安全苛求系统的交叉验收框架

交叉验收是一个涉及技术和法律的工作,其目的是在新项目中能够尽快地应用类似的产品、系统和方法(PSP)。交叉验收的PSP首先要求在原始的应用中能够满足可靠性、安全性和环境要求。PSP目标和原始的应用应具有很好的相似性,因此,不需要很大的改动,在技术上和经济上可行性会很强。当然,交叉验收从根本上来说和PSP的安全性和适用性有关。目前交叉验收缺乏系统的指导和专门的标准,笔者阐述的一个基于风险分析的结构化PSP交叉验收框架包括7个主要原则。该框架基于笔者多年在安全苛求系统和铁路领域开发应用控制风险和安全确信系统框架的经验,采用通行的原则,对于目前还未建立交叉验收系统框架的安全苛求系统尤其适用。     

Soil enzymatic activities and microbial community structure with di erent application rates of Cd and Pb

This study focused on the changes of soil microbial diversity and potential inhibitory effects of heavy metals on soil enzymatic activities at different application rates of Cd andor Pb. The soil used for experiments was collected from Beijing and classified as endoaquepts. Pots containing 500 g of the soil with different Cd andor Pb application rates were incubated for a period of 0, 2, 9, 12 weeks in a glasshouse and the soil samples were analyzed for individual enzymes, including catalase, alkaline phosphatase and dehydrogenase, and the changes of microbial community structure. Results showed that heavy metals slightly inhibited the enzymatic activities in all the samples spiked with heavy metals. The extent of inhibition increased significantly with increasing level of heavy metals, and varied with the incubation periods. The soil bacterial community structure, as determined by polymerase chain reaction-denaturing gradient gel electrophoresis techniques, was different in the contaminated samples as compared to the control. The highest community change was observed in the samples amended with high level of Cd. Positive correlations were observed among the three enzymatic activities, but negative correlations were found between the amounts of the heavy metals and the enzymatic activities.