不同盐基离子对黑土胶体zeta电位及凝聚过程的影响

以黑土胶体为研究对象,比较黑土胶体在不同浓度的四种盐基离子Na+、K+、Ca2+、Mg2+体系中的zeta电位、颗粒凝聚动力学过程和平均凝聚速率,明确不同离子界面行为对黑土胶体zeta电位和凝聚过程的影响。研究发现土壤胶体较高的颗粒密度(0.61 g L-1)更有利于获得稳定的zeta电位值;二价阳离子与一价离子相比,因其有更强的压缩双电层能力而引起zeta电位的降低和较强的土壤胶体凝聚过程;同价离子对zeta电位和土壤胶体聚沉影响的差异表现为离子浓度同为200 mmol L-1时,黑土胶体在K+体系中的凝聚速率是Na+体系中的7.65倍,离子浓度同为4 mmol L-1时,黑土胶体在Ca2+体系中的凝聚速率是Mg2+体系中的2.79倍。除了其自身体积的差异还与离子在表面强电场中的极化作用有关。不同盐离子受土壤表面附近电场的强烈影响,在土壤胶体表面固-液界面上被诱导极化,从而易引起胶体zeta电位的不同。该研究为表征土壤胶体表面性质及胶体凝聚过程和团聚体形成理论研究提供基础。     

蒙脱石表面碱金属离子的亚稳平衡吸附及其特异性效应

离子吸附的亚稳平衡是描述离子交换吸附中实际反应平衡特征及限度的重要理论范式。本研究旨在从理论上推导离子吸附的亚稳态平衡模型,建立离子平衡吸附量与活化能之间的数学关系,探讨碱金属离子亚稳平衡吸附的特异性效应。结合恒流混合置换技术及基于表面静电场理论的离子吸附动力学模型,探究了钾离子(K⁺)、钠离子(Na⁺)、锂离子(Li⁺)三种碱金属离子在铯离子(Cs⁺)-蒙脱石饱和样表面可能存在的亚稳平衡吸附作用;通过开展K⁺、Na⁺和Li⁺在Cs⁺-蒙脱石表面的吸附动力学实验,对理论模型进行验证。研究结果表明：(1)K⁺、Na⁺、Li⁺在Cs⁺-蒙脱石饱和样表面表现出显著的亚稳平衡吸附特征,交换离子的吸附活化能(能量势垒)来源于吸附态Cs⁺的解吸过程;(2)相同离子浓度条件下,表面静电场引起的离子强极化作用导致各离子的...     

碱金属离子在蒙脱石-Cu2+表面吸附的离子特异性

研究离子交换中的离子特异性效应有助于揭示离子-带电表面相互作用机制。以蒙脱石Cu2+饱和样为研究对象,采用恒流法研究不同浓度碱金属离子Li+、Na+和K+的吸附动力学过程,并建立1︰1型(LiNO3、NaNO3、KNO3)电解质溶液中离子平衡吸附量与体系吸附活化能之间的关系。结果发现:(1)Li+、Na+和K+在蒙脱石-Cu2+表面的吸附过程仅呈现出弱静电力作用下的一级动力学特征,并存在明显的离子特异性效应。(2)离子非经典极化作用与体积效应共同决定了离子在双电层中的位置,从而导致表面电位存在差异;并且表面电位(绝对值)随着电解质浓度降低而增加,表现为Li+>Na+>K+。(3)根据新建立的模型可预测吸附离子在双电层中的位置,进而求出体系的吸附活化能,并发现离子特异性效应产生的根本原因是由活化能决定的,同时本研究表明建立的新模型在固/液界面反应中具有普适性。本研究将对固/液界面反应理论的完善提供新思路。     

