亚铁对水稻土中尿素氮去向的影响

生产实践和研究表明^[1,2],土壤中还原物质积累过多,常是直接或间接导致潜育性水稻土上水稻生长不良和产量较低的原因之一。Fe⁺⁺又是土壤还原物质的主要成分。因此,我们曾于1981年以施用Fe⁺⁺、葡萄糖、紫云英的方法,模拟田间土壤还原条件,进行了水稻盆栽试硷,对潜育性水稻土中N素供应特性及N素平衡作了初步研究^[3]。试验表明,施入亚铁使水稻明显减产,但却促进了水稻对化肥N素的吸收利用,减少了N素的损失。为了进一步摸清和验证施入Fe⁺⁺对水稻土中尿素N素平衡的影响,1982年继续进行了这项工作。     

甲醛肟比色法测定土壤中Mn2+时对干扰的消除

本文介绍一种简单、安全、可靠的方法来消除甲醛肟比色法测Mn²⁺时Fe²⁺和Fe³⁺的干扰,在试液中铁的总浓度不超过20mg/L的情况下,可得到良好的结果。溶液中如存在有色的有机化合物时,可预先用浓硫酸和浓硝酸消煮除去。     

不同熟化度红壤及红壤性水稻土的腐殖质组成及其特性

土壤腐殖质是评价红壤肥力的重要因素^[2],根据前人研究^[8,3,1]:一般土壤腐殖质的含量及组成受土壤地带性的影响。胡敏酸与富啡酸的比值自南向北逐渐递增,红壤胡敏酸与富啡酸的比值小于1。本文着重研究同一地区自然成土因素类同的情况下,红壤通过水旱耕作和培肥,土壤腐殖质的组成及特性的变化。     

胡敏酸吸附解吸Fe3+反应特征研究

采用C-25葡聚糖凝胶层析方法研究了在不同酸度、离子强度、温度条件下胡敏酸（HA）吸附解吸Fe3^＋特征.结果表明,在相同离子强度、反应温度条件下,随着pH的升高,HA对Fe（Ⅲ）最大吸附量Smax和吸附平衡常数k增加,标准摩尔自由能变△Gom绝对值减小.相同pH和温度下,离子强度从0.00到0.10mol L^-1,HA对Fe（Ⅲ）最大吸附量Smax和吸附亲和力常数k增加,自由能变△G^o m绝对值减小,但离子强度从0.10 mol L^-1继续上升到0.15 mol L^-1,则上述特征常数变化刚好相反.温度升高,胡敏酸吸附Fe3^＋的最大吸附量、吸附平衡常数k、自由能变△G^o m绝对值均较大幅度降低,表明升高温度对吸附反应不利.吸附反应的焓变△H^o m和熵变△S^o m均小于零,为放热反应,反应向更有序状态进行;在相同条件下,pH越大,焓变△H^o m和熵变△rS^θ m绝对值越大,表明pH越大,越有利于吸附反应的进行.随着pH的升高,Fe3^＋被还原的百分率η减小,用幂函数方程拟合,相关系数达到显著水平.随着pH的降低,胡敏酸铁Fe3^＋解吸率增大;对解吸率曲线进行拟合,线形方程具有显著的相关系数.胡敏酸吸附Fe3^＋的反应为包括胡敏酸内部和外部结合的“两相”反应.     

长期施肥条件下土壤养分的动态和平衡——Ⅰ对土壤腐殖质积累及其品质的影响

长期施用有机肥和化肥,对土壤腐殖质积累和改善品质的作用研究,于1986～1991在俄罗斯季米里亚捷夫农学院等地进行。主要结果如下:.1.有机肥对土壤腐殖质的积累作用大于NPK化肥。施肥所增加的土壤腐殖质,除了砂壤土外,主要是在0～60cm土层,60cm以下土层施肥效果不明显。.2.长期施用有机肥和NPK化肥,提高了胡敏酸组分Ⅰ(游离的及与活性R₂O₃结合态)的含量和腐殖酸相对迁移率,而与Ca⁺⁺离子结合的胡敏酸组分Ⅱ含量下降。由于胡敏酸组分Ⅱ与Ca⁺⁺离子结合减弱,增加了腐殖质在水中的溶解,使之在大雨或大量灌水时易于淋失。.3.施用有机肥和NPK化肥,水溶性腐殖物质的含量明显提高,缓解了干旱条件下土壤高浓度矿物盐的影响。.4.长期施肥提高了土壤的亲水性;其膨胀容积、膨胀速度常数、土壤吸水量、土壤表面积等指标均不同程度的提高,但砂壤土增加了幅度低于粉砂壤土和粘壤土。.5.胡敏酸甲氧基功能团的含量多寡是衡量土壤腐殖质化的重要指标。试验表明,长期施肥下低肥力酸性土壤中胡敏酸甲氧基含量提高了46％～300％,高肥力非酸性土壤提高了17％～32％。     

