Langmuir,Temkin和Freundlich方程应用于土壤吸附锌的比较

本文分别用Langmuir,Temkin和Freundlich方程拟合土壤吸附锌的等温线。结果表明,吸附数据能很好地符合Freunblich方程,而Langmuir和Temkin方程拟合程度较差。作者从吸附热角度证明了土壤表面不均匀性是造成这种差别的最主要因子。土壤吸附锌过程中吸附热与吸附量的关系满足Freundlich方程模型中关于能量的假设。所以Freundlich方程能比较真实地反映土壤吸附锌的本质,可用予锌吸附机制的探讨。     

长期施肥与土壤性质对水稻土磷吸附的影响

基于长期定位试验(始于1981年),采用磷等温吸附试验方法,研究了不同施肥措施(包括无肥、单施化肥、稻草还田、沼肥)及相关土壤性质对耕层水稻土(0~15 cm)磷吸附特性的影响。结果表明,等温吸附试验中,不同施肥处理的水稻土,随着磷浓度的增加,磷的吸附量逐渐增大。对磷等温吸附曲线,用Langmuir方程拟合效果比Freundlich和Temkin方程好,各处理拟合优势度均在0.99以上。基于Langmuir方程计算,土壤磷最大吸附量(X_m)大小顺序为沼肥稻草单施化肥无肥,且沼肥处理显著高于其余3个处理(P0.05);同时,沼肥处理的磷吸附饱和度亦显著高于其它处理,但处理间土壤磷吸附常数与磷最大缓冲容量无显著差异。X_m值与土壤草酸浸提态磷(P-ox)、无定型铁(Fe-ox)、无定型铝、交换态钙、镁的含量有较高的相关性,其中与P-ox、Fe-ox的相关性最显著,相关系数分别为0.95(P0.01)、0.64(P0.05);主成分分析表明,无定型铁、铝与交换态钙、镁是引起不同施肥处理磷吸附差异的主要因素。与无肥及单施化肥相比,长期施用沼肥显著提高了土壤无定型铁、铝的含量(P0.05),从而增强了土壤磷吸附能力。     

蒙脱石对不同施肥处理土壤胡敏酸及其级分的吸附特征Ⅰ.蒙脱石对胡敏酸的吸附特征

以17年不同施肥处理土壤胡敏酸为材料,研究了不同性质胡敏酸与钙饱和蒙脱石的 吸附特征。结果表明,钙饱和蒙脱石对土不同施肥处理胡敏酸的吸附曲线可用单表面Langmuir方程、双表面Langmuir方程以及Freundlich方程来描述。由单表面Langmuir方程计算的有机肥处理（厩肥、秸秆）胡敏酸的吸附量和吸附强度大于无肥、化肥处理。温度升高各处理胡敏酸吸附量增加,但吸附强度下降。双表面Langmuir揭示,蒙脱石对胡敏酸的吸附呈现高低两种能位的吸附。高能点位的吸附以化学吸附为主,是吸热反应,低能点位的吸附以物理吸附为主,是放热反应。有机肥处理和无肥、化肥处理相比,高能点位吸附相对减弱,低能点位吸附相对增强。     

土壤对铜的吸附-解吸特征及对土地利用的响应

用吸附平衡法研究黄河三角洲地区土壤对Cu2+的吸附和解吸特征,对比了农田和未利用地土壤吸附与解吸能力的差异,并分析了差异形成的原因。结果表明,土壤对Cu2+的吸附量随着平衡液Cu2+质量浓度的增加而增加,其吸附作用可用Langmuir,Temkin和Freundlich方程来拟合,以Langmuir方程拟合结果最佳。根据Langmuir方程计算出的两种土壤最大吸附量分别为3 961mg/kg和3 521mg/kg,农田土壤对Cu2+的吸附能力强于未利用地土壤;土壤Cu2+的解吸量远远小于土壤对Cu2+的吸附量,与农田土壤相比,未利用地土壤Cu2+的解吸有滞后现象;农田土壤和未利用地土壤Cu2+的解吸率变化范围分别为0.1%～0.35%和0.15%～1.8%,农田土壤的解吸率明显低于未利用地土壤。综合分析认为,两种土壤吸附—解吸特征的差异与农田土壤具有较高的有机质含量,从而在土壤胶体表面形成较多的吸附位点有关。     

