Within season and carry-over effects following exposure of grassland species mixtures to increasing background ozone

Few studies have investigated effects of increased background ozone in the absence of episodic peaks, despite a predicted increase throughout the northern hemisphere over the coming decades. In this study Leontodon hispidus was grown with Anthoxanthum odoratum or Dactylis glomerata and exposed in the UK to one of eight background ozone concentrations for 20 weeks in solardomes. Seasonal mean ozone concentrations ranged from 21.4 to 102.5 ppb. Ozone-induced senescence of L. hispidus was enhanced when grown with the more open canopy of A. odoratum compared to the denser growing D. glomerata. There was increased cover with increasing ozone exposure for both A. odoratum and D. glomerata, which resulted in an increase in the grass:Leontodon cover ratio in both community types. Carry-over effects of the ozone exposure were observed, including delayed winter die-back of L. hispidus and acceleration in the progression from flowers to seed-heads in the year following ozone exposure.     

大流量孔口流量计的校准、数据处理及误差分析

用罗兹流量计校准孔口流量计,用温度和大气压力对孔口流量计的负压进行修正,使孔口流量计的流量和压力修正项间的关系为一直线,得到孔口流量计的标准曲线并评价其精度。探讨了孔口流量计流量不确定度的主要来源,为精度控制提供了理论依据。      

污水处理厂罗茨鼓风机噪声治理

对污水处理过程中产生的二次污染源——罗茨鼓风机噪声特性进行了分析,提出噪声综合治理措施,并结合治理实例说明治理效果。     

鼓风曝气系统噪声综合治理研究

某城市污水处理厂采用射流曝气活性污泥法水处理工艺 ,鼓风曝气系统噪声污染极其严重。在噪声分析评价基础上 ,充分利用原有设备 ,采取改进隔声罩设计、加接消声器、控制管道再生噪声、提高风机房围护结构隔声能力等综合治理措施 ,厂界噪声降低了 32dB(A) ,达到国家允许标准