Adsorption of xanthan polymer on allophane and effect on the changes in colloidal stability of allophane by heavy metal ions

The influence of divalent cations at concentrations of 10^-6.0 to 10^-4.0 M on the colloidal stability of partially deflocculated allophane by gum xanthan (GX) polysaccharide at pH 6.5 was investigated at two GX concentrations. Experiment in the presence of 10^-2.0 g L^-1 GX showed that the stability decreased by the addition of divalent cations and the effect of the decrease due to the cationic species was evident in a higher concentration range, i.e., 10^-5.0 to 10^-4.0 M. The order of the effect was Pb >Zn > Cd > Mg. Experiment in a 10^-4.5 g L^-1 GX solution revealed that (i) the stability increased by the addition of heavy metal cations at 10^-5.0 M (the order of the effect was Pb > Zn > Cd) and decreased at a concentration above 10^-4.5 M, (ii) whereas the stability decreased by the addition of Mg ion. The striking difference in the stability behavior due to the difference between the two GX-concentrations was attributed to the (i) degree of GX-adsorption (and hence negative charge from the carboxyl group in GX) onto allophane based on the electrophoretic mobility, (ii) complexation of heavy metal cations by organic ligand (carboxyl group) in GX which was adsorbed onto allophane, and (iii) surface complexation by heavy metal cations and hydroxyl groups on allophane. The results were discussed in relation to the characteristics of the particles of allophane, viz., (i) polymer-coated soft particles, and (ii) semi-soft particles on which the rigid (hard) surface of allophane substantially remained.     

Shear strength of surface soil as affected by soil bulk density and soil water content

This paper proposes a new method to measure the soil strength parameters at soil surface in order to explain the processes of soil erosion and sealing formation. To simulate the interlocks between aggregates or particles within top 2 mm of the soil, a piece of sandpaper (30 particles cm⁻²) was stuck on the bottom face of a plastic box of diameter of 6.8 cm with stiffening glue and used as shear media. The soil strength for the soils from sandy loam to clayey loam was measured with penetrometer and the new shear device at soil surface at different bulk density and soil water content. The normal stresses of 2, 5, 8, 10 and 20 hPa were applied for the new shear device. The results indicated that significant effect of bulk density on soil strength was detected in most cases though the difference in bulk density was small, ranging from 0.01 to 0.09 g cm⁻³. It was also indicated that the measurement with the new shear device at soil surface was reproducible. The changes in soil shear strength parameters due to changes in bulk density and soil moisture were explainable with the Mohr–Coulomb’s failure equation and the principles of the effective stress for the unsaturated soils. The implications of the method were later discussed.     

猪场废水污灌土壤的Cr和Ni空间变异及积累分析

为了解长期施用猪场废水对农田土壤Cr和Ni（以下简称重金属）的影响,采集了河北省京安猪场周边农田清洁区和灌溉8年猪场废水的污灌区耕层（0～20cm）共52个土壤样品,并测定了样品中pH、养分及重金属全量和有效态含量,应用GIS结合地统计学方法对重金属进行了空间结构和分布特征分析,探讨规模化猪场周边农田土壤重金属积累的影响因子及其贡献。结果表明,Cr和Ni全量和有效态含量变异函数理论模型均符合球状模型,具有中等程度自相关。根据背景调查,重金属与pH值和土壤养分的相关性分析以及重金属变异函数分析,研究区土壤Cr和Ni主要受成土母质的影响,受污灌猪场废水影响不大。富集因子分析表明,污灌猪场废水对土壤Cr和Ni几乎没有积累。灌溉猪场废水会降低土壤pH值,提高土壤Cr和Ni有效态含量。     

水土保持功能评价及其在水土保持区划中的应用

随着国家对生态文明建设的日益重视,以及国家及地方主体功能区规划的实施,对于水土保持的功能研究也越来越多.结合全国水土保持规划工作的需要,提出水土保持功能的概念、类型确定原则和功能类型,阐述了水土保持基础功能和社会经济功能的评价方法,以及各基础功能的评价指标体系.以太行山东部山地丘陵区为例,举例说明水土保持功能评价的过程和结果.对全国水土保持区划三级区基础功能进行统计分析,明确各功能的区域比例,提出8个一级区水土保持工作主要方向,维护和提高区域水土保持功能将成为水土保持工作的重点和方向.     

