of HA,and the formation constants of Cu^2+ were much greater than those of Co^2+ ,Ni^2+ and Zn^2+,The potentiometric titration methon for determining formation constants are also discussed in the article.

Relationships between humic substance-bound mercury contents and soil properties in subtropical zone

The bioavailability of humic substance-bound mercury （HS-Hg） has been established, while the distribution of HS-Hg in soils in relation to soil properties remains obscure. Path analysis and principal component analysis were employed in present study to investigate how soil factors influence the contents of HS-Hg in soils. Results showed that HS-Hg ranged from 0.0192 to 0.2051 mg/kg in soils. The two fractions existed in soils as humic acid-bound mercury （HA-Hg） 〉 fulvic acid-bound mercury （FA-Hg） and the ratio of HA-Hg/FA-Hg was 1.61 on the average. Soil organic carbon （OC） and HS favorably determined soil HS-Hg and the two fractions. The mercury source forming HS-Hg derived from soil total mercury and HS-Hg. FA-Hg and HA-Hg served as mercury source for each other. In acidic soils, FA-Hg and HA-Hg consistently rose with the increase of OC, and generally HA-Hg increased more dramatically. Soils with lower pH and lighter texture contained more HS-Hg, particularly fraction of FA-Hg. Among all influencing factors, organic material source showed the strongest effect, followed by other soil properties and soil mercury source.

Formation of Black Patina on Bronze Mirrors Caused by Humic Acid

The formation of black patina caused by soil humic acid under different conditions has been studied,and the black, grey and brown shiny surfaces prepared in laboratory have been analysed. The formation of tin-rich shiny black surface on mirrors was the product of the soil corrosion of the bronze mirrors. It is formed by reaction between the alloy and the humic acid in soil, and leaching of copper and lead oxides through a long period of time when the mirrors were buried under the ground. A dense cormsion-resistallt layer on the bronze mirrors consisted predominantly of stannic oxide.

Effects of Water Regime and Reaction of Soil on Properties of Newly-Formed Humic Substances

The effects of soil water regime and soil reaction on nitrogen distribution and fractional composition of newly-formed humus (decayed products) and the structural characteristics of the newly-formed humic acids(HAs) were studied in an incubation experiment,with the following results obtained: 1.The humus newly formed under submerged conditions was higher in the relative content of α-amino acid-N and the humic acid/fulvic acid (HA/FA) ratio than that under upland conditions.The HAs extracted from the former were also higher in C/O ratio,aromaticity and the contents of methoxyl groups and lignin-like components,but lower in the content of carboxyl groups than the HAs from the latter. 2.Under upland conditions,the C/ organic N ratio and the relative content of mobile HA of newly-formed humus were lower,but the HA/FA ratio was higher in the CaCO2-amended treatment than in non-amended treatment.The presence of CaCO3 also resulted in a decrease of C/N ratio of HA and a slight increase of its carboxyl group content.On the other hand,there was no significant change in the composition and properties of the newly-formed humus with the addition of CaCO3 under submerged conditions. 3.Compared with soil HAs,the newly-formed HAs contained more carbohydrates,polypeptides and lignin-like components,and were in lower degrees of oxidation and humification.

玉米秸秆还田下深松年限对土壤有机碳含量及胡敏酸结构特征的影响

为明确不同秸秆还田结合耕作措施下土壤有机碳组分的变化特征,基于6 a秸秆还田长期定位试验,利用三维荧光光谱技术,对CK(不深松+不秸秆还田)、NFG(不深松+每年秸秆还田)、EFG(隔一年深松+每年秸秆还田)、TFG(隔两年深松+每年秸秆还田)和SFG(连年深松+每年秸秆还田)处理下土壤有机碳(SOC)含量及胡敏酸(HA)结构特征进行分析。结果表明:与CK相比,EFG处理0~10 cm土层的SOC、HA含量和PQ值分别显著增加25.23%、16.19%和4.27%,FA含量降低4.55%。10~20 cm土层,EFG处理的SOC含量最高,较CK增加13.18%;SFG处理的HA和FA含量较CK提高最多,增幅分别为13.27%和32.74%。通过HA三维荧光图谱发现,与CK(Ex/Em=270/455,270/460)相比,EFG(Ex/Em=280/455,270/465)处理下0~10 cm和10~20 cm土层中的HA荧光峰波长均有红移现象。土壤胡敏酸中包含两个组分,C1(Ex/Em=270/280)和C2(Ex/Em=440/515)同为类腐殖酸物质,胡敏酸整体腐殖化程度较高,结构较为复杂;其中EFG和TFG处理的C2组分所占比例最高,分别为28.59%和31.38%。各处理的C1和C2组分F_(max)值均较CK有所增加,即腐殖化程度增加。综上所述,EFG处理(隔一年深松+每年秸秆还田)通过提升土壤有机碳及腐殖酸类物质含量,增加腐殖化程度,加强了土壤的供肥能力,为黑龙江黑土区较佳的耕作技术措施。

