Global environmental change places unavoidable pressure on water resources and agronomic crop production systems. Irrigation development is a credible measure to alleviate the challenge of food safety under water shortages, but it needs sufficient basis. The aim of this study is to address the problem of balancing water scarcity with food requirements, which are the key components of water security in regions with population growth. Marginal water productivity (MWP) indices for irrigation water performance and productivity evaluation were established in the current study. Based on the analysis of the regional water-crop relationship and spatial differences of MWP in China, the priorities for developing irrigation areas in different types of regions are discussed in this study. The results show that high MWPs are mainly in semi-arid regions with precipitation (P) between 500 and 1000 mm, while low MWPs mostly occur in areas with P more than 1000 and less than 500 mm. The significance and spatial distribution patterns of MWP are different than those of conventional irrigation water use efficiency evaluation indices, so its role cannot be replaced for the real production capacity of irrigation water evaluation. The strategies for global environmental change adaptation suggested in this study are taking MWP for irrigation water productivity evaluation and the priority irrigation schemes for agronomic crop determination; increasing MWP by means of irrigation efficiency and crop variety improvement worldwide; and raising global food production through the expansion of irrigation area in the regions hold high MWP and abundant water resources.
This paper discusses the basic concept and connotation of population modernization. The author briefly analyzes the actuality of population modernization in China, gives some advice and puts forward some measures. 相似文献
Activated carbon adsorption is commonly used to control dioxin-like congener (PCDD/Fs and PCBs) emissions. Partitioning of PCDD/Fs and PCBs between vapor and solid phases and their removal efficiencies achieved with existing air pollution control devices (APCDs) at a large-scale municipal waste incinerator (MWI) and an industrial waste incinerator (IWI) are evaluated via intensive stack sampling and analysis. Those two facilities investigated are equipped with activated carbon injection (ACI) with bag filter (BF) and fixed activated carbon bed (FACB) as major PCDD/F control devices, respectively. Average PCDD/F and PCB concentrations of stack gas with ACI+BF as APCDs are 0.031 and 0.006ng-TEQ/Nm(3), and that achieved with FACB are 1.74 and 0.19ng-TEQ/Nm(3) in MWI and IWI, respectively. The results show that FACB could reduce vapor-phase PCDD/Fs and PCBs concentrations in flue gas, while the ACI+BF can effectively adsorb the vapor-phase dioxin-like congener and collect the solid-phase PCDD/Fs and PCBs in the meantime. Additionally, the results of the pilot-scale adsorption system (PAS) experimentation indicate that each gram activated carbon adsorbs 105-115ng-PCDD/Fs and each surface area (m(2)) of activated carbon adsorbs 10-25ng-PCDD/Fs. Based on the results of PAS experimentation, this study confirms that the surface area of mesopore+macropore (20-200A) of the activated carbon is a critical factor affecting PCDD/F adsorption capacity. 相似文献
In the past decade, the treatment amount of municipal solid waste (MSW) by incineration has increased significantly in Taiwan. By year 2008, approximately 70% of the total MSW generated will be incinerated. The energy content (usually expressed by lower heating value [LHV]) of MSW is an important parameter for the selection of incinerator capacity. In this work, wastes from 55 sampling sites, including villages, towns, cities, and remote islands in the Taiwan area, were sampled and analyzed once a season from April 2002 to March 2003 to determine the waste characteristics. The LHV of MSW in Taiwan was predicted by the multilayer perceptron (MLP) neural networks model using the input parameters of elemental analysis and dry- or wet-base physical compositions. Although all three of the models predicted LHV values rather accurately, the elemental analysis model provided the most accurate prediction of LHV values. Additionally, the wet-base physical composition model was the easiest and most economical. Therefore, the waste treatment operators can choose the more appropriate analysis method considering situations themselves, such as time, equipment, technology, and cost. 相似文献
Hydrogen peroxide (H2O2), historically, due to its broad applications in the chemical industries, has caused many serious fires and explosions around the world. Its thermal hazards may also be incurred by an incompatible reaction with other chemicals, and a runaway reaction may be induced in the last stage. This study applied thermal analytical methods to explore the H2O2 leading to these accidents by incompatibility and to discuss what might be formed by the upset situations. Thermal hazard analysis contained a solvent, propanone (CH3COCH3, so-called acetone), which was deliberately selected to mix with H2O2 for investigating the degree of thermal hazard. Differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2) were employed to evaluate the thermal hazard of H2O2. The results indicated that H2O2 is highly hazardous while mixed with propanone, as a potential contaminant. The time to maximum rate (TMR) was used as emergency response time in the chemical industries. Therefore, TMR of H2O2 was calculated to be 70 min for runaway reaction (after T0) and TMR of H2O2/propanone was discovered to be 27 min only. Fire and explosion hazards could be successfully lessened if the safety-related data are properly imbedded into manufacturing processes. 相似文献