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891.
矿山酸性废水重金属沉淀分离研究 总被引:3,自引:0,他引:3
矿山酸性废水对环境的污染包括酸性废水和重金属离子两个方面,矿山酸性废水的治理也包括酸性废水和重金属离子处理两方面的内容。重金属沉淀分离是利用重金属离子的氢氧化物和硫化物沉淀溶度积不同,在控制不同的沉淀条件下,进行特定离子的沉淀分离,从而使得废水中的重金属离子得到处理,分步沉淀使得回收沉淀物保持较高的有价金属品位,更易于资源化。分步沉淀反应后,进行相应的固/液分离,并回流部分沉淀物至沉淀反应池,固/液分离后出水,经pH调节,可以达标排放或回用。 相似文献
892.
Sex ratios of ants have been shown to vary with food resource levels in several studies, but it is not known whether forest
clear-cutting has any effect on sex ratio of aphid-tending forest-dwelling ants. We investigated whether the offspring sex
ratio of the forest dwelling ant Formica aquilonia varied as a response to clear-cutting. We found that the proportion of males was smaller in clear-cuts than in adjacent forests.
Our results are among the first showing that anthropogenic changes in forest structures may have a potential to modify sex
ratios of social insects and other forest-dwelling animals. 相似文献
893.
894.
Gerard W. Wall Richard L. GarciaFrank Wechsung Bruce A. Kimball 《Agriculture, ecosystems & environment》2011,144(1):390-404
Atmospheric CO2 concentration (Ca) is rising, predicted to cause global warming, and alter precipitation patterns. During 1994, spring barley (Hordeum vulgare L. cv. Alexis) was grown in a strip-split-plot experimental design to determine the effects that the main plot Ca treatments [A: Ambient at 370 μmol (CO2) mol−1; E: Enriched with free-air CO2 enrichment (FACE) at ∼550 μmol (CO2) mol−1] had on several gas exchange properties of fully expanded sunlit primary leaves. The interacting strip-split-plot irrigation treatments were Dry or Wet [50% (D) or 100% (W) replacement of potential evapotranspiration] at ample nitrogen (261 kg N ha−1) and phosphorous (29 kg P ha−1) fertility. Elevated Ca facilitated drought avoidance by reducing stomatal conductance (gs) by 34% that conserved water and enabled stomata to remain open for a longer period into a drought. This resulted in a 28% reduction in drought-induced midafternoon depression in net assimilation rate (A). Elevated Ca increased A by 37% under Dry and 23% under Wet. Any reduction in A under Wet conditions occurred because of nonstomatal limitations, whereas under Dry it occurred because of stomatal limitations. Elevated Ca increased the diurnal integral of A (A′) that resulted in an increase in the seasonal-long integral of A′ (A″) for barley leaves by 12% (P = 0.14) under both Dry and Wet - 650, 730, 905 and 1020 ± 65 g (C) m−2 y−1 for AD, ED, AW and EW treatments, respectively. Elevated Ca increased season-long average dry weight (DWS; crown, shoots) by 14% (P = 0.02), whereas deficit irrigation reduced DWS by 7% (P = 0.06), although these values may have been affected by a short but severe pea aphid [Acyrthosiphon pisum (Harris)] infestation. Hence, an elevated-Ca-based improvement in gas exchange properties enhanced growth of a barley crop. 相似文献
895.
Soil management practices for sustainable agro-ecosystems 总被引:1,自引:0,他引:1
A doubling of the global food demand projected for the next 50 years poses a huge challenge for the sustainability of both
food production and global and local environments. Today’s agricultural technologies may be increasing productivity to meet
world food demand, but they may also be threatening agricultural ecosystems. For the global environment, agricultural systems
provide both sources and sinks of greenhouse gases (GHGs), which include carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). This paper addresses the importance of soil organic carbon (SOC) for agro-ecosystems and GHG uptake and emission in agriculture,
especially SOC changes associated with soil management. Soil management strategies have great potential to contribute to carbon
sequestration, since the carbon sink capacity of the world’s agricultural and degraded soil is 50–66% of the historic carbon
loss of 42–72 Pg (1 Pg=1015 g), although the actual carbon storage in cultivated soil may be smaller if climate changes lead to increasing mineralization.
The importance of SOC in agricultural soil is, however, not controversial, as SOC helps to sustain soil fertility and conserve
soil and water quality, and organic carbon compounds play a variety of roles in the nutrient, water, and biological cycles.
No-tillage practices, cover crop management, and manure application are recommended to enhance SOC storage and to contribute
to sustainable food production, which also improves soil quality. SOC sequestration could be increased at the expense of increasing
the amount of non-CO2 GHG emissions; however, soil testing, synchronized fertilization techniques, and optimum water control for flooding paddy
fields, among other things, can reduce these emissions. Since increasing SOC may also be able to mitigate some local environmental
problems, it will be necessary to have integrated soil management practices that are compatible with increasing SOM management
and controlling soil residual nutrients. Cover crops would be a critical tool for sustainable soil management because they
can scavenge soil residual nitrogen and their ecological functions can be utilized to establish an optimal nitrogen cycle.
In addition to developing soil management strategies for sustainable agro-ecosystems, some political and social approaches
will be needed, based on a common understanding that soil and agro-ecosystems are essential for a sustainable society. 相似文献
896.
Evaluation of carbon stock variation in Northern Italian soils over the last 70 years 总被引:1,自引:0,他引:1
Carbon (C) sequestration in soils is gaining increasing acceptance as a means of reducing net carbon dioxide (CO2) emissions to the atmosphere. Numerous studies on the global carbon budget suggest that terrestrial ecosystems in the mid-latitudes
of the Northern Hemisphere act as a large carbon sink of atmospheric CO2. However, most of the soils of North America, Australia, New Zealand, South Africa and Eastern Europe lost a great part of
their organic carbon pool on conversion from natural to agricultural ecosystems during the explosion of pioneer agriculture,
and in Western Europe the adoption of modern agriculture after the Second World War led to a drastic reduction in soil organic
carbon content. The depletion of organic matter is often indicated as one of the main effects on soil, and the storage of
organic carbon in the soil is a means of improve the quality of soils and mitigating the effects of greenhouse gas emission.
The soil organic carbon in an area of Northern Italy over the last 70 years has been assessed In this study. The variation
of top soil organic carbon (SOC) ranged from −60.3 to +6.7%; the average reduction of SOC, caused by agriculture intensification,
was 39.3%. This process was not uniform, but related to trends in land use and agriculture change. For the area studied (1,394 km2) there was an estimated release of 5 Tg CO2-C to the atmosphere from the upper 30 cm of soil in the period 1935–1990. 相似文献
897.
898.
899.
Xiaoqiang Gong Jinbiao Li Scott X. Chang Qian Wu Zhengfeng An Chengpeng Huang Xiangyang Sun Suyan Li Hui Wang 《Frontiers of Environmental Science & Engineering》2022,16(3):39
900.
为快速恢复因灾受损的血液供应链的救援能力,针对血液这一重要医疗物资,研究考虑移动医院的应急供应链重构。设计包含移动医院和临时献血点选址、血液外调与自采和血液与伤员转运的混合整数规划模型,并以红细胞为例,将模型应用于我国龙门山地震带的灾害救治案例中。结果表明:重构的供应链能够综合运用移动医院等资源,快速恢复血液救援能力,最大程度缓解灾害影响。即便是在灾情最严重的情况下,缺血量可减少12.95%。管理者在进行人道主义应急救援决策时,应综合考虑移动医院等医疗资源的有效利用。 相似文献