用凝胶层析法和示踪技术评估腐植酸分子量分级组成及其与Cd、Zn的络合特性

通过凝胶层析法对土壤腐植酸进行了分组提取,并对其各分子量分级组成及其与Cd、Zn的络合特性进行了研究.结果表明:土壤胡敏酸通过G-50可以分成3个较集中的组分,分子量分别为M=78180、M=48339及M=22863;通过G-100可以得到2个组分,分子量分别为M=63343和M=19870.富里酸通过G-50、G-100层析,则从总体上成为单一的宽带,分子量约为M=2300.腐植酸对Cd、Zn络合量的测定显示:胡敏酸对Cd、Zn的络合量呈2个明显的峰值,而富里酸只有1个峰值.两者对Cd、Zn络合量随洗脱体积的变化曲线与其吸光值随洗脱体积的变化曲线相一致.65Zn示踪技术研究65Zn与胡敏酸、富里酸络合的结论与常规方法一致.     

不同腐殖酸组分对湖泊沉积物中重金属释放的影响

腐殖酸作为湖泊沉积物中有机质的主要成分．对重金属具有强烈的富集能力，从而影响湖泊沉积物中重金属向水中的释放。本文深入探讨了腐殖酸的不同组分对沉积物中Cu、Zn、Pb、Cd向水中释放的影响。结果表明：腐殖酸的添加使沉积物中重金属的释放置明显受到影响。Cu、Zn、Pb、CA4种重金属随着胡敏酸和富里酸的添加．释放量逐渐增加，并且两种腐殖酸的用量越大．重金属的释放量越大。向沉积物中加入同等量的胡敏酸、富里酸，两种腐殖酸对重金属释放的促进作用胡敏酸〉富里酸。向沉积物中加入不同用量的富里酸FA，沉积物中Cu、Zn、Pb、Cd的释放率分别为73％～80％，18．5％～22％，7．5％～10％．97％～99％；而在相同条件下，向沉积物中加入不同用量的胡敏酸HA，对以上4种重金属的释放率分别为66．5％～72％，15．5％～19．5％．6％～8．5％，96％～98．5％。在腐殖酸用量相同的情况下，溶液的pH对沉积物中重金属的释放也会产生影响。即随着pH值上升．释放量逐渐减少。当pH=8时，释放量基本上已不再发生变化，说明此时沉积物中的重金属基本上与腐殖酸的羧基反应完毕。     

不同施肥处理土壤胡敏酸及其级分 与 Fe2+的络合特征 Ⅰ.胡敏酸原样与 Fe2+的络合特征

采用 17年不同施肥处理 (无肥、化肥、秸秆、厩肥 )土耕层土样 ,在对土壤胡敏酸性质研究的基础上 ,着重研究不同施肥处理土壤胡敏酸与Fe2+的络合特征 ,揭示络合作用与胡敏酸性质以及环境条件的关系。结果表明 ,不同施肥处理土壤胡敏酸与Fe2+的络合能力不同。和无肥处理相比 ,化肥处理胡敏酸的络合能力加强 ,logk值 (络合稳定常数 )增大 ,有机肥处理则使胡敏酸的络合能力下降 ,logk值减小。logk值大小与胡敏酸的羧基、酚羟基以及总酸度有关。pH值、温度、离子强度是影响络合稳定常数大小的环境因素 ,pH值由 4到 7,各处理胡敏酸的logk值增大 ,络合配位数也有增加趋势。温度升高 ,离子强度增大 ,logk值降低。胡敏酸与Fe2+络合反应是一个自发的放热反应 ,络合后整个体系的有序性增强 ,熵值减小。     

不同处理牛粪对植菜土壤腐殖质结构特征的影响

通过元素组成分析法、红外光谱分析法(IR)、核磁共振光谱分析法(13 C-NMR)等现代分析方法,研究施用新鲜牛粪、腐解牛粪和蛴螬牛粪2a后对植菜轮作土壤胡敏酸(HA)和富里酸(FA)的影响。结果表明,与单施化肥(CK)相比,不同牛粪处理对植菜土壤胡敏酸和富里酸的元素组成影响有较大的差异,各牛粪处理均引发植菜土壤胡敏酸C含量和C/H降低,O含量、O/C和(N+O)/C升高,富里酸C含量和C/N升高,N、O含量和O/C降低,降低了植菜土壤胡敏酸的缩合程度,升高了土壤胡敏酸的氧化程度和极性,降低了植菜土壤富里酸的氧化程度。不同牛粪处理使植菜土壤胡敏酸的脂肪族化合物减少,且均含有苯基碳、酚羟基C、芳香醚和(或)与O、N等取代基邻、对位的连H芳香C,使芳构化程度增加,富里酸的脂肪族化合物增加,芳香类、羧基类化合物减少,芳构化程度降低。不同牛粪处理的植菜土壤未改变土壤腐殖质的基本结构特征,只引起植菜土壤的结构单元和官能团数量上的差异。     

