Search

This paper studied the health risk of air pollutants SO2, NO2 and PM10 in all the districts and counties of Beijing with exposure-response analysis. Different ecological risk areas based on health risk of air pollutants are recommended in Beijing. The result shows that SO2 and NO2 brought a relatively low health risk, while PM10 brought a relatively high health risk. Air pollutants health risk exists in all the districts and counties of Beijing, and most ecological conservation development zones are low risk areas, while urban functional center zones, urban functional development zones and new urban development zones are mainly in medium risk level.

Based on two different methods, the ecological risk of heavy metals in soils of Beijing was assessed. With the assess method of PaPant ecological risk index, the Rapant ecological risk index of center region is 1.365, which indicates a medium ecological risk, while the other districts of Beijing are in low ecological risk level and the main influential factor is Hg. Based on the assess result by the method of Hakanson potential ecological risk index, The highest value of RI is 141.95, which is still in the low ecological risk level but also close to the lower limit of medium level; the main influential factors is Hg and Cd. Therefore, to focus on the monitoring and management of Cd and Hg in center region is necessary in Beijing.

The soil heavy metal pollution have be paid more attention because the sources of soil heavy metals become multiple and complicated with the accelerated urbanization. According to this research, the order of spatial distribution of soil heavy metal Cu, Zn and Cd pollution in Beijing shows that: the center district > suburb > outer suburb. The soil pollution by Zn is more serious in Beijing and the grade of the soil Zn pollution has reached highest in the central district. By comparison, the soil pollution by Cu and Cd is slight, the soil in central district, Chaoyang, Changping and Miyun has caught light Cu pollution, and only in center district, Chaoyang and Fengtai has caught light Cd pollution.

This paper introduces the composition of pump and valve control system of parallel connection and the output flux of pump and valve is distributed optimally. Then, establish the state-space model of pump and valve system, the system is simulated by Simlink and AMESim software, the simulation results obtained.

In the process of lead-electrolysis, when we take off the cathode lead plate from electrolyte, we should take out the cathode collector bar. Next cathode lead plate will be melted and make into ingot. The cathode collector bar can be used next time. The design is a new kind of appliance of taking out the cathode collector bar. The appliance, which limits the cathode plate horizontally, uses the way of single taking out. It is proved that this way is steady and efficient.