保护地土壤盐分积累及其离子组成对土壤pH值的影响

在沈阳市于洪地区采集保护地土壤样品,测定土壤盐分含量、离子组成和土壤pH值,研究保护地土壤盐分积累及其与土壤pH值变化的关系。结果表明:(1)保护地土壤的盐分含量和电导率均明显高于露地土壤,露地土壤平均盐分含量为0.29 g/kg,改为保护地10年左右土壤的平均含盐量上升至1.56 g/kg,相应的电导率(EC)值达到0.53 mS/cm,已超过作物的生育障碍临界点(EC>0.50 mS/cm);(2)保护地土壤酸化趋势明显,建成保护地栽培蔬菜6年,土壤pH值从6.5降低至5.5以下,超过了蔬菜出现生理障碍的临界土壤pH值(5.52),保护地土壤酸化与土壤的次生盐渍化已成为限制当地保护地生产可持续发展的重要因素;(3)保护地土壤NO3-、SO42-、Cl-和Ca2+、Mg2+、K+、Na+等盐基离子含量均较露地土壤大大增加,但HCO3-低于露地土壤或与露地土壤持平,NO3-、SO42-数量与土壤pH值下降关系密切,Ca2+、Na+在全盐中的相对比例下降也是导致土壤pH值下降的重要原因。

Determination of urinary oxidative DNA damage marker 8-hydroxy-2 '-deoxyguanosine and the association with cigarette smoking

8-hydroxy-2'-deoxyguanosine (8OHdG) has been widely used as a biomarker of oxidative DNA damage in both animal models and human studies. To evaluate the effect of cigarette smoking on oxidative stress, we studied the levels of urinary 8OHdG from smokers and non-smokers and investigated the association with cigarette smoking. The urinary 8OHdG concentrations were determinated by capillary electrophoresis with end-column amprometric detection (CE-AD) after a single-step solid phase extraction (SPE), and then quantitatively expressed as a function of creatinine excretion. To increase the concentration sensitivity, a dynamic pH junction was used and the focusing effect was obvious when using 30 mM phosphate (pH 6.50) as sample matrix. The limit of detection is 4.3 nM (signal-to-noise ratio S/N = 3). The relative standard deviation (R.S.D.) was 1.1% for peak current, and 2.3% for migration time. Based on the selected CE-AD method, it was found that the mean value of urinary 8OHdG levels in the smokers significantly higher than that in non-smokers (31.4 +/- 18.9 nM versus 14.4 +/- 7.6 nM, P = 0.0004; 23.5 +/- 21.3 mug g(-1) creatinine versus 12.6 +/- 13.2 mug g(-1) creatinine, P = 0.028). (C) 2004 Elsevier B.V. All rights reserved.

不同N素形态对落叶松苗木根/土界面pH值及养分有效性的影响

The effect of different nitrogen and phosphorus sources on pH and the availability of mineral nutrients in the root/soil interface of Larix gmelinii seedlings were studied by means of root-mat method. The results showed that the addition of NH~+_4-N decreased the pH in the root/soil interface, while the addition of NO~-_3-N increased the pH in contrast with the control treatment. The sort of the P sources and the distance from the root plane remarkably influenced the changes of pH in the root/soil interface induced by the addition of the nitrogen sources. Compared with the addition of only NH~+_4-N, the extent to which the pH in the root/soil interface decreased was obviously smaller when treated by NH~+_4-N and rock P. When treated with different P sources, the contents of available P in the root/soil interface were affected by the sort of the N sources. When treated with soluble P, the contents of the available P in the root/soil interface obviously increased for the addition of both NH~+_4-N and NO~-_3-N. When treated with rock P, the contents of the available P increased only in the area 0～3 mm from the root plane for NH~+_4-N, whereas the contents of available P in the root/soil interface changed little for NO~-_3-N. The results above showed that the protons excreted by the roots were the main driving force for the solution of the rock P in the root/soil interface. The availability of Fe in the root/soil interface increased as a result of acidity induced by the NH~+_4-N, whereas the availability of Fe in the root/soil interface decreased because of the pH increase induced by the NO_3~-_N. The effect of different N sources on the availability of Fe in the root/soil interface was also affected by the sort of P sources. The concentrations of P、Fe in the leaves remarkably differed when treated by different N、P sources and concentrations of the P、Fe in the root/soil interface were correlated to those in the leaves of the seedlings.

