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991.
江苏省酸雨污染十五年趋势分析 总被引:9,自引:1,他引:9
根据江苏省的酸雨监测资料,对该省酸雨污染现状及“七五”末以来的变化趋势进行了分析,结果表明:淮河以南酸雨污染普遍重于淮河以北地区;“七五”末以来酸雨频率有降低的趋势,但降水酸度并未减弱;降水组份中,硫酸根离子当量浓度仍占首位,酸雨带来的污染和生态破坏未得到明显减轻。 相似文献
992.
研究了8503和8505二白种在以白酒糟、薯干酒精糟及两糟混合的培养液中培养,对该酒糟培养液中还原糖的利用率和氮的转化率的分析检测方法.通过对绝于菌体质量的时变曲线与菌种对碳源利用率和氮源转化率的时变曲线的对比研究,可以看到该菌种在酒糟培养液中对碳源和氮源的利用率与转化率的规律性,经48h或72h发酵后碳源利用率可达90%左右,本实验最高达92.92%,氮源转化率一般可达50%~70%,本实验最高达68.41%,每100ml培养液中绝干菌体质量最高达0.78399。 相似文献
993.
994.
Halonen I. Tarhanen J. Ollikainen S. Ruokojrvi P. Tuppurainen K. Ruuskanen J. 《Chemosphere》1994,28(12):2129-2137
Aliphatic liquid as a basic fuel was incinerated in a laboratory scale pilot plant. Inorganic chlorine and organic chlorine mixed with basic fuel were used as additive chemicals. Sodium chloride (NaCl) and tetrachloroethylene (C2Cl4) were used as the sources of inorganic and organic chlorine. Combustion parameters were adjusted for optimum combustion and, consequently, the amount of particles in flue gases was low. The concentrations of chlorine in flue gases were high enough for possible formation reactions of organic chlorinated compounds in all of the chlorine input tests. An increase in chlorine input did not significantly increase the amounts of highly chlorinated organic compounds, like PCDD/Fs. The main result was that chlorophenol concentrations increased in parallel with organic chlorine input. Comparing organic chlorine to inorganic chlorine tests showed that more highly substituted PCDD/F congeners were formed when organic chlorine was the additive chlorine source. The formation of highly chlorinated organic compounds such as PCDD/Fs requires not only chlorine and aliphatic fuel to be formed, but some catalysts are also needed. 相似文献
995.
E. Menichini N. Iacovella F. Monfredini L. Turrio-Baldassarri 《Atmospheric environment (Oxford, England : 1994)》2007,41(40):9518-9529
PAHs and PCBs were collected simultaneously indoors and outdoors at eight non-smoking homes located in four buildings in high-traffic areas of Rome. The purpose was to evaluate the relevance of indoor air in contributing to the overall exposure of the urban population. The vertical distribution was also investigated by collecting outdoor samples at both road and roof level, and indoor samples in both a high and a low floor flat of each building. At one coal-heated building, samples were collected during both the heating and the non-heating season. No evident PAH source was present indoors. Indoor and outdoor daily concentrations of benzo[a]pyrene (BaP) ranged, respectively, 0.1–4.6 ng m−3 and 0.7–2.3 ng m−3. With the heating on, indoor PAH concentrations equalled or exceeded those outdoors, with BaP indoor/outdoor ratios up to 4; during the warm season, ratios decreased to 0.2–0.6. Indoor PAHs at the low floors exceeded the high-floor ones when the heating was off (vehicle exhausts being the dominant source), while being equal or lower with the heating on; the vertical gradient of indoor PAHs between different floors was within a factor of 2. Outdoor PAHs at roof level were 20–70% of those at road level, which in turn exceeded those at the medium-traffic station up to a factor of 4. The outdoor concentrations of Σ6 indicator PCBs ranged 0.1–1.6 ng m−3. Indoor PCB concentrations exceeded those outdoors by an approximate factor of 2–50. No vertical gradient was observed. The results indicated that indoor air may contribute to the overall exposure to PAHs and PCBs more than the urban air. They were also consistent with recent findings suggesting that indoor air can be a relevant source of PCBs for outdoor air. 相似文献
996.
