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401.
Summary. The among-leaves allocation of DIBOA, a hydroxamic acid associated with plant resistance, in the shoot of rye (Secale cereale) was evaluated over the vegetative development of the plant. The appropriateness of using the concentration of secondary
metabolites, DIBOA in this case, as the parameter to evaluate defense allocation in plants is discussed. Both biological and
statistical arguments are put forward to suggest that allocation of chemical defenses should refer to absolute content and
not to concentration. Results showed that leaf age was significantly linked to leaf concentration of DIBOA, young leaves having
higher concentrations. In contrast, leaf content of DIBOA, our proposed currency of allocation, was not significantly higher
in younger leaves. Furthermore, a regression analysis showed that the DIBOA content of leaves was better explained by the
leaf relative biomass (proportion of shoot biomass) than by leaf biomass itself. It is suggested that, rather than leaf age,
leaf relative biomass is the major factor determining DIBOA allocation in rye shoots. It is proposed that studies addressing
within-plant defense allocation should use chemical defense content as the currency, emphasizing the major factors driving
this process and its underlying mechanisms. Likewise, it is proposed that studies aiming at characterizing optimal patterns
of plant defense should use chemical defense concentration as the currency, and be accompanied by evaluations of the actual
resistance against herbivores of the plant parts analyzed, together with the effect on plant fitness.
Received 19 February 1999; accepted 28 April 1999. 相似文献
402.
An overview of the application of organic geochemistry to the analysis of organic matter on aerosol particles is presented
here. This organic matter is analyzed as solvent extractable bitumen/ lipids by gas chromatography-mass spectrometry. The
organic geochemical approach assesses the origin, the environmental history and the nature of secondary products of organic
matter by using the data derived from specific molecular analyses. Evaluations of production and fluxes, with cross-correlations
can thus be made by the application of the same separation and analytical procedures to samples from point source emissions
and the ambient atmosphere. This will be illustrated here with typical examples from the ambient atmosphere (aerosol particles)
and from emissions of biomass burning (smoke).
Organic matter in aerosols is derived from two major sources and is admixed depending on the geographic relief of the air
shed. These sources are biogenic detritus (e.g., plant wax, microbes, etc.) and anthropogenic particle emissions (e.g., oils,
soot, synthetics, etc.). Both biogenic detritus and some of the anthropogenic particle emissions contain organic materials
which have unique and distinguishable compound distribution patterns (C14-C40). Microbial and vascular plant lipids are the dominant biogenic residues and petroleum hydrocarbons, with lesser amounts
of the pyrogenic polynuclear aromatic hydrocarbons (PAH) and synthetics (e.g., chlorinated compounds), are the major anthropogenic
residues.
Biomass combustion is another important primary source of particles injected into the global atmosphere. It contributes many
trace substances which are reactants in atmospheric chemistry and soot paniculate matter with adsorbed biomarker compounds,
most of which are unknown chemical structures. The injection of natural product organic compounds into smoke occurs primarily
by direct volatilization/steam stripping and by thermal alteration based on combustion temperature. Although the molecular
composition of organic matter in smoke particles is highly variable, the molecular tracers are generally still source specific.
Retene has been utilized as a tracer for conifer smoke in urban aerosols, but is not always detectable. Dehydroabietic acid
is generally more concentrated in the atmosphere from the same emission sources. Degradation products from biopolymers (e.g.,
levoglucosan from cellulose) are also excellent tracers. An overview of the biomