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。     

两种土壤中邻苯二胺对铜离子吸附—解吸平衡影响的研究

采用室内测试方法，研究了低浓度的外源铜离子在两种不同性质土壤中的吸附、解吸过程及其受邻苯二胺的影响。结果发现，外源铜离子在红壤中的吸附随pH的变化明显变化，而在黑土中的吸附则随pH变化改变较小，吸附在红壤中的铜较吸附在黑土中的铜更易于解吸，有机物邻苯二胺对铜在两种土壤中的吸附和解吸过程产生了明显影响。酸性条件下邻苯二胺的存在增加了红壤对铜的吸附量，但同时也增加了铜的解吸百分数。而邻苯二胺基本不改变铜在黑土中的表观吸附量，但显著影响铜的解吸百分数。     

不同pH下黄棕壤镉的吸附-解吸特征

对黄棕壤在pH2 7不同浓度下Cd2 的吸附与解吸进行了测定。结果表明,Cd2 吸附量随平衡液中Cd2 浓度增加而增大,两者关系较好地符合Langmuir吸附方程。根据吸附等温线参数与pH的相关方程,得到镉吸附等温线的pH依存模式,如Langmuir方程为:C/X=69 334e-1 7183pH (5 5793pH-3 0383)·C。式中,X为土壤Cd2 吸附量(mg/kg),C为平衡液中Cd2 之浓度(mg/L)。解吸Cd2 的数量随pH升高和吸附Cd2 的数量增加而增加,但解吸Cd2 占吸附Cd2 的比例随pH升高而降低,在pH3 7下,黄棕壤解吸Cd2 的比例为42%～95%,平均为75%,说明黄棕壤Cd2 以非专性吸附为主,吸附Cd2 的有效性高。     

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     

可变电荷土壤和恒电荷土壤CI^—吸附特性的研究

对不同浓度KCI和不同pH下，3种可变电荷土壤和4种恒电荷土壤CI^-吸附量进行了测定。结果表明，土壤CI^-吸附量随平衡CI^-浓度C（e）增加而增大，恒电荷土壤呈线性，可变电荷土壤在添加CI^-0.5-5.0mmol/L下，符合Langmuir吸附等温式。同一浓度下的CI^-吸附量及其随浓度增加的速率均为砖红壤＞红壤＞赤红壤＞黄棕壤＞棕壤、暗棕壤和黑土，与这些土壤所带正电荷量顺序相一致。Langmuir方程K值较小且几种土壤差异不大。恒电荷土壤对CI^-的吸附量很小，在浓度较低时常出现负吸附，其吸附机理可能更多的是与K^ 吸附时的同时吸附。7种土壤CI^-吸附量均随pH增加而降低，但降低强度可变电荷土壤远大于恒电荷土壤。     

土壤对镉的吸附与解吸——Ⅰ.土壤组份对镉的吸附和解吸的影响

采用选择溶解法研究了有机质、游离铁、无定型硅、铝等土壤组份对青黑土、黄棕壤、红壤和砖红壤胶体吸附和解吸Cd的影响。结果表明,去除有机质后胶体吸附Cd减少,这可能是由于交换吸附的减少所致;游离铁的去除使得黄棕壤、红壤和砖红壤的吸附量显著减少,显示了在这些土壤中游离氧化铁专性吸附的重要性;随着无定形铝含量的上升,吸附量下降,这是因为铝离子占据了高能量的吸附位。经不同处理后的土壤胶体,其Cd的解吸顺序(解吸%)大致为:去无定型硅、铝者>去游离铁者>去有机质者>原胶体,但在不同土壤和不同pH条件下该顺序略有差别。研究结果为控制和改造土壤Cd污染提供了理论依据。     

金霉素在不同耕作土壤中的吸附－解吸行为

用批平衡吸附试验研究了金霉素在河南封丘潮土、南京黄棕壤、常熟水稻土和江西鹰潭红壤4种土壤中的吸附行为。结果表明,金霉素的土壤吸附-解吸行为均可用Freundlich模型和Langmuir模型进行良好的线性拟合。其Kf值差异较大,分别为潮土1135Lkg-1,黄棕壤1250Lkg-1,水稻土2618Lkg-1和红壤4315Lkg-1,显示金霉素在4种土壤中的吸附行为存在较大的差异。此外,金霉素在4种土壤上的解吸过程存在明显的滞后现象。研究还表明4种土壤中金霉素的吸附参数Kf值与土壤pH呈显著负相关。     