泥炭土腐殖酸环境室内模拟试验研究

为能提供一种贴合天然环境的泥炭土腐殖酸环境,通过在冲洪积黏性土中掺入胡敏酸(Humic Acid, HA)试剂和富里酸(Fulvic Acid, FA)试剂人工制备泥炭土试样,并将试样浸泡在富里酸液中来模拟泥炭土腐殖酸环境。采用腐殖酸含量检测试验、扫描电镜(Scanning Electron Microscope, SEM)、X射线衍射(X-Ray Diffraction, XRD)、X射线荧光光谱(X-Ray Fluorescence spectroscopy, XRF)和无侧限抗压强度(qu)试验来评估模拟效果及可行性。结果表明,在pH值为6.0的浸泡液中浸泡90 d后,试样中富里酸实测质量分数超过了初始掺量,而胡敏酸的实测质量分数相较于初始掺量表现出波动性。试样中孔隙随着腐殖酸掺量的增加而逐渐发育连通,试样所含的原生矿物主要为石英和云母,主要元素为O、Si、Al和Fe。通过与天然泥炭土环境对比分析,揭示了模拟的腐殖酸环境在微观特征上与天然腐殖酸环境具有相似性。宏观力学试验结果表明,模拟试样的qu随腐殖酸掺量的增加而降低,对比分析显示模拟试样的力学性能与天然泥炭土的力学性能接近。以上结果表明,采用所提出的方法可以模拟出与天然泥炭土环境相近的泥炭土腐殖酸环境。

硫酸钙与腐植酸配施对大蒜产量及土壤性质的影响

为明确河南蒜区大蒜生产和碱性潮土改良最佳措施,设常规施肥(CK)、常规施肥+硫酸钙(T1)、常规施肥+腐植酸(T2)、常规施肥+硫酸钙+腐植酸(T3)的处理,研究了不同施肥方式对大蒜产量、叶片抗氧化能力、土壤酶活性、土壤结构的影响,分析了不同施肥方式对大蒜产量和碱性潮土改良的效果。结果表明,在常规施肥的基础上配合施用硫酸钙与腐植酸,能显著提高叶片SOD、POD、CAT活性,增强土壤酶活性,对团粒直径>0.25mm土壤水稳性团聚体的形成有促进作用,效果优于CK、T1、T2;T3大蒜产量达15620.95 kg·hm^(-2),比当地常规施肥极显著增产11.97%。综上所述,硫酸钙与腐植酸配施对河南蒜区的大蒜产量和土壤性质的改善具有较好的效果。

煤基与生物基腐植酸配施对土壤结构改良的影响

为探究煤基腐植酸与生物基腐植酸混合对土壤结构的影响并筛选出一种效果最佳的混合比例,本研究采用土壤培养方法,通过将煤基腐植酸与生物基腐植酸按不同质量比设计成复合腐植酸改良半生土,以不施腐植酸为对照(CK),分析培养10、25、50 d时复合腐植酸对土壤团聚体、孔隙度等结构指标的影响。结果显示:土壤各项理化指标整体改良效果表现为50 d>25 d>10 d;土壤团聚体含量、平均质量直径随煤基腐植酸含量增加而增加,单施煤基腐植酸时最佳,培养50 d时土壤团聚体含量较CK组增加116.36%,平均质量直径较CK组增加了21.80%;比较发现,培养10 d时土壤总孔隙度、田间持水量随生物基腐植酸比例增大而增加,容重随之降低,而培养25 d和50 d时,总孔隙度和田间持水量则随煤基腐植酸比例增大而增加,容重随之降低;煤基和生物基腐植酸7∶3组合最佳,50 d时该组合土壤总孔隙度和田间持水量分别较CK组增加10.46%和43.52%,容重降低8.25%。研究表明,煤基腐植酸和生物基腐植酸均可有效改善土壤结构,当混合质量比为7∶3时效果最佳。该混合比例的复合腐植酸可综合生物基腐植酸和煤基腐植酸的优点,有效改善土壤结构,为退化土壤修复提供一定的技术支撑和科学依据。