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1.
以高岭石、蒙脱土、针铁矿和三水铝石四种单一典型土壤矿物以及针铁矿-蒙脱石和三水铝石-蒙脱石（质量比为1:1）两种代表性土壤矿物复合体为吸附材料，采用吸附平衡实验、能谱分析（(EDS）、红外光谱、扫描电镜、酸碱滴定和zeta电位测定等方法，研究了铁铝氧化物与层状硅酸盐矿物之间的相互作用对Cr(Ⅵ)和As(Ⅴ)吸附的影响及其机制。吸附平衡实验和EDS实验结果表明，两种复合体对Cr(Ⅵ)和As(Ⅴ)的吸附容量均小于其两种组成矿物单一体系吸附量的平均值，即铁铝氧化物与蒙脱石的互作降低了这些氧化物对Cr(Ⅵ)和As(Ⅴ)的吸附能力。表面性质表征结果表明，与蒙脱石复合后，针铁矿与三水铝石表面的正电荷均被完全中和，电荷符号发生反转。与理论值相比，三水铝石-蒙脱石复合体的表面位点总浓度无明显变化，比表面积减小。针铁矿-蒙脱石复合体的比表面积与理论值无明显差异，但矿物表面位点浓度减小，表面羟基红外吸收峰强度减弱。氧化物与层状硅酸盐矿物互作改变了矿物表面性质，这可能是导致氧化物对Cr(Ⅵ)和As(Ⅴ)的吸附能力降低的主要原因。当评估污染元素在土壤中有效性时应当考虑土壤固相组分间的互作对离子吸附的影响。 相似文献
2.
锑(Sb)在土壤胶体微界面的吸附解吸深刻影响其迁移、转化和归趋。土壤矿物、有机物、微生物等胶体组分多结合在一起,形成复杂的矿物–有机复合体。目前,锑在单一土壤组分上的吸附研究颇多,但较少有学者关注锑在土壤矿物–有机复合胶体界面的吸附过程和机制。通过宏观吸附以及光谱学技术探究锑在典型铝氧化物–细菌复合胶体上的吸附行为,结果表明:α-Al_2O_3纳米级颗粒覆盖在蜡状芽孢杆菌表面,形成一层不完整的"矿物膜"。朗格缪尔(Langmuir)模型可以很好地拟合Sb(Ⅴ,Ⅲ)的等温吸附数据(R~20.98);α-Al_2O_3对Sb的吸附量远大于细菌;Sb在Al_2O_3–细菌复合胶体上的吸附不符合"组分相加"原则,存在显著的促进效应。扫描电镜-能谱分析显示Sb主要结合在复合胶体的矿物组分上。X-射线光电子能谱结果表明铝羟基、羧基和氨基参与了Sb的吸附,且细菌会抑制Sb(Ⅲ)在α-Al_2O_3表面的氧化。本研究证实,细菌不仅影响锑在矿物界面的吸附量,还影响其氧化还原反应,因此,在预测锑在土壤中的形态转化、迁移和归趋时必须考虑矿物–微生物相互作用。 相似文献
3.
采用温室盆栽土培方法,研究了土壤中不同浓度重金属铅（Pb,0-800 mg.kg^-1）、镉（Cd,0-50 mg.kg^-1）单一及其复合处理对玉米（Zea mays L.）生长及土壤微生物（细菌、放线菌、真菌）数量的影响。结果表明,在重金属Pb、Cd单一及其复合处理下,玉米的株高、干重均低于对照,重金属Pb、Cd处理对玉米的生长存在负面影响。重金属Pb、Cd单一处理抑制细菌、真菌的生长,中低浓度Pb（≤300 mg.kg^-1）、Cd（≤10 mg.kg^-1）单一处理促进放线菌数量的增加,高浓度（Pb≥800 mg.kg^-1、Cd≥50 mg.kg^-1）则呈现抑制效应;Pb、Cd复合在高中低浓度下都抑制土壤微生物生长,减少微生物数量。玉米株高同土壤微生物之间相关性不显著;玉米干重同土壤细菌、真菌显著相关,同土壤放线菌之间相关性不显著。 相似文献
4.