用电导频散法研究Cl-、SO42-和H2PO4-阴离子与土壤的相互作用

本文介绍了采用电导频散装置测量分别含有10^-4mol/LHCl、5×10^-5mol/L H₂SO₄和10^-4mol/L H₃PO₄的黄棕壤、棕壤、黑土和砖红壤悬液(20-30g/kg)的电导频散曲线,频散曲线上均呈现频率范围相当宽的坪区,频散曲线的特性分析结果表明,黄棕壤和棕壤在3种酸溶液中的始散频率(0.6-1kHz)低于黑土悬液(16-28kHz),而砖红壤的始散频率最高(25-47kHz;Cl^-、SO₄^2-和H₂PO₄^-离子与4种土壤的相对亲合力(REC_1.5/REC_tp-1)顺序为Cl^- < SO₄^2- < H₂PO₄^-,在不同土壤之间的顺序则随酸溶液而异.     

可变电荷土壤对SO42-的吸附

本文研究了三种带可变电荷的红壤在恒定pH和Cl^-离子存在条件下对SO₄^2-的吸附.三种红壤的OH^-释放量分别仅占SO₄^2-吸附量的12%,14%和20%.砖红壤在pH5.0时的电荷变化占所吸附的SO₄^2-的64-82%.作者认为大部分SO₄^2-以置换水合基的方式被吸附.     

可变电荷土壤和矿物Pb2+ and Cu2+吸附动力学: Ⅶ. Pb2+吸附后H+释放的动力学

The kinetics of H⁺ releasing after Pb²⁺ adsorption was studied by the potentiometric method combined with the acid-base titration curve technique. Results showed that pH of latosol, red soil and kaolinite suspensions dropped sharply, and then decreased gradually. Most of the H⁺ exchanged, more than 60%, was displaced at the first minute after Pb²⁺ was added into the suspension. More H⁺ was released at a higher concentration of Pb²⁺ added for a given sample and the amount of H⁺ released decreased in the order of red soil > latosol > kaolinite at a given concentration. The time-dependent data of H⁺ releasing of latosol, red soil and kaolinite at two concentrations could be fitted best with the second-order equation among the six equations, including second-order equation, two-constant equation, Elovich equation, parabolic diffusion equation, first-order equation and exponential equation. The H⁺/Pb²⁺ exchange stoichiometry increased with time, and a stable ratio of H⁺/Pb²⁺, being 1.73, 1.92 and 2.01 for kaolinite, latosol and red soil, respectively, was reached 25 minutes later.     

应用15N固体核磁共振技术研究苯醌——蛋白质聚合物的氮素形态

本世纪90年代以来,借助于¹⁵N核磁共振技术已经查明,无论是新生成的土壤胡每酸和富啡酸,或是各类土壤中原有的胡敏酸和富啡酸,其非酸解性氮均主要以酸胺态氮存在。     

SO42-和Cl-对稻田土壤养分及其吸附解吸特性的影响

利用长期定位试验 ,比较了长期施用含SO₄^2-和Cl^- 化肥 22年后稻田土壤的 pH值、养分状况及其吸附解吸特性。结果表明 ,长期施用含SO₄^2-化肥 ,土壤有机质、速效氮和速效钾的含量较高 ,但全量氮磷钾的含量较低 ;长期施用含Cl^- 化肥 ,土壤全量氮磷钾和速效磷的含量较高 ,但pH值相对较低。长期施用含上述二种阴离子的化肥后 ,土壤对H₂PO₄^-的最大吸附量均较大 ,且在Cl^- 处理下土壤对H₂PO₄^-吸附的结合能较大 ,而SO₄^2-处理下土壤在同等吸附量时对H₂PO₄^-的解吸量相应较多。长期施用含SO₄^2-的化肥亦使土壤对钾素的供应强度较大 (ΔK0的绝对值较大 )、缓冲能力增强 (AR0值较高 ) ,而长期施用含Cl^- 的化肥时则与SO₄^2-相反     

Bonding and oxidation state of iron in humic complexes extracted from some Greek soils

