森林土壤阳离子特性对土壤溶液离子动态的影响

<正>1 前言要掌握土壤溶液的溶解元素的移动特性,重要的是要搞清溪流的水质特性,以及明确森林土壤对酸性降落物等外部影响的净化机能和森林生态系统的物质循环机理。一般来说,阴离子比阳离子难被粘土矿物吸附,所以土壤溶液的离子动态受不稳定的阴离子制约。据研究,pH值低的土壤,随着土壤溶液阴离子浓度的上升,土壤溶液的A1~(3+)浓度也上升。坡位和土壤深度不同,土壤的交换性阳离子量不同,土壤溶液的离子动态也随之变化。于是,在柳杉、扁柏林撒施NH_4Cl,使土壤溶液的NO_3~-和Cl-浓度增加,依此研究土壤的交换性阳离子量与土壤溶液的阳离子     

土壤矿物对有机质的吸附与固定机制研究进展

鉴于土壤有机质在生态系统及碳储存方面的重要性,关于土壤矿物对土壤有机质的吸附与固定机理方面的研究越来越受到了学术界的广泛关注。本文综述了近年来报道较多的土壤矿物对土壤有机质的吸附机制,以及主要影响因素。在众多矿物类型中,水合铁、铝氧化物及黏土矿物对有机质的吸附性较强,配体交换、络合、氢键、阳离子桥接、缩合及范德华力作用是土壤矿物与有机质之间的主要作用机制。土壤pH是影响矿物表面电荷及吸附位点的关键因素,进而影响矿物对有机质的吸附。土壤矿物表面的有机质含量对其继续吸附有机质具有一定的影响。吸附态有机质大多呈层状结构,越接近矿物表面的有机质与土壤矿物的结合越紧密。土壤有机质的稳定性受有机质与矿物间的作用力影响,一般而言,以化学键合吸附在矿物表面的有机质最稳定,其次为直接与矿物表面作用的电子"供体-受体"机制,范德华力和静电作用稳定性较差。近年来,随着分析设备和技术的进步,一些新的表征与探测方法(如热重分析、差示扫描量热法、傅里叶转换红外光谱、扫描电子显微镜、原子力显微镜、扫描透射X射线显微镜、中子散射技术等)被用于"矿物-有机质"结合机制的研究中,这些新手段毫无疑问会帮助更好地认识矿物与有机质间的作用机理。关于微生物在矿物吸附有机质、"矿物-有机质"复合体形成和演化过程中所起的作用,研究相对较少,但很明显这是至关重要的。     

磷酸根在矿物表面的吸附-解吸特性研究进展

综述了磷酸根在一些常见土壤矿物表面吸附–解吸特性的研究进展。磷酸根在矿物表面的吸附特性受环境pH、离子强度、温度、反应时间、矿物类型等多种因素的共同影响。一般说来,矿物表面的磷吸附量随pH降低而增加,受离子强度的影响较小。磷酸根在矿物表面的吸附动力学过程可分为快速吸附过程和慢速吸附过程,且在弱结晶矿物中存在微孔扩散过程。磷酸根在矿物表面的解吸过程通常存在两个阶段(初始快速解吸和随后的缓慢解吸),在解吸反应后期甚至还会发生再吸附。此外,磷酸根的吸附特性也受共存阴离子配体或金属阳离子的影响。其中,共存阴离子通过位点竞争、静电作用和空间位阻效应等机制影响磷酸根的吸附。天然有机质(包括胡敏酸和富里酸)降低了磷酸根在矿物表面的吸附,特别是在低p H条件下。通常,富里酸比胡敏酸更能有效降低磷酸根在矿物表面的吸附。金属阳离子可通过表面静电效应、形成三元络合物以及形成表面沉淀等机制促进磷酸根和金属在矿物表面的共吸附。最后,展望了与磷酸根在矿物表面吸附特性有关的研究热点和方向。     