Removal process estimation of population size for a population with a known sex ratio 总被引:2,自引:0,他引:2
A removal model for estimating population size which uses the known population sex ratio is studied. A maximum likelihood estimate and an optimal martingale estimate of the population size are proposed. Their standard errors and large sample properties are obtained. Simulation studies are reported, and the performance of the proposed estimators are compared with the standard maximum likelihood estimator which ignores the sex ratio information. An example on a capture study of deer mice is given. 相似文献
997.
Eric Lichtfouse Michel Lichtfouse Michaele Kashgarian Roland Bol 《Environmental Chemistry Letters》2005,3(2):78-81
Measuring the amount of fossil fuel carbon stored in the vegetation is now crucial to understand the mechanisms ruling climate
changes. In this respect, highly polluted areas such as major towns represent “natural” laboratories because fossil fuel CO2 (14C-free) is isotopically distinct from mean atmospheric CO2 (14C-labeled). Here, a14C study of urban grasses near a major highway in Paris, France, shows that plants store up to 13% of fossil fuel carbon. The
14C composition of urban grasses is thus a novel parameter to assess the fossil fuel CO2 pollution. 相似文献
998.
K. E. Ruckstuhl A. Manica A. D. C. MacColl J. G. Pilkington T. H. Clutton-Brock 《Behavioral ecology and sociobiology》2006,59(5):694-703
We analysed 16 years of census data gathered on the island of Hirta (archipelago of St. Kilda) to investigate the effects
of castration, population density, sex ratio, season and group type on habitat use and social segregation of Soay sheep. From
1978 to 1980, 72 male lambs were castrated. We used this experiment to study how a change in reproductive status could affect
sociality and habitat choice of these males. Males, females and castrates were all segregated outside the rutting season in
autumn. Castrates were the least segregated from females in spring and summer but were most segregated from them during the
pre-rut. The more equal the sex ratios, the higher was the degree of social segregation. The three sex classes used similar
habitat types, namely, Holcus agrostis, Agrostis festuca and Calluna habitats. Holcus agrostis and Agrostis festuca were top- and second-ranked in female and castrate habitat use, while Holcus agrostis and Calluna were the two top habitat types used by rams. It is unclear why males included Calluna heath habitats, but it cannot be excluded that they might have shifted their use depending on forage availability. A lack
in differences in habitat use between castrates and females suggests that body size differences alone cannot be the driving
factor for habitat segregation in male and female Soay sheep and that there are reasons other than body size that could motivate
reproductive males to use additional habitat types, such as Calluna heath. Although habitat use shifted from one habitat type to the next between low- and high-population-density years and
between seasons, there was no clear link between population density and how different groups (male, female or castrate) used
these areas. We discuss effects of reproductive status, population density and sex ratio on social segregation and habitat
use and suggest that these factors need to be taken into account when investigating causes of sexual segregation in ungulates. 相似文献
999.
雌雄异株植物与性别比例有关的性别差异研究现状与展望 总被引:4,自引:0,他引:4
雌雄异株植物是陆地生态系统的重要组分,自然种群中其雌雄个体的性别比例通常为1∶1,但随水分、养分、CO2浓度、温度、光照和干扰水平等的不同而有所不同.一般来说,在逆境下性别比例偏雄性,这是雌雄异株植物性别分离的常见模式.雌雄异株植物不同性别间的差异主要体现在:(1)存活率,(2)形态特征,(3)生理生化特性,(4)物候期,(5)资源分配模式等方面,但对于雌雄个体差异的分子机理未见报道.这些差异导致了雌雄植株个体环境适应性的不同,从而表现为在不同环境下雌雄异株植物性别比例偏倚的现象.基于此,可结合不同树种雌雄性的不同用途,开展有关研究.参59 相似文献
1000.
从某大型储罐复合地基沉降机理分析入手,合理选择沉降计算公式,对建造在该类复合地基上的大型储罐沉降量作计算,并经实测沉降资料对比后,验证该类储罐沉降计算方法的适用性,为今后类同工程地质条件下,储罐基础的优化设计积累经验.图1,表1,参3. 相似文献