Electron spin resonance and Mössbauer spectroscopy were used to obtain information on the nature of the bonding and of the oxidation state of iron in complexes of iron-humic substances, some prepared in the laboratory and others extracted from samples of Greek soils developed under different vegetative covers. In the synthetic FeHA complexes prepared at pH 2.8, iron was found to be both in trivalent and bivalent states. At pH 4.0, iron was in the trivalent state and only traces of Fe²⁺ were found.The ESR spectra of the natural HA's and FA's indicated that iron forms complexes with both of them. The Mössbauer spectra, however, did not provide verification for existence of Fe³⁺ organically bound to the humic acids. All the Mössbauer spectra of the natural humic acids showed minute quantities of iron in the ferrous state. The respective parameters indicated that the Fe²⁺ is directly bound to HA's. The ferrous iron probably resulted from the reduction of Fe³⁺ during the humification process. The Mössbauer spectrum of an FeFA complex prepared in the laboratory with a fulvic acid: metal ratio of (1:1) at pH 4.0 showed that iron occurred in both trivalent and bivalent states.Differences in the vegetative cover and in the taxonomic category of the soils studied did not have any effect on the Mössbauer parameters of the natural HA's, but differences were reflected in the ESR spectra of the FA's.     

Complexation of Cu2+ and Pb2+ by peat and humic acid

The binding of metal to humic substances is problematical. The approaches for studying metal binding to organic matter are briefly reviewed. Ion-selective electrodes (Cu²⁺ and Pb²⁺) were used to measure metal complexation by a whole peat and an extracted humic acid (HA) fraction. Scatchard plots and calculation of incremental formation constants were used to obtain values for the binding constants for the metals onto both peat and HA. Both the peat and the humic acid had a larger maximum binding capacity for Pb²⁺ than for Cu²⁺ (e.g. at pH = 5 HA gave 0·188 mmol Cu²⁺ g^?1 and 0·564 mmol Pb²⁺ g^?1: peat gave 0·111 mmol Cu²⁺ g^?1 and 0·391 mmol Pb²⁺ g^?1). Overall, the humic acid had a larger metal binding capacity, suggesting that extraction caused conformational or chemical changes. The binding constants (K₁) for Cu²⁺ increased with increasing pH in both peat and humic acid, and were larger in the peat at any given pH (e.g. at pH = 5 HA gave log K₁= 2·63, and peat gave log K¹= 4·47 for Cu²⁺). The values for Pb²⁺ showed little change with pH or between peat and humic acid (e.g. at pH = 5 HA gave log K¹= 3·03 and peat gave log K¹= 3·00 for Pb²⁺). In the peat, Cu²⁺ may be more able to bind in a 2:1 stoichiometric arrangement, resulting in greater stability but smaller binding capacity, whereas Pb²⁺ binds predominantly in a 1:1 arrangement, with more metal being bound less strongly. Whole peat is considered to be more appropriate than an extracted humic acid fraction for the study of heavy metal binding in organic soils, as this is the material with which metals introduced into an organic soil would interact under natural conditions.     

Infrared spectra of Cu2+ Pb2+ and Ca2+ complexes of soil humic substances

An infrared spectroscopic investigation of the complexes of Cu²⁺, Pb²⁺, and Ca²⁺ with humic and fulvic acids demonstrated the participation of OH and CO groups in addition to COOH in the binding of heavy-metal cations. The degree to which metal-carboxylate linkages are ionic or covalent cannot be accurately determined from the positions of antisymmetric and symmetric carboxylate stretching vibrations due to interference from covalent bonding with other groups. The apparent order of the reaction of three divalent cations with humic and fulvic acids was Cu²⁺ > Pb²⁺ > Ca²⁺.     

硅缓解水稻根系铁毒害

Silicon (Si) can enhance the resistance of plants to many abiotic stresses. To explore whether Si ameliorates Fe2+ toxicity, a hydroponic experiment was performed to investigate whether and how Si detoxifies Fe2+ toxicity in rice (Oryza sativa L.) roots. Results indicated that rice cultivar Tianyou 998 (TY998) showed greater sensitivity to Fe2+ toxicity than rice cultivar Peizataifeng (PZTF). Treatment with 0.1 mmol L-1 Fe2+ inhibited TY998 root elongation and root biomass significantly. Reddish iron plaque was formed on root surface of both cultivars. TY998 had a higher amount of iron plaque than PZTF. Addition of Si to the solution of Fe treatment decreased the amount of iron plaque on root surface by 17.6% to 37.1% and iron uptake in rice roots by 37.0% to 40.3%, and subsequently restored root elongation triggered by Fe2+ toxicity by 13.5% in the TY998. Compared with Fe treatment, the addition of 1 mmol L-1 Si to the solution of Fe treatment increased xylem sap flow by 19.3% to 24.8% and root-shoot Fe transportation by 45.0% to 78.6%. Furthermore, Si addition to the solution of Fe treatment induced root cell wall to thicken. These results suggested that Si could detoxify Fe2+ toxicity and Si-mediated amelioration of Fe2+ toxicity in rice roots was associated with less iron plaque on root surface and more Fe transportation from roots to shoots.     