邻苯二胺对铜在红壤和砂姜黑土中吸附和解吸的影响

研究了铜在红壤和砂姜黑土中的吸附和解吸过程以及有机污染物邻苯二胺对铜在两种土壤中吸附和解吸行为的影响。结果表明 ,砂姜黑土较红壤对铜具有更高的吸附量 ,同时 ,被吸附的铜离子从土壤中的脱附百分数也是砂姜黑土大于红壤 ,吸附在砂姜黑土中的铜较红壤更易被 1molL- 1 MgCl2 所置换。pH 3 .5～ 7.5范围内 ,土壤对铜的吸附量均随溶液pH的升高而升高 ,呈现S形。邻苯二胺增加了红壤对铜的吸附量 ,同时也增加了铜的脱附百分数。而邻苯二胺虽未改变砂姜黑土对铜的吸附量 ,但却显著改变了铜的脱附百分数。文中对邻苯二胺与铜的交互作用过程及其机理进行了推测     

As(Ⅲ)在可变电荷土壤中的吸附与氧化的初步研究

用一次平衡法研究了两种可变电荷土壤与As(Ⅲ)之间的吸附和氧化还原反应。结果表明,当As(Ⅲ)溶液平衡浓度由0·25上升到1·0mmolL-1,砖红壤对砷的吸附量由15·0增加至25·9mmolkg-1,红壤由7·6增至13·0mmolkg-1,砖红壤对砷的吸附量约为红壤的2倍,这是因为前者铁、铝氧化物的含量高于后者。在pH3~7范围内,土壤对As(Ⅲ)的吸附量随pH的增加而增加。砖红壤中的氧化锰能将As(Ⅲ)氧化为As(V),砷的氧化量在pH3~7范围内随体系pH的增加而减小。砷在红壤中的氧化反应不显著。用1·0molL-1的KNO3对吸附性砷进行解吸的结果表明,砷的解吸率在35%以下,说明大部分砷通过形成内圈型表面络合物为土壤所吸附。在pH2~7范围内,砷的解吸率随吸附体系pH的升高而增加,说明较高pH下外圈型表面络合物的比例增加。     

几种有机酸对恒电荷和可变电荷土壤吸附Cu2+的影响

以恒电荷土壤(黄褐土和黄棕壤)和可变电荷土壤(红壤和砖红壤)为供试材料,研究了乙酸、草酸、酒石酸和柠檬酸对土壤吸附重金属铜离子(Cu2 )的影响。结果表明,在相同酒石酸浓度下,土壤对酒石酸的吸附量依次为黄棕壤(2 1 8mmolkg-1) >红壤(15 4mmolkg-1) >砖红壤(9 5mmolkg-1) ,土壤吸附有机酸后负电荷量增加,相同条件下增幅为砖红壤>红壤>黄棕壤;无有机酸配体时,供试土壤对Cu2 的吸附量为黄褐土>黄棕壤>砖红壤>红壤;加入有机酸时,随有机酸浓度增高,土壤对Cu2 的吸附一般表现为“峰”形曲线,峰所对应的有机酸浓度因有机酸类型而异,且随土壤可变电荷性质增强而增高;土壤吸附有机酸后对Cu2 的次级吸附不同于有机酸与铜共存时的竞争吸附,且因土壤性质表现迥异。这些结果意味着在存在有机酸配体的根际环境中,恒电荷土壤与可变电荷土壤对Cu2 的吸附明显不同,并将影响重金属离子在根际的转化与有效性     

Effects of Organic Acids,o-Phenylenediamine and Pyrocatechol on Cadmium Adsorption and Desorption in Soil

This article studied the interaction of cadmium (Cd) and lowmolecular weight organics in Indicotic black (IB) soil.Cadmium adsorption isotherm in this soil was satisfactorilysimulated using Freundlich equation as Q = 905.6C^0.49 with high correlation (r² = 0.984), and its adsorption quantity increased with increasing pH. The presence of citricacid and EDTA significantly reduced Cd adsorption in soil,which was due to the formation of soluble Cd-organic complex. Concentration of cadmium ions in equilibrium solution was determined and percentages of [CdH₂Cit⁺]/[Cd-complex_Total],[CdHCit]/[Cd-complex_Total] and [CdCit^-]/[Cd-complex_Total] vs. pH were successfully calculated. Desorption percentage ofCd, adsorbed in the presence of citric acid and EDTA decreased, compared with that adsorbed in NaNO₃ media. It suggeststhat free sites for Cd adsorption in soil increased in thepresence of organic acid. When o-phenylenediamine, pyrocatechol and aminoethonic acid appeared in Cd equilibrium media, Cd adsorption quantity increased by increasing cation exchange ofpositively charged cadmium complex with soil at low pH. Compared with that performed in the absence of these organics, the exchangeable Cd, desorbed by 0.1 mol L^-1 NaNO₃, reduced obviously, which suggests that Cd-complex was moredifficult to be desorbed than Cd²⁺. Moreover, % Cd desorbedwas linearly correlated with the reverse of the total Cd adsorptionunder unsaturated adsorption.     