Model experimental study on the migration behavior of heavy metals in electrokinetic remediation process for contaminated soil

Recently in Japan, like in other industrialized countries, treatment of contaminated soil or ground has become an important issue in redeveloping such areas as old factories, mining sites, and other polluted sites. In these cases, measures such as a construction of cut-off walls and disposal to controlled waste disposal sites have been so far taken. But, the treatment of contaminated soils has become more difficult nowadays. Therefore, remediation of contaminated soil by removal or extraction of contaminants is necessary and various methods have been developed and applied in many countries. Authors have tried to develop an electrokinetic remediation method for soil contaminated with heavy metals and some basic and pilot scale experiments have been carried out. In this paper, the results of a model experiment using an artificial soil contaminated with Cu or Ph or Cr are presented as follows. i) In the electrokinetic process, migration of water to the cathode by electroosmosis, migration of ions to the cathode or anode by electrophoresis and electrolysis of water occur spontaneously. ii) Upon DC loading, Cu and Pb migrate to the cathode and accumulate as oxides or hydroxides near the cathode but are not removed from contaminated soil. However, in the case of Cr contaminated soil, Cr in the form of Cr(VI) migrates to the anode and is removed from soil through the drainage water. iii) After DC loading for 2 weeks, the concentration of exchangeable cations and composition of soil changed drastically while the CEC and clay mineralogy did not change appreciably.     

Nickel phytotoxicity in relationship to soil ph manipulation and chelating agents

Abstract

The main objective of this study was to ascertain effects of some edaphic factors on the uptake and influence of Ni on plant growth sinee Ni is a common trace element contaminant as well as an important component of serpentine soils. Corn (Zea mays L. inbred Ys₁/Ys₁) was rown in Yolo loam soil amended to give soil pH values of 4.2, 5.6, 7.5, and 8.2. A level of 100 μg Ni/g soil was not toxic to the corn. Shoot concentrations of Ni increased as soil pH decreased for both application rates of Ni. A level of 250 μg Ni/g soil decreased yields more at soil pH below 7 than above 7. Iron, Zn, and Mn levels in shoots did not appear to be directly related to the Ni applications although Fe levels tended to increase as a result of smaller plant size. PI54619–5–1 soybeans (Glycine max L. ) were grown in soil at two different pH values (with and without CaCO₃) and with and without a level of 1000 μg Ni/g added as the sulfate and thoroughly mixed with the soil and equilibrated for 1 month prior to transplanting the soybeans with and without application of a chelating agent, DTPA (diethylene triamine pentaacetic acid), commonly used to correct Fe deficiency in plants. Plants were killed in the soil of pH 6.2 when the 1000 μg Ni/g soil was added. The pH 7.2 soil decreased the toxicity of Ni. The DTPA had little effect on yields, but increased the amount of Ni in plants. Nickel decreased the Fe, Zn, Cu, and Mn concentrations of the plants. Stems contained less Ni than did leaves. In another experiment, EDTA (ethylenediamine tetraacetate) greatly increased Ni concentrations in bush beans (Phaseolus vulgaris L. C.V. Improved Tendergreen) and in barley (Hordeum vulgare L.C.V. Atlas 57) grown in Yolo loam soil, and simultaneously increased Fe concentrations. Lime (CaCO₃ or MgCO₃) decreased toxicity of Ni in bush beans. DTPA increased Ni transport in bush beans and increased the ratio of Ni in leaves to that in stems at soil pH 7.5 and 8.2, but not at pH 4.0 and 5.8.     

用模糊综合评判法评价土壤重金属污染程度

通过对南宁市郊 1 2个主要菜区土壤中重金属 ( Cu、Zn、Cd、Pb)含量的调查和分析测定 ,采用模糊综合评判方法对土壤重金属污染状况进行评价。结果表明 :南宁市郊部分蔬菜区土壤不同程度地受到Cu、 Zn、 Pb、 Cd的污染 ,污染程度依次是 :Cd>Pb>Zn>Cu。 1 2个样点污染程度依次为 n2 =n6 =n1 1 >n7=n8=n9>n1 =n4 >n5>n1 2 >n3=n1 0     

