pH对砷在贵州红壤中的吸附的影响

本文研究了贵州遵义红壤中pH对砷(As)的吸附和形态的影响。结果表明,当溶液中As的浓度增大时,土壤对As的吸附量增大,吸附率逐渐降低,As从红壤的低能位点位逐渐进入到高能位吸附点位,吸附反应速率减慢。Langmuir方程拟合等温吸附效果较好,可决系数达到0.969 (P < 0.001)。体系pH是影响红壤对As吸附、解吸的重要因素,As的吸附量随着体系pH的升高而降低,吸附态As的解吸量随着体系pH的升高而增大。酸性环境(pH = 4 ~ 6.5)有利于As的吸附,碱性环境(pH = 7 ~ 8.5)有利于As的解吸。     

土壤砷吸附及砷的水稻毒性

在砖红壤、红壤和黄棕壤上的试验结果表明，砖红壤对Ａｓ＾５＋和Ａｓ＾３＋的吸附最强，红壤次之，黄棕壤最弱，但土壤中砷对水稻的毒性却以砖红壤最大，红壤次之，黄棕壤最小，表明土壤砷对植物的毒性，未必受土壤吸附性能所制约。     

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。     

土壤矿物质吸附砷的研究进展

砷是一种有毒的重金属元素,由于自然和人为的原因,世界上的许多国家存在砷污染问题,因此有关砷污染的研究与控制日益受到人们的关注。本文介绍了土壤砷污染的产生原因及污染状况,重点集中在探讨土壤中的各种矿物质对砷吸附行为的作用机理。这些矿物质包括铁铝氧化物和氢氧化物、锰氧化物、黏土矿物和碳酸盐类。关于砷在各类矿物质上的吸附机理,普遍接受的观点认为:砷氧阴离子与矿物质的表面发生了配位体交换过程并通过共价键的作用,形成了表面配位体。表面配位体以内层双齿双核鳌合形式为主,受矿物质的种类、pH值和氧化还原电位等因素的影响,外层吸附和其他鳌合状态可能存在。砷在土壤矿物质上的吸附效果强烈依赖于体系的pH值,这与吸附的理论模型和数学计算结果相一致。矿物质的种类、组成、结晶状态和表面积等影响了砷的吸附过程和吸附效果。土壤中存在的各种阴阳离子通过与砷阴离子竞争吸附位而影响砷在矿物质上的吸附。     

土壤砷的吸持研究

本对土壤砷的吸附行为进行了综述，包括吸附反应，影响因素，且对砷的吸附研究进行了展显。     

不同开垦年限白浆土磷素吸附特征

选取开垦0,1,10,20,30年白浆土为研究对象,采用室内培养方法,以Langmuir方程研究白浆土磷素吸附特征,并分析Langmuir方程特征参数.结果表明:在外源磷浓度为0～50 mg/L时,随平衡液浓度增加,不同开垦年限白浆土磷素吸附量显著增加;不同开垦年限白浆土间磷素吸附量存在明显差异,开垦30年明显低于其他开垦年限,开垦10年显著高于其他开垦年限土壤.长期耕作施肥可显著降低白浆土磷素吸附亲和力常数(k)、最大缓冲容量(MBC)、标准需磷量(SPR).其中又以开垦30年土壤的k、MBC、SPR值最低.施肥对最大吸附量(Xm)的影响不显著.     

不同造林模式对铁尾矿地土壤性质的影响

为了了解不同造林模式对尾矿地物种多样性的影响以及对土壤物理、化学和生物性质的影响,采用空间替代时间的研究方式,分别调查未造林尾矿地、紫穗槐纯林、沙棘纯林以及沙棘—紫穗槐—桑树人工混交林下土壤的物理、化学及生物性质。结果表明:(1)与裸尾矿相比,紫穗槐纯林、沙棘纯林以及混交林林下土壤容重、田间持水量、毛管持水量以及毛管孔隙度均有不同程度的下降,土壤饱和持水量、总孔隙度及非毛管孔隙度有所上升,且混交林林下土壤物理性质的变化最大,土壤容重、田间持水量、毛管持水量与毛管孔隙度较裸尾矿分别下降了12.07%,3.49%,4.66%,3.67%,土壤饱和持水量、总孔隙度及非毛管孔隙度分别增加了6.44%,9.29%,12.96%;(2)与裸尾矿相比,紫穗槐纯林、沙棘纯林以及混交林林下土壤有机质含量及各种养分元素含量明显增加,土壤pH值下降,尤以混交林的变化最为明显;(3)造林后土壤主要微生物类群的数量及主要酶活性均有所上升,且以混交林上升最明显。由此可以看出,在尾矿地进行人工造林可以在一定程度上改善尾矿土壤的性质,且营造混交林模式对尾矿土壤的改良效果最佳。     

