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31.
本文研究了湖南省中亚热带次生林的种群动态,建立了静态生命表、存活曲线、结构模型以及材积或生物量动态模型,提出了中亚热带次生林的演替基本模式。 相似文献
32.
本文通过种群自我调节的规律以及Leslie模型进行数量动态分析,从而提出了次生林数量动态与经营的生态经济对策。 相似文献
33.
Zhuofei Du Min Hu Jianfei Peng Song Guo Rong Zheng Jing Zheng Dongjie Shang Yanhong Qin He Niu Mengren Li Yudong Yang Sihua Lu Yusheng Wu Min Shao Shijin Shuai 《环境科学学报(英文版)》2018,30(4):348-357
Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds(VOCs). However,little information on secondary aerosol formation from exhaust for Chinese vehicles and fuel conditions is available. In this study, chamber experiments were conducted to quantify the potential of secondary aerosol formation from the exhaust of a port fuel injection gasoline engine. The engine and fuel used are common in the Chinese market, and the fuel satisfies the China V gasoline fuel standard. Substantial secondary aerosol formation was observed during a 4–5 hr simulation, which was estimated to represent more than 10 days of equivalent atmospheric photo-oxidation in Beijing. As a consequence, the extreme case secondary organic aerosol(SOA) production was 426 ± 85 mg/kg-fuel, with high levels of precursors and OH exposure. The low hygroscopicity of the aerosols formed inside the chamber suggests that SOA was the dominant chemical composition. Fourteen percent of SOA measured in the chamber experiments could be explained through the oxidation of speciated single-ring aromatics. Unspeciated precursors, such as intermediate-volatility organic compounds and semi-volatile organic compounds, might be significant for SOA formation from gasoline VOCs. We concluded that reductions of emissions of aerosol precursor gases from vehicles are essential to mediate pollution in China. 相似文献
34.
结合教学实际实施环境教育初探 总被引:1,自引:0,他引:1
教育系统应制定切实可行的规划,结合当地实际和行业特点,有针对性地幼儿、小学生、中学生和大、中专院校的学生实施系统的环境教育工程,使学生具有保护环境的知识、技能和良好行为,从而提高人们的环境保护素质。 相似文献
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A new environmental chamber for evaluation of gas-phase chemical mechanisms and secondary aerosol formation 总被引:1,自引:0,他引:1
William P.L. Carter David R. Cocker III Dennis R. Fitz Irina L. Malkina Kurt Bumiller Claudia G. Sauer John T. Pisano Charles Bufalino Chen Song 《Atmospheric environment (Oxford, England : 1994)》2005,39(40):7768-7788
A new state-of-the-art indoor environmental chamber facility for the study of atmospheric processes leading to the formation of ozone and secondary organic aerosol (SOA) has been constructed and characterized. The chamber is designed for atmospheric chemical mechanism evaluation at low reactant concentrations under well-controlled environmental conditions. It consists of two collapsible 90 m3 FEP Teflon film reactors on pressure-controlled moveable frameworks inside a temperature-controlled enclosure flushed with purified air. Solar radiation is simulated with either a 200 kW Argon arc lamp or multiple blacklamps. Results of initial characterization experiments, all carried out at 300–305 K under dry conditions, concerning NOx and formaldehyde offgasing, radical sources, particle loss rates, and background PM formation are described. Results of initial single organic–NOx and simplified ambient surrogate–NOx experiments to demonstrate the utility of the facility for mechanism evaluation under low NOx conditions are summarized and compared with the predictions of the SAPRC-99 chemical mechanism. Overall, the results of the initial characterization and evaluation indicate that this new environmental chamber can provide high quality mechanism evaluation data for experiments with NOx levels as low as 2 ppb, though the results indicate some problems with the gas-phase mechanism that need further study. Initial evaluation experiments for SOA formation, also carried out under dry conditions, indicate that the chamber can provide high quality secondary aerosol formation data at relatively low hydrocarbon concentrations. 相似文献
39.
底泥对河流的二次污染浅析 总被引:39,自引:1,他引:39
根据底冲中污染物质累积和释放过程和底泥对河流二次污染的机理,运用适用的模式和苏州河的实测资料,可得到二次污染BOD和COD的年释放量,以及增加上覆河上的BOD和COD浓度。由此认为,对于底泥污染严重的河流,疏浚是必不可少的,其目的在于清除或隔绝黑富集层上覆河上的二次污染。 相似文献
40.
Diego Rubolini Maria Romano Roberta Martinelli Barbara Leoni Nicola Saino 《Behavioral ecology and sociobiology》2006,59(4):549-560
Mothers may profoundly affect offspring phenotype and performance by adjusting egg components, including steroid hormones.
We studied the effects of elevated prenatal testosterone (T) exposure in the ring-necked pheasant on the expression of a suite
of male and female traits, including perinatal response to stress, immune response, growth, and secondary sexual traits. Prenatal
T levels were increased by injecting the yolk of unincubated eggs with physiological doses of the hormone. Yolk T injection
resulted in a reduced length of male tarsal spurs, a trait which positively predicts male success in intra- and intersexual
selection and viability, whereas no direct effect on male wattle characteristics or plumage traits of either sex was observed.
Female spur length was also negatively affected by T, but to a lesser extent than in males. In addition, the covariation between
male secondary sexual traits, which are reliable quality indicators, differed between T and control males, suggesting that
the manipulation may have altered the assessment of overall male quality by other males and females. In conclusion, the negative
effects of elevated yolk T on spur length, a trait which positively predicts male fitness, coupled with the lack of effects
on growth or other traits in both sexes, provided limited evidence for mothers being subjected to a trade-off between positive
and negative consequences of yolk T deposition on offspring traits and suggest that directional selection for reduced yolk
T levels may occur in the ring-necked pheasant. 相似文献