A {Co-32} Nanosphere Supported by p-tert-Butylthiacalix[4]arene

Calixarene-capped Co-32 clusters are constructed by a sodalite Co-24(II) cage and an encapsulated Co-8(III) cube. The spherical units are arranged into three isomeric structures, two of which are stacked by the bcc lattices and the third of which is assembled by the cubic closest packing of the spherical units.

SUPERCONDUCTIVITY IN BI1.5PB0.4SBXSR2CA2CU2OY SYSTEM (X=0-0.32)

The effect of doping with various amount of Sb (0.06-0.32) to (Bi,Pb):Sr:Ca:Cu = 1:1:1:1 system were studied with XRD and Tc measurements. The presence of Sb promotes the conversion of low Tc phase (2212 phase) to high Tc phase (2223 phase) and at around Sb = 0.18 the 2212 phase nearly completely disappears; but at the same time a new phase of unknown structure appears even with Sb = 0.06 showing that the incorporation of Sb into the Bi-based superconducting phase is of very low concentration. Tc measurements show that the optimum concentration of Sb-doping is around 0.10 and that unknown phase has an adverse effect to the superconducting properties; a composition disproportion at the surface of pellet was observed.

城市生活垃圾填埋场释放汞的形态初步研究

大气的人为汞释放源研究已经较为广泛,但国内外对垃圾填埋场这一潜在的大气汞释放源还没有重视,尤其是垃圾填埋场释放汞的形态研究较为缺乏。2003 年11 月下旬,对贵阳市一新建的生活垃圾填埋场排放气体中的总汞( TGM) 、单甲基汞(MMHg) 、二甲基汞(DMHg) 进行了初步的研究。结果显示填埋半年、填埋一年与填埋两年的垃圾填埋场排气筒气体中总汞浓度分别为665. 52 ±291. 25 ng/ m3 ( n = 305) 、25. 6 ±3. 2 ng / m3 ( n = 13) 、14. 5±1. 8 ng/ m3 ( n = 28) ;填埋半年与填埋两年的垃圾填埋场排气筒气体中单甲基汞浓度分别为2. 06 ±1. 82 ng/ m3( n = 11) 、0. 18 ±0. 06 ng/ m3 ( n = 2) ,二甲基汞浓度为9. 45 ±5. 18 ng/ m3 ( n = 12) 。这一结果初步说明垃圾填埋场不仅是大气总汞的释放源类型之一,也是大气中毒性更强的单甲基汞与二甲基汞的释放源之一。

贵州赫章土法炼锌导致的土壤重金属污染特征及微生物生态效应

贵州省赫章县妈姑镇新关寨附近的土法炼锌不仅导致植被的破坏，而且使附近土壤中重金属有不同程度的积累，Zn达到162.23-877.88mg/kg,Pb为37.24-305.56mg/kg,Cd为0.50-16.43mg/kg，大大超过了当地的土壤背景值；而且重金属含量（特别是Pb和Zn含量）与土壤中的Fe2O3和Al2O3有极显著的正相关关系，显示土壤中铁氧化物和粘土矿物对重金属的固定作用。化学形态研究表明，Pb和Zn在土壤中主要表现为铁锰氧化物结合态与残渣态，而Cd的情况与Pb和Zn完全相反，其形态以可交换态为主。本区土壤微生物生物量（用含碳量表示）较低，仅为57.00-388.00μg/g，而且与土壤重金属间有显著的负相关关系，特别是与Zn的相关系数高达-0.7801，反映出重金属对微生物的毒害作用。Biolog测试结果表明，土壤微生物群落结构间没有明显的差别；土壤微生物DNA经PCR（聚合酶链式反应）和DGGE（变性梯度胶电泳）反应后的基因片段非常一致，反映出不同程度的重金属污染并没有导致土壤微生物群落结构的改变和基因损伤，另一方面也表明，土壤本身有强烈的固定重金属能力，抵御了重金属对土壤生物的进一步毒害。