不同pH的酚酸溶液对杉木及萝卜幼苗生长的影响

通过四因素五水平的二次回归正交旋转试验设计 ,研究 pH值、肉桂酸、对羟基苯甲酸、香草醛四个因素对杉木和萝卜幼苗生长的影响。结果表明 ,杉木幼苗的鲜重生长随酚酸溶液的pH值的增大而增加 ,而随肉桂酸、对羟基苯甲酸和香草醛浓度的增大而减小。比较 3种不同酚类物质对杉木幼苗生长的影响 ,肉桂酸对杉木幼苗生长的影响 >对羟基苯甲酸 >香草醛 ,且 pH值与肉桂酸之间 ;肉桂酸与香草醛之间 ;对羟基苯甲酸与香草醛之间的交互作用都达到显著水平。萝卜幼苗生长对不同pH的酚酸溶液的反应与杉木幼苗相类似 ,随酚酸溶液的pH值的增大而增加 ,而随肉桂酸、对羟基苯甲酸和香草醛浓度的增大而减小。但对羟基苯甲酸对萝卜幼苗生长的影响 >肉桂酸 >香草醛 ,酚酸溶液的 pH值与所有 3种酚酸之间的交互作用都达到显著水平 ;肉桂酸与香草醛的交互作用对萝卜幼苗生长的影响也达到F0 0 1水平显著。

Repeatedly usable immobilized pH gradient in a monolithic capillary column

Glycidyl methacrylate (GMA) and ethylene dimethacrylate (EDMA) were used to synthesize a monolithic capillary column containing reactive epoxy groups. Glutaraldehyde was introduced and linked to the monolith after a process of amination. An aqueous solution of commercial carrier ampholytes (CAs, Ampholine) was focused in such a polymer column. The primary amino groups of CAs reacted with glutaraldehyde along the capillary. CAs were immobilized at different positions in the column according to their isoelectric points (pl), resulting in a monolithic immobilized pH gradient (M-IPG). Isoelectric focusing (IEF) was performed without CAs in such an M-IPG column. Due to the covalent attachment of the CAs this M-IPG can be repeatedly used after its preparation. Good stability, linearity, and reproducibility were obtained.

不同培养基、pH值、水势和温度对2种外生菌根真菌生长的影响

在不同培养基、pH值、水势及温度条件下,研究了沙地樟子松林下2种常见外生菌根真菌松乳菇和高大环柄菇的生长。结果表明,在所选择的培养基上,2种菌株都能生长;高大环柄菇对pH值适应范围较广,在中性条件下生长最好,松乳菇在弱酸性条件下生长较好;温度对菌株生长影响较大,2种菌株最适生长温度范围均为25~28℃;极端水势条件下(-1500kPa),高大环柄菇和松乳菇均不能生长,低胁迫(-170kPa,-230kPa)能促进高大环柄菇和松乳菇的生长。

潮棕壤不同利用方式pH和Olsen-P的垂直变化特征

对潮棕壤4种土地利用方式经过14年后土壤pH和Olsen-P在0～150cm土体10个土层中的垂直分布情况进行的比较研究表明,不同利用方式下土壤pH和Olsen-P含量的剖面分布差异显著,说明不同利用方式对土壤pH和Olsen-P有较大影响。林地和撂荒地0～5cm土层pH分别为>7.0和6.5～7.0,玉米地0～20cm各土层土壤pH基本为6.0以下;20cm以下各土层中的pH,水稻田土壤呈微碱性,玉米地和撂荒地接近中性,林地呈微酸性。土体中Olsen-P平均含量为撂荒地>林地>水稻田>玉米地。水稻田和玉米地0～20cm的3个土层Olsen-P含量明显高于20～80cm的4个土层,表明耕地土壤由于施P肥而导致的P素表聚性;林地和撂荒地0～5cm土层的Olsen-P含量大大高于5～80cm的6个土层,这可能与林地和撂荒地的P素生物归还及基本不受人为扰动有关。4种土地利用方式下土壤各层次Olsen-P含量垂直分布的散点折线图呈现出较为相似的特征。80cm以下的3个土层Olsen-P含量接近或超过表层土壤,主要是受母质层相对较高的全P含量影响所致,也可能与地下水作用有关,不过具体原因还有待于进一步研究。

Retention modeling and simultaneous optimization of pH value and gradient steepness in RP-HPLC using feed-forward neural networks

A novel approach is proposed for the simultaneous optimization of mobile phase pH and gradient steepness in RP-HPLC using artificial neural networks. By presetting the initial and final concentration of the organic solvent, a limited number of experiments with different gradient time and pH value of mobile phase are arranged in the two-dimensional space of mobile phase parameters. The retention behavior of each solute is modeled using an individual artificial neural network. An "early stopping" strategy is adopted to ensure the predicting capability of neural networks. The trained neural networks can be used to predict the retention time of solutes under arbitrary mobile phase conditions in the optimization region. Finally, the optimal separation conditions can be found according to a global resolution function. The effectiveness of this method is validated by optimization of separation conditions for amino acids derivatised by a new fluorescent reagent.

