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91.
潮土中磷锌交互作用机制探讨及磷对锌吸附-解吸的影响 总被引:2,自引:0,他引:2
采用室内培养和吸附解吸两种方法,探讨了潮土中磷、锌交互作用机制。结果表明:土壤中DTPA提取态锌质量分数随添加锌量的增加而增加,低磷质量分数处理可提高土壤锌有效性,但高磷质量分数处理却降低了土壤锌的有效性;土壤速效磷质量分数均随锌添加量的增加而有所降低。在施锌25 mg.kg-1背景下,土壤中DTPA提取态锌质量分数随施磷质量分数的增加呈先增加后降低趋势,在添加磷量小于180 mg.kg-1时,土壤DTPA提取态锌质量分数显著地高于其他处理,但随添加磷量的增加,土壤DTPA提取态锌质量分数显著降低,当磷添加量大于540 mg.kg-1时,土壤DTPA提取态锌质量分数明显低于其他磷处理,说明当添加磷量小于180 mg.kg-1时,磷提高土壤中锌有效性的主要机制是二者竞争吸附土壤胶体表面吸附点位的竞争机制;当添加磷量大小540 mg.kg-1时,磷影响锌有效性的主要机制为沉淀作用。在土壤施磷量为180 mg.kg-1时,随添加锌质量分数的提高,土壤中速效磷质量分数呈先升高后降低趋势。吸附-解吸研究表明,随土壤中速效磷质量分数的提高(27.60~2773.86 mg.kg-1),土壤对锌的吸附量先降低再增加,而KCl解吸的锌量却是先增加再降低。因此潮土中磷锌交互作用机制为,土壤中磷和锌质量分数均较低时,磷与锌有效性呈协同作用;当磷或锌质量分数过高时,协同作用减弱;磷和锌质量分数再增加二者的有效性将出现拮抗作用。 相似文献
92.
93.
《环境科学学报(英文版)》2023,35(2):491-504
Ce1-xZrxO2 composite oxides (molar, x = 0-1.0, interval of 0.2) were prepared by a cetyltrimethylammonium bromide-assisted precipitation method. The enhancement of silver-species modification and catalytic mechanism of adsorption-transformation-desorption process were investigated over the Ag-impregnated catalysts for low-temperature selective catalytic oxidation of ammonia (NH3-SCO). The optimal 5 wt.% Ag/Ce0.6Zr0.4O2 catalyst presented good NH3-SCO performance with >90% NH3 conversion at temperature (T) ≥ 250°C and 89% N2 selectivity. Despite the irregular block shape and underdeveloped specific surface area (∼60 m2/g), the naked and Ag-modified Ce0.6Zr0.4O2 solid solution still obtained highly dispersed distribution of surface elements analyzed by scanning electron microscope-energy dispersive spectrometer (SEM-EDS) (mapping), N2 adsorption-desorption test and X-ray diffraction (XRD). H2 temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) results indicated that Ag-modification enhanced the mobility and activation of oxygen-species leading to a promotion on CeO2 reducibility and synergistic Ag0/Ag+ and Ce4+/Ce3+ redox cycles. Besides, Ag+/Ag2O clusters could facilitate the formation of surface oxygen vacancies that was beneficial to the adsorption and activation of ammonia. NH3-temperature programmed desorption (NH3-TPD) showed more adsorption-desorption capacity to ammonia were provided by physical, weak- and medium-strong acid sites. Diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments revealed the activation of ammonia might be the control step of NH3-SCO procedure, during which NH3 dehydrogenation derived from NHx-species and also internal selective catalytic reduction (i-SCR) reactions were proposed. 相似文献
94.