基于Gouy-Chapman理论估算碱金属离子在Cu2+-蒙脱石表面Hofmeister能

Hofmeister效应在离子交换吸附过程中具有重要的科学意义。本研究基于Gouy-Chapman理论研究三种碱金属阳离子（Na+、K+、Cs+）在Cu2+-蒙脱石饱和样表面吸附过程的Hofmeister效应,进一步计算了离子-表面Hofmeister能以及表观电荷系数。研究发现：（1）Na+ 、K+ 、Cs+在Cu2+-蒙脱石表面的吸附均表现为弱静电力作用下的一级动力学过程, 平均吸附速率以及平衡吸附量均表现出明显的Hofmeister效应,呈现出Na+ < K+ < Cs+的趋势;（2）Hofmeister能随着电解质浓度的降低而增加,在Cs+-粘土矿物相互作用中,Hofmeister能为主要贡献者,在K+/Na+-粘土矿物相互作用,经典库伦能中为主要贡献者;（3）非经典极化作用显著增大了离子的表观电荷系数,Na+、K+、Cs+的表观电荷系数分别从标准的+1值增加为+1.14、+1.76和+2.78。本研究明确了Hofmeister效应主要来源于离子的非经典极化作用引起的离子与表面相互作用能的差异,为阐明土壤这一特殊体系的界面反应机制提供了新的思路。     

Alkaline Hydrolyzable Organic Nitrogen as an Index of Nitrogen Mineralization in Soils: Relationship with Activities of Arylamidase and Amidohydrolases

ABSTRACT

This study investigated the relationship between a recently proposed alkaline hydrolysis method for estimating the chemical index of nitrogen (N) mineralization potential of soils and the activities of arylamidase and four amidohydrolases involved in hydrolysis of organic N (ON) in soils. Nitrogen mineralization was studied in 13 soils from uncultivated fields in Iowa, USA, by direct steam distillation of 1 g field-most soil treated with 1 M KOH or 1 M NaOH. The distillate was collected in boric acids, which was changed every 5 min for a total of 40 min. The NH₄ ⁺-N in the distillate was determined by titration with 0.005 M H₂SO₄. The cumulative amounts of N hydrolyzed were fitted to the first-order exponential equation to determine the “potentially hydrolyzable N (N_max )” for the soils. The activities of arylamidase, L-asparaginase, L-glutaminase, amidase, and L-aspartase were assayed at their optimal pH values. Results showed that estimated N_max values were strongly correlated with the activities of arylamidase and amidohydrolases. The activities of arylamidase and the amidohydrolases were significantly correlated, indicating that the activities of the two groups of enzymes are coupled in mineralization of ON in soils. Based on the specificity of enzyme reactions and the strong relationship between estimated N_max values and the activities of arylamidase and amidohydrolases, we concluded that similar amide-N bonds were susceptible to enzymatic and alkaline hydrolysis, and that alkaline hydrolyzable ON can be used as an index of N mineralization in soils.     

Comparison of the Properties of Humic Acids Extracted from Soils by Alkali in the Presence and Absence of Oxygen

Eurasian Soil Science - Humic acids (HAs) make up to 30–50% of the soil organic matter, which is the main reservoir of organic carbon in the biosphere. The common isolation protocol for HAs...     

生物有机肥对重金属的吸附解吸作用的影响

通过室内培养的方法比较了生物有机肥和干鸡粪对重金属离子Pb2+、Cd2+、Cr3+、As6+的吸附与解吸特性。研究结果表明:生物有机肥和鸡粪对4种重金属离子的吸附量大小依次为Cr3+>Pb2+>Cd2+>As6+,解吸量大小顺序为Pb2+>Cd2+>Cr3+>As6+,而解吸率的大小顺序为As6+>Pb2+>Cd2+>Cr3+,这主要与四种金属离子的电荷种类、数量及水合离子半径等密切相关。与干鸡粪相比,生物有机肥增加了对4种重金属离子的吸附率,同时降低了对4种重金属离子的解吸率。     

Flour Particle Size,Starch Damage,and Alkali Reagent: Impact on Uniaxial Stress Relaxation Parameters of Yellow Alkaline Noodles

Three patent flours, each possessing three different levels of starch damage were prepared from a single hard white spring wheat. Each flour was sieved to yield three flours with different particle size distributions (85–110, 110–132, 132–183 μm). Raw alkaline noodles were prepared from the nine flours using either 1% w/w kansui (sodium and potassium carbonates in 9:1 ratio) or 1% w/w sodium hydroxide. Uniaxial stress relaxation parameters percent stress relaxation (SR%), initial rate of relaxation (k₁) and the extent of relaxation (k₂) were measured on the raw noodles immediately after production (t = 0 min) and at 60 min. Raw noodles after resting for 60 min were optimally cooked and stress relaxation parameters were measured. Raw noodles at t = 0 min exhibited SR%, k₁, and k₂ that were significantly (P < 0.0001) influenced by both the degree of starch damage and the type of alkaline reagent used. Flour particle size only influenced SR% and k₁ (P < 0.025) but had no impact on k₂. In raw noodles aged for 60 min, both SR% and k₂ were significantly influenced by alkaline reagent, particle size, and starch damage (P < 0.01) while k₁ was only affected by the degree of starch damage (P < 0.0001). Cooked noodle SR parameters were all significantly (P < 0.0001) influenced by alkaline reagent, particle size, and the degree of starch damage. Cooked noodles prepared from starch with low damaged flours within any given particle size range, regardless of the type of alkali employed, yielded the most rheologically elastic‐like (firmer) noodles. Two potential mechanisms by which the degree of starch damage influences noodle elastic like texture are discussed.     

