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。

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的分布特征

本文研究了中国东北地区不同纬度梯度农田土壤Olsen-P在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含量在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含量为暗棕壤>黑土>棕壤,高纬度地点Olsen-P含量具有高于低纬度地点的趋势;20～100cm各土层Olsen-P含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含量有明显影响,其他土层Olsen-P含量可能主要受磷素运移特点和成土母质等因素影响。