中国超大城市空气污染和人体健康 (APHH-Beijing) 中英联合研究计划 最终报告

Chinese versio

Determination of Trace Mercury Species in Water and Soil Samples with Atomic Fluorescence Spectrometry

采用氢化发生-冷原子荧光光谱法,测定了厦门市集美周边地区的几种水和土壤样品中汞的不同形态含量。在仪器优化条件下直接进样测定水中微量无机汞的含量,再用溴酸钾-溴化钾消解水样并测定其总汞含量,由总汞与无机汞含量之差计算出有机汞含量;采用微波消解体系测定土壤样品中的总汞含量,同时用连续化学浸提法提取测定包括可交换态汞、盐酸溶汞、元素汞、腐殖酸结合态汞、有机质结合态汞和硫化汞的不同汞形态含量,并最终测定残态汞含量。实验结果表明,实验室排放水中汞含量高于Ⅰ类污水综合排放标准(GB8978—1996),说明实验室排放水是严重的汞环境污染源之一。而公路边土壤、近海沉积物和菜园土壤的汞形态含量均低于相应的国家标准,但由于人为污染造成菜园土壤汞的不断积累应引起高度重视。实验同时对水和土壤样品的测量检出限及方法回收率进行试验,结果表明在优化的实验条件下水和土壤汞的检出限分别为0.0008μg·L-1和0.0723μg·kg-1,3个水平的加标平均回收率分别为93.7%和93.8%,方法准确、可靠。With hydride generation-cold atomic fluorescence spectrometry (HG-AFS), the method of determining trace mercury species in water and soil samples in Jimei, Xiamen city, China was established. The content of inorganic mercury in water was measured by sample direct injection, while the total mercury was measured after digestion with the reagents of KBrO3-KBr. The soil samples were digested with microwave for total mercury measurement. Sequential extraction procedure was carried out for determining different mercuric species in soil samples. The results indicated that the mercury concentration of wastewater from chemical laboratory exceeded the limit of the integrated wastewater discharge standard of China (GB 8978—1996). It is one of the serious pollution sources of mercury in environment. The mercury contents from soil samples including the sideward soil of highway, the sea sediment and the garden soil were under the limits of relative national standards of China. However, attention should be paid to the accumulation of mercury in garden soil due to the artificial pollution. Meanwhile, the average recoveries for water and soil samples tested with adding standards were 93.7% and 93.8%, respectively. Meanwhile, the detection limits estimated with 3-fold standard deviation were 0.000 8 μg·L-1 for water and 0.072 3 μg·kg-1 for soil, respectively. The results indicated that the established method, with the merits of high sensitivity and precision, was suitable for the measurement of trace mercury species in environmental samples.国家自然科学基金项目(20175022);; 福建省基金项目(D0610016);; 厦门市科技项目(3502Z20055025);; 集美大学创新团队基金项目(2006A003)资

Thermocapillary Convection of Evaporating Thin Nanofluid Layer in a Rectangular Cavity

Thermocapillary convection of nanofluid with evaporating phase change interface occurs in a variety of industrial processes such as micro/nano fabrication, ink-jet printing, thin film coatings, etc. Previous studies have mostly focused on the phenomena of thermocapillary convection in pure fluids without phase change. This paper reports the first fundamental experimental work on the thermocapillary flow of a thin nanofluid layer under the effect of evaporation. This research focuses on the behavior of a volatile thin nanofluid layer in a rectangular test cell under the effects of horizontal temperature gradient. The buoyancy effect can be neglected inside this thin liquid layer as in microgravity conditions. HEE7200 and HFE7200-Al2O3 nanofluid are used as working fluids to analyze the effect of nanoparticle addition. The results indicate that the linear relationship between the thickness of the liquid layer and the duration of evaporation is not changed by nanoparticles. HFE7200-Al2O3 nanofluid always has a higher evaporation rate than its base fluid with the temperature ranging from 2.98 & DEG;C to 13.92 & DEG;C. The critical Marangoni number for the nanofluid is lower than that of the pure fluid, which indicates that the addition of nanoparticles promotes the flow pattern transition

三相线钉扎的大液滴蒸发实验

利用实践十号返回式科学实验卫星蒸发对流箱，开展了三相线处于钉扎状态且接触半径大于毛细长度的无水乙醇大滴在加热PTFE表面蒸发的地基科学实验。实验发现，液滴体积随时间线性递减，但钉扎大液滴蒸发过程中没有出现恒定接触角（CCA）阶段。与小液滴蒸发的恒定接触半径（CCR）阶段相同，大液滴的平均蒸发速率也与初始体积无关，表明受重力影响明显的大液滴蒸发主要发生在三相线附近区域。瞬时蒸发速率经历了迅速上升和之后的长时间内保持稳定两个阶段。与数值模拟结果对比分析发现，准静态扩散模型低估了三相线处于钉扎状态的大液滴瞬时蒸发速率，而同时考虑蒸气扩散与空气中自然对流经验模型的准确性取决于实验所用工质

Thermocapillary-buoyancy Convection Driven by a Horizontal Temperature Gradient in a Thin Liquid Layer: The Effect of Evaporation

The effects of phase change on the stability of a horizontally heated liquid layer are studied experimentally in this paper. Results are obtained for two volatile liquids with similar Prandtl numbers in a rectangular geometry with different temperature differences. Three different flow states occur with the variation of the liquid depth, namely oscillating multicellular convection, hydrothermal waves and steady flow. The critical conditions for the transition between the different flow states are identified and discussed. In addition, the presence of evaporation at the interface plays an essential role in the flow instabilities. The results show that evaporation at the surface and associated surface deformation tend to inhibit the development of a hydrothermal wave but conversely promote the transition of oscillating multicellular convection. Furthermore, the transient nature of HTWs is shown to be little affected by the phase change