滇池沉积物金属污染及潜在生态风险研究

对滇池126个采样点沉积物0～5 cm、5～10 cm和10-20 cm中Cu、Zn、Pb、Cr、Cd、Hg和As等7种金属的含量进行了分析测定,各金属含量测定结果均高于相应的参比值,表明滇池沉积物受到了不同程度的金属污染.各金属含量的水平分布很不均衡,Zn、Pb、Cd、Hg和As含量随沉积物深度的减小而增大,Cu和Cr含量则随沉积物深度减小而减小,表明滇池沉积物中Cu和Cr污染整体上出现了减缓的趋势,而Zn、Pb、Cd、Hg和As污染在不断加剧.用H(a)k(a)nson潜在生态风险指数对滇池沉积物金属污染的生态风险进行了分析,结果表明:滇池沉积物存在轻微的Cu、Zn、Pb、Cr和As污染生态风险,以及中等的Hg和Cd污染生态风险;全湖沉积物金属污染的平均生态风险指数RI值为205.03,属中等生态风险,但有快速加大的趋势.     

铵饱和沸石对几种重金属离子的吸附解吸特性影响研究

通过室内分析的方法比较了天然沸石及铵饱和沸石对重金属离子Cd2+、Zn2+、Cu2+、Pb2+的吸附及解吸特性。研究结果表明:铵饱和沸石对4种重金属离子的吸附量大小顺序依次为Pb>Cu>Zn>Cd,而解吸量和解吸率的大小顺序为Cd>Zn>Cu>Pb,这主要与四种金属离子的水合离子半径和水合能密切相关。与天然沸石相比,铵饱和沸石一方面增加了对4种重金属离子的吸附,同时又降低了其解吸率。原因是铵饱和沸石的阳离子交换量和比表面积有所增加,同时铵饱和沸石的孔穴和通道也较天然沸石更加均一和畅通。因此,铵饱和沸石在农业生产实践中,特别是土壤污染治理方面具有广阔的应用前景。     

Interactive Sorption of Metal Ions and Humic Acids onto Mineral Particles

The sorption of metal ions (Pb2+, Zn2+ and Cu2+) and soil humic acids (HA) from aqueous solutions onto mineral particles (sand, calcite and clay) was investigated using a batch equilibrium system. The sorption reactions in two- component systems (heavy metals-mineral particles and humic acids- mineral particles), as well as interactions in three-component system (heavy metals-humic acids-mineral particles) were examined. Results showed that the presence of humic acids, dissolved or bound onto mineral surfaces, considerably influenced the fixation of heavy metals. The various effects, depending on mineral type, humic concentration and specific metal-ion, were observed in three- component system. Sorption of Cu2+-ions on all minerals studied rapidly increased as the concentration of dissolved HA increased. The amount of Pb2+-ions sorbed on sand slightly decreased, while on kaolin increased between 15 and 20%. Sorption of Zn2+-ions on all minerals studied decreased at pH 4. At pH 5.5 the sorption of Zn2+-ions onto calcite decreased, while on kaolin and sand increased as a function of the humic acid concentration giving the curve with maximum at c(HA) = 2.5 mmol C L-1. At pH 6.5 sorption onto kaolin and sand increased. This effect occurs as a result of the conditional stability constant of Zn-HA complexes increasing at higher pH which in turn promotes the chelation of Zn2+-ions to mineral- bound humic substances. The enhanced sorption of metal ions from the aqueous phase in three-component systems is not only the result of mineral sorption of free metals but also the result of chelation with HA sorbed on the mineral surface.     

