Adsorption of chloride and nitrate by variable charge soils in relation to the electric charge of the soil

A cell consisting of a chloride-selective electrode and a nitrate-selective electrode was directly put in the soil suspension to determine the concentration ratio NO₃^?/Cl^? for studying the adsorption of these two ions by three soil samples from variable charge soils. It was found that such factors as the iron oxide content of the soil, the pH of the suspension, the concentration of the respective anion, the kind of accompanying cations, and the dielectric constant of solvent etc. can all affect the amounts and the ratio of the two anions adsorbed. The adsorption was chiefly caused by coulombic force, but another mechanism, presumably a covalent force between the anion and the metal atom on the surface of soil particles, may also be involved, at least for chloride ions.     

恒电荷土壤及可变电荷土壤与离子间相互作用的研究 I.共存离子对NO_3~-吸附的影响

研究了我国典型３种可变电荷土壤和４种恒电荷土壤在陪伴阳离子分别为Ｋ十、Ｎａ十、Ｃａ２＋时和１ｍｍｏｌＬ－１ＫＣ１、Ｋ２ＳＯ４支持电解质中ＮＯ３－的吸附。结果表明，ＮＯ３－吸附量随ｐＨ的增加而减小。在添加相同浓度ＮＯ３－时，３种可变电荷土壤对ＮＯ３－的吸附量顺序为Ｃａ（ＮＯ３）２＞ ＫＮＯ３＞ＮａＮＯ３＞ＫＮＯ３十ＫＣＩ＞ＫＮＯ３＋Ｋ２ＳＯ４；在初始ＮＯ３－浓度０．５－５ｍｍｏｌＬ－１的范围内，吸附量随浓度变化的关系符合Ｌａｎｇｍｕｉｒ等温吸附式．由此求出与ＮＯ３－吸附结合能有关的常数（Ｋ）在不同共存离子存在下数值较小且差异不大，因此认为不同陪伴阳离子和不同伴随阴离子对ＮＯ３－吸附的电性机理影响不大，只是改变了土壤表面的正电荷数量从而使吸附量发生变化。４种恒电荷土壤对ＮＯ３－的吸附量通常很小，其中在Ｃａ（ＮＯ３）２介质中较在其他介质中稍大，最大吸附量仅为１．５～ｍｍｏｌ ｋｇ－１左右，约为可变电荷土壤的１／１０，且在浓度较低时常观察到负吸附。     

伊朗西部地区碱性土壤中共离子对Zn吸附的影响

Zinc(Zn) is essential to plant growth and relatively mobile in soils.This study was conducted to assess the effect of common ions(Ca 2+,K +,Na +,NH + 4,Cl,NO 3,and H 2 PO 4) on sorption of Zn in surface samples of ten calcareous soils from western Iran using 10 mmol L 1 KCl,KNO 3,KH 2 PO 4,Ca(NO 3) 2,NaNO 3,and NH 4 NO 3 solutions as background electrolytes.The results indicated that both NH + 4,K +,and Ca 2+ equally decreased Zn sorption as compared to Na +.Zinc sorption was decreased by H 2 PO 4 as compared to NO 3 and Cl.The Langmuir and Freundlich equations fitted closely to the sorption data of all ions.The Langmuir maximum,bonding energy constant,and Freundlich distribution coefficient for Zn sorption differed among the various ionic background electrolytes.Langmuir sorption parameters showed that the presence of H 2 PO 4 decreased the maximum Zn adsorbed,but increased the bonding energy.Although K + and NH + 4 equally influenced maximum Zn adsorbed,they differed in their effect on the distribution coefficient of Zn in soils.Values of saturation index calculated using Visual MINTEQ indicated that at the low Zn concentration,Zn solubility was controlled by sorption reactions and at the high Zn concentration,it was mainly controlled by sorption and mineral precipitation reactions,such as precipitation of Zn 3(PO 4) 2.4H 2 O,Zn 5(OH) 6(CO 3) 2,and ZnCO 3.For most ionic background electrolytes,soil pH,CaCO 3,and cation exchange capacity(CEC) were significantly correlated with sorption parameters.     