有机酸作用下黄壤无机纳米微粒对Cd~(2+)吸附动力学特性

为探究有机酸对镉在纳米粒级土壤上的有效性及其形态的影响,基于超声—离心—冻融法,应用到四川省名山河流域老冲积黄壤中,获得纳米微粒(≤100 nm),分别研究不同分子量有机酸(柠檬酸、富里酸、EDTA)及其组合(柠檬酸+EDTA、柠檬酸+富里酸、富里酸+EDTA)对土壤纳米微粒吸附Cd~(2+)动力学特性的影响。结果表明,土壤纳米微粒对Cd~(2+)的动力学吸附量大小关系表现为:柠檬酸+EDTA富里酸柠檬酸+富里酸柠檬酸富里酸+EDTAEDTA。总的来看,EDTA的抑制作用最强,最能降低土壤纳米微粒对Cd~(2+)的吸附。     

有机酸对活化土壤中镉和小麦吸收镉的影响

向土壤中加入外源有机酸,研究有机酸对活化土壤中镉的作用和小麦吸收镉的影响。结果表明：有机酸对土壤中镉有一定的活化能力,对镉活化能力强弱顺序为ＥＤＴＡ〉缺铁小麦根分泌物〉柠檬酸〉苹果酸〉水。但ＥＤＴＡ却降低了小麦地上部镉的含量,缺铁小麦根分泌物明显增加了小麦地上部镉含量。与对照相比,柠檬酸和苹果酸对小麦地上部的镉含量有一定的促进作用,也增加了小麦地上部镉含量。     

甘草根瘤菌CCNWGX035的抗逆特性及结瘤特征研究

Thirty-nine rhizobial isolates were isolated from the root nodules of Glycyrrhiza uralensis and Glyeyrrhiza glabra, growing in the arid and semiarid regions of northwestern China, to test their taxonomic position and stress tolerance and to select one promising putative inoeulant strain for further studies. On the basis of 113 physiological and biochemical characteristics, the isolates were clustered into three groups. One isolate CCNWGX035 was found to have high tolerance to NaC1, pH, and temperature. By sequencing the 16S rDNA, isolate CCNWGX035 was placed in genus Mesorhizobium. Nodulation tests demonstrated that the isolate not only formed nitrogen-fixing nodules on its original host plant Glyeyrrhiza glabra, but also on Sophora vieiifolia, Lotus cornieulatus, Trifolium repens, Melilotus suaveolens, and Sophora alopecuroides. On the basis of sequence analysis of the nodA gene, isolate CCNWGX035 was closely related to strains of the genus Mesorhizobium, exhibiting some novel characteristics of root nodule bacteria.     

低分子量有机酸强化烟草修复镉污染土壤的适用性研究

采用盆栽试验,以0.125mmol/kg EDTA为对照,研究3种低分子量有机酸(酒石酸、柠檬酸和草酸)在强化烟草修复镉污染土壤中应用的可行性。3种低分子量有机酸(LMWOA)均可显著降低土壤pH,提高镉的有效含量,酒石酸和草酸对镉在烟草中转运有抑制作用,柠檬酸在酸性土壤中促进镉在烟草中转运,在中性土壤中则起抑制作用。31.25mmol/kg LMWOA对烟草地上部的生长有一定的促进作用,该浓度的柠檬酸和草酸使酸性土壤中烟草地上部镉累积量分别提高42.95%和28.67%,柠檬酸还使中性土壤中烟草地上部镉的累积量提高40.91%,所有酒石酸处理镉在烟草地上部的累积量均降低,EDTA使酸性土壤中烟草地上部镉的累积量提高24.56%,对中性土壤中烟草地上部镉累积量的影响不显著。表明柠檬酸和草酸具有强化烟草地上部对镉的吸收、提高烟草提取土壤镉效率的作用,但要获得与EDTA相当的效果,需大大提高其用量,这必然导致修复成本大大提高,故不宜用于强化烟草修复镉污染土壤。     