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。     

不同植被恢复模式对铁尾矿物种多样性及土壤理化性质的影响

为全面了解不同植被恢复模式对铁尾矿物种多样性及土壤理化性质的影响,在唐山迁安选取基于造地工程的植被恢复模式(紫穗槐林)、基于水保工程的植被恢复模式(六孔砖模式)、灌木纯林植被直接恢复模式(沙地柏直接造林模式)、乔木混交林植被直接恢复模式(沙棘-桑树混交直接造林模式),对其物种组成、数量特征和土壤理化性质进行调查,并与裸尾矿和未被破坏的天然灌丛进行对比分析。结果表明:(1)不同植被恢复模式的物种α多样性指数的变化趋势基本相同,丰富度指数和多样性指数均为沙棘-桑树乔木混交林>紫穗槐林>沙地柏灌木纯林>六孔砖;(2)与裸尾矿相比,沙棘-桑树乔木混交林模式、紫穗槐林模式及沙地柏灌木纯林模式下的土壤容重分别减少了6%,15%,14%,总孔隙度分别增加了16%,1%,8%,毛管孔隙度分别减少了19%,16%,4%,非毛管孔隙度分别增加了118%,46%,22%;沙棘-桑树乔木混交林模式、紫穗槐林模式下的土壤毛管持水量分别减少了18%,7%,而沙地柏灌木纯林恢复模式下的土壤毛管持水量增加了21%;(3)通过植被恢复后,相对于裸尾矿土壤,沙棘-桑树乔木混交林模式、紫穗槐林模式和沙地柏灌木纯林模式下的土壤有机质、速效钾含量明显增加;不同植被恢复模式的铁尾矿土壤养分的恢复效果从高到低依次为沙棘-桑树乔木混交林模式、紫穗槐林模式、沙地柏灌木纯林模式。     

中国南方富铁铝化土壤土系建立进展

土壤基层分类单元划分，特别是土系建设是土壤系统分类的基础，也能直接为农业生产提供更详细的科学指导。富铁铝化土壤（砖红壤、赤红壤和红壤）在我国南方广泛分布，为了解其在中国土壤系统分类中归属以及土系建设情况，本文综述了自2008年以来土系研究的相关成果，系统分析了富铁铝化土壤诊断层和诊断特性检索、高级分类单元归属以及基层分类单元建设现状，并展望了土系建设的发展方向：进一步细化土系划分和描述标准，加强新土系建设，加强新技术和新方法在土系建设中的应用，加大和扩展土系建设成果的运用，旨在为我国南方富铁铝化土壤系统分类研究提供参考。     

胶体存在时不同质地土壤对锌镉的吸附试验研究

以重金属离子Zn和Cd及胶体为对象,通过等温静态批量平衡吸附试验,分析了3种不同质地土壤对Zn、Cd单一吸附和等量竞争吸附特征,胶体对土壤吸附Zn、Cd的影响,并用Langmuir和Freundlich方程对试验结果进行了拟合。结果表明,随着平衡液中Zn2+、Cd2+浓度的增加,土壤对Zn、Cd的吸附量逐渐增大;3种质地土壤对Zn、Cd吸附量顺序为砂壤>粉壤>壤砂土;Zn2+、Cd2+共存时,土壤对这两种离子的吸附量比单一离子存在的情况下明显下降;胶体存在时抑制了土壤对Zn的吸附,促进了土壤对Cd的吸附;就本试验来说,Freundlich方程拟合效果优于Langmuir方程。     

