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271.
This study investigated allelopathy and its chemical basis in nine switchgrass (Panicum virgatum L.) accessions. Perennial ryegrass (Lolium perenne L.) and alfalfa (Medicago sativa L.) were used as test species. Undiluted aqueous extracts (5 g plant tissue in 50 ml water) from the shoots and roots of
most of the switchgrass accessions inhibited the germination and growth of the test species. However, the allelopathic effect
of switchgrass declined when extracts were diluted 5- or 50-fold. Seedling growth was more sensitive than seed germination
as an indicator of allelopathic effect. Allelopathic effect was related to switchgrass ecotype but not related to ploidy level.
Upland accessions displayed stronger allelopathic potential than lowland accessions. The aqueous extract from one switchgrass
accession was separated into phenols, organic acids, neutral chemicals, and alkaloids, and then these fractions were bioassayed
to test for allelopathic potential. Alkaloids had the strongest allelopathic effect among the four chemical fractions. In
summary, the results indicated that switchgrass has allelopathic potential; however, there is not enough evidence to conclude
that allelopathic advantage is the main factor that has contributed to the successful establishment of switchgrass on China’s
Loess Plateau. 相似文献
272.
Isotopic evidences for provenance of East Asian Dust 总被引:1,自引:0,他引:1
Jiedong Yang Gaojun Li Wenbo Rao Junfeng Ji 《Atmospheric environment (Oxford, England : 1994)》2009,43(29):4481-4490
We have systematically collected samples in the possible source regions (the deserts and sandy lands of North China, northeastern past of the Tibetan Plateau, Chinese Loess Plateau and southern part of Mongolia) of the East Asian dust. Based on Nd–Sr isotopic ranges, the source regions can be divided into four isotopic regions: Region A1: the Gurbantunggut Desert in Junggar basin and Hunlun Buir sandy land in northeastern China; Region A2: the Hunshandake sandy land, Horqin sandy land and southern part of Mongolia; Region B: the Taklimakan Desert in Tarim basin, northeastern past of the Tibetan Plateau, Chinese Loess Plateau, Badain Jaran Desert and Tengger Desert in Alashan Plateau; Region C: the Hobq Desert and Mu Us Desert in the Ordos Plateau. Through comparison of Nd–Sr isotopes, it can be inferred that the sediments of the north-central Pacific and dust particles in the Greenland ice cores are mainly derived from Region B. Dusts of East Asian dust storm are derived mostly from Region B also, and less from Region A2. The materials of dust storm at Beijing area in April 2006, originated largely from the Hobq Desert and Mu Us Desert in the Ordos Plateau. The floating dust at Beijing area in April 2006, is the mixing of dust of distant deserts and local dust at Beijing area. Loess of the Chinese Loess Plateau may largely originate from Region B. 相似文献
273.
苏南地区洪涝危险区的划定及其治理对策 总被引:1,自引:1,他引:1
根据水文学和计算水力学的方法,计算出本区1954年雨型、现状地面条件下各断面日平均最高水位,同时再综合分析各圩区的堤高、排涝能力及灾害水文等资料,制定出危险圩区的标准。凡不及上述标准的圩区及圩外地区,均划为洪涝危险区,即在遇到大暴雨后,这些地区是可能出现洪涝灾害危险程度最大的地区。 相似文献
274.
Spruce (Picea abies (L.) Karst.) needles were exposed to exhaust gas containing polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) generated by combustion of polyvinyl chloride, wood, high-density polyethylene, and styrene. Photodegradation of PCDD/Fs adsorbed on spruce needles under sunlight irradiation was studied. The photodegradation of PCDD/Fs follows pseudo-first-order reaction kinetics, with photolysis half-lives ranging between 40 and 100 h. The photolysis rates of PCDF congeners are higher than PCDD congeners with the same chlorinated substitutions. Higher chlorinated PCDD/Fs tend to photolyze slowly. The wax components in spruce needles may act as proton donors and accelerate the photolysis rate. C-Cl cleavage through the addition of protons to PCDD/F molecules may be an important route for PCDD/Fs photodegradation. 相似文献
275.
活性炭吸附-微波技术再生处理粘胶纤维废气的研究 总被引:1,自引:0,他引:1
针对粘胶纤维厂冷凝处理后的废气浓度低的特点,开发了吸附-微波再生处理技术.主要考察了吸附剂的种类、H2S和CS2进口浓度、湿度的影响,同时还对微波再生条件和效果进行了实验.结果表明,活性炭对二硫化碳的吸附效果较好;H2S和CS2进口浓度很低(Ci<200 mg/m^3)时对吸附影响不明显;湿度对吸附影响很大.实验亦证实,微波再生后的活性炭性能有很大的改善. 相似文献
276.
Niu J Chen J Martens D Quan X Yang F Kettrup A Schramm KW 《Environmental pollution (Barking, Essex : 1987)》2003,123(1):39-45
Photolysis of polycyclic aromatic hydrocarbons (PAHs) sorbed on surfaces of spruce [Picea abies (L.) Karst.] needles under sunlight irradiation was investigated. PAHs were produced by combustion of polyvinyl chloride (PVC), wood, high-density polyethylene (HDPE), and styrene in a stove. The factors of sunlight irradiation on the surfaces of spruce needles were taken into consideration when investigating the kinetic parameters. The photolysis of the 18 PAHs under study follows first-order kinetics. The photolysis half-lives range from 15 h for dibenzo(a,h)anthracene to 75 h for phenanthrene. Photolysis of some PAHs on surfaces of spruce needles may play an important role on the fate of PAHs in the environment. 相似文献
277.
研究了利用电厂粉煤灰作为非均相催化剂,催化H2O2氧化对氨基苯酚(PAP),讨论了各种因素对PAP去除率的影响。结果表明,在30℃,pH=1.5,H2O2和PAP的起始浓度分别为0.50mol/L和0.10mol/L,反应时间为100min,粉煤灰用量为6.0%,搅拌速度为1000r/min的条件下,粉煤灰具有良好的催化活性,能有效地催化H2O2氧化PAP,PAP的去除率可达81%左右。该法可用于预处理含PAP的工业废水。 相似文献
278.
279.
280.
新型反应器(SUFR)去除城市污水中氮和磷的试验研究 总被引:3,自引:0,他引:3
开发了一种新的污水生物处理反应器——螺旋升流式反应器(Spiral Up-Flow Reactor,SUFR),与传统的“池型反应器”(如氧化沟)相比,既提高了反应器中稳定的活塞流流态的容积利用率,又便于工程应用。运用SUFR对生物脱氮除磷进行了研究,系统连续稳定运行6个月的结果表明,该系统能保证出水平均质量浓度COD小于31mg/L,总氮小于10mg/L,总磷小于0.50mg/L,对COD、TN和TP的去除率分别达94%、86%和96%以上。对去除性能的分析结果表明,(1)SUFR系统厌氧反应器、缺氧反应器和好氧反应器对COD的去除量分别占去除总量的51.2%、12.5%和36.3%;(2)在去除总氮时,好氧反应器表现出了同步硝化反硝化功能,其对总氮的去除量约占SUFR系统去除总量的10%~20%;(3)去除总磷时,缺氧反应器表现出了反硝化吸磷现象,吸磷的量与进水COD质量浓度有关。 相似文献