名山河流域黄壤组分对微团聚体吸附解吸镉的影响

选取名山河流域4种土地利用方式（林地、水田、茶园、旱地）的黄壤为研究对象,采用平衡液等温吸附法和NH4OAC、EDTA溶液解吸法,研究土壤组分（有机质、游离氧化铁）对微团聚体吸附解吸Cd2＋的影响。结果表明：去除土壤组分前后,原土及各粒径微团聚体对Cd2＋的吸附量均随Cd2＋初始浓度增大而增大,吸附量均按以下次序递减：（〈0.002mm）〉2～0.25mm〉原土〉0.053～0.002mm〉0.25～0.053mm,与有机质、游离氧化铁、CEC呈极显著正相关。吸附减少量大小关系为：去除有机质〉去除游离氧化铁,有机质的贡献率大于游离氧化铁。Freundlich方程拟合效果最佳,达到极显著水平,分布系数Kd值与Cd2＋初始浓度呈曲线负相关。NH4OAC解吸率随原吸附Cd2＋初始浓度增大而增大,以最大解吸率计,递减规律为：0.25～0.053mm〉0.053～0.002mm〉原土〉2～0.25mm〉（〈0.002mm）;EDTA解吸率随原吸附Cd2＋初始浓度增大而减小,递减规律与NH4OAC解吸率相反。去除土壤组分后,NH4OAC解吸率上升,EDTA解吸率下降,茶园与旱地黄壤非解吸率减小,林地与水田黄壤非解吸率增大。去除土壤组分后,非专性吸附与吸附总量呈极显著正相关,专性吸附与吸附总量呈极显著负相关。     

Pollution and Desorption Kinetics of Heavy Metals at Agricultural Soils in Southeastern Iran

Desorption of heavy metals is an important factor in determining heavy-metal availability in soils. The objective of this research was to determine the applicability of kinetic equations to describe the kinetics of copper (Cu) and cadmium (Cd) desorption at two agricultural soils of Kerman Province in Iran. For Cd and Cu desorption studies, 5 g of the air-dried <2-mm soil fraction was extracted with 25 ml of 0.01 M ethylenediamenetetraacetic acid (EDTA) at pH 7.0 with a shaker for periods of 5 to 2880 min. The desorption patterns of Cu and Cd were generally characterized by an initial fast reaction, followed by a slower continuing reaction. Desorption of Cu and Cd from the two soils was equally well described by the two-constant rate and simple Elovich equations. The results of this study can be used to make better prediction about the mobility and bioavailability of the Cu and Cd in soil.     

Solubility,sorption and desorption of native and added cadmium in relation to properties of soils in New Zealand

Solution cadmium (Cd) concentrations and sorption and desorption of native and added Cd were studied in a range of New Zealand soils. The concentration of Cd in solution and the concentrations and patterns of native soil Cd desorbed and added Cd sorbed and desorbed varied greatly between the 29 soils studied. Correlation analysis revealed that pH was the most dominant soil variable affecting solution Cd concentration and sorption and desorption of native and added Cd in these soils. However, organic matter, cation exchange capacity (CEC) and total soil Cd were also found to be important. Multiple regression analysis showed that the log concentration of Cd in solution was strongly related to soil pH, organic matter and total Cd, which in combination explained 76% of the variation between soils. When data from the present study were combined into a single multiple regression with soil data from a previously published study, the equation generated could explain 81% of the variation in log Cd solution concentration. This reinforces the importance of pH, organic matter and total Cd in controlling solution Cd concentrations. Simple linear regression analysis could at best explain 53% of the total variation in Cd sorption or desorption for the soils studied. Multiple regression analysis showed that native Cd desorption was related to pH, organic matter and total Cd, which in combination explained 85% of the variation between soils. For sorption of Cd (from 2 μg Cd g^–1 soil added), pH and organic matter in combination explained 75% of the variation between soils. However, for added Cd desorption (%), pH and CEC explained 77%. It is clear that the combined effects of a range of soil properties control the concentration of Cd in solution, and of sorption and desorption of Cd in soils. The fraction of potentially desorbable added Cd in soils could also be predicted from a soil’s K_d value. This could have value for assessing both the mobility of Cd in soil and its likely availability to plants.     

Effect of Organic Matter on the Release Behavior and Extractability of Copper and Cadmium in Soil

Land disposal of organic waste materials may alter the heavy-metal status of the soil by affecting metal solubility or dissociation kinetics. The aim of this investigation was to study the influences of poultry manure and pistachio compost (at the rate of 300 g kg^?1) on release behavior and extractability of copper (Cu) and cadmium (Cd) in two soils of Iran. For release studies, samples after incubation were extracted with ethylenediaminetetraacetic acid (EDTA) at pH 7.0 with shaker for periods of 5 to 2880 min. Results showed that during the reaction periods, Cu and Cd release rates were rapid at first and then became slower until equilibrium was achieved. In the two soils, extractability of Cu increased with poultry manure treatment and decreased with pistachio compost treatment as compared to the control soil, and extractability of Cd decreased with both pistachio compost and poultry manure treatments as compared to the control soil.