潮棕壤不同利用方式pH和Olsen-P���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���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���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���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���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���量明显高于20～80cm的4个土层,表明耕地土壤由于施P���而导致的P���表聚性;林地和撂荒地0～5cm土层的Olsen-P���量大大高于5～80cm的6个土层,这可能与林地和撂荒地的P���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���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���量接近或超过表层土壤,主要是受母质层相对较高的全P���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。

Synthesis of novel P-ketimine bidentate ferrocenyl ligands with central and planar chirality and comparsion in the catalytic activity between P-ketimine and P-aldimine

A series of novel ferrocenylphosphine-ketimine ligands 6 were prepared by reaction of (R,S-p)-PPFNH2-R or (S,S-p)-PPFNH2 with a variety of m-substituted acetophenones. A different catalytic activity was observed between ferrocenylphosphine-ketimine ligands and corresponding aldimine ligands. The efficiency and diastereomeric impact of these ferrocenylphosphine-ketimine ligands in Pd-catalyzed asymmetric allylic alkylation were first investigated, and higher enantioselectivity of over 98% e.e. with 95% yield was obtained by the use of ferrocenylphosphine-ketimine ligands. However, in Rh-catalyzed asymmetric hydrosilylation of aryl ketones, only 42% e.e. was obtained by the use of ferrocenylphosphine-ketimine ligands compared to 90% e.e. with the use of aldimine ligands. (C) 2003 Elsevier Ltd. All rights reserved.

东北地区不同纬度梯度农田土壤Olsen-P���分布特征

本文研究了中国东北地区不同纬度梯度农田土壤Olsen-P���0～100cm剖面中的分布特征。结果表明,除公主岭和大石桥外,其他各点土壤Olsen-P���量在0～20cm土层较高,20～40cm土层迅速下降,40～100cm各土层又逐渐升高,但底层要远低于表层。不同纬度梯度下各点0～20cm土层Olsen-P���量为暗棕壤>黑土>棕壤,高纬度地点Olsen-P���量具有高于低纬度地点的趋势;20～100cm各土层Olsen-P���量总体表现为黑土和暗棕壤相对较高,棕壤区偏低,没有明显的纬度分异现象。施肥等农田管理措施对0～20cm土壤Olsen-P���量有明显影响,其他土层Olsen-P���量可能主要受磷素运移特点和成土母质等因素影响。

Heat capacities and thermodynamic functions of p-chlorobenzoic acid

The heat capacities of p-chlorobenzoic acid were measured in the temperature range from 80 to 580 K by means of an automatic adiabatic calorimeter equipped with a small sample cell of internal volume of 7.4cm(3). The construction and procedures of the calorimetric system were described in detail. The performance of this calorimetric apparatus was evaluated by heat capacity measurements on alpha-Al2O3. The deviations of experimental heat capacities from the corresponding smoothed values lie within +/-0.28 per cent, while the inaccuracy is within +/-0.40 per cent, compared with the recommended reference data in the whole experimental temperature range. A fusion transition at T = 512.280 K was found from the C-p-T curve of p-chlorobenzoic acid. The enthalpy and entropy of the phase transition, as well as the thermodynamic functions {G((T)) - G((298.15))}, {H-(T) - H-(298.15)} and {S-(T) - S-298.15}, were derived from the heat capacity data. The mass fraction purity of p-chlorobenzoic acid sample used in the present calorimetric study was determined to be 0.99935 by fraction melting approach. (C) 2002 Elsevier Science Ltd. All rights reserved.

阜蒙县乡镇域土壤N、P���K的空间变异性分析

以阜蒙县建设镇为研究区域,采用传统统计学和地统计学相结合的方法,对该区域内粮田土壤中土壤养分的含量和空间变异特征进行研究,通过克吕格方法进行空间插值作图。结果表明,不同土壤养分的变异情况各不相同,P���变异系数最大;土壤各养分与高程呈负相关趋势,随高度的增加,其含量减少;各元素呈高度空间相关性,具有一定的渐变性分布规律,这一基本趋势对土壤养分分区管理是有利的。

固氮树种在混交林中的作用研究Ⅱ.固氮树木叶部N、P���分动态特征

研究了 2 3种固氮与非固氮树种叶部N、P���量的季节变化、输出率以及叶片衰老过程中N、P���输出过程 .结果表明 ,供试树种叶部N、P���量均存在着明显的季节变化 ,平均变化率为 2 1～ 2 3% ,最大变化率出现在叶片衰老期 .在衰老期内不同树种表现出不同的N、P���态特征 .固氮树种表现出低输出率 ,落叶中N含量是非固氮树种的 1 .6～ 3.7倍 .固氮树种生长季叶部N含量在 2 .5%左右 .