为保证小型旋翼无人机近距编队悬停状态的安全性,采用数值模拟方法研究不同横向和纵向间隔双机悬停流场特征和气动参数变化规律,通过与实验结果对比,验证数值仿真方法的准确性。研究结果表明:无人机内部旋翼间的气动干扰会导致整机单旋翼拉力降低、扭矩增大,使整机气动效率下降;当双机无横向间隔时,双机下洗流场保持对称,同时2股下洗流叠加,呈现较明显的横向扩张趋势,此时后机所受气动影响主要为拉力损失,当纵向间隔大于5 D时,该影响基本消失;当横向间隔X=1 D时,位于尾流区一侧的旋翼拉力减小,后机所受俯仰力矩作用显著,无人机有侧翻风险;横向间隔X≥2 D时,2机之间气动干扰较弱,为较安全区域。 相似文献
95.
A. Roulin J. Gasparini P. Bize M. Ritschard H. Richner 《Behavioral ecology and sociobiology》2008,62(4):507-519
One hypothesis for the maintenance of genetic variation states that alternative genotypes are adapted to different environmental
conditions (i.e., genotype-by-environment interaction G×E) that vary in space and time. Although G×E has been demonstrated
for morphological traits, little evidence has been given whether these G×E are associated with traits used as signal in mate
choice. In three wild bird species, we investigated whether the degree of melanin-based coloration, a heritable trait, covaries
with nestling growth rate in rich and poor environments. Variation in the degree of reddish-brown phaeomelanism is pronounced
in the barn owl (Tyto alba) and tawny owl (Strix aluco), and variation in black eumelanism in the barn owl and Alpine swift (Apus melba). Melanin-based coloration has been shown to be a criterion in mate choice in the barn owl. We cross-fostered hatchlings
to test whether nestlings sired by parents displaying melanin-based colorations to different extent exhibit alternative growth
trajectories when raised by foster parents in poor (experimentally enlarged broods) and rich (experimentally reduced broods)
environments. With respect to phaeomelanism, barn owl and tawny owl offspring sired by redder parents grew more rapidly in
body mass only in experimentally reduced broods. With respect to eumelanism, Alpine swift offspring of darker fathers grew
their wings more rapidly only in experimentally enlarged broods, a difference that was not detected in reduced broods. These
interactions between parental melanism and offspring growth rate indicate that individuals display substantial plasticity
in response to the rearing environment which is associated with the degree of melanism: at least with respect to nestling
growth, phaeomelanic and eumelanic individuals are best adapted to rich and poor environments, respectively. It now remains
to be investigated why eumelanism and phaeomelanism have a different signaling function and what the lifelong consequences
of these melanism-dependent allocation strategies are. This is important to fully appraise the role played by environmental
heterogeneity in maintaining variation in the degree of melanin-based coloration. 相似文献
96.
Tadashi Hasegawa Kakeru Usuba Soichiro Kondo Yutaka Maeda 《Environmental Chemistry Letters》2008,6(2):107-111
Here, we show that association of stilbene molecules is facilitated by water on silica gel because of hydrophobic interaction
and photodimerization becomes the main photochemical process. Irradiation of trans-stilbene (t-1) on silica gel gives cis-stilbene (c-1), phenanthrene (2), benzaldehyde (3), and dimers r-ctt-4 and r-tct-4. The yields of the dimers increase and those of 2 and 3 decrease with an increase in the amount of t-1 loaded on silica gel. Atmospheric oxygen is responsible for the formation of 2 and 3. The yields of the dimers also increase with an increase in the water on a silica-gel surface and change drastically at the
point where the percentage of water to silica gel is around 25 wt%. All active sites on a silica-gel surface would be covered
completely with 25 wt% of water. 相似文献
97.