Two Metal Ions Improve Brightness in Wheat-Dough Products and Affect Aqueous Dispersion of Gluten

Zinc and aluminum ions at 0.05% of wheat flour, dry basis (7.4 and 18.5 mmol/100 g, respectively), improved the brightness of raw and dried spaghetti and salt and alkaline noodles. They also retarded bacteria and yeast and mold growth in salt noodles held at 25°C for two days as determined by total plate counts. Neither metal ion caused a change in noodle cooking quality, but they imparted a slight aftertaste in cooked noodles. Wheat flour dough mixed with 0.05% zinc or 0.025% aluminum ion (fwb), when kneaded in aqueous 0.1% calcium chloride, gave gluten with increased brightness. Zinc and aluminum ions appear to complex with enzymic browning chromophores in wheat dough and gluten and change their spectral properties. Zinc and aluminum ions affected the dispersion of gluten in water at pH ~5.0 and facilitated its spray-drying, but they were not detrimental to baking quality. Citric and tartaric acids at 5 mmol/100 g of gluten (db) gave wet gluten with pH ~4.5, which improved its brightness and water dispersibility.     

福建沿海农田土壤重金属污染与潜在生态风险研究

分析了取自福建沿海农田185件表层土壤样品的重金属含量与分布特征,采用连续提出的方法研究重金属元素的赋存状态。结果表明福建沿海稻田土壤中的Hg、Cd、As、Cr、Ni、Cu、Zn和Pb的平均含量分别为0.41mgkg-1、0.20mgkg-1、6.62mgkg-1、35.65mgkg-1、12.7mgkg-1、128.39mgkg-1、109.65mgkg-1和63.56mgkg-1。相对于区域土壤背景值与国家土壤环境质量标准,污染较突出的元素是Hg和Cd。有46%样品中的Hg含量高于土壤质量的Ⅱ标准值,有13%的样品的Cd高于土壤质量的Ⅱ标准值。Hg高含量的样品主要分布福州、漳州等城镇等附近,同时它在土壤中主要以有机结合态的形式存在,土壤中Hg含量的升高可能主要来自于后期污染的叠加。Cd高含量的样品的分布则较分散,并不都集中在工业活动区,同时它在土壤中是以残渣态和铁锰氧化物态的形式存在,说明其高含量可能更多是受到成土母质的地球化学背景影响。农田土壤中的Hg和Cd具有较高的生态风险。该区主要是栽种水稻,而水稻对Cd具有强吸收的特性,土壤酸化还会促进Cd的吸收。本区土壤呈酸性,所以Cd污染可能导致大米的食品安全应引起足够重视。     

不同金属离子对稻田自然生物膜磷酸酶活性的影响

以稻田自然生物膜为研究对象,研究不同浓度金属离子对生物膜酸性和碱性磷酸单酯酶(ACPase和ALPase)活性与酶反应动力学参数的影响。发现K⁺和Na⁺在0～1.0 mmol/L浓度下均对ACPase和ALPase无明显影响,Ca²⁺和Mg²⁺对ACPase和ALPase活性均有激活效应,可使磷酸酶活性最大提高14.1%和46.7%;Zn²⁺、Cu²⁺、Mn²⁺、Al³⁺和Ag⁺对ACPase和ALPase活性均有抑制作用。Co²⁺在低浓度时对ACPase和ALPase活性有一定的激活作用,高浓度时变为抑制作用;Cr⁶⁺在0.1 mmol/L时对ACPase活性有促进作用,而在离子浓度0.25～1 mmol/L的范围内,均对ACPase活性产生抑制作用。通过酶反应动力学分析发现,Mg²⁺的加入使ACPase与底物的亲和力与催化...     

Decomposition of Zn-rich Arabidopsis halleri Litter in Low and High Metal Soil in the Presence and Absence of EDTA

Hyperaccumulating plants are increasingly investigated in combination with EDTA addition to soil for phytoremediation of heavy metal contaminated soils. A 60-day incubation experiment was carried out to investigate the effects of heavy metal release during the decomposition of Zn-rich (15.7 mg g^?1 dry weight) Arabidopsis halleri litter on C mineralization, microbial biomass C, biomass N, ATP, and adenylate energy charge (AEC). These effects were investigated in two soils with different Zn, Cu, and Pb levels, with and without EDTA addition to soil. The sole addition of Zn-rich A. halleri litter to the two soils did not increase the contents of NH₄NO₃ extractable Zn, only with the combined additions of EDTA and litter was there a considerable increase, being equivalent to three times the added amount in the low metal soil and to 50% in the high metal soil. Litter amendment increased the CO₂ evolved; being equivalent to 44% of the added C in the two soils, but EDTA addition had no significant effect on CO₂ evolution. Litter amendment resulted also in an 18% increase in microbial biomass C, 27% increase in ATP and 6% increase in AEC in the two soils, but EDTA had again no effect on these indices at both metal levels. In contrast, the sole addition of litter had no effect on microbial biomass N, but EDTA addition increased microbial biomass N on average by 49%. The application of EDTA for chelate-assisted phytoextraction should in the future consider the risk of groundwater pollution, which is intensified by resistance of EDTA to microbial decomposition.     

