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.     

除草剂咪草烟在土壤上吸附-脱附过程及作用机理

本文研究了咪唑啉酮类除草剂咪草烟在不同土壤固－液相间的分配及与土壤组分作用的定量相关性。结论指出：咪草烟在土壤固－液相的分配主要受土壤粘粒,有机质及土壤ｐＨ的影响。它们在土壤上的吸附－脱除均可用Ｆｒｅｕｎｄｌｉｃｈ方程描述;通过运用红外及Ｘ－衍射技术,从分子水平研究了咪草烟与蒙脱石的作用机理,发现咪草烟与蒙脱的作用不仅发生在表面,而且咪草烟还能进入蒙脱石内层与其层间阳离子形成配合物。     

土壤中五碳醣的比色測定法

土壤有机质是一个极其复杂的体系。在此复杂体系中碳水化合物的状况无疑地将对土壤的肥力状况产生多方面的作用。例如,Martin等^[1-3]证明,多醋类物厦对水稳性团聚体的形成具有良好的效应。Broadbent等^[4.5]认为,能源物质的含量直接影响微生物的活动性,从而与氮素的有效性密切相关。     

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     

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。     

有机修饰(土娄)土对CrO_4~(2-)吸附特征的初步研究

以CTMAB(十六烷基三甲基溴化铵)单一修饰和CTMAB SDS(十二烷基磺酸钠)混合修饰土耕层、粘化层土样,从修饰比例、土层、温度角度探讨了有机修饰土对CrO42-的平衡吸附特征。结果表明,各供试土样中CrO42-平衡吸附量均随CrO42-平衡浓度增高而增大,有机修饰土对CrO42-的吸附等温线呈现L型等温线形式,原土土样的吸附等温线基本上类似于S型吸附等温线形式,两层次各土样对CrO42-的吸附量呈现100CB>120CS>50CB>CK的顺序(100,120,50分别表示修饰比例为100,100 20,50;CB为CTMAB修饰;CS为CTMAB SDS修饰;CK为未修饰原土);随着平衡浓度的增大,耕层原土对CrO42-的吸附能力增加较快而粘化层原土增加较慢,土粘化层修饰土样对CrO42-的平衡吸附量均高于土耕层土样,但修饰比例增高导致两层次土样对CrO42-吸附亲和力的差异减小;未修饰原土对CrO42-吸附呈现增温效应,粘化层CK土样增温效应高于耕层CK土样,表明增温促进粘粒矿物对CrO42-的专性吸附。随平衡浓度的增大,修饰土样CrO42-吸附温度效应比值均变化不大,耕层各修饰土样对CrO42-吸附呈现增温负效应,而粘化层修饰土样对CrO42-吸附的温度效应则与修饰剂和修饰比例有关。     

REACTIONS OF SOLUBLE PHOSPHATE WITH ACID SOILS: THE INTERPRETATION OF ADSORPTION-DESORPTION ISOTHERMS

Adsorption-desorption and isotopic-exchange isotherms for acids soils of known clay mineralogy indicated that when all the surfa? P accessible to the solution was considered, the bonding energy for phosphate decreased exponentially with site coverage. The soils differed markedly in the quantities of surface P held at sites of very high bonding energy, defined as those in equilibrium with a solution concentration < 1 μM; the values ranging from 9 μmol g^?1 in a soil with 40 per cent gibbsite in the clay fraction, to 1 μmol g^?1 in a soil with only 1 per cent gibbsite and no interlayered material. The reversibility of current P adsorption on soil surfaces depended on the immediate history of the soil sample. Complete reversibility occurred when soil, previously enriched with soluble P and stored for 4 to 5 months at constant temperature, was suspended in solutions of constant pH and ionic strength. It is suggested that irreversibility occurs due to incomplete attainment of equilibrium during the adsorption phase, a condition predisposed by high initial P concentrations (>1mM), and the use of soils that are naturally in dis-equilibrium because of recent fertilizer additions or severe depletion of P by plant uptake.     

THE REACTION OF FLUORIDE WITH SOILS AND SOIL MINERALS

The reaction of sodium fluoride solution with soils and soil minerals at constant pH has been assessed as a possible single-value characteristic in the classification of soils, particularly those containing significant amounts of poorly ordered inorganic material. A suitable method involves reaction of the soil or clay at 25°C with 0·85 M sodium fluoride at pH 6·8, the amount of OH^? released after 25 min being taken as the single-value characteristic. There was a statistically significant correlation between the amount of OH^? released and the amount of alumina extracted with cold 5 per cent sodium carbonate solution from both freely drained and poorly drained Scottish soils. The multiple correlation coefficients were improved for freely drained soils by including the dithionite-extracted ferric oxide and the silica soluble in 5 per cent sodium carbonate solution. The procedure is not suitable for surface soils, because of interference by organic matter, or for carbonate-containing soils unless carbonate is removed.     

