Geological environment impact analysis of a landfill by the Yangtze River

In order to assess the geological environment impact of a city landfill by the Yangtze River, soils from different depths in the dumpsite were sampled and analyzed. It was found that pollutants content at the site was distinctly higher than that in nearby environments. The content of heavy metals, such as Cd, Hg, As, Pb and Cu, reduces as depth increases; the content of elements F, Cl and N is the contrary. Pollutants migration driven by underground water flow was analyzed, considering the hydro-geological conditions of the site. It is believed that, due to leaching after rainfall infiltration, pollutants in the garbage layer migrates deeper, the cohesive soil in the underlying surface prevents them from spreading to the deeper aquifer; additionally, the high pressure tolerance of the deep groundwater is a key factor in preventing pollutants from entering the aquifer. Furthermore, human control has reduced the annual fluctuation range of water level in nearby rivers, weakening the hydrodynamic relations with phreatic water, and thus reducing the spreading of pollutants to nearby surface waters.

基于丙二酸的碳量子点合成及其光学性质研究

以丙二酸为唯一碳源,分别通过微波合成法和水热合成法制备了稳定性高,水溶性较好的蓝色荧光碳量子点(CQDs)。两种制备方法获得的碳量子点都是单分散的类球形颗粒,粒径大小相近,粒径范围在2. 0~4. 5 nm之间,荧光发射依赖激发波长,有两个荧光寿命,表面状态不均一。微波合成法制备的碳量子点平均粒径为2. 32 nm,激发波长为340 nm,发射波长为410 nm;而水热法制备的碳量子点,平均粒径稍大,为2. 47 nm,激发波长为340 nm,发射波长为416 nm。从荧光量子产率来看,水热法合成的CQDs荧光量子产率为4. 25%优于微波法。为进一步研究丙二酸制备碳量子点提供了参考。