三种铁氧化物对As(Ⅲ)和As(Ⅴ)的吸附研究

采用批量吸附试验,研究实验室制备的水铁矿、磁铁矿和纤铁矿对As(Ⅲ)和As(Ⅴ)的吸附性能。结果表明,在p H中性条件下,结晶差的水铁矿吸附砷的能力明显优于结晶较好的磁铁矿和纤铁矿,准二级动力学方程拟合效果较好,说明存在多种吸附过程,并可能涉及专性吸附作用;在酸性条件下,三种铁氧化物对As(Ⅲ)和As(Ⅴ)的吸附能力大小顺序均为水铁矿磁铁矿纤铁矿,铁氧化物吸附As(Ⅴ)的能力优于As(Ⅲ),Langmiur方程和Freundlich方程拟合效果均较好,说明铁氧化物对砷的吸附为均匀介质表面的单层吸附或非均匀介质表面的多层吸附;在弱酸至弱碱范围内,三种铁氧化物对As(Ⅲ)的吸附效果均较好且吸附量变化不大,强酸和强碱条件都会引起铁氧化物吸附As(Ⅲ)量的降低,三种铁氧化物对As(Ⅴ)的吸附均随着p H升高而逐渐减少;由于竞争吸附作用,磷酸盐浓度的增加使三种铁氧化物对As(Ⅲ)和As(Ⅴ)的吸附显著减少;随着腐殖酸浓度的增加,三种铁氧化物对As(Ⅲ)的吸附能力逐渐减小,低浓度的腐殖酸微弱地促进铁氧化物对As(Ⅴ)的吸附,高浓度的腐殖酸抑制As(Ⅴ)的吸附。     

五氯酚在酸性土壤表面的吸附-解吸特征研究

本实验研究五氯酚在江西红壤和南京黄棕壤表面的吸附-解吸特征,结果表明:Freundlich和Langmuir等温吸附方程均能较好地描述PCP在两种土壤表面的吸附,且黄棕壤表面的最大吸附量大于红壤。用动力学方程对PCP在红壤中的吸附过程进行拟合,Elovich方程、双常数方程和一级动力学方程均得到较好的结果,其相关系数(R2)在0.96 ~ 0.99之间,达到极显著水平。Elovich方程反映出PCP在土壤表面吸附的能量非均质分布;而抛物线扩散方程不能描述PCP的吸附过程,其相关系数0.46 ~ 0.48。PCP在土壤中的解吸率与有机质含量和pH值相关,随有机质含量增加,PCP解吸率降低,即黄棕壤表土<黄棕壤底土,红壤表土<红壤底土;随模拟酸雨的pH值降低,土壤因对PCP的吸附能力增加,其解吸率降低。     

不同温度下镉在典型农田土壤中的吸附动力学特征

按土重的3%和5%向采自海南和广西的3种可变电荷土壤中添加由稻草制备的生物质炭,混合培养30 d后用一次平衡法研究了生物质炭对土壤吸附Cd（Ⅱ）的影响及其与土壤表面电化学性质的关系,旨在阐明生物质炭促进可变电荷土壤吸附和固定Cd（Ⅱ）的机制。结果表明,添加稻草炭显著提高了3种土壤的阳离子交换量（CEC）和土壤pH,并使土壤胶体Zeta电位向负值方向位移。因此,添加稻草炭增加了土壤表面的负电荷量,土壤表面对Cd（Ⅱ）的吸附容量增强,使3种可变电荷土壤对Cd（Ⅱ）的吸附量增加,且Cd（Ⅱ）吸附量的增幅随稻草炭添加水平的提高而增加。Freundlich方程和Langmuir方程可以拟合3种土壤对Cd（Ⅱ）的吸附等温线,但Freundlich方程拟合效果更好,该方程表征吸附容量的常数k也随着稻草炭添加水平提高而增大。研究表明在pH3.0~5.0范围内,稻草炭均增加土壤对Cd（Ⅱ）的吸附量。添加稻草炭提高土壤pH,促进Cd（Ⅱ）的吸附,因为Cd（Ⅱ）的吸附量随pH升高而增加。解吸实验表明,添加稻草炭处理Cd（Ⅱ）的解吸量高于对照处理,说明生物质炭提高了土壤对Cd（Ⅱ）的静电吸附量。     