阳离子与金霉素在土壤中竞争吸附的研究

<正>有研究表明,不同土壤对金霉素的吸附能力存在差异。同时其Kf值与土壤吸附平衡溶液pH之间显著负相关[1]。作为两性抗生素,金霉素在不同土壤溶液pH下的解离状态或存在状态不同,其随介质pH不同而呈阳离子、一价阴离子、二价阴离子或兼性离子状态,从而导致了其在4种不同类型土壤中的吸附差异。     

除草剂在土壤中的行为

<正> 一、吸附吸附和在土壤一除草剂系统中吸附一解吸平衡的特点在很大程度上决定了制剂的除草活性、它们对土壤性质的影响程度及在土壤剖面中的移动。吸附的特点、程度和稳定性是由很多因素决定的,其中最重要的是吸附剂和被吸附物质的性质、土壤溶液的 pH和水分温度状况。1.吸附剂的性质土壤的吸附能力是随着高分散或粘粒组分含量的增加而增加,在这些组分中发现大部分被吸附的除草剂。在土壤胶体中有机质具最高比表面积和阳离子代换容量,这些物质在吸附中的主导作用已被许多研究者指出。     

土壤吸附重金属的影响因素研究现状及展望

重金属元素在土壤中的吸附特征是重金属污染研究的重点之一。重金属元素在土壤中的吸附反应极为复杂,受多方面因素的影响。土壤对重金属的吸持依赖于土壤的类型、物理化学性质,如土壤的矿物特性,有机组成,土壤溶液的组成和pH,也与重金属离子本身的特征,外加阴阳离子、人工有机和无机络合剂有关。在今后的土壤吸附研究中应该结合形态分析和放射性同位素示踪的方法,并加强对根际土壤这一新领域的研究。     

镉与柠檬酸、EDTA在几种典型土壤中交互作用的研究

采用批平衡实验方法研究了镉在青黑土 (IB)、黄棕壤 (YB)和红壤 (R)三种土壤上的吸附和解吸过程以及吸附介质酸度、共存有机酸等对此过程的影响。结果表明 :柠檬酸、EDTA的存在明显降低了镉在黄棕壤和青黑土上的吸附 ,同时镉解吸率较在硝酸钠体系要小 ,有机物的存在增加了土壤中镉的相对非饱和吸附点位。而在红壤上有机物的存在对镉的影响则随介质pH的改变而发生显著变化。酸性条件下 ,有机物的存在增加镉在红壤上的吸附 ,而随pH的增加 ,有机物减少镉的吸附。同时镉在硝酸钠体系中的解吸率随总吸附量的增加而呈现峰形的变化规律。土壤类型变化显著影响镉与有机物之间的交互作用过程     

共存阳离子（Ca、Zn、K）对土壤镉有效性的影响

采用盆栽与吸附试验,研究了镉污染赤红壤上,施用相同摩尔浓度的钙、钾与锌对小油菜生物量、镉吸收量及土壤镉吸附的影响。结果表明,低和高镉污染赤红壤上,施用锌明显增加小油菜地上部生物量,较对照分别增产21.1%和7.82%。不同阳离子（钠、钙、钾和锌离子）共存改变土壤吸附镉能力的程度不同,与钠体系相比,钙、钾和锌体系中土壤镉吸附量分别降低65.6%、72.0%和96.9%,共存离子降低土壤镉吸附量的次序为锌离子〉钾离子和钙离子,锌离子的影响最为明显。高镉污染赤红壤上,钙和钾使小油菜吸镉量分别增加5.5%和14.4%,低于低镉污染赤红壤上钙和钾使小油菜吸镉的增加量（分别为16.6%和19.6%）;锌明显降低小油菜吸镉量,高和低镉污染赤红壤上,较对照分别减少45.8%和35.0%。3种阳离子与镉共存时,对土壤镉生物有效性的影响差异取决于竞争吸附与竞争吸收的大小,其机制有待进一步探讨。     