恒电荷土壤与可变电荷土壤K+的吸附特性

对我国 3种典型可变电荷土壤和 4种恒电荷土壤在不同 K 浓度和 p H下 K 的吸附特性进行了研究。结果表明 ,两类土壤 K 吸附量均随平衡 K 浓度增加而增加 ,在低浓度 (添加K 0 .1～ 1.0 mmol/ L )时两者符合线性 ,在高浓度 (添加 K 0 .5～ 5 .0 mmol/ L )下两者符合Langmuir方程。L angmuir方程的参数 K两类土壤间差异不大 ,但以可变电荷土壤 >恒电荷土壤 ,说明前类土壤 K吸附结合能较大 ,吸附 K 不易解吸 ,K 有效性较低。p H降低使土壤 K 吸附量减少 ,但恒电荷土壤与可变电荷土壤减少的机理不同 ,前者主要是由于 H 与 K 的竟争吸附 ,而后者主要是由于表面负电荷减少而引起的电性引力的改变。     

恒电荷土壤与可变电荷土壤对Cl~-和NO_3~-吸附的差异及其机理

对 3种可变电荷土壤和 4种恒电荷土壤在不同 pH、不同浓度、不同相伴阴阳离子下混合体系中Cl-和NO3-的吸附进行了测定。结果表明 ,在Cl-和NO3- 共存体系中 ,Cl-比例增大使可变电荷土壤Na+吸附量及OH-释放量增加 ,而对恒电荷土壤影响不大。Cl-和NO3-吸附量随平衡Cl-和NO3-浓度增加而增大 ,随pH升高而减少。但恒电荷土壤在上述各种条件下对Cl-和NO3-吸附均相同 ,而可变电荷土壤对Cl-吸附量大于NO3-的吸附量 ;NO3-、Cl-的选择系数为 0.51～0.78,Cl-和NO3-的相对吸附量分别为56.9%和 43.1%。在不同相伴阳离子下 ,可变电荷土壤平衡溶液Cl-/NO3-比值均小于 1,且为Na+K+Ca2+Mg2+Fe3+;而恒电荷土壤Cl-/NO3-比值为 1左右 ,且不受阳离子类型的影响。由此认为 ,Cl-和NO3-在两类土壤中均以电性吸附为主 ,恒电荷土壤对Cl-和NO3-的亲合力及吸附机理相同 ;而可变电荷土壤对Cl-的亲合力 NO3- ,Cl-存在着专性吸附     

恒电荷土壤和可变电荷土壤动电性质的研究 Ⅱ.阴离子吸附和pH的影响

本工作研究了阴离子吸附和ＰＨ对恒电荷土壤（黄棕壤和黑土）和可变电荷土壤（砖红壤）动电性质的影响。结果表明,砖红壤吸附不同阴离子后的ζ电位随ＰＨ升高由正电位移至负电位,在ζ电位－ＰＨ曲线上均有一个等电点（ＩＥＰ）在ＰＨ３．５～８之间,相同ＰＨ升高由正电红壤的ζ电位随吸附阴离子的负移顺序是ＨＰＯ４＾２－〉Ｆ＾－〉ＳＯ４＾２－〉Ｃｌ＾－〉ＮＯ３＾－。作为恒电荷土壤的黄棕壤和黑土,在不同电解发质溶液中的ε     

恒电荷土壤及可变电荷土壤与离子间相互作用的研究 Ⅱ.共存体系中Cl-的吸附特性

对 3种可变电荷土壤和 4种恒电荷土壤在陪伴阳离子分别为Na 、K 、NH 4 、Mg2 、Ba2 、Al3 和共存SO2 -4下Cl- 的吸附量进行了测定。结果表明 ,供试土壤的Cl-吸附量顺序均为AlCl3>BaCl2 和MgCl2 >KCl和NH4 Cl>NaCl,其中可变电荷土壤的差异较大。不同电解质溶液中Cl- 吸附量的顺序与土壤所带正电荷量的顺序一致。Langmuir方程的K值较小 ,且在不同介质中的差异不大。随SO2 -4浓度的增大 ,可变电荷土壤对Cl- 的吸附量减少 ,平衡液的pH值增大 ,而恒电荷土壤则变化甚微 ,说明共存的SO2 -4使可变电荷土壤的表面负电荷增加 ,但对恒电荷土壤则影响不大。这些结果说明 ,Cl- 以电性吸附的机理不因介质而变。可变电荷土壤在一价阳离子存在时 ,除土壤本身所带的正电荷外 ,还有一价阳离子吸附后产生的正电荷以及由此引起的对Cl- 的协同吸附。在二、三价阳离子存在时 ,还有Cl- 的离子对吸附 ,而恒电荷土壤在所有介质中 ,似乎总是以与Cl- 的协同吸附为主     