稻草生物质炭对3种可变电荷土壤吸附Cd（Ⅱ）的影响

按土重的3%和5%向采自海南和广西的3种可变电荷土壤中添加由稻草制备的生物质炭,混合培养30 d后用一次平衡法研究了生物质炭对土壤吸附Cd（Ⅱ）的影响及其与土壤表面电化学性质的关系,旨在阐明生物质炭促进可变电荷土壤吸附和固定Cd（Ⅱ）的机制。结果表明,添加稻草炭显著提高了3种土壤的阳离子交换量（CEC）和土壤pH,并使土壤胶体Zeta电位向负值方向位移。因此,添加稻草炭增加了土壤表面的负电荷量,土壤表面对Cd（Ⅱ）的吸附容量增强,使3种可变电荷土壤对Cd（Ⅱ）的吸附量增加,且Cd（Ⅱ）吸附量的增幅随稻草炭添加水平的提高而增加。Freundlich方程和Langmuir方程可以拟合3种土壤对Cd（Ⅱ）的吸附等温线,但Freundlich方程拟合效果更好,该方程表征吸附容量的常数k也随着稻草炭添加水平提高而增大。研究表明在pH3.0~5.0范围内,稻草炭均增加土壤对Cd（Ⅱ）的吸附量。添加稻草炭提高土壤pH,促进Cd（Ⅱ）的吸附,因为Cd（Ⅱ）的吸附量随pH升高而增加。解吸实验表明,添加稻草炭处理Cd（Ⅱ）的解吸量高于对照处理,说明生物质炭提高了土壤对Cd（Ⅱ）的静电吸附量。     

磷肥和有机肥对不同磷水平土壤磷吸附-解吸的影响

采用培养试验结合Langmuir吸附等温方程进行拟合求出吸附、解吸的相关参数的方法,研究了磷肥和有机肥对不同磷水平土壤磷吸附和解吸特性的影响。结果表明,随土壤磷水平和磷肥和有机肥用量的增加,土壤最大吸磷量、土壤磷最大缓冲能力显著降低;土壤易解吸磷和土壤磷的解吸率显著增加。土壤易解吸磷和土壤磷的解吸率与土壤Olsen-P呈显著正相关;土壤最大吸磷量、土壤磷最大缓冲容量与土壤Olsen-P呈显著负相关。单位量磷肥所增加的土壤易解吸磷随着磷肥用量和土壤磷水平的增加而增大;土壤磷水平和磷用量是影响土壤磷最大吸磷量和土壤磷最大缓冲能力的重要因素。     

不同类型土壤对汞和砷的吸附解吸特征研究

为了探明不同类型土壤对重金属汞和砷吸附、解吸的影响,以性质差异显著的红壤、黑土和潮土为供试土壤,采用批量平衡法,研究了Hg(Ⅱ)和As(Ⅴ)在不同土壤中的吸附-解吸行为。结果表明:(1)Freundlich方程和Langmuir方程均能较好地拟合这3种土壤对Hg(Ⅱ)和As(Ⅴ)的吸附,其中Hg(Ⅱ)的最大吸附量分别为451.33、1699.46和1635.21mg/kg,大小顺序为黑土>潮土>红壤,相关系数(R2)在0.8533～0.9911之间;As(Ⅴ)的最大吸附量分别为818.44、561.87和112.77mg/kg,大小顺序为:红壤>黑土>潮土,相关系数(R2)在0.9223～0.9949之间;而线性方程则不能较好地拟合这3种土壤对Hg(Ⅱ)和As(Ⅴ)的等温吸附。(2)Hg(Ⅱ)和As(Ⅴ)的解吸量随Hg(Ⅱ)和As(Ⅴ)吸附量的增加而增加,两者之间呈显著或极显著的线性正相关,Hg(Ⅱ)的相关系数(R2)分别为0.8668**、0.8971**、0.9969**,As(Ⅴ)的相关系数(R2)分别为0.9987**、0.9964**、0.9858**。研究结果对于探明土壤中汞和砷的环境行为具有重要意义。     

Adsorption and desorption of arsenate in Louisiana rice soils

Adsorption and desorption of arsenic (As) in the soil are dominant parameters that affect the mobility and bioavailability of arsenic. Batch arsenate adsorption and desorption experiments were conducted using soils collected from three Louisiana, USA, aquaculture ponds representing different crayfish farming and rice cultural practices. Arsenate adsorption behavior in the soils was investigated using Freundlich and Langmuir sorption equations. Results demonstrated that the Langmuir isotherm model was the best fit based on statistical correlation with soil properties governing adsorption, for the entire range of arsenate concentrations for all soils. Adsorption of As(V) was governed by soil physicochemical properties especially Fe and Al oxides, clay and organic matter. Desorption of As(V) was initially fast, but with increasing incubation times desorption occurred progressively slower. Chemical fractionation of arsenic in the soils showed that the most mobile fraction represented 4.74–5.18% of the total arsenic. A part of this mobile fraction could potentially be taken up by rice and enter the food chain, but would require additional research to quantify.     