Interactions of aluminium and fulvic acid in moderately acid solutions: stoichiometry of the H+/Al3+ exchange

Complexation with organic matter controls the activity of dissolved Al³⁺ in many soils. The buffering intensity of these soils is largely dependent on the H⁺/Al³⁺ exchange ratio, i.e. the number of protons consumed by the solid phase when one Al³⁺ is released. Here, the H⁺/Al³⁺ exchange ratio was determined from batch titrations using solutions of fulvic acid (FA) as a model for soil organic matter. Aluminium was added, from 1.04 to 6.29 mmol Al per g FA, which is within the range of humus‐bound Al found in the upper B horizon of podzolized soils. Furthermore, pH was varied with NaOH to give values between 3.5 and 5.0. The H⁺/Al³⁺ exchange ratio ranged between 1.49 and 2.23 with a mean of 1.94. It correlated positively with pH and the total concentration of Al present. Theoretically, this can be explained with a partial hydrolysis of bound Al. The slope of logAl (log₁₀ of Al³⁺ activity) against pH generally underestimated the actual exchange ratio, which can partly be attributed to the systems being diluted (100 mg FA l^?1). However, where 4 mmol Al or more had been added per g FA, the logAl slope gradually approached ?3 between pH 4.5 and 5.0. This might be the result of a shift from Al³⁺ activity control by humus complexation to control by Al(OH)₃(s).     

The H+/M2+ exchange stoichiometry of calcium and zinc adsorption by ferrihydrite

The specific adsorption of Ca²⁺ and Zn²⁺ by ferrihydrite results in the net release of H⁺. The rate and H⁺/M²⁺ exchange stoichiometry of this reaction were monitored with a pH-stat. A rapid reaction of less than 6 min was followed by a slower reaction which continued at a diminishing rate for at least 2 days. Adsorption of Ca²⁺ at pH 7.8 and Zn²⁺ at pH 5.4 resulted in the net release of 0.92 and 1.70 mol H⁺/mol M²⁺ adsorbed, respectively. For Zn²⁺ adsorption, this stoichiometry was shown to be independent of pH. These estimates agree well with independent estimates based on the pH dependence of adsorption. The difference between the Ca²⁺ and Zn²⁺ stoichiometries was related to the differing acidity of the –OH₂ ligands attached to the adsorbed ions.     

褐煤腐植酸对钾的吸附特性研究

为给褐煤的有效利用和腐植酸缓效肥的研制提供理论依据，本试验采用吸附等温线的试验方法，探讨了K⁺平衡溶液浓度、平衡时间、pH值及固液比对褐煤腐植酸钾吸附的影响。结果表明：介质pH值升高有利于腐植酸样品对钾的吸附，且能加快吸附反应的速度；当pH<4.4时，K_d1>K_d2，此时以物理吸附为主。当7.12K_d1<K_d2，化学交换占主导地位。其等温吸附曲线符合Langmuir吸附形式，动力学吸附用Elovich方程描速最佳。经硝酸处理后的褐煤腐植酸样品对钾的吸附能力有了一定程度的提高。适宜的固液比能提高2种样品对钾的单位吸附量，分别在固液比为0.06和0.04时达最大，其单位吸附量分别为0.079 g/g和0.094 g/g。     

Influences of Humic Acid on Cr(VI) Removal by Zero-Valent Iron From Groundwater with Various Constituents: Implication for Long-Term PRB Performance

A 9-month-long continuous flow column study was carried out to investigate Cr(VI) removal by Fe⁰ with the presence of humic acid. The study focused on the influences of humic acid promoted dissolved iron release and humic acid aggregation in Fe⁰ columns receiving synthetic Cr(VI) contaminated groundwater containing various components such as bicarbonate and Ca. The effects of humic acid varied significantly depending on the presence of Ca. In Ca-free columns, the presence of humic acid promoted the release of dissolved iron in the forms of soluble Fe-humic acid complexes and stabilized fine Fe (hydr)oxide colloids. As a result, the precipitation of iron corrosion products was suppressed and the accumulation of secondary minerals on Fe⁰ surfaces was diminished, and a slight increase in Cr(VI) removal capacity by 18% was record compared with that of humic acid-free column. In contrast, in the presence of Ca, as evidenced by the SEM and FTIR results, humic acid greatly co-aggregated with Fe (hydr)oxides and deposited on Fe⁰ surfaces. This largely inhibited electron transfer from Fe⁰ surfaces to Cr(VI) and reduced the drainable porosity of the Fe⁰ matrix, resulting in a significant decrease in Cr(VI) removal capacity of Fe⁰. The Cr(VI) removal capacity was decreased by 24.4% and 42.7% in humic acid and Ca receiving columns, with and without bicarbonate respectively, compared with that of Ca and humic acid-free column. This study yields new considerations for the performance prediction and design of Fe⁰ PRBs in the environments rich in natural organic matter (NOM).     