Adsorption of Potassium and Calcium Ions by Variable Charge Soils

Interactions of potassium and calcium ions with four typical variable charge soils in South China were examined by measuring pK-0.5pCa value with a potassium ion-selective electrode and a calcium ion-selective electrode,and pK value with a potassium ion-selective electrode.The results showed that adsorption of potassium and calcium ions increased with soil suspension pH,and the tendency of the pK-0.5pCa value changing with pH differed with respect to pH range and potassium to calcium ratio.Adsorption of equal amount of calcium and potassium ions led to release of an identical number of protons,suggesting similar adsorption characteristics of these two ions when adsorbed by variable charge soils.Compared with red soil,latosol and lateritic red soil had higher adsorption selectivities for calcium ion.The red soil had a greater affinity for potassium ion than that for calcium ion at low concentration,which seems to result from its possession of 2:1 type minerals,such as vermiculite and mica with a high affinity for potassium ion.The results indicated that adsorption of potassium and calcium ions by the variable charge soils was chiefly caused by the electrostatic attraction between the cations and the soil surfaces.Moreover,it was found that sulfate could affect the adsorption by changing soil surface properties and by forming ion-pair.     

可变电荷土壤中铜离子的解吸

研究了我国四种可变电荷土壤红壤、赤红壤、砖红壤和铁质砖红壤以及二种恒电荷土壤黄棕壤和黑土中吸附性铜离子的解吸特征。研究结果表明 ,可变电荷土壤吸附的一部分铜离子可以被去离子水解吸 ,而且在pH～解吸率曲线上在一定pH值时出现解吸率最大值。在最大值时不同土壤中铜离子解吸率的大小与土壤中氧化铁的含量有关。氧化铁的含量越高 ,在最大值时铜离子的解吸率越大。当用中性电解质解吸可变电荷土壤吸附的铜离子时 ,电解质的浓度越大 ,解吸率越低。与此相反 ,恒电荷土壤吸附的铜离子不能被去离子水解吸 ,只能被中性电解质解吸 ,且电解质的浓度越高 ,解吸率越大。这表明 ,可变电荷土壤中吸附性铜离子的解吸规律 ,完全不同于恒电荷土壤中者。本文初步讨论了其原因     

Effect of Low Molecular Weight Organic Anions on Adsorption of Aluminum by Variable Charge Soils

To examine the effect of organic anions on adsorption of Al by variable charge soils at different pH values, the adsorption by three soils in the presence of three low-molecular-weight aliphatic carboxylic acids was investigated. The results showed that the effect depended on pH, the type of organic anions and their concentration. The presence of citrate and oxalate led to an increase in the adsorption of Al at low pH and low concentration of organic anions, with citrate showing a stronger effect than oxalate. For example, the maximum increments of Al adsorption in the presence of citrate were 131.9, 104.8 and 32.9% in the Hyper-Rhodic Ferralsol, the Rhodic Ferralsol and the Ferric Acrisol, respectively, whereas in the presence of oxalate it was 36.1% in the Rhodic Ferralsol. At high pH or high concentration of organic anions, they showed an inhibiting effect on the adsorption of Al. For example, citrate caused the increase in Al adsorption by 164.0, 131.0 and 61.0% at pH3.85 and the decrease in Al adsorption by 15.2, 19.5 and 45.6% at pH 4.8 for the Hyper-Rhodic Ferralsol, the Rhodic Ferralsol and the Ferric Acrisol, respectively. In the citrate and oxalate systems, the adsorption of Al increased with the increase in the concentration of organic anions, reaching a maximum values at about 0.4 mmol L^?1, and then decreased. When the concentration of organic anions was higher than about 1.0 mmol L^?1, both citrate and oxalate inhibited the adsorption of Al. The ability of organic anions in increasing the adsorption at low pH and decreasing the adsorption at high pH followed the same order: citrate > oxalate > acetate. The increase of Al adsorption at low pH is caused by the increase in soil negative surface charge as a result of the adsorption of organic anions by variable charge soils, while the decrease of Al adsorption at high pH and high concentration of organic anions is related to the competition of organic ligands for aluminum ions with soil surface. After the removal of free iron oxides from the soil, Al adsorption decreased in the presence of citrate, the anion species most strongly adsorbed by variable charge soils and complexed with aluminum ions. For example, for the Rhodic Ferralsol and the Ferric Acrisol, the removal of free iron oxides caused a decrease in the adsorption of Al in the presence of citrate at pH4.4 by 26.2 and 21.9%, respectively.     