Immobilization of soil copper using organic and inorganic amendments

This experiment aimed to immobilize Cu in polluted agricultural soils via the application of agrochemicals to reduce its bioavailability to plants. A greenhouse pot experiment was established using a Cu contaminated vineyard topsoil collected from a farm in Greece. The soil was mixed with inorganic [i.e., zeolite (Z), Al‐oxide (AX), Mn‐oxide (MX), and phosphate rock (PR)] as well as organic amendments [i.e., activated charcoal (AC), commercial peat soil material (CP), and compost from olive oil processing wastes (COW)] with an application rate of 2.5% and cultivated by corn (Zea maize). After plant harvesting, Cu was measured separately in the aboveground biomass and roots, respectively, whereas the soil samples were analyzed for DTPA‐extractable and geochemical fractions of Cu (soluble + exchangeable fraction, sorbed and carbonate fraction, Fe‐/Mn‐oxides fraction, and organic fraction). The immobilizing agents, except MX, reduced the soluble plus exchangeable Cu in the treated soil. The lowest concentrations of the soluble plus exchangeable Cu occurred in the soil amended with AC followed by CP, AX, COW, PR, and Z, respectively. The amendments decreased the uptake of Cu by corn. Concentrations of Cu were between 11 and 38% lower in the above ground biomass and 19 and 48% lower in the roots than the control. The organic amendments were more effective than the inorganic additives. The AC was the most effective organic additive and AX was the most effective inorganic amendment.     

Chelate-Assisted Phytoextraction of Cadmium and Lead using Mustard and Fenugreek

A screen-house experiment was conducted to study cadmium (Cd) and lead (Pb) phytoextraction using mustard and fenugreek as test crops. Cadmium was applied at a rate of 20 mg kg^?1 soil for both crops, and Pb was applied at 160 and 80 mg kg^?1 soil for mustard and fenugreek, respectively. The disodium salt of ethylenediamine tetraacetic acid (EDTA) was applied at 0, 0.5, 1.0, and 1.5 g kg^?1 soil. Dry-matter yield (DMY) of both crops decreased with increasing rates of EDTA application. Application of 1.5 g EDTA kg^?1 soil caused 23% and 70% declines in DMY of mustard and fenugreek shoots, respectively, in the soils receiving 20 mg Cd kg^?1 soil. Similarly, in soil with 160 mg Pb kg^?1 soil, application of 1.5 g EDTA kg^?1 resulted in 25.4% decrease in DMY of mustard shoot, whereas this decrease was 55.4% in fenugreek grown on a soil that had received 80 mg Pb kg^?1 soil. The EDTA application increased the plant Cd and Pb concentrations as well as shoot/root ratios of these metals in both the crops. Application of 1.5 g kg^?1 EDTA resulted in a 1.50-fold increase in Cd accumulation and a 3-fold increase in Pb accumulation by mustard compared to the control treatment. EDTA application caused mobilization of Cd and Pb from carbonate, manganese oxide, and amorphous iron oxide fractions, which was evident from decrease in these fractions in the presence of EDTA as compared to the control treatment (no EDTA).     

Effects of compaction on soil surface water repellency

Water repellency can reduce the infiltration capacity of soils over timescales similar to those of precipitation events. Compaction can also reduce infiltration capacity by decreasing soil hydraulic conductivity, but the effect of compaction on soil water repellency is unknown. This study explores the effect of compaction on the wettability of water repellent soil. Three air‐dry (water content ～4 g 100 g^?1) silt loam samples of contrasting wettability (non‐repellent, strongly and severely water repellent) were homogenized and subjected to various pressures in the range 0–1570 kPa in an odeometer for 24 h. Following removal, sample surface water repellency was reassessed using the water drop penetration time method and surface roughness using white light interferometry. An increase in compaction pressure caused a significant reduction in soil surface water repellency, which in turn increases the soil's initial infiltration capacity. The difference in surface roughness of soils compacted at the lowest and highest pressures was significant (at P > 0.2) suggesting an increase in the contact area between sessile water drops and soil surfaces was providing increased opportunities for surface wetting mechanisms to proceed. This suggests that compaction of a water repellent soil may lead to an increased rate of surface wetting, which is a precursor to successful infiltration of water into bulk soil. Although there may be a reduction in soil conductivity upon compaction, the more rapid initiation of infiltration may, in some circumstances, lead to an overall increase in the proportion of rain or irrigation water infiltrating water repellent soil, rather than contributing to surface run‐off or evaporation.     