可变电荷土壤对As(Ⅲ)和As(Ⅴ)的吸附及二者的竞争作用 总被引：4，自引：0，他引：4
三种可变电荷土壤对砷的吸附实验结果表明,在pH3~7范围内,As(Ⅲ)的吸附量随pH的升高而增加,三种土壤对As(Ⅲ)吸附能力的大小顺序为砖红壤>黄壤>红壤。红壤和砖红壤对As(Ⅴ)的吸附量随pH的升高而降低,黄壤中呈相反的变化趋势,三种土壤对As(Ⅴ)吸附能力的大小顺序是黄壤>砖红壤>红壤。三种可变电荷土壤对As(Ⅴ)的吸附能力较对As(Ⅲ)大得多,砷的吸附量既与土壤游离氧化铁的含量有关,又与氧化铁的结晶形态密切联系,由于黄壤中水化氧化铁在游离铁中所占比例较高,其对As(Ⅴ)吸附能力较砖红壤和红壤大。As(Ⅲ)与As(Ⅴ)共存体系的研究结果表明,两种形态的砷可以竞争可变电荷土壤表面的吸附位,但在酸性条件下As(Ⅴ)较As(Ⅲ)有更强的竞争能力,因为As(Ⅴ)使土壤对As(Ⅲ)的吸附量显著减小,而As(Ⅲ)对红壤和砖红壤吸附As(Ⅴ)有一定的影响,对黄壤中As(Ⅴ)的吸附几乎没有影响。 相似文献
5.
采用批量培养和平衡吸附法,选取原土及微团聚体颗粒组为对象,研究Zn(II)、Cd(II)单一存在、二元竞争及竞争体系中加入柠檬酸(0.1,1,10mmol/L)等3种处理的等温吸附特性及影响。结果表明:(1)以专性吸附方式为主的多层吸附随Zn~(2+)、Cd~(2+)强度增加逐渐饱和,吸附能力以0.002mm最优、0.05~0.002mm和原土次之,0.25~0.05mm和2~0.25mm结合能力稍差,不同条件下Cd较Zn更易积累。吸附过程为自发吸热反应,热力学Freundlich方程(Zn:R2=0.960~0.997;Cd:R2=0.957~0.995)拟合结果优于Langmiur方程(Zn:R2=0.952~0.995;Cd:R2=0.913~0.991)。最大吸附量与有机质含量具有显著相关性。(2)单一处理Zn、Cd的固持效果明显、共存处理时Zn、Cd竞争行为表现为彼此削弱,Zn对Cd的吸附具有更强抑制作用。(3)添加不同浓度柠檬酸后Zn、Cd吸附水平介于单一及共存处理之间呈动态变化(Zn、Cd接近),0.1~1mmol/L利于Zn、Cd固持,增至10mmol/L后加速淋洗,仅0.002mm粒径富集量持续提升。表明柠檬酸作为一种调节剂,能适度保持土壤Zn供给并弱化Cd迁移活性,缓解茶园土壤复合污染。 相似文献
6.