可变电荷土壤吸附铜离子时氢离子的释放

可变电荷土壤吸附铜离子后 ,土壤的中和曲线上不出现pH突跃 ,而变成一条平缓变化的曲线。当土壤悬液的pH低于一定数值时 ,加入铜离子后不释放氢离子。该pH值与土壤中氧化铁的含量有关。氧化铁的含量越高 ,该pH值越高。对于大多数可变电荷土壤 ,此pH值为 4左右。对可变电荷土壤 ,pH值越接近 4,氢离子释放的快速过程越不明显。在pH 4左右 ,加入铜离子后 1 0分钟时 ,释放的氢离子量仅占 6 5分钟时释放量的 3 0 %左右。但当pH值高于 4 5时 ,在大多数情况下 ,加入铜离子后半分钟时释放的氢离子量即可占 6 5分钟时的 5 0 %以上。恒电荷土壤吸附铜离子时氢离子的释放速度比可变电荷土壤快得多。即使pH值低至 3 8,在加入铜离子后半分钟时氢离子的释放量即占 6 5分钟时的 5 6 %以上。可变电荷土壤吸附铜离子时的H/Cu比比恒电荷土壤大得多。当恒电荷土壤悬液中加入0 1mo1L- 1 NaNO3作支持电解质时 ,吸附铜离子时的H/Cu比增大。     

Solubility control of KCl extractable aluminum in soils with variable charge

Abstract

Solubility and kinetic data indicated that concentrations of aluminum (Al) extracted with 1 M KCl are determined by the solubility of a precipitated A1(OH)₃ phase in soils dominated by variable charge minerals. Kinetic studies examining the release of Al on non‐treated and KCl treated residues indicated the precipitation of an acid‐labile Al phase during the extraction procedure. The log ion activity products estimated for the KCl extracts ranged between 8.1–8.6 for the reaction Al(OH)₃ + 3H⁺ < = > Al³⁺+ 3H₂O, which was similar to the solubility product of several Al(OH)₃phases. The mechanism proposed for Al precipitation indicated that Al released by exchange with added K⁺ hydrolyzed and released H⁺ that was readily adsorbed on surfaces of variable charge minerals. The increased ionic strength of the extracting solution further increased the amount of H⁺adsorbed to the variable charge surface and reduced the H⁺ concentration in the aqueous phase. Consumption of H⁺ induced further hydrolysis of Al, resulting in supersaturation of the extracting solution and formation of polynuclear hydroxy Al species. It was concluded that the 1 M KCl extraction does not quantitatively extract salt exchangeable Al from variable‐charge soils.     

恒电荷土壤及可变电荷土壤与离子间相互作用的研究 Ⅰ.共存离子对NO3-吸附的影响

研究了我国典型3种可变电荷土壤和4种恒电荷土壤在陪伴阳离子分别为K+、Na+、Ca2+时和1mmolL-1KCl、K2SO4支持电解质中NO-3的吸附.结果表明,NO-3吸附量随pH的增加而减小.在添加相同浓度NO-3时,3种可变电荷土壤对NO-3的吸附量顺序为Ca(NO3)2＞KNO3＞NaNO3＞KNO3+KCl＞KNO3+K2SO4;在初始NO-3浓度0.5～5mmolL-1的范围内,吸附量随浓度变化的关系符合Langmuir等温吸附式.由此求出与NO-3吸附结合能有关的常数(K)在不同共存离子存在下数值较小且差异不大,因此认为不同陪伴阳离子和不同伴随阴离子对NO-3吸附的电性机理影响不大,只是改变了土壤表面的正电荷数量从而使吸附量发生变化.4种恒电荷土壤对NO-3的吸附量通常很小,其中在Ca(NO3)2介质中较在其他介质中稍大,最大吸附量仅为1.5mmolkg-1左右,约为可变电荷土壤的1/10,且在浓度较低时常观察到负吸附.     

