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481.
新疆草原蝗、鼠灾害与控制策略 总被引:10,自引:2,他引:8
以最近14年新疆治蝗灭鼠现状为依据,分析了草原蝗虫害鼠的为害与防治现状,指出牧业防治和生物防治是今后的方向,健全测报是做好防治的根本,认为加强研究,开放思维、引资合作,共图效益是较为理想的有害生物控制途径。 相似文献
482.
Biosynthetic origin of carbon-based secondary compounds: cause of variable responses of woody plants to fertilization? 总被引:10,自引:0,他引:10
Erkki Haukioja Vladimir Ossipov Julia Koricheva Tuija Honkanen Stig Larsson Kyösti Lempa 《Chemoecology》1998,8(3):133-139
Summary. We propose that variation in the responses of carbon-based secondary compounds to fertilization in woody plants has a biosynthetic
cause. The synthesis of phenylpropanoids and derived compounds (e.g., condensed tannins) competes directly with the synthesis of proteins, and therefore with plant growth, because of a common
precursor, phenylalanine. In contrast, the biosynthesis of terpenoids and of hydrolyzable tannins proceeds presumably without
direct competition with protein synthesis. Therefore, accelerated plant growth induced by fertilization may cause a reduction
in concentrations of phenylpropanoids but may affect less or not at all the levels of other classes of secondary compounds.
A meta-analysis based on fertilization experiments with 35 woody plant species supported the predicted differences fertilizing
significantly decreased concentrations of phenylpropanoids but not of terpenoids or hydrolyzable tannins.
Received 14 May 1998; accepted 23 June 1998. 相似文献
483.
Phenolic compounds are partly known as endocrine disruptors with various harmful effects including feminization and carcinogenesis at very low concentrations. Consequently, the pathways and removal of these compounds in natural and artificial sewage treatment systems such as wetlands have received wide concern. In this paper, a natural reed bed wetland with an area of 695 ha located in the Liaohe River estuary in Northeast China was employed as a demonstration site to study the retention and removal efficiency of phenolic compounds including 4-nonylphenol (4-NP), bisphenol A (BPA), 4-t-octylphenol (4-t-OP), and 2,4-dichlorophenol (DCP), and to evaluate their purification capacity via water and mass balance analyses during an irrigation period from May 9 to September 8, 2009. The results showed that the phenolic compounds could be retained in the wetland system and removed through various processes. On average, 27.5% of phenolic compounds could be retained by the wetland substrate during the initial three-day irrigation period with a retention capacity order of 4-t-OP > 4-NP > BPA > DCP. During the following 120 d irrigation period, the phenolic compounds could be efficiently removed with an average percentage of 91.6%. It is estimated that 1.76 kg d−1 of phenolic compounds could be removed by the Liaohe River estuarine wetland (∼8 × 104 ha). The reed bed wetland system therefore provides a feasible mitigation option for phenolic pollutants in sewage and wastewater. 相似文献
484.
485.
486.
张明 《中国人口.资源与环境》2011,21(7)
随着工业化和城市化进程的加快,山东省能源消耗量逐渐增大,2008年山东省能源消耗占全国的11.3%.因此研究山东省能源消耗对促进节能减排有重要的意义.能流图可以直观、形象地展示能源流动情况,在国际上得到广泛的应用.能源统计数据是能源分析的基础,但我国的能源统计体系与国外有较大区别.按国际准则的能源供需体系和有关专家的意见,适当调整了山东省能源平衡表.本文的主要目的是绘制山东省2008年能流图,在此基础上分析山东省能源现状和能源利用效率.得到如下结论:①煤炭是山东的主要能源,占一次能源供应的71.84%;②山东省电力以火电为主,火电占总发电量的99.9%;③山东雀2008年能源利用效率约为35.83%;④工业部门能源消耗占终端能源消耗的74.9%.进一步说明能流图不但能够直观、定量地展示能源供应、转换和使用数量的全貌,而且可以揭示各个环节的能源利用效率水平. 相似文献
487.