西北黄土地区土壤腐殖物质的研究

本研究了西北黄土地区土壤腐殖质的含量、组成、性质与分布。其结果是：1.土壤腐殖质含量，是从东南向西北呈由高到低的分布规律。2.胡敏酸的含量、胡敏酸/富里酸的比值及胡敏酸的芳构化程度，均以陕西靖边县草原植被下的轻黑垆土为中心，向西和西北荒漠草原植被下的棕钙土与白绵土；向南森林草原与森林植被下的滕土和褐土；向东是黄绵土逐渐降低。胡敏素的含量是向西、北、南及东逐渐增加。3.与钙结合的胡敏酸，以黑垆土为中心是向西、北、南和东递减；与铁铝结合的胡敏酸是向西、北、南和东递加。4.胡敏酸芳构化程度：草原土壤>干草原与森林草原土壤>荒漠草原和森林土壤。     

草炭溶解态有机物质与Cu^2＋、Cd^2＋络合稳定性

研究了由草炭提取的胡敏酸（HA），富里酸（FA），水溶解态有机物质（WSOM）的基团特征，分子量分布及其与Cu^2 、Cd^2 两种金属离子之间的强合生。对HA，FA及WSOM的红外光谱研究显示三者的官能团组成相似，只是含量略有不同。固态^13C-NMR对HA，FA及WSOM结构特征的描述以及水相凝胶色谱法对三种有机质样品的分子量及分子量分布的测定结果显示HA分子最大且含有大量的长链烷烃，而FA分子小得多，结构以碳水化合物及多糖为主，WSOM的分子量略低于FA。结果与FA相近。离子交换平衡法对三种有机质样品与Cu^2 、Cd^2 的络合配位数和稳定常数的测定结果显示两种介质条件下络合配位数（x)，络合稳定常数（logk)的次序均为：Cu^2 ＞Cd^2 ；同一介质条件下，对不同有机质而言均满足：M－HA＞M－FA＞M－WSOM。     

生物炭对紫色土中腐植酸淋溶的影响

为了减少紫色土腐植酸的流失,提高龙川江流域紫色土肥力,采用土柱室内模拟方法,通过模拟降雨淋溶,研究了不同生物炭处理下(CK、1%、3%、5%和10%)对紫色土淋溶液p H值、电导率、体积以及胡敏酸和富里酸的影响。结果表明:在29 d试验过程中,淋溶液的p H值和电导率随着生物炭比例增加而增加;与CK相比,在1%、3%、5%和10%的生物炭处理条件下紫色土水分损失分别减少了6.33%、10.13%、16.46%和25.32%;胡敏酸浓度和累积淋失量随着生物炭比例增加而减小;除了1%和3%之外,富里酸浓度和累积淋失量也随着生物炭比例增加而减小;生物炭比例为10%的处理条件下对紫色土淋溶液中胡敏酸和富里酸浓度及累积淋失量最小,胡敏酸浓度和累积淋失量分别为1.46 mg/L、0.12 mg,富里酸浓度和累积淋失量分别为149.64 mg/L、29.60 mg,该处理有利于更大程度吸附胡敏酸和富里酸,减少其流失。     

四川成都经济区土壤腐殖质重金属元素含量特征研究

通过对四川成都经济区16件土壤样品腐殖质组成及其各组分中重金属元素含量的分析表明,胡敏素是土壤腐殖质的主要组成部分,富里酸和胡敏酸次之。土壤腐殖质中重金属元素含量占土壤全量20%～44%,是土壤重金属污染元素主要存在方式。重金属元素在腐殖质不同组分中的含量具有很大的差异,Cr主要赋存在胡敏素中,Cd、As、Cu、Zn等元素主要赋存在富里酸中。各重金属元素在腐殖酸中含量较高,富里酸中的含量均大于胡敏酸,其机理是富里酸对重金属元素的络合是腐殖酸与重金属相互作用的主要方式。     