Effect of Water Extract of Compost on the Adsorption of Arsenate by Two Calcareous Soils

The increasing mobility of arsenate will increase its leachingpotential to groundwater and uptake by plants. The mobility ofarsenate in soils is related to the competitive adsorption with other substances. The effect of organic substances on the adsorption of arsenate by soils was evaluated using the water extract of compost (WEC) as a complex anion source in a batch experiment. Two calcareous slate alluvial soils, Chiwulan andShuipientou, with higher arsenic contents of 23.7 and 12.9 mg kg^-1, respectively, were used. The Langmuir equation has been used to describe successfully the As adsorption isotherm for the two soils. The maximum adsorption of As was 6.098 and 4.785 μmol g^-1 for Chiwulan and Shuipientou soils, respectively. There was competitive adsorption for binding siteson the soils between arsenate oxyanions and organic anions derived from the dissolved organic carbon (DOC) of WEC. Differentcritical pH values were for arsenate addition related to arsenateadsorption on both soils in the absence of DOC of WEC but not inthe presence of DOC of WEC. The soil properties related to arsenate adsorption by the two soils may govern the critical pH values.     

Adsorption of Arsenate on Coarse Loamy Mixed Hyperthermic Fluventic Haplustept Soil of Punjab,Northwest India

A laboratory experiment studied the adsorption of arsenate on coarse loamy mixed hyperthermic Fluventic Haplustept soil of Punjab to serve as cheap materials for removal of arsenic (As) from water with elevated As concentration. The arsenate adsorptions onto soil and soil + iron fillings are described by a two‐region Langmuir isotherm equation; that is, the plots showed two distinct linear portions. The bonding energy and adsorption maxima for arsenate adsorption by soil increased slightly at higher equilibrium temperature of 305 K relative to 280 K in the Langmuir plot for region I but followed an appreciative decline in both parameters for region II. The addition of iron fillings enhanced the adsorption maxima of arsenic soils by 2.5‐fold because of physical adsorption and 4.44‐fold because of chemisorptions or precipitation at weak and strong As concentrations, respectively, in soil–water equilibrated systems. Thus, the results of the present investigation suggest that water withdrawn from shallow aquifer containing elevated As concentrations should be equilibrated with mixtures of soil and iron fillings for removal of As. After an equilibration period, separation of water by decantation or filtration could be used for drinking purposes for humans and domestic animals.     

THE HIGH- AND LOW-ENERGY PHOSPHATE ADSORBING SURFACES IN CALCAREOUS SOILS

The two-surface Langmuir equation was used to study P adsorption by 24 calcareous soils (pH 7.2-7.6; 0.8-24.2 per cent CaCO₃) from the Sherborne soil series, which are derived from Jurassic limestone. High-energy P adsorption capacities (x″_m) ranged from 140–345 μg P/g and were most closely correlated with dithionite-soluble Fe. Hydrous oxides therefore appear to provide the principal sites, even in calcareous soils, on which P is strongly adsorbed (x″_m 6–51 ml/μg P). The low-energy adsorption capacities (x″_m) ranged from 400–663 μg P/g and were correlated with organic matter contents and the total surface areas of CaCO₃ but not with per cent CaCO₃, pH, or dithionite-soluble Fe. Total surface areas of CaCO₃ in the soils ranged from 4.0 to 8.5 m²/g soil. Low-energy P adsorption capacities agree reasonably with values (100 pg P/m²) for the sorption of phosphate on Jurassic limestones but phosphate was bonded much less strongly by soil carbonates (k″= 0.08–0.45 ml/μg P) than by limestones (k～10.0 ml/μg P). Low-energy P adsorption in these soils is tentatively ascribed to adsorption on sites already occupied by organic anions (and probably also by bicarbonate and silicate ions) which lessen the bonding energy of co-adsorbed P.     

菜园土壤锌的吸附——解吸特性研究

本文研究了菜园土壤锌的吸附 -解吸特性。实验结果表明 ,三种菜园土壤吸附Zn2 + 均随平衡液中Zn2 + 浓度的增加而增大 ,且均可用Langmuir方程和Freundlich方程来描述 ,相关系数均大于 0 .9,达极显著水平。由Langmuir方程求得的菜园土壤对Zn2 + 的最大吸附量的大小顺序为 :黄松土 >粉泥土 >江涂砂 ,但对Zn2 + 的吸附作用力强度和最大缓冲容量的顺序则相反 ,以江涂砂 >粉泥土 >黄松土。菜园土壤对Zn2 + 的解吸量随其吸附量的增加而增加 ,两者之间呈显著线性正相关。     