秸秆还田对土壤Cd(Ⅱ)吸附-解吸的影响 总被引：1，自引：0，他引：1
[目的]探讨不同秸秆还田类型及还田水平(水稻、油菜秸秆全量、1/2量)对3种土壤类型﹝沈桥红壤(SQ)、朝山红壤(CS)、新桥水稻土(XQ)﹞Cd(Ⅱ)吸附-解吸行为的影响,为控制土壤中Cd(Ⅱ)环境行为及其调控提供依据。[方法]采用室内模拟培养试验和等温吸附相结合的方式。[结果](1)秸秆还田促进了土壤对Cd(Ⅱ)的吸附,在3种土壤的各处理间差异显著(p0.05)。在XQ上,秸秆还田处理提升Cd(Ⅱ)吸附量的效果较2种红壤显著,其中,油菜秸秆1/2量还田处理(RP1)、油菜秸秆全量还田处理(RP2)土壤Cd(Ⅱ)吸附量与对照相比分别增加了9.30%和10.47%。对SQ,CS而言,以Langmuir模型的拟合度最佳,相关系数均大于0.990 9,而在XQ中,适用于描述不规则表面吸附的Temkin方程的模拟效果较好。(2)3种土壤Cd(Ⅱ)的解吸量、解吸率都随着土壤中Cd(Ⅱ)吸附量的增加而增加,秸秆还田处理的土壤Cd(Ⅱ)的解吸量明显低于对照,尤其以油菜秸秆全量还田处理土壤Cd(Ⅱ)解吸量最小。[结论]秸秆还田对不同土壤Cd(Ⅱ)吸附-解吸行为的影响具有显著差异,油菜秸秆还田增强了土壤Cd(Ⅱ)专性吸附,较水稻秸秆有更好地降低Cd(Ⅱ)风险的效果。 相似文献
7.
《水土保持学报》2014,(2)
为了比较2种类型改良剂对土壤中Cd(Ⅱ)的修复作用,向土壤中添加0.5%和2%的秸秆炭和沸石,培养60d后分析土壤性质的变化,并用一次平衡法研究秸秆炭和沸石对土壤吸附Cd(Ⅱ)的影响。结果表明,添加秸秆炭和沸石均能提高土壤CEC,秸秆炭还可以显著提高土壤pH,0.5%和2%添加量使土壤pH提高0.37和0.66,添加沸石对于土壤pH没有明显提高。等温吸附实验结果表明,添加秸秆炭和沸石均可以增加土壤对Cd(Ⅱ)的吸附量,并且随着添加量的增加而增加,当Cd(Ⅱ)初始浓度为150mg/L时,Cd(Ⅱ)的吸附量提高8.5%~32.5%。随着体系pH的升高,土壤对Cd(Ⅱ)的吸附量增加,在pH较高的体系下,秸秆炭对土壤吸附能力的促进作用更大。解吸实验表明,添加秸秆炭和沸石后土壤Cd(Ⅱ)的解吸量高于对照,说明秸秆炭和沸石提高了土壤对Cd(Ⅱ)的静电吸附量。Freundlich方程更适合拟合添加秸秆炭和沸石后土壤对Cd(Ⅱ)的吸附等温线,R2值均在0.96以上。从该方程表征吸附容量的参数Kf可以看出,秸秆炭促进Cd(Ⅱ)的吸附效果优于沸石,2%添加量的促进效果要优于0.5%添加量。因此,对于辽宁地区的草甸土,秸秆炭对土壤中Cd(Ⅱ)具有更好的修复作用。 相似文献
8.
不同pH下两种可变电荷土壤中Cu(II)、Pb(II)和Cd(II)吸附与解吸的比较研究 总被引：6，自引：0，他引：6
对两种可变电荷土壤的研宄表明,土壤对Cu(Ⅱ)、Pb(Ⅱ)和Cd(Ⅱ)的吸附量均随pH的增加而增加,但Cu(Ⅱ)与Pb(Ⅱ)吸附量之间的差值随pH增加而减小,Cu(Ⅱ)和Pb(Ⅱ)与Cd(Ⅱ)吸附量之间的差值随pH增大呈增大趋势.土壤吸附的Cd(Ⅱ)的解吸量随吸附平衡液pH的增加而增加;但Cu(Ⅱ)和Pb(Ⅱ)的解吸量先随pH增加而增加,在某一pH时达最大,随后再逐渐减小.3种重金属离子在可变电荷土壤中吸附和解吸行为的不同特征是pH导致的土壤表面电荷的变化和离子水解程度的变化共同作用的结果.本文的研究结果对可变电荷土壤中重金属的控制和污染土壤的修复具有一定的指导意义. 相似文献
9.
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。 相似文献
10.
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。 相似文献
11.