THE INTERACTION OF PHOSPHATE WITH AN ANION EXCHANGE RESIN

Phosphate adsorbed on an anion exchange resin was titrated with sodium hydroxide. The inflection point which corresponds to the second pK value of phosphoric acid in solution, was lowered 0.9 pH-unit when the acid was absorbed on the resin. This shift was fully explained by the exclusion of H⁺ from the resin due to a Donnan equilibrium. The adsorption characteristic of the single and double charged phosphate ion on an anion exchange resin was examined at different pH values and phosphate:resin ratios. A model was suggested for the observed adsorption pattern.     

变用扫描电镜对几种土壤特征层的微形态观察

近十年来,扫描电镜已在土壤微形态和矿物风化超微特征方面广泛应用,丰富了微土壤学的研究内容^[3,4]。本文应用JEM-100B电子显微镜二次电子扫描附属装置对东北地区几种土壤(表1)的特征层进行了观察,试图通过对土体中粘粒和其它细土物质部分的表面形态、空间排列和它们在形成微孔隙中的结构特征观察,进一步认识土壤中粘粒和某些细土物质的性状和作用。     

几种土壤和粘土矿物上磷的解吸

用0.5NHOAc、0.5NNH₄F和0.1NNaOH浸提的方法,研究了几种土壤和粘土矿物上磷的解吸与矿物组成和时间的关系,以及追加吸附及其解吸状况,结果表明,全部供试样品磷的解吸量都随吸磷量的增加而增加;解吸平衡的时间除红壤需要1天外,其余样品均在1小时内基本上达到平衡,同时可见缓慢解吸作用的存在;追加吸附中可见到从吸附正值到吸附负值的转变,以及0.1NNaOH解吸磷量的明显变化。     

两广地区不同植被类型与土壤性质的关系

我国热带和亚热带地区幅员辽阔,自然地理条件较为复杂;在热带和亚热带所特有的生物气候因子影响下,土壤向着富铝化的方向进行,造成大面积的红壤、黄壤和砖红壤,后者在广东的南部分布尤广。尽管这些土壤占据着华南相当大的面积,但对其生成发育、特别是发生学上的生物化学过程、植被对土壤性质的影响等方面的研究工作,虽然近年已有论著涉及^[1]。     

THE EFFECT OF POLY(VINYL ALCOHOL) ON THE CRUST STRENGTH OF SILTY SOILS

Fourteen samples of soils were collected from localities in England where crusting and consequent depression of seedling emergence had been recorded. Natural aggregates of these soils were sprayed with poly(vinyl alcohol) (PVA), subjected to simulated heavy rain, and dried under IR lamps. In most soils, aggregate stability was enhanced by increasing applications of PVA and crust formation was prevented. Some soils, however, were unresponsive to PVA and crusts formed whether or not it was applied. Responsive and unresponsive soils did not differ in particle size distribution, or porosity characteristics. Removal of iron oxides and organic matter did not alter their adsorption characteristics towards PVA. Unresponsive soils, however, were found to have the mineral chlorite as a major component and it is suggested that PVA is unable to bind particles together when the surfaces presented for adsorption of PVA consist of gibbsite, the interlayer material of chlorite.     

THE ASSOCIATION OF VANADIUM AND MOLYBDENUM WITH IRON OXIDES IN SOILS

High concentrations of V and Mo in ironstone gravels have previously been reported. Examination of soils in which ironstone concretions have formed during pedogenesis indicates that Mo/Fe ratios are in fact higher in the finer fractions than in these gravels, whereas the V/Fe ratios tend to be independent of particle size. In the lateritic podzolic soils examined, the observed association between V and Fe in the iron oxides of the fine earth fraction (< 2 mm) is maintained during any solution of this fraction and any subsequent transportation and precipitation involved in the development of the gravels. Differences in the degree of association with Fe shown by Mo and V are considered to be due to different modes of transport of these elements through the soil. It is suggested that V moves as a vanadyl cation whereas Mo is transported as a complex anion.     

不同种植年限大棚蔬菜地土壤养分状况研究

以江苏省苏南地区大棚蔬菜地土壤为例,研究了种植年限分别为1~2年、5年左右、10年左右大棚土壤的养分变化情况。研究结果显示随着种植年限的增加,土壤有机质、全N、全P、速效P含量逐渐增加;土壤盐分、NO3--N也随着种植年限的增加而逐渐增加,5年左右的大棚土壤含量最高,之后逐渐降低;而土壤pH、全K随着种植年限的增加缓慢降低。     

黄泛平原不同质地土壤的持水特性

用压力膜法对黄泛平原不同质地潮土的持水特性进行了研究.结果指出,土壤的持水性、孔径分布和水容量都与土壤质地有密切关系.在高吸力情况下,土壤的持水性随土壤质地变粘而增强.土壤孔径分布与土壤质地的关系是:重力水孔隙随土壤质地变粘而减小;迟效水孔隙和无效水孔隙随质地变粘而增加;而易效水孔隙偏粘的土壤有减小的趋势.土壤水容量也受土壤质地的影响,重力水水容量随质地变粘而增加,易效水水容量是壤土高于砂性土和粘性大,而迟效水水容量则是轻粘土高于其它质地的土壤.