Effect of Nanoclinoptilolite/Nanohydroxyapatite mixtures on phosphorus solubility in soil

Phosphorus (P) is a vital element for plant growth and maturity, yet most soils have low P availability. The aim of the present study was to synthesize a mixture of nanohydroxyapatite (nHA) and saturated nanoclinoptilolite (nCp) and compare its ability to improve the P solubility with that of a natural system (Cp/rock phosphate). Consequently, as nCp were saturated with different salt solutions, the P solution concentration decreased in the following order: ((NH₄)₂SO₄) NH₄–nCp > (NH₄Cl) NH₄–nCp > (KCl) K–nCp > (K₂SO₄) K–nCp. Higher P availability was achieved at higher ratios of nCp/nHA. The nCp/nHA appear twice more effective in P released than Cp/PR (42.73% vs 19.23%). The greatest increase (5 mg/L) in the quantity of P released was at a nCp/nHA ratio of 15. Parabolic diffusion and power function equations fitted best to the data. This work demonstrates that nCp/nHA can act as an effective P fertilizer in calcareous soils.     

水土保持措施对板栗林土壤呼吸的影响

为阐明板栗林土壤呼吸对水土保持措施的响应,采用IRGA法,对不同类型板栗林的土壤呼吸从2009年3月至2010年9月开展为期1年半的定位观测。结果表明:1)采取水土保持措施后,样地的土壤水分状况得到一定程度的改善,尤其随着采取水土保持措施年限的延长,其对土壤水分时空分布影响更为显著。2)4个板栗林样地的土壤呼吸速率均呈明显的单峰曲线变化,水土保持措施对土壤呼吸的季节动态无明显影响。3)样地Ⅰ和Ⅲ的参考呼吸R10分别为1.718和1.595μmol/(m2.s);而采取水土保持措施后,样地Ⅱ和Ⅳ的R10均表现为一定程度的降低,分别为1.092和1.324μmol/(m2.s)。样地Ⅰ和Ⅲ的土壤呼吸的温度敏感性指数Q10分别为1.927和1.899;采取水土保持措施后,样地Ⅱ和Ⅳ的Q10均表现为略微增加。采取水土保持措施后,土壤温度和土壤湿度对土壤呼吸速率的影响有一定程度的增强。研究结果可为把水土保持措施作为土壤严重侵蚀地区一种潜在的固碳减排模式提供基础数据。     

不同改良剂对黄绵土水稳性团聚体的改良效果及其机制

通过室内土柱培养,采用聚丙烯酰胺(Polyacrylamide,PAM)、沃特保水剂、β-环糊精、腐殖酸等4种土壤结构改良剂对黄绵土水稳性团聚体进行改良。结果表明:4种改良剂均可促进>0.25 mm水稳性团聚体的形成,在浓度0.05%～0.40%范围内,其改良效果表现为PAM>β-环糊精>沃特保水剂>腐殖酸,且黄绵土团聚体分形维数显著降低,尤以PAM改良效果最明显;在低浓度条件下,4种改良剂均可有效地降低土壤密度;土壤粒径分布表明,PAM改良黄绵土水稳性团聚体的机制是使<1 mm粒径的团聚体团聚为更大的团聚体,尤其是团聚为>5 mm的团聚体,PAM在4种改良剂中对黄绵土改良效果最好。阐明不同改良剂对黄绵土水稳性团聚体的改良效果及机制,可为合理利用改良剂改良土壤结构提供理论依据。     

水源涵养基本功能区水力侵蚀现状分析简

针对全国水土保持区划中确定的22个具有水源涵养功能的基本功能区,利用第1次全国水利普查获取的水力侵蚀数据,分析这些区域的水力侵蚀现状.结果表明：1）水源涵养基本功能区水力侵蚀以轻中度侵蚀为主,超过80％,强烈、极强烈、剧烈面积分布较少,与全国基本状况相似;2）与第2次全国土壤侵蚀遥感调查成果相比,水源涵养基本功能区水力侵蚀整体上有所好转,水力侵蚀总面积减少3.75％,轻中度侵蚀面积大幅减少,减幅超过20％;3）水源涵养基本功能区局部地区水力侵蚀形势严峻,极强烈和剧烈侵蚀面积虽然不大,但是与第2次遥感调查成果相比,面积均有所增加,相对增幅较大,说明局部地区存在水力侵蚀恶化的现象.     