基于农田土壤镉污染修复后糙米镉的指标筛选

目前农田土壤镉污染修复以降低糙米镉含量为标准,而忽略了其变化的关键性的土壤物理、化学及生物指标。基于此,采用方差分析、多元回归分析、通径分析、随机森林和结构方程模型等统计方法分析了土壤pH值、有机质、容重、阳离子交换量、速效养分、质地、微团聚体、酶活性、微生物数量等23个土壤指标对土壤有效态Cd和糙米Cd含量重要性排序。结果表明,总体上施用土壤调理剂提高了土壤pH值、容重和阳离子交换量,改变了土壤质地组成,增加了大粒级团聚体,并影响了微生物环境,有效降低了土壤有效态Cd和糙米Cd含量,但抑制了部分酶活性和微生物数量。通过逐步回归分析,表明土壤pH值和放线菌可以解释土壤有效态Cd 64.32%的变化,阳离子交换量、速效钾、有效磷和蔗糖酶可以解释糙米Cd 82.10%的变化;通径分析表明大粒径团聚体、有机质、黏粒、砂粒、放线菌和真菌对土壤有效态Cd和糙米Cd的直接效应较大;随机森林分析表明土壤pH值是影响土壤有效态Cd和糙米Cd含量的主导因素;结构方程模型表明糙米Cd含量主要受土壤pH值、有机质、阳离子交换量和有效磷的影响,土壤有效态Cd主要受土壤酶活性和微生物数量的影响。不同分析方法侧重点不同,总体上对糙米Cd含量影响较大的是pH值、阳离子交换量、有效磷和有机质等,对土壤有效态Cd含量影响较大的是pH值、放线菌和有机质等。     

鄂、湘两省山地土壤粘粒矿物的研究──Ⅳ.幕阜山土壤的粘粒矿物与表面性质

本文对幕阜山五个海拔高度计２１个土层的土样，测定了粘粒矿物组成，阳离子交换量，电荷量和对磷酸根的吸附。结果表明，随着海拔升高、粘粒的层状矿物，氧化物组成和有机质含量出现规律性变化，从而导致了粘粒的表面电荷性质和离子吸附特性出现相应差异，表现为阳离子交换量和阴离子交换量升高，土壤可变电荷量增高，对磷酸根离子的吸附量增大，解吸率降低。     

Adsorption of pentachlorophenol by soils

The adsorption studies using soils various in the species of clay minerals and organic matter content indicate:

1) That apparent adsorption occurs to the greatest extent on the strong acid soil system compared to the moderate acid soil system, regardless of the species of clay mineral and organic matter content. And there is no adsorption on the slightly acid or neutral soil system.

2) The apparent adsorption involves adsorption of molecules and/or anions and precipitation of molecules in the micell and the external liquid phase.

3) The magnitude of adsorption occurs in the decreasing order of humus-allophanic, allophanic, montmorillonitic, and halloysitic soils.

4) The major factor governing the magnitude of apparent adsorption is pH.     

Competitive sorption between imidacloprid and imidacloprid-urea on soil clay minerals and humic acids

Soil organic matter and clay minerals are responsible for the adsorption of many pesticides. Adsorption and competitive sorption of imidacloprid on clay minerals and humic acids (HA) were determined using the batch equilibration method. The sorption coefficient of imidacloprid on humic acids was significantly higher than that on Ca-clay minerals, indicating that soil organic matter content was a more important property in influencing the adsorption of imidacloprid. Competitive sorption was investigated between imidacloprid and its main metabolite imidacloprid-urea on HA and Ca-clay minerals. The results showed that the sorption capacity of imidacloprid on clay minerals and HA was reduced in the presence of the metabolite, implying that imidacloprid-urea could occupy or block adsorption sites of imidacloprid on soil, potentially affecting the fate, transport, and bioavailability of imidacloprid in the environment. The interactions between a Ca-clay or HA-clay mixture and adsorption of imidacloprid and imidacloprid-urea were studied using IR differential spectra on thin films made of the adsorbent. The possible mechanisms were discussed from the shift of characteristic IR absorption bands of imidacloprid and imidacloprid-urea after sorption.     