多藻浅水体中pH值和溶解氧协同周期性变化初探

在多藻浅水体中 ,每日 9:0 0～ 15 :0 0的pH值和溶解氧都呈上升趋势 ,两者呈协同周期性变化。经相关性回归分析 ,pH值的变化规律与溶解氧呈非常显著正相关 ,多藻浅水区pH值和溶解氧的回归关系相关系数r =0 912 9>r0 0 1(70 ) (r0 0 1(70 )=0 3 0 2 )。这可能与水体中氧化还原电位和水生植物光合作用伴随的代谢活动有关。这种相关性和协同周期性变化具有一定的生态学意义 ,并会对水体净化产生影响。

Retention modeling and optimization of pH value and solvent composition in HPLC using back-propagation neural networks and uniform design

A novel method for the optimization of pH value and composition of mobile phase in HPLC using artificial neural networks and uniform design is proposed. As the first step. seven initial experiments were arranged and run according to uniform design. Then the retention behavior of the solutes is modeled using back-propagation neural networks. A trial method is used to ensure the predicting capability of neural networks. Finally, the optimal separation conditions can be found according to a global resolution function. The effectiveness of this method is validated by optimization of separation conditions for both basic and acidic samples.

Specific Adsorption of Trace Amounts of Calcium and Strontium by Hydrous Oxides of Iron and Aluminum1

Freshly prepared Fe and Al hydrous oxide gels and the amorphous product of heating gibbsite selectively adsorbed traces of Ca and Sr from solutions containing a large excess (∼1M) of NaNO3. The fraction of the added Ca (Sr) adsorbed depended principally on the suspension pH, the amount of solid present, and to a lesser extent on the NaNO3 concentration. Significant Ca and Sr adsorption occurred on the Fe and Al gels, and heated gibbsite, at pH values below the points of zero charge (8.1, 9.4, and 8.3±0.1, respectively), indicating specific adsorption. The pH (± 0.10) at which 50% of the Ca was adsorbed (pH50) occurred at pH 7.15 for the Fe gel (0.093M Fe), 8.35 for the Al gel (0.093M Al), and 6.70 for the heated gibbsite (0.181M Al); for Sr, the pH50 values were 7.10, 9.00, and 6.45, respectively. For the Fe gel and heated gibbsite, an empirical model based on the law of mass action described the pH dependence of adsorption reasonably well and suggested that for each Ca or Sr fraction adsorbed, approximately one proton was released. Failure of the Al gel to fit this model may have resulted from its rapid aging.

SR型野外人工模拟降雨装置

SR型人工降雨装置是一种多喷头、多单元组合式的间歇降雨装置。选用目前国内外较理想的喷头 ,在喷头处辅以可改变喷头降水方式的机械传动装置 ,以间歇方式降雨来满足其降雨强度 ,雨滴直径大小及其分布与自然降雨相似。每个单元的有效降雨面积为 2 m× 5 m;如果 4个单元组合成 ,其长度可增加 4倍 ,有效降雨面积即 2 m× 2 0 m。装置采用轻型铝合金材料制成 ,结构简单 ,易于安装拆卸 ,适用于野外工作。

辽宁植烟土壤pH值状况及其与烟叶主要品质指标的相关分析

以辽宁省7个植烟县为对象,采集了154个土壤和中部烟叶样品,在测定土壤pH值的基础上,测定烟叶中的烟碱含量、还原糖含量、总糖含量以及氮钾含量。通过数理统计的方法分析了土壤pH值与烟叶内在质量指标之间的关系,结果表明:辽宁烟区植烟土壤的pH值大多比较适合烟叶生长,但是仍有12%的植烟土壤pH值过高或过低,需要进行改良。土壤pH值与烟叶总氮含量、烟碱含量、钾含量两两之间均呈显著或极显著的曲线相关关系,即当土壤pH值从4.0变化到6.5时土壤pH值与烟碱含量之间为负效应关系,当土壤pH值从6.5变化到9.0时土壤pH值与烟碱含量之间为正效应关系,土壤pH值与总氮含量、钾含量、总糖含量之间为负效应关系。