北京石质山区不同水土保持措施对土壤物理性质及抗冲性的影响——以房山区蒲洼小流域为例

为评价北京山区多年来小流域综合治理的水土保持效果,也为以后小流域治理和植被重建提供理论支撑,以房山区蒲洼小流域为研究地,采用典型样地调查、野外抗冲性实验和室内样品处理的方法,对比分析不同水土保持措施的土壤物理性质、土壤质地和抗冲性.结果表明:随着土层加深,各类措施下土壤密度均呈现增大趋势,总孔隙度和毛管孔隙度呈现减小趋势,而非毛管孔隙度没有明显规律.不同水土保持措施下,土壤密度、总孔隙度和毛管孔隙度均有改善(侧柏林除外),改善程度由好到差依次为:辽东栎次生林＞油松落叶松混交林＞石坎梯田＞油松林＞落叶松林＞灌丛;各类措施下土壤颗粒均以细、中粉粒为最多,分形维数显示各类水保措施土壤通透性均较为良好;相比荒地,各类措施下土壤冲刷量显著减小,径流时间延长,冲刷量依次为油松落叶松混交林(0.82 kg/cm3)＜侧柏林(1.14 kg/cm3)＜落叶松林(1.30 kg/cm3)＜辽东栎次生林(3.91 kg/cm3)＜油松林(5.96 kg/cm3)＜荆条灌丛(10.88 kg/cm3),延缓径流冲刷时间由大到小依次为:辽东栎次生林(55.65 s/m)＞油松落叶松混交林(46.82 s/m)＞落叶松(28.19 s/m)＞荆条灌丛(22.39s/m)＞侧柏林(17.48 s/m)＞油松林(16.94 s/m).土壤抗冲性与细、中粉粒体积分数(正相关)、非毛管孔隙度呈显著(负相关)关系最为密切,由此推出大根径的根系穿插形成的非毛管孔隙对土壤抗冲性是负效应.综上,油松落叶松林混交林提升土壤蓄水持水性能、土壤抗冲性均显示出很大的优势;石坎梯田效果也较好,是小流域治理应首先考虑的2类措施.     

Determination of nitrite in soil extracts and water samples by a nitrogen oxide electrode

Abstract

Work to evaluate the Orion nitrogen oxide electrode indicated that this electrode can be used satisfactorily for determination of nitrite in soil extracts and water samples. The electrode method of analysis described is simple, rapid, and precise, and its results agree closely with those obtained by the colorimetric method of Griess‐Ilosvay. The electrode method has the advantage that its results are not affected by color or turbidity or by Cu²⁺ and Hg²⁺ present in samples under analysis     

Glomalin-related soil protein and water relations in mycorrhizal citrus (Citrus tangerina) during soil water deficit

Glomalin-related soil protein (GRSP), a glycoprotein of arbuscular mycorrhizal fungi (AMF) secreted into soil, governs the aggregate stability, but the role of GRSP in soil and plant water is sparsely studied. The 24-week-old red tangerine (Citrus tangerina) inoculated with Glomus etunicatum and G. mosseae were subjected to a soil drying for 12 days as soil water deficit (SWD). Length of SWD significantly reduced mycorrhizal colonization, soil hyphal length, and leaf and soil water potential (Ψ), but increased total GRSP (T-GRSP), easily extractable GRSP (EE-GRSP), and proportion of water-stable aggregates (WSAs) in >0.25 mm size, irrespective of AMF source. The AMF-inoculated seedlings showed significantly higher T-GRSP, EE-GRSP, and leaf/soil Ψ than non-AMF seedlings during SWD. A significantly positive correlation was observed for mycorrhizal colonization versus leaf or soil Ψ, and hyphal length versus leaf Ψ, suggesting that root intra- and extra-radical hyphae participated in water transport. Interestingly, in GRSP fractions, only T-GRSP was significantly positively correlated with 0.25–1 and >0.25 mm WSA and negatively with leaf and soil Ψ. These results revealed a strong glue function of T-GRSP (not EE-GRSP and hyphae) to alter the proportional distribution of WSA size, thereby aiding toward prevention of soil water loss for improving soil–plant water relations.     

路域土壤特征及其成因研究

通过对西禹高速合阳段路域土壤的调查和分析,并和未受人为干扰的自然土壤进行比较,研究了公路路域土壤的成因、特点及其限制因子,并总结出如下特点:(1)土壤物理性质差;(2)有机质和养分贫乏,pH值普遍偏高;(3)土壤成分复杂,侵入体多;(4)有效土层有限,植物扎根受限;(5)土壤重金属污染因素增多。