Yang Ruijia Tao Jie Huang Qiaoyun Tie Boqing Lei Ming Yang Yuan Du Huihui 《Journal of Soils and Sediments》2019,19(3):1319-1327
Purpose
Heavy metal and metalloid commonly coexist in soils and sediments, and interact frequently with various minerals. The coexistence of Sb and Cd is commonly observed in Sb mine area, but their co-adsorption behaviors to soil minerals still remain poorly understood. This study aimed to elucidate the co-adsorption characteristics of Cd(II) and Sb(III) by ferrihydrite (Fh) under anoxic condition.
Materials and methodsBatch experiments were performed to determine the sorption capacity of Cd(II) and Sb(III) in both single and binary systems. The major functional groups that were responsible for Cd(II) and Sb(III) sorption were determined by X-ray photoelectron spectroscopy (XPS), while the thermodynamic sorption mechanisms were elucidated using isothermal titration calorimetry.
Results and discussionCd(II) sorption on Fh increases with increasing pH levels (4–8) whereas Sb(III) sorption shows less variation with pH level variations. The Langmuir adsorption capacity is 55.54 mg/g for Cd(II) and 188.19 mg/g for Sb(III). In Cd–Sb binary systems, Cd(II) sorption is significantly diminished whereas Sb(III) uptake is close to single Sb(III) sorption. XPS indicates the Fe–OH groups are mainly responsible for the binding of Cd and Sb, possibly through the formation of inner-sphere complexes. This hypothesis is further confirmed by the positive entropy (ΔS) after Cd and/or Sb binding. A larger ΔS in the binary Cd–Sb titration than in their single titrations implies the formation of a ternary Fh–Sb–Cd complex, which results in a higher disorder of the sorption system.
ConclusionsThe presence of Sb(III) reduces Cd(II) sorption whereas Cd(II) has a negligible effect on Sb(III) sorption to ferrihydrite; moreover, Sb(III) and Cd(II) might form surface ternary complexes in binary systems. These new findings have important implications for predicting the sequestration, migration, and fate of Cd and Sb in soils.
相似文献12.
The prediction of the mobility of arsenic (As) is crucial for predicting risks in soils contaminated with As. The objective of this study is to predict the distribution of As between solid and solution in soils based on soil properties and the fraction of As in soil that is reversibly adsorbed. We studied adsorption of As(V) in suspensions at radiotrace concentrations for 30 uncontaminated soils (pH 4.4–6.6). The solid–liquid distribution coefficient of As (Kd) varied from 14 to 4430 l kg?1. The logarithm of the concentration of oxalate‐extractable Fe explained 63% of the variation in log Kd; by introducing the logarithm of the concentration of oxalate‐extractable P in the regression model, 85% of the variation in log Kd is explained. Double labelling experiments with 73As(V) and 32P(V) showed that the As to P adsorption selectivity coefficient decreased from 3.1 to 0.2 with increasing degree of P saturation of the amorphous oxides. The addition of As(V) (0–6 mmol kg?1) reduced the Kd of 73As up to 17‐fold, whereas corresponding additions of P(V) had smaller effects. These studies suggest that As(V) is adsorbed to amorphous oxides in soils and that sites of adsorption vary in their selectivity in respect of As and P. The concentration of isotopically exchangeable As in 27 contaminated soils (total As 13–1080 mg kg?1) was between 1.2 and 19% (mean 8.2%) of its total concentration, illustrating that a major fraction of As is fixed. We propose a two‐site model of competitive As(V)–P(V) sorption in which amorphous Fe and Al oxides represent the site capacity and the isotopically exchangeable As represents the adsorbed phase. This model is fitted to 73As adsorption data of uncontaminated soils and explains 69% of the variation of log Kd in these soils. The log Kd in contaminated soils predicted using this two‐site model correlated well with the observed log Kd (r = 0.75). We conclude that solubility of As is related to the available binding sites on amorphous oxides and to the fraction of As that is fixed. 相似文献
13.