Effects of Organic Anions on Phosphate Adsorption and Desorption from Variable—Charge Clay Minerals and Soil

Effects of citrate and tartrate on phosphate adsorption and desorption from kaolinite,goethite,amorphous Al-oxide and Ultisol were studied.P adsorption was significantly decreased as the concentration of the organic anions increased from 10^-5 to 10^-1 M.At 0.1 M and pH 7.0,tartrate decreased P adsorption by 27.6%-50.6% and citrate by 37.9-80.4%,depending on the kinds of adsorbent.Little Al and/or Fe were detected in the equilibrium solutions,even at the highest concentration of the organic anions.Effects of the organic anions on phosphate adsorption follow essentially the competitive adsorption mechanism.The selectivity coefficients for competitive adsorption can be used to compare the effectiveness of different organic anions in reducing P adsorption under given gonditions. Phosphate desorption was increased by 3 to 100 times in the presence of 0.001 M citrate or tartrate compared to that in 0.02 M KCl solution alone.However,for all the soil and clay minerals studied the amount of P desorbed by citrate or tartrate was generally lower than or close to that of isotopically exchangeable P.The effect of organic anions on phosphate desorption arises primarily from ligand exchange.     

Effect of soil composition on adsorption of lead as reflected by a study on a natural forest soil profile

The adsorption characteristics of lead on each genetic horizon of a natural brown forest soil profile were studied to recognize the possible immobilizing effect of a mineralogical diverse soil profile in the case of a possible lead contamination. Lead adsorption experiments were carried out on whole soil samples, soil clay fractions, as well as on their carbonate and organic matter free variant. TEM-EDS analyses were performed to characterize the adsorption capacity of individual mineral phases. The most important lead adsorbents in order of importance are the organic matter, the clay minerals, and the iron oxides. The most significant process is the ion exchange of calcium by lead with the respect to adsorption. The organic matter adsorbs more lead than clay minerals, and clay fractions adsorb more lead as compared to the whole soil samples. Among mixed layer clay minerals, those containing swelling component have the highest lead adsorption capacity, but the exact distinguishing of the individual clay mineral particles with the respect to their adsorption capacity is not possible. The calcite influences the lead adsorption through its buffering capacity: high calcite content results in lead precipitation. Soils characterized by high amount of organic matter, swelling clay mineral accumulation horizon and calcareous subsoil are suitable medium to immobilize a significant lead pollution.     

THE ADSORPTION OF COPPER BY SOIL MATERIALS AT LOW EQUILIBRIUM SOLUTION CONCENTRATIONS

The adsorption of copper by individual soil components (organic matter fractions, oxides and clay minerals) was examined at equilibrium solution concentrations of copper within the range found in natural soils, the distribution of copper between solution and solid phases being measured by means of labelling with radioactive ⁶⁴Cu. At these low solution concentrations it was found that the copper adsorption isotherms were essentially linear. The oxides and organic materials adsorbed the greatest amounts of copper. The concentration of copper in natural soil solutions will be controlled by these materials to a far greater extent than by the clay minerals, the influence of which may be negligible in some soils. Solution concentrations of copper are relatively unaffected by both the background concentration of major cations and by changes in pH within the ionic strength and pH range found in normal agricultural soils. Copper adsorption studies with humic and fulvic acids showed that total solution copper concentrations could be greatly enhanced above the equilibrium levels for ionic copper by the presence of soluble organic complexes. The importance of taking into account the presence of such copper complexes in soil copper studies is emphasised.     

Adsorption of Cadmium and Zinc onto Micaceous Minerals: Effect of Siderophore Desferrioxamine B