土壤供氮能力指标研究

本文对国内外土壤供氮能力指标的研究进行了论述 ,作者根据自己的研究结果认为 :在土壤起始NO- 3 N含量较高时 ,用KCl煮沸浸取出的一定深度土壤的NO- 3 N就可作为土壤供氮能力指标 ,反映出当前土壤的供氮能力 .而在土壤起始NO- 3 N含量较低或考虑到起始NO- 3 N的影响后 ,1mol/LNaOH扩散出的NH+ 4 N或KCl煮沸法在酸性土壤上浸取出的NH+ 4 N则是较好的土壤供氮能力指标 ,反映了土壤潜在的供氮能力     

土壤电化学性质的研究--Ⅶ.土壤中氯化钠的平均活度的田间测定

氯化钠是盐渍化土壤中可溶性盐的一个重要组成分,对土壤性质和植物生长有直接影响。为了测定土壤中的氯化钠含量,通常采用一定的水土比例将盐溶出,然后用化学法或电化学法测定两种离子。但是在关于土壤盐分与植物生长的关系的研究中,较为关心的是植物根系所处的实际土壤环境。如果能够不将土壤取出而直接原位测定该种条件下的离子状况,应该具有重要意义。近年来离子选择性电极的发展,使这种测定成为可能。     

Adsorption of sulphate and fluoride by variable charge soils

The adsorption of sulphate and fluoride by three variable charge soils was studied. Adsorption increased with increase in the amount of sulphate added at constant _pH, and decreased with increase of _pH.
The ratios of the amount of released OH⁻to that of the adsorbed SO^2-₄ at pH 5–0 were 0.12, 0.14 and 0.20 for the three soils, respectively, much lower than the corresponding OH⁻/F⁻ ratios which ranged from 0.3 to 1.0. For a ferric acrisol the OH⁻ released accounted, on average, for only 15% of the SO^2-₄ adsorbed, leaving more than 60% to be explained by the decrease in positive charge and the increase in negative charge carried by the soil.     

A Model for Anion Electric Adsorption on Variable Charge Soils

A model was established for anion electric adsorption on variable charge surfaces and an equation to describe the relationship of adsorption amount with equalibrium concentration and suspension pH was derived according to the principles of surface reaction between variable charge surface and anions.The adsorption behaviours of nitrate and chloride on variable charge soils were modelled and the results showed that the model could describe the adsorption of nitrate very well.     

磷酸盐吸附对可变电荷土壤正负电荷的影响

本文研究了华南地区不同类型的可变电荷土壤，并对磷酸盐的吸附量和吸附磷后土壤的正、负电荷的变化，以及ｐＨ和游离氧化铁对这种变化的影响进行了研究。结果表明，土壤吸磷量与土壤游离氧化铁含量成良好的正相关。土壤吸磷后正电荷减少，负电荷增加，土壤电荷量与吸磷量之间呈抛物线状相关。吸附１摩尔磷酸盐对土壤净负电荷的贡献在０．３－１．０摩尔之间。土壤中的游离氧化铁使吸附的磷对土壤负电荷的贡献减少。     

离子强度和pH对可变电荷土壤与铜离子相互作用的影响

研究了离子强度和pH对可变电荷土壤表面电荷与铜离子吸附的影响。作为对照 ,也研究了它们对恒电荷土壤黄棕壤的有关性质的影响。结果表明 ,随pH升高 ,土壤的表面负电荷增加 ,正电荷减少。对于可变电荷土壤 ,可出现电荷零点 (pH0 )。随pH升高 ,土壤对Cu2 的吸附量增大。随着离子强度增大 ,恒电荷土壤对Cu2 的吸附百分率明显降低 ,可变电荷土壤对Cu2 离子的吸附百分率也降低 ,但降低的幅度比恒电荷土壤者小得多。土壤中氧化铁的含量越高 ,降低的幅度越小。对于含 2 1 %左右游离氧化铁的铁质砖红壤 ,即使支持电解质NaNO3的浓度高达 1molL- 1,对Cu2 的吸附仍然几乎没有影响。从离子强度和pH与土壤表面电荷和铜离子吸附的关系 ,可以推测在土壤对铜离子的吸附中 ,既存在电性吸附 ,又存在专性吸附。在可变电荷土壤对铜离子的吸附中 ,专性吸附较为重要     

大气CO2浓度升高和氮肥施用对小麦生长期间土壤溶液阴离子含量的影响

在中国稻/麦轮作 FACE(Free-Air CO2 Enrichment)平台上,采用根际土壤溶液取样器来研究大气CO2 浓度升高和不同 N 肥水平对小麦生长期间土壤溶液离子组成的影响。结果表明,高 CO2 浓度条件对土壤溶液pH 值无显著影响,但却普遍降低土壤溶液中 Cl-、NO3 和 SO4 3 种主要阴离子含量;相对于 N 150 kg/hm2 施 N - 2-水平,N 250 kg/hm2 施用量显著降低土壤溶液中 NO3 含量,同时也明显降低 Cl-和 SO4 含量。 - 2-