《Communications in Soil Science and Plant Analysis》2012,43(13-14):2132-2151
Batch adsorption experiments were conducted to assess the effects of pH and ionic strength (I) on cadmium (Cd) adsorption by two Brazilian Oxisols. Adsorption envelopes were constructed through soil sample reactions with 0.01, 0.1, and 1 mol L?1 calcium nitrate [Ca(NO3)2] solutions containing 5 mg L?1 of Cd, with an increasing pH value from 3 to 8. The adsorption increased drastically with increasing pH, varying from 20 to 90% in a narrow pH range (4–6 in topsoil and 5–6 in subsoil). Gibbs energy (ΔG) for Cd adsorption was negative, and the phenomenon became more thermodynamically spontaneous with an increase in pH. Under the standard 0.01 mol L?1 I and at pH close to natural, the ΔG values ranged from ?796 to ?3427 J mol?1. No effect of I was observed on the ΔG values for Cd adsorption at pH values less than 6. At values greater than pH 6, sharp changes in the Cd adsorption pattern were observed on subsoil samples. The only soil attribute significantly correlated with the spontaneity of Cd adsorption was the effective cation exchange capacity, ECEC (r = 0.97; p < 0.1). 相似文献
14.
Georg J. Lair Martin H. Gerzabek Georg Haberhauer Michael Jakusch Holger Kirchmann 《植物养料与土壤学杂志》2006,169(1):60-68
This study investigated the effect of different farming practices over long time periods on the sorption‐desorption behavior of Cu, Cd, and Zn in soils. Various amendments in a long‐term field experiment over 44 y altered the chemical and physical properties of the soil. Adsorption isotherms obtained from batch sorption experiments with Cu, Cd, and Zn were well described by Freundlich equations for adsorption and desorption. The data showed that Cu was adsorbed in high amounts, followed by Zn and Cd. In most treatments, Cd ions were more weakly sorbed than Cu or Zn. Generally, adsorption coefficients KF increased among the investigated farming practices in the following order: sewage sludge ≤ fallow < inorganic fertilizer without N ≈ green manure < peat < Ca(NO3)2 < animal manure ≤ grassland/extensive pasture. The impact of different soil management on the sorption properties of agricultural soils for trace metals was quantified. Results demonstrated that the soil pH was the main factor controlling the behavior of heavy metals in soil altered through management. Furthermore, the constants KF and n of isotherms obtained from the experiments significantly correlated with the amount of solid and water‐soluble organic carbon (WSOC) in the soils. Higher soil pH and higher contents of soil organic carbon led to higher adsorption. Carboxyl and carbonyl groups as well as WSOC significantly influenced the sorption behavior of heavy metals in soils with similar mineral soil constituents. 相似文献
15.
本文提出了吸附势(logKa)和解吸势(logKd或相对解吸势logKdr)两个有关吸附和解吸的强度概念,并进行了理论推导和实验验证。logKa和logKd或logKdr是影响土壤或胶体吸附和解吸因素的综合反应。实验证实logKa可用于表征土壤胶体对Cd的相对选择性,并且对胶体吸附Cd有着良好的预测性;logKdr可用于表征土壤胶体对Cd的相对固定能力,并可用于估测Cd的污染程度。盆栽试验表明,随着土壤胶体logKa的增加,或logKdr的降低,稻草或糙米中Cd的含量下降。可以预期,吸附势和解吸势不但在土壤物理化学,土壤环境化学研究中,而且在植物营养化学、水化学、以及界面化学等方面有可能获得实际应用。 相似文献
16.
Mohsen HAMIDPOUR Maliheh KARAMOOZ Abdolreza AKHGAR Ahmad TAJABADIPOUR Gerhard FURRER 《土壤圈》2019,29(5):590-597
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 KF 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. 相似文献
17.