Activite des complexes acides humiques-invertase: Influence des cations floculants

-Humic acid (AH) and invertase (I) may be complexed with one of the following cations Ca²⁺, Co²⁺, Cu²⁺, Mg²⁺, Mn²⁺, Al³⁺ or Fe³⁺ in order to study their catalytic activity and longevity. Provided that enough cations are supplied there is an immediate, almost total flocculation with Cu²⁺, Al³⁺ and Fe³⁺, or a slow flocculation with Ca²⁺, Co²⁺ and Mn²⁺ or no flocculation at all with Mg²⁺, depending on the reactivity between organic matter and cation. The six kinds of complexes have very different enzymatic activities in magnitude and longevity.No correlation was found between enzymatic activity and the atomic weight and valency of the cation used to prepare the complex. There is a pH at which flocs occur that is closely related to the pH of the metal chloride and to the affinity of each cation for precipitate; this pH value largely determines the structure of the humic material and consequently the catalytic activity of the enzymatic complex produced. For Cu²⁺, Al³⁺ and Fe³⁺ complexes, the pH values are low, between 1.7 and 3.2 and correspond to high conversion rates if the AH-I-cation reaction time is short; in cases where the reaction time is more protracted, enzyme molecules bound to the outer surface of the micellae are denatured by these very low pH values and the complexes irreversibly lose much of their activity. For Ca²⁺, Co²⁺ and Mn²⁺, the pH values lie between 4.30 and 5.65 and correspond to nearly ten times lower enzymatic activities; here, however, a prolonged reaction enhances activity. For Mg²⁺, the pH is 6.25–6.45; for this value, the humic material remains highly dispersed in buffer and the complex AH_Mg-I cannot be separated.The possibility of a relation between the number of enzyme molecules retained in complexes and the cationic radii on the one hand, and between the longevity of the complexes and the bound-state of humic acid-flocculating cation, on the other hand, is suggested.     

KINETICS OF ION EXCHANGE IN SOIL ORGANIC MATTER. IV. ADSORPTION AND DESORPTION OF Pb2+, Cu2+, Cd2+, Zn2+ AND Ca2+ BY PEAT

The equilibria as well as the rates of adsorption and desorption of the ions Pb²⁺, Cu²⁺, Cd²⁺, Zn²⁺, and Ca²⁺ by soil organic matter were determined in batch experiments as a function of the amount of metal ions added to an aqueous suspension of HCl-washed peat. Simultaneous determination of the metal ions and hydrogen ions in the solution by atomic absorption spectrophotometry and pH-measurements showed that the adsorption of one divalent metal ion by peat was coupled with the release of two hydrogen ions. Since this equivalent ion-exchange process causes a corresponding increase of the electric conductivity of the solution, the rates of the adsorption and desorption processes were determined by an immersed conductivity electrode. The distribution coefficients show that the selective order for the metal adsorption by peat is Pb²⁺ > Cu²⁺ > Cd²⁺≌ Zn²⁺ > Ca²⁺ in the pH range of 3·5 to 4·5. The slope of -2, as observed in a double logarithmic plot of the distribution coefficients versus the total solution concentration confirms the equivalence of the ion-exchange process of divalent metal ions for monovalent H₃O⁺ -ions in peat. The absolute rates of adsorption, as well as the rates for the fractional attainment of the equilibrium, increase with increasing amounts of metal ions added. This behaviour is also observed for the subsequent desorption of the metal ions by H₃O⁺-ions. At a given amount of metal ions added, the absolute rates of adsorption decrease in the order Pb²⁺ > Cu²⁺ > Cd²⁺ > Zn²⁺ > Ca²⁺, while the rates for the fractional attainment of the equilibrium decrease in the order Ca²⁺ > Zn²⁺≌ Cd²⁺ > Pb²⁺ > Cu²⁺. The half times for adsorption and desorption were in the range of 5 to 15 sec.