Adsorption isotherms of some heavy metals under conditions of their competitive adsorption onto highly calcareous soils of southern Iran

Recently, application of sewage sludge or effluents resulted in raising the concentrations of some heavy metals in some agricultural soils of Iran. Experiments were conducted to evaluate the competitive adsorption of lead (Pb), copper (Cu), zinc (Zn), and cadmium (Cd) on six calcareous soils. Adsorption characteristics were evaluated by equilibration of 1 g of each soil sample with 20 ml of 0, 10, 20, 30, 40, 50, 100, or 200 mg L^?1 of their nitrate solutions and 0.01 M NaNO₃ as background electrolyte. Furthermore, solid/liquid distribution coefficients (K_d) of studied metals, as an index of soil capacity to resist a change of the soil solution concentration, were calculated. Results indicated that amounts of adsorbed Pb, Cu, Zn, and Cd increased with increase in their concentrations in the contact solutions, but this trend was more pronounced for Pb and Cu than the others. For all studied soils and metals, Langmuir equation described the adsorption behavior fairly well. Furthermore, Langmuir and Freundlich equation parameters were positively correlated to cation exchange capacity (CEC) and smectite contents; whereas, they were negatively correlated to sand content. Considering K_d values, the selectivity sequence of the metal adsorption was Pb > Cu > Zn > Cd. Therefore, the risk of leaching and also plant uptake of Zn and Cd will be higher as compared to those of the other elements.     

Phosphate adsorption by soils 1. Influence of time and ionic environment on phosphate adsorption

Abstract

The influence of reaction time and ionic environments, on phosphate adsorption were studied using one calcareous soil from India, and one calcareous and two latosols from Hawaii.

Phosphorus adsorption by soils has a initial rapid phase followed by a slow process. For plant nutrition studies, where emphasis is on P concentration of solutions from which plants derive P, isotherms should be constructed using data obtained after near‐equilibration has been attained. This condition does not obtain in a few hours and may require 6 days or more.

Calcium chloride as suspending electrolyte always gave lower phosphate solubility than when KC1 was used as electrolyte. Phosphate retention increased with increasing ionic strength. The necessity for obtaining clear supernatant solutions and the desirability for maintaining reasonable constant equilibrium conditions make 0.01 M CaCl₂ a reasonable choice for constructing P sorption isotherms, even though 0.01 M CaCl₂ is not representative of Ca concentrations in many soil solutions. Saturation extracts of soils investigated here were in the range 0.0002 to 0.005 M Ca.

Adsorption of calcium by highly weathered soils was high suggesting specific adsorption. Calcium adsorption was increased by phosphate additions to a Hydrandept.     

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.     

不同耕种年限红壤性水稻土理化性质的变化特征

以江西省余江县不同种植年限的红壤性水稻土为对象,研究了土壤有机质、pH、阳离子交换量(CEC)、游离氧化铁含量和氧化铁活化度随时间变化趋势;选择耕种7、22和80年的土壤剖面,研究了游离氧化铁和无定形氧化铁在剖面不同层次的分布。结果表明,耕层(0～20cm)土壤有机质含量随着水稻种植年限的增加而增加,淹水种稻导致土壤pH升高,但主要发生在种稻的前7年,7～80年间土壤pH变化不大。土壤CEC随着种植年限的增加而增加,在17年达到最大,然后随种稻时间的进一步增加而减小。土壤游离氧化铁含量随种稻时间呈下降趋势,但种稻后土壤氧化铁的活化度高于母土旱地红壤。对7年和80年水稻土,表层土壤游离氧化铁的含量低于底层土壤,说明铁在剖面中存在淋溶迁移。7年和22年水稻土表层土壤无定形氧化铁含量高于底层土壤,但对80年水稻土,土壤无定形氧化铁随采样深度的增加而增加。     

