320米塔上测量的湍流统计特征量的初步分析

应用320米塔上第一次获得的垂直风速脉动量的垂直分布资料,根据湍流扩散统计理论并结合半经验近似,讨论由欧拉参数估算边界层下层扩散参数的主要方法,得到了湍流统计特征量K_(?)、σ_w及ε随高度和稳定度变化的经验关系,为北京地区大气扩散规律研究及污染模式的建立提供实验基础.     

一个适用于中距离范围的湍流扩散型

从最简单的二阶闭合假设导出的物质连续方程出发。用近几年来整个行星边界层(PBL)的实测平均风,湍流统计量和拉氏时间尺度随高度和稳定度变化的新结果。对定常的三维方程作数值解,得到一适用于中距离范围的湍流扩散型。该扩散型由纯湍流,地面有效粗糙度,风向切变以及气象参数垂直切变引起的σy随高度和σx随横风方向变化等四个因子组成。在10—100km范围内,扩散型与实测资料和现有的理论扩散型有相当好的一致性。本文的结果无论对PBL内扩散本质的认识还是中距离范围污染模式的建立均有益处。     

非均匀性和风速切变对中距离垂直扩散影响的一个数值分析

根据文献[1]中的表达式(10),数值分析了非均匀性和风速切变对中距离(10—100km)垂直扩散的影响,得到了一些有益的结果。     

Plants emit sulfate-, phosphate- and metal-containing nanoparticles

Environmental Chemistry Letters - The presence of engineered and natural nanoparticles in the atmosphere is of concern for health and climate. Actually there are few studies on the release of...     

Discovery of nano-sized gold particles in natural plant tissues

Biological effects of nanoparticles have attracted widespread attention. However, the interaction between plants and nanoparticles remains unclear. The purpose of this study was to investigate characteristics of nano-sized metal particles in two representative plant species, Erigeron canadensis and Boehmeria nivea, in the Guangdong Province, China. The stems of the plants were sliced and placed on Ni–C grids for field-emission transmission electron microscopy (TEM). The metal-bearing nanoparticles were further analysed for their size, shape, composition, content and other characteristics using X-ray energy spectrum analysis, scanning TEM and selected-area electron diffraction pattern. The results revealed that the plants contain nano-sized Au-bearing particles with a diameter of 5–50 nm, ellipsoid, spherical and bone-rod shapes or irregular morphology with smooth edges. These nanoparticles primarily consisted of Au, Cu, O and Cl. The discovery of Au-bearing nanoparticles in natural plant tissues is of great significance for biological nanoscience. Here, we discuss the function and absorption mechanism of Au-bearing nanoparticles in plants and present the influence of the discovery of Au-bearing nanoparticles in natural plants.     

用三维平流扩散模式预测滇池地区氟化物污染

根据包含有PBL湍流统计量的三维物质连续方程,作者设计了一个同时考虑大气参数的时空(三维)变化、多个连续污染源、线性的化学转化和迁移以及复杂地形影响的三维平流扩散模式,并将滇池地区整个PBL内连续实测的湍流统计量、拉氏时间尺度、中尺度流场和混合层厚度直接输入模式,对山谷风、湖陆风和城市热岛(昆明市)中尺度局地环流控制下的氟化氢浓度的日变化作了预测。结果表明,在输入同一资料情况下,预测的结果与实测值大体上一致。     

北京地区边界层厚度特征的统计研究

本文采用北京气象台和320米塔多年来测得的风和温度资料,统计分析了各稳定度类的边界层厚度(BLD)特征,得到北京地区稳定度类频率、平衡条件下的BLD、BLD的诊断模式及夜间BLD的预报模式,为中远距离的输送扩散、污染模式及边界层结构的研究提供依据.