高温快速发酵对鸡粪重金属形态分布及有机质含量影响

以鸡粪、玉米秸秆为主要原料,通过添加酵素进行好氧堆肥发酵试验,研究了不同温度和时间下堆肥 pH值、EC值、重金属含量与形态、腐殖质含量变化以及红外光谱特征。结果表明,与堆肥前相比,pH值随温度升高和时间的延长而增大,最大可增加 0.53个单位,而 EC值随堆肥时间延长表现为先增加后降低的趋势,在 85℃处理下最低。由于浓缩效应,重金属含量均不同程度增加,Cu、Zn、Cr、Cd和 As含量较堆肥前相比最大增幅分别达到35.6%、11.5%、35.0%、35.3%和23.8%。然而,重金属可交换态分配率则有所降低,残渣态比例相应增加,与堆肥前相比,鸡粪有机肥中Cu、Zn、Cr、Cd和 As钝化率分别为24.8%、26.0%、27.6%、26.9%和13.9%。高温处理下,胡敏酸和富里酸含量较低,胡敏酸 /富里酸(HA/FA)比值随着堆肥时间和温度增加而增大,且随着堆肥进程脂肪族、芳香族、羧酸类分子以及多糖类物质均有所减少。结果显示高温下(85℃)不仅加快堆肥发酵进程,而且可以有效钝化重金属,可达到无害化效果。     

秸秆和猪粪的施用对土壤镉有效性的影响和机理研究

用盆栽试验研究作物秸秆和腐熟猪粪对土壤镉（Cd）有效性的影响及机理。结果表明,施用秸秆促进油麦菜对Cd的吸收,而施用猪粪降低油麦菜对Cd的吸收,这主要是由于秸秆显著地增加了交换态Cd含量,而猪粪则显著降低交换态Cd含量。秸秆或猪粪对交换态Cd含量的影响则主要与土壤胡敏酸（HA）和富里酸（FA）的变化有关。施用秸秆对土壤中FA增加幅度大于对HA的增加幅度,即HA/FA比值降低。而施用猪粪则增加了HA/FA比值。相关分析表明,施用秸秆和猪粪情况下土壤HA/FA与交换态Cd含量之间呈显著负相关关系（P＜0.05）。结果还表明,秸秆和猪粪对土壤交换态Cd含量的影响还与其对腐殖酸芳构化程度的影响有关,添加猪粪比添加秸秆的土壤腐殖酸芳构化程度大。因此,有机物质对土壤Cd有效性的影响与土壤有机质组成的变化密切相关。     

Stability constants of complexes of metals with humic and fulvic acids under non-acid-conditions

Stability constants of complexes of four divalent metal ions viz. Cu²⁺, Zn²⁺, Mn²⁺ and Ca²⁺ with humic (HA) and fulvic acids (FA) at pH values of 7 and 8 were determined. The log K (logarithm of the stability constant) ranged from 3.09 to 7.77 and from 2.22 to 5.98 for metal-humic and metal fulvic acid complexes, respectively. Sequentially, the order of stability constants were as follows: Cu> Ca> Mn> Zn and Cu> Ca> Zn> Mn for metal -HA and metal-FA complexes, respectively, indicating a higher degree of complexation with Cu metal ion.     

不同分子量腐植酸的结构特征及其对土壤镉有效性的影响

为探究不同分子量腐植酸组分的结构特征,本研究利用褐煤粉提取腐植酸进行超滤分级,获得四个不同分子量的腐植酸组分。研究发现,分子量大于50 kDa和小于1 kDa的腐植酸分别占总腐植酸的49.66%、47.07%,中间两个组分占比很小；腐植酸的理化性质和功能主要是由1 kDa以下的腐植酸和50 kDa以上的腐植酸所决定的。1 kDa以下的腐植酸总酸性基、羧基和酚羟基官能团含量最高,酚羟基占总酸性基的比例也较高,腐植酸的芳香化程度、缩合度随分子量的增大而增大,含氧官能团含量、E4/E6值随分子量的增大而减少。通过盆栽试验,探索了不同分子量腐植酸对土壤镉有效性的影响,土壤对镉的吸附量随腐植酸分子量的增大而减少,各处理均在500 mg/L时达到吸附平衡；土壤镉的解吸量亦随腐植酸分子量的增大而减少。小分子量腐植酸的酸性官能团丰富,对土壤重金属的吸附络合能力更强,可以降低土壤对镉的吸持能力,提高其移动性和生物有效性；大分子腐植酸则主要起吸持和固定作用,降低重金属的移动性和生物有效性。     

Über die Hemmung der Aminopeptidase K (aus Tritirachium album Limber) durch Huminstoffe

The Inhibition of Aminopeptidase K (from Tritirachium album Limber) by Humic Acids Interactions between Aminopeptidase K (from Tritirachium album Limber) and thirteen humic acids were examined. Ten of the humic acids were extracted from different types of soil; three were preparations based on hydroquinone, two of these were chemically modified by methylation and acetylation. All of the humic acids were found to cause complete inhibition of the enzyme, with no significant difference between the effects of natural and synthetic humic acids. The reaction constants showed the type of inhibition to be noncompetitive. The inhibited enzyme could be partially reactivated by the addition of zinc. It is assumed that zinc causes enlargement of the humic acid particles and thus a decrease in the number of inhibiting particles. An interesting relation between the average particle weight and the number of humic acid particles could be pointed out. With a molecular weight smaller than 10000, an increasing number of humic acid particles is necessary for affecting the activity of Aminopeptidase K.     