Christer Wiklund Adrian Vallin Magne Friberg Sven Jakobsson 《Behavioral ecology and sociobiology》2008,62(3):379-389
Insects that hibernate as adults have a life span of almost a whole year. Hence, they must have extraordinary adaptations
for adult survival. In this paper, we study winter survival in two butterflies that hibernate as adults and have multimodal
anti-predator defences—the peacock, Inachis io, which has intimidating eyespots that are effective against bird predation, and the small tortoiseshell, Aglais urticae, which does not have an effective secondary defence against birds. We assessed predation on wild butterflies hibernating
in the attic of an unheated house, as well as survival of individually marked butterflies placed by hand on different sites
in the attic. Our objectives were to assess (1) the number of butterflies that were killed during hibernation, (2) whether
survival differed between butterfly species, and (3) how predation was related to hibernation site and the identity of the
predator. There was a strong pulse of predation during the first 2 weeks of hibernation: 58% of A. urticae and 53% of I. io were killed during this period. Thereafter, predation decreased and butterfly survival equalled 98% during the final 16 weeks
of hibernation. There was no difference in survival between the two butterfly species, but predation was site-specific and
more pronounced under light conditions in locations accessible to a climbing rodent, such as the common yellow-necked mouse,
Apodemus flavicollis. We contend that small rodents are likely important predators on overwintering butterflies, both because rodents are active
throughout winter when butterflies are torpid and because they occur at similar sites. 相似文献
98.
采用一次性单种培养的方法,研究了磷和光照对铜绿微囊藻和四尾栅藻生长以及叶绿素形成的影响.结果表明,光照水平的提高能够提高藻类最大比增长率,延长藻类指数生长期;但达到一定水平后,光照水平的增加会抑制单细胞藻类体内叶绿素的合成.在试验设定的浓度范围内,磷对藻类最大比增长率的影响不大;而不利于藻类叶绿素的形成.对于铜绿微囊藻的生长,磷与光照表现出明显的交互作用,但对于四尾栅藻,二者的交互作用并不明显. 相似文献
99.
Pd/CZ/Al2O3催化剂的制备、表征与三效催化性能 总被引:6,自引:0,他引:6
以共浸渍法制得的氧化铝负载铈锆固溶体为载体,并浸渍贵金属Pd得到了Pd/CZ/Al2O3催化剂.实验结果表明,该催化剂在老化前后都表现出良好的三效催化活性,新鲜样品Pd/CZ/Al2O3活性与Pd/CZ相当,老化后样品前者优于后者.结合XRD,BET,TPR等表征手段,讨论了Pd/CZ/Al2O3的催化活性特别是高温老化后活性与其组成结构之间的内在关系,揭示了其老化后仍具有较高活性的主要原因在于保持了Pd与CZ/Al2O3复合载体之间的强相互作用(SMSI). 相似文献
100.
上海城市土地利用转变类型及其空间关联分析 总被引:15,自引:0,他引:15
基于多时段TM遥感影像资料,通过地图代数和空间关联分析、相邻度分析等空间分析手段的综合应用,论文对上海地区近10年来城市土地利用变化类型、形成过程和相关空间机制进行了研究,结果表明:①近10年来上海城市土地利用扩展经历了“单核扩展”模式为主(1987~1990年)到“单核扩展”、“多核扩展”与“点-轴”扩展模式并存(1990~1995年),直至“多核扩展”及“点-轴”等复杂扩展模式为主(1995~2000年)的变化过程,导致上海中心城区和郊县城镇规模急剧扩张,交通干道沿线区域城市化过程明显增强,并形成整个上海地区城市化网络结构;②面积贡献率较大、转变频率较低的城市土地利用变化类型,与其他类型之间具有较高的关联度和空间亲和性,构成中心城区或卫星城、郊区城镇的扩展核心;③面积贡献率较低的类型,其转变频率较高,分布零散,构成扩展核的外围部分,这些城市周边地区存在一定程度紊乱、不合理的土地利用、开发活动;④城市化过程的内在空间机制与土地利用类型的面积和转变频率有密切关系。在更精细的尺度上依据转变频率划分的类别在一定程度上能更好体现城市土地利用变化类型的空间分异,及其作为宏观驱动机制的社会经济因子所具有的空间差异性。 相似文献