改进抽油机井“功率平衡”测试实现节能降耗 总被引:2,自引:0,他引:2
目前在抽油机井管理中普遍采用的平衡标准是"电流平衡",并认定电流平衡度在80%~120%之间时抽油机即为平衡。而真正判断抽油机平衡的标准是"功率平衡",即抽油机运行过程中,下冲程内电机平均功率与上冲程内电机平均功率相等。抽油机功率平衡既能实现节能目的,又能保证抽油机安全运行。从2008年7月开始率先在胜利油田进行抽油机功率平衡技术的试验及推广,2008年共调整抽油机功率平衡118井次,平均单日节电21.4kW.h,平均节电率9.90%,取得了良好的节能效果。 相似文献
488.
Niels Jonkers 《Environmental pollution (Barking, Essex : 1987)》2009,157(3):714-723
This study focused on the occurrence and behaviour in wastewater and surface waters of several phenolic endocrine disrupting compounds (EDCs) including parabens, alkylphenolic compounds, phenylphenol (PhP) and bisphenol A (BPA). Analytical procedures using solid-phase-extraction and LC-MS/MS techniques were applied to samples of influents and effluents of wastewater treatment plants (WWTPs) discharging into the Glatt River (Switzerland) as well as to river water samples. A mass flow analysis provided insight into the main sources and the fate of these contaminants during different weather conditions. Concentrations in influents were in the low μg/L range for most analytes. Removal of parabens in the WWTPs was mostly above 99%. Nonylphenol polyethoxylates (A9PEO) removal amounted to 98%, but in some cases nonylphenoxy acetic acid (A9PEC) or nonylphenols (NP) were formed. In effluents, concentrations were highest for the A9PEC, A9PEO and NP. Concentrations in river water were in the high ng/L range for alkylphenolic compounds and in the low ng/L range for BPA, PhP and the parabens. During the sampling period, in which several rain events occurred, both water flows and mass flows varied strongly. Mass flows in WWTP effluents and in the river increased with increasing water flows for most compounds indicating that higher water flows do not lead necessarily to a proportional dilution of the pollutants. Throughout the low water flow period, mass flows predicted from the known inputs were similar to the actual mass flows at the end of the river for most analytes. For none of the EDCs, significant in-stream removal could be observed. In the periods with high water flows, mass flows in the river were much higher than can be explained by the initially defined sources. Discharge of untreated wastewater influent into the river was assessed as an additional source. Adding this source improved the mass balance for some, but not all of the analytes. 相似文献
489.
从中国土地利用现状出发,根据目前的中国粮食生产、粮食需求关系和地区经济水平差异等因素,建立了粮食调拨运输模型--计划经济型(非市场原理型)和市场原理型(自由购买型)。并将这两种模型分别应用到中国华中-华南地区,讨论了中国华中-华南地区的粮食储备变化特点。模拟结果显示:非市场原理型运输模型中,随着粮食运输强度系数的增大,城市地区的粮食不足现象逐步得到缓解;而粮食产地的粮食储量也将相应减少,粮食分布的区域不平衡不会长期存在。依据市场原理型运输模型,随着粮食吸收系数的增大,粮食储备迅速集中到沿海城市,此后粮食生产地区的粮食储备开始减少,内陆地区会出现大范围的粮食短缺现象。这种粮食分布的区域不平衡现象越来越大。 相似文献
490.
从不同尺度分析了我国2008年粮食生产、消费中的虚拟耕地含量及虚拟耕地平衡空间分布规律.主要结论为:①2008年粮食生产虚拟耕地北方比南方多32396.8×107m2,人均粮食生产虚拟耕地量北方远远高于全国平均水平和南方,因粮食生产形成较为典型的虚拟耕地“北土南调”现象.②2008年粮食消费虚拟耕地北方比南方多6851.62×107m2.③从粮食生产与消费的虚拟耕地平衡空间分布规律来看,2008年虚拟耕地调出区全部位于我国北方地区,集中分布在两大地带:一是由黑龙江、吉林、内蒙古、新疆、宁夏5省(区)组成的我国北方边境沿线地带,二是由河南、安徽组成的中部区;调入区则集中在由东部沿海地区、中部省份和西部内陆省份组成的环状地带. 相似文献