Equilibrium Isotherm Studies for the Sorption of Divalent Metal Ions onto Peat: Copper,Nickel and Lead Single Component Systems

The sorption of three divalent metal ions — copper, nickel and lead — from aqueous solution onto peat in single component systems has been studied and the equilibrium isotherms determined. The experimental data have been analysed using the Langmuir, Freundlich, Redlich-Peterson, Toth, Temkin, Dubinin-Radushkevich and Sips isotherm models. In order to determine the best fit isotherm for each system, six error analysis methods were used to evaluate the data: the coefficient of determination, the sum of the errors squared, a hybrid error function, Marquardt's percent standard deviation, the average relative error and the sum of absolute errors. The error values demonstrated that the Sips equation provided the best model for the three sets of experimental data overall.     

pH及共存金属离子对生物质炭吸附铅稳定性的影响

生物质炭对重金属吸附性能的稳定性是评价生物质炭修复效果的重要指标。本文研究了不同pH、金属离子Cd和Al存在下,Pb在不同炭化温度(100℃、400℃、700℃)生物质炭上的脱附性能及脱附过程。结果表明,pH越低,Pb的脱附率越大。其主要是由于H~+的竞争效应,以及生物质炭表面官能团的质子化,促进了Pb的重新活化。在Cd和Al共存时,Pb的脱附率进一步增加。当pH=3.5时,Cd和Al的存在分别使Pb从CM100、CM400和ZKZ700上的脱附率提高了13.9%、1.0%、3.4%和26.8%、13.0%、11.3%。这主要归因于多金属的水解使得更多的H~+得以释放,进而促进了Pb的脱附。Pb在生物质炭上的脱附率随脱附时间的延长而不断增加,反应前4 h,脱附率迅速增加并均已达最大脱附率的70%,4 h后脱附速率减慢。Pb的脱附动力学符合伪一级动力学模型及颗粒内扩散模型(前4 h)。当Cd和Al存在时,解吸液对Cd、Al易解吸态的优先脱附降低了Pb的脱附速率并延长了其脱附所达平衡的时间。     

Influence of Potential Determining Ions on the Microstructural Performance and Contaminant Adsorption of a Homoionic Illitic Clay

Contaminant adsorption properties of clays are markedly influenced by the type of clay minerals, the nature of the exchangeable ions, and the type of clay microstructure present. Clay soils, due to their high buffering capacity and low permeability, are very helpful materials as barriers in waste disposal projects. On the other hand, the different microstructures of clay soils, due to their different surface areas and the different quantity of these surfaces exposed to the water, cause different contaminant attenuation levels for clay minerals. Even though the dispersive structures of soils might cause some geotechnical problems, in geo-environmental projects they might be of use as an excellent contaminant absorbent due to the fact that their clay particles are well-exposed to the soil pore fluid. The present study investigates the role of various types and concentrations of pore fluid on the microstructure and contaminant adsorption of illite. A series of pH measurements, a turbidity experiment, an XRD analysis, batch equilibrium testing and soil adsorption evaluation were performed to achieve the aforementioned objective. Homo-ionic illite mineral was prepared and some experiments were performed on it to support the findings. The results of this study show that although the theoretical calculation of the double layer theory does not take into account the effect of different anion types on the variation of the thickness of double layer, the anion type has a major impact on the microstructure variations of clay minerals. In addition, the turbidity measurement and the monitoring of XRD peak intensity of the major basal spacings of illite are appropriate tools for evaluating its dispersivity behaviour. It is shown that the PDI treated illite has more capacity for adsorption of heavy metal contaminant than that of illite or Ca–illite. It is concluded that the observed geo-environmental behaviour is noticeably a function of changes in the microstructure of illite.