氧化还原条件下红壤磷吸附与解吸特性及需磷量探讨

研究了5个酸性红壤由氧化条件转为还原条件的P吸附和解吸特性,以及确定供试红壤作为水田或旱地相应的施P量。结果表明:5个土样P吸附量随P液浓度的增加而增加,土壤对P的吸附曲线均可用Langmuir方程拟合,氧化条件下P最大吸附量变化范围为794.22～956.75mg/kg,还原条件下P最大吸附量变化范围为867.31～1195.62mg/kg。P解吸量随P吸附量的增加而增加,P解吸率的结果表明,淹水不同程度地降低土壤P解吸量。以Langmuir方程计算土壤溶液中P浓度在0.2mg/kg时的土壤需P量作为施P量的依据,淹水后土壤标准需P量增加。     

Affinity constants and behavior of Cd sorption in some acid soils

Cadmium sorption was studied in several acidic soils in a pH range from 4.5 to 6.5. The soils had two classes of surfaces with acidity constants (pKa₁ = 4.09 and pKa₂ = 6.39) similar to those for weakly and very weakly cidic carboxyls, and N-containing groups in fulvic acid. Titratable H and acidity constants were used to estimate the number of exchange sites at each pH level. Sorption of Cd was closely related to Cd concentration, pH, and soil type. Although the inclusion of pH and organic C contents in a regression accounted for some variations in the Cd distribution coefficient defined as the ratio of the quantity of Cd sorbed to the solution Cd concentration, the number of sorption sites was a more appropriate factor to explain the variability. Because of a negligible contribution to the number of exchange sites from Fe oxides, the sorption of Cd at pH = 4.5 was considered to be of a one-surface Langmuir type. A two-surface Langmuir equation was considered to model sorption at higher pH values. The average affinity constants (log K) were 3.61 and 4.89 for Cd sorption by the two classes of surfaces.     

Pb和Cd在塿土不同剖面土壤中的竞争吸附作用

多种金属离子的共存影响土壤对重金属离子的吸附作用,从而影响其生物有效性和迁移特征。利用等温吸附方法研究了塿土不同发育层次土壤对Pb~(2+)、Cd~(2+)单一离子和两种离子共存的吸附特征。对于单一的离子吸附,Pb~(2+)在塿娄土耕层、黏化层和钙积层的分配系数为8.0、8.1和6.1,Langmuir方程最大吸附量为6.1、5.8和6.0 mmol kg~(-1);而Cd~(2+)的分配系数为4.2、7.1和4.7,最大吸附量为5.5、4.8和2.9 mmol kg~(-1);三种土壤对Pb~(2+)的吸附性能均强于对Cd~(2+)的吸附。当Pb~(2+)、Cd~(2+)共存时,两种离子间存在竞争吸附作用,致使Pb~(2+)、Cd~(2+)的吸附量均降低,Pb~(2+)、Cd~(2+)互为竞争性吸附离子的亲和力效应在0.8~0.9之间,竞争性的Langmuir吸附方程可用于描述Pb~(2+)、Cd~(2+)的竞争吸附。     

几种土壤对砷酸盐的吸附

砷化合物一般都具有毒性,它对环境的污染引起人们的重视.砷污染土壤后,被土壤吸附、贮存.同时,通过植物的摄取,可进入动物和人体中.植物吸收的砷量和受害的程度,不仅与土壤砷的水平有关,而且还受土壤吸附砷的状况的影响.中国科学院南京土壤研究所试验研究指出,按土壤对砷的吸附量的差异而规定各种土壤的最大允许残留量.     

Molybdenum Determination in Mehlich‐1 and Mehlich‐3 Soil Test Extracts and Molybdenum Adsorption in Brazilian Soils

Abstract

The extractant Mehlich‐1 is routinely used in Brazil for determination of soil nutrients, whereas Mehlich‐3 has been suggested as a promising extractor for soil fertility evaluation. Both were used for extraction of molybdenum (Mo) in Brazilian soils with Mo dosage by the KI+H₂O₂ method. The Langmuir and Freundlich isotherms were used to study soil Mo adsorption. Mehlich‐1 extracted more Mo than Mehlich‐3 in soils with high contents of organic matter, clay, and iron (Fe) oxides. Mehlich‐3 and Mehlich‐1 extractions correlated positively and significantly with amorphous Fe oxides, crystalline Fe oxides, and organic matter. Molybdenum recovering rates correlated to crystalline Fe oxides and clay contents but not to organic matter, pH, and Mo adsorption capacity. Amorphous and crystalline Fe oxides, clay, and organic matter were responsible for most of the Mo adsorption. The Langmuir isotherm described better the Mo adsorption to soil amorphous Fe oxides and organic matter than the Freundlich isotherm.