Research on geochemical characteristics and environmental risk of Be,Sb and Tl in surface sediments of the Nansihu Lake

The South-to-North Water Diversion Project is one of the biggest water transfer projects with the largest beneficiary population in the world. Nansihu Lake is the biggest reservoir lake in the east route of South-to-North Water Diversion Project. This study analyzed contents distribution and speciation characteristics of beryllium(Be),antimony(Sb) and thallium(Tl) in surface sediments of the Nansihu Lake. Their environmental risks were evaluated by multiple methods. Based on the results given by the predecessors,the toxic response factors of Be,Sb and Tl were defined in this paper. The results showed that the average contents of Be and Sb were a little higher than their background values,and Tl content was lower than its background value. Speciation analysis showed that the residual forms of Be,Sb and Tl accounted for over 65%,70%,and 84% respectively,while the contents of the acid soluble was very low which led to low mobility and bio-availability. The surface sediments of Nansihu Lake had low Be,Sb and Tl enrichment degree, and therefore the ecological risk was low. Be,Sb and Tl were mainly from nature and ancillary from human activity. Different from Be and Tl,the main human activity source of Sb might be atmospheric settlement. Distributions of Be,Sb and Tl in the sediments were affected by particle size,TOC,and Al/Fe/Mn to some extent.</p

CrN/CrAlSiN涂层海水环境下的摩擦学性能

为提高海洋装备摩擦零部件的摩擦学性能,采用多弧离子镀技术在316L不锈钢上制备了CrN/CrAlSiN涂层。通过XRD、XPS表征涂层的物相及成分,SEM和TEM表征涂层的形貌和微观结构,并用纳米压痕仪测试其硬度,采用摩擦磨损试验机对涂层在大气和海水环境中的摩擦磨损性能进行测试。结果表明:CrN/CrAlSiN涂层的微观结构主要有CrN相、AlN相以及非晶态Si_3N_4包裹CrN、AlN相,(111)择优取向最为明显;基于微观结构与CrN过渡层的设计,CrAlSiN涂层硬度高达35.5 GPa;较之于316L基底,涂层致密的结构使其在海水环境下表现出更好的耐腐蚀性能;在大气和海水环境下,CrN/CrAlSiN涂层的摩擦因数及磨损率均明显降低,在海水环境下达到最优

Preliminary Study on Removal of Cadmium from Contaminated Soil by Magnetic Clay Particles

A millimeter-level magnetic clay particle adsorption material recorded as MSAZ was used to test its soil Cd removal efficiency.For different simulated Cd-contaminated soils,the results showed that the optimal mass ratio of MSAZ:soil was 1︰5.With this application ratio,the removal rate of 0.43 mol/L HNO_3 extracted Cd in the simulated red soil was as high as 95% in a single application,and the removal rates could also reach 75%-80% in the brown and black soils.For dryland soils with high Cd background values and Cd-contaminated paddy soils,the results showed that the removal rate of 0.43 mol/L HNO_3 extracted Cd by MSAZ was about 40% from the two soils in a single application.After five times of repeated use,the cumulative removal rate of 0.43 mol/L HNO_3 extracted Cd on MSAZ reached 98% from the actual Cd-contaminated paddy soil.The MSAZ still maintained 85% adsorption capacity,and its recovery rate was higher than 80% after five reusing cycles.The magnetic clay particles tested in this study has excellent soil Cd removal performance and showed potential application prospect,which can provide materials and technical supports for subsequent in-situ treatment of Cd pollution in farmland soil