The mobility, bioavailability, and environmental fate of heavy metals in soil are controlled by their adsorption onto soil minerals and solid organic matter. The adsorption is strongly affected by the presence of various low-molecular-weight organic acids. In this study, effect of hydroxamate siderophore desferrioxamine B (DFOB) on cadmium (Cd) and zinc (Zn) adsorption onto two micaceous clay minerals, muscovite and phlogopite, was evaluated in batch experiments. Results showed that the presence of DFOB diminished the adsorption of Cd and Zn onto both minerals, particularly under neutral to alkaline pH conditions. For instance, at pH 8.2, the presence of DFOB caused a decrease in the adsorption of Zn onto phlogopite by nearly 50%. The equilibrium adsorption of Cd and Zn was satisfactorily described using Freundlich isotherm. The adsorption isotherms showed that the affinity of Cd and Zn onto the minerals decreased in the presence of DFOB. For example, at pH 8.0, the presence of siderophore caused a decrease in the Freundlich adsorption isotherm coefficient K_F for Zn adsorption onto muscovite and phlogopite from 4.60 to 0.07 L g^-1 and from 3.56 to 0.36 L g^-1, respectively. These findings confirm the potential influence of siderophore on the fate of Cd and Zn in arid soils containing substantial contributions of micaceous silicate minerals.     

有机酸对高岭石, 针铁矿和水铝英石吸附镉的影响

Effects of organic acids （oxalic, acetic, and citric） on adsorption characteristics of Cadmium （Cd） on soil clay minerals （kaolinite, goethite, and bayerite） were studied under different concentrations and different pH values. Although the types of organic acids and minerals were different, the effects of the organic acids on the adsorption of Cd on the minerals were similar, i.e., the amount of adsorbed Cd with an initial solution pH of 5.0 and initial Cd concentration of 35 mg L^-1 increased with increasing concentration of the organic acid in solution at lower concentrations, and decreased at higher concentrations. The percentage of Cd adsorbed on the minerals in the presence of the organic acids increased considerably with increasing pH of the solution. Meanwhile, different Cd adsorption in the presence of the organic acids, due to different properties on both organic acids and clay minerals, on kaolinite, goethite, or bayerite for different pHs or organic acid concentrations was found.     

Equilibrium adsorption of isoproturon on soil and pure clays

The adsorption of isoproturon on soil and pure clay minerals has been investigated as a means of understanding its mobility in soils. Measured adsorption coefficients are correlated with soil and clay mineral properties. Soil organic matter controlled the adsorption of isoproturon at organic carbon contents exceeding 27 g kg^?1, whereas at less than this threshold, clay mineral surfaces appeared to control adsorption. The effect of varying temperature suggests that adsorption of isoproturon is a physical process. From the comparison of the fits of linear, Freundlich, and Langmuir adsorption isotherms to the data, the adsorption is best described as a partition process.     

Physicochemical properties of the soils associated with shifting cultivation in Northern Thailand with special reference to factors determining soil fertility

Abstract

Recently agricultural activity in the mountainous area of northern Thailand has increased and problems relating to soil fertility have arisen. In order to gain basic information about the soil properties associated with shifting cultivation, physicochemical properties of the surface soils (0–10 cm) and subsoils (30–40 cm) were investigated in selected villages in the area. The physicochemical properties of the soils studied are summarized as follows: 1) The soils were rich in organic matter, content of which ranged from 11.4 to 63.3 g C kg^?1 in the surface soil. 2) The pH(H₂O) of the soils mostly ranged from 5 to 7 and soil acidity was more pronounced in the deeper horizons. In the surface soils, exchangeable Ca and Mg were generally dominant, whereas exchangeable Al was often predominant in the subsoils. 3) Most of the soils showed a medium to fine texture with more than 30% clay. The clay mineral composition was characterized by various degrees of mixture of kaolin minerals and clay mica with, in some cases, a certain amount of 2:1-2:1:1 intergrades. 4) According to the ion adsorption curves, most of the B horizon soils were characterized by the predominance of permanent negative charges. On the other hand, organic matter contributed to the increase of variable negative charges in the surface soils. The content of organic matter and the percentage of the clay fraction were essential for determining the CEC of the soils of the surface 10 and 30–40 cm depths, respectively. Under the field conditions, the composition of exchangeable cations largely reflected the soil acidity. In addition, the content of organic matter also showed a significant correlation with that of available N in the surface soils. Thus, soil acidity both in the surface soils and subsoils, organic matter content in the surface soils, and clay content in the subsoils were considered to be the main factors that affected soil chemical fertility in the area.