Y. K. SOON 《European Journal of Soil Science》1981,32(1):85-95
The mechanisms governing the retention and release of Cd in two soils, a loam and a loamy sand, pretreated with anaerobically digested sewage sludges or with chemical fertilizers, were studied using batch equilibration in 0.05 m Ca(NO3)2 solution containing up to 6 μg Cd/ml. Adsorption rather than precipitation as Cd3(PO4)2 limited solution Cd2+ concentration. With the addition of 50 μg Cd/g, however, precipitation as CdCO3 was likely at pH 7.6. Cadmium adsorption increased with increasing soil pH. The differences in Cd adsorption between different soil treatments were attributed mainly to the soil pH (6.9 to 7.9) induced by sludge application. About 82 to 92 per cent of adsorbed Cd was retained by cation exchange and complexing sites. Soils treated with sludge increased the amount of exchangeable Cd but reduced the amount of complexed Cd compared with the fertilized soil. Cadmium retention by cation exchange became more dominant as the amount of Cd in the soil was increased. 相似文献
18.
土壤主要理化性质对湘粤污染农田镉稳定效果的影响 总被引：3，自引：0，他引：3
利用盆栽试验研究了稳定剂(石灰、海泡石联合施用)对湖南、广东两省区不同性质土壤上生长的小青菜(Brassica chinensis L.)生物量、重金属吸收以及土壤pH和重金属提取态含量的影响,探讨了影响镉(Cd)稳定修复效果的土壤性质参数。结果表明:施加稳定剂对增加酸性土壤上小青菜生物量效果显著,土壤pH、有机质(OM)、全量Cd和黏粒是影响小青菜生物量变化的主要因素;土壤pH、阳离子交换量(CEC)、OM、黏粒是影响小青菜Cd含量变化的主要因素;土壤pH、CEC、全量Cd和黏粒是影响土壤提取态Cd含量变化的主要因素。 相似文献
19.
The efficiency of As(III) oxidation by MnO2, and retention of oxidation products varies with system pH. Maximum retention by hydrous Mn(IV) oxide occurs at pH < 5, declining at higher pH to about half total As at pH 10. The adsorption capacities of pyrolusite and cryptomelane at pH ～6.5 for As(V) species were 10 and 25 mmol kg?1, respectively. HMO surface saturation (～10 mmol kg?1) was reached with equilibrium As(V) levels of 5 to 8 × 10?6 M but this was supplemented at higher levels by an absorption process where uptake increased linearly with concentration (e.g., 68 mmol kg?1 with 2 × 10?5 M As(V)). Added As(III) was avidly oxidized and most product retained at pH 3. At higher pH increasing amounts of As(III) remained unoxidized due to initial reactions apparently blocking access to internal pores. Added Na+ reduced the amount of As retained by the HMO, with the phosphate salt having a significant effect. Extraction studies confirmed that most As could be released by exposure to reducing agents or chelating agents (EDTA). The environmental significance of the results has been considered. 相似文献
20.
石灰石和海泡石组配对水稻糙米重金属积累的影响 总被引：14，自引：0，他引：14
为了研究组配改良剂(石灰石+海泡石,LS)对于重金属Pb、Cd、Cu和Zn复合污染稻田的修复效果,在湘南某矿区附近稻田中进行了组配改良剂的田间试验。结果表明:施用0~1.8 kg m-2的组配改良剂LS使土壤pH和CEC显著增加,使土壤中Pb、Cd、Cu和Zn交换态含量显著降低。土壤Pb、Cd、Cu和Zn交换态含量的降低是pH升高,土壤胶体的CEC增加及土壤吸附能力增强的共同作用。施用组配改良剂LS显著降低了3个水稻品种(黄华占、丰优9号、Ⅱ优93)糙米中Pb、Cd和Cu的累积量,最大降幅分别为55.8%、66.9%、37.4%,而对糙米中Zn的含量没有明显影响。当LS施用量为1.8 kg m-2时,能使丰优9号糙米中Cd含量(0.195 mg kg-1)达到国家食品中污染物限量标准(0.20 mg kg-1)以下。土壤中交换态Pb、Cd和Cu含量的降低是糙米中重金属累积量减少的原因。土壤交换态Pb、Cd和Cu含量的对数值(lnC交换态)与其糙米中含量(lnC糙米)的对数值之间存在显著的线性相关关系。 相似文献