不同母质发育的红壤电荷特性研究

研究了3种不同母质发育的红壤中电荷的差异,比较了不同母质对电荷的影响。结果表明:3种母质发育的红壤中,紫色土发育的红壤中全部负电荷含量明显高于花岗岩发育的红壤和第四纪红色黏土发育的红壤;第四纪红色黏土发育的红壤中正电荷的含量明显高于花岗岩发育的红壤和紫色土发育的红壤;第四纪红色黏土发育的红壤、花岗岩发育的红壤和紫色土发育的红壤中正电荷与pH呈显著性负相关;第四纪红色黏土发育的红壤正电荷与有机质呈显著负相关,花岗岩发育的红壤和紫色土发育的红壤中正电荷与有机质含量呈显著正相关;第四纪红色黏土发育的红壤和紫色土发育的红壤正电荷与黏粒含量呈一元二次线性关系,花岗岩发育的红壤正电荷与黏粒含量呈极显著负相关;紫色土发育的红壤吸附的NH4+-N含量最高,第四纪红色黏土发育的红壤吸附的NO3--N含量最高。通过对3种母质发育的土壤电荷特性的研究,可为不同母质的红壤进行合理施肥与管理提供科学依据。     

Biochemical properties of range and forest soils in Mediterranean mountain environments

Biochemical properties are at present considered to be the best indicators for assessing soil quality, but their use is limited by the lack of available data, at least for certain ecosystems. In an attempt to offset this lack of data, the present study provides information on different biochemical properties of soils from Sierra Nevada and Sierra María (southern Spain), covering a range of altitudes between 1,000 and 3,000 m. In general, the values of the properties analyzed were similar to those of other mountain soils, although the values of basal respiration were particularly low, possibly due to the low levels of humidity at the time of sampling. The biochemical properties were closely correlated with each other, as observed in soils from other type of environments. Altitude had a clear effect on the biochemical properties because of its effect on climate and vegetation. At both sites, the soil samples showing the most homogenous pattern of biochemical properties (seen through star diagrams) were those corresponding to intermediate altitudes.     

不同土地利用方式土壤对铜、镉离子的吸附解吸特征

采用一次平衡法对Cu²⁺、Cd²⁺在城市及城郊农田、林地、草地3种土地利用方式土壤中的吸附解吸过程进行比较研究, 结果表明: Cu²⁺、Cd²⁺在3种土地利用方式土壤中的吸附量均随平衡液浓度的增加而增大, Cu²⁺、Cd²⁺在农田土壤上的吸附量均高于林地和草地土壤。分别用Langmuir和Freunlich两种等温吸附方程对吸附过程进行拟合, 3种土壤对Cu²⁺的吸附过程运用Langmuir方程拟合效果好, 而对Cd²⁺的吸附过程运用Freunlich方程拟合效果更好。Cu²⁺在3种土壤的解吸量大小顺序为农田>林地>草地, Cd²⁺在3种土壤的解吸量大小顺序为农田>草地>林地。两种离子在3种土壤中的动态吸附是个快速反应的过程, 随时间延长, 吸附反应趋于平衡。运用双常数函数方程和Elovich方程能较好地拟合重金属在土壤上的吸附动力学过程。Cu²⁺、Cd²⁺的吸附与土壤黏粒含量、有机质含量、CEC和pH均有关。     

发育程度对海南玄武岩发育土壤吸附铬酸根和磷酸根的影响

选择海南岛北部3个不同年代喷发的玄武岩发育的土壤研究了其对铬酸根(CrO42-)和磷酸根(PO43-)的吸附特征,结果表明随着母岩年龄的增加,土壤发育程度提高,土壤游离氧化铁和表面正电荷数量增加,对2种阴离子的吸附量增加。土壤CrO42-的解吸率在19.8%~39.6%之间,表明土壤对CrO42-的吸附涉及静电吸附和专性吸附2种机制,且随着土壤发育程度增加,CrO42-静电吸附所占比例增加。土壤对PO43-的吸附以非静电吸附为主,吸附的PO43-的解吸量非常低,其解吸率不超过6%。吸附PO43-在去离子水中的解吸量高于在0.1 mol/L NaNO3和KNO3中的解析量,KNO3体系中的解吸量低于NaNO3体系中的,电解质主要通过改变胶体表面离子吸附面上的静电电位影响PO43-的解吸。