MOLECULAR WEIGHT DISTRIBUTION OF SOIL ORGANIC MATTER AS AFFECTED BY ACID PRE-TREATMENT AND FRACTIONATION INTO HUMIC AND FULVIC ACIDS

Effects of acid pre-treatment and fractionation on the molecular weight distribution of OIM Na₄P₂O₇ organic matter extracts were investigated in a chronosequence of weakly weathered soils developed on aeolian sand in New Zealand. Acid pre-treatment of soils with OIM HCl followed by OIM HCI:03M HF was found to enhance the polydispersion in the nominal molecular weights of the extracts. The same treatment resulted in significant increases in yield and reduction in ash content. However, prolonged standing of extracts in the acids led to acid-induced polymerization, resulting in a predominance of organic matter in the higher nominal molecular weight ranges. Fractionation of organic matter extracts by acid precipitation into humic and fulvic acids did not separate them according to molecular weight as commonly believed. Instead, fulvic acids from most soils were found to have similar nominal molecular weight distributions to those of their humic acid counterparts. A large proportion of soil fulvic acid compounds was in the > 100 000 nominal molecular weight range.     

Protonation reactions of fulvic acids

The protonation reactions of fulvic acids are described in terms of a model involving a mixture of n monoprotic acids HA, HB, HC … pH titration data were analysed by nonlinear least squares methods, using a model having n independent 'titration' (protonation) constants, K_i i= 1 to n , and n– 1 independent acid concentrations. The best fit was obtained with n =4. The results for three fulvic acid samples were in the range log K₁ 6.5–6.7 (∼8% of total carboxyl acidity), log K₂ 5.3–5.6 (∼15%), log K₃ 3.9–4.8 (∼20–30%) and log K₄ 2.6–2.7 (∼50–70%).
The results indicate a comparatively small proportion (∼ 10–20%) of polyprotic carboxyl moieties in the diverse fulvic acid structures. They give some support to the Wershaw model of fulvic acids as strongly associated aggregates of acids, each of comparatively low molecular weight.     

A COMPARISON OF THE POLYCARBOXYLIC ACIDS EXTRACTED BY WATER FROM AN AGRICULTURAL TOP SOIL WITH THOSE EXTRACTED BY ALKALI

Humic and fulvic acids were isolated from an agricultural soil by conventional means. The same soil was extracted with water and the organic matter freed of inorganic and low molecular weight substances. The usual chemical differences between humic acid and fulvic acid were confirmed and the water extract was shown to resemble fulvic acid quite closely. Further fractionation of the fulvic acid and water extract showed that the elemental composition, carboxyl and acidic hydroxyl contents, molecular weights, and infrared spectra of the purified polycarboxylic acids were virtually identical. Both promoted the same growth response in cultured isolated tomato roots. It is suggested that the qualitative similarity of fulvic acid to the polycarboxylic acid extracted by water justifies the use of the more easily isolated fulvic acid in physiological experiments on the direct effects on plants of soil organic matter.     

Chemical heterogeneity of humic substances: characterization of size fractions obtained by hollow-fibre ultrafiltration

To investigate the chemical heterogeneity of humic substances in relation to molecular size, fulvic and humic acids were extracted and purified from the surface horizon of a Humic Gleysol in northern Switzerland. A fractionation scheme using hollow‐fibre ultrafiltration cartridges was developed and used to obtain four size fractions of the humic acid with nominal molecular weight ranges > 300 kDa, 100–300 kDa, 30–100 kDa, and 10–30 kDa. The fulvic acid and all humic acid fractions were characterized by size exclusion chromatography, elemental analysis (C, H, N, S), as well as spectroscopic techniques including UV‐VIS, CP‐MAS ¹³C‐NMR, FT‐IR, and fluorescence spectroscopy. Clear chemical differences between the humic acid size fractions were observed. Smaller size fractions of the soil humic acid contained more chargeable functional groups and a larger percentage of aromatic carbon than the larger size fractions. Conversely, the percentage of aliphatic carbon increased with increasing apparent molecular weight. The chemical composition of the smallest humic acid fraction differed clearly from the fulvic acid fraction, despite similar apparent molecular size and carboxyl carbon content. Small humic acids contained much more aromatic carbon and less aliphatic carbon than the fulvic acid fraction. Apparently, humic size fractions differ in their chemical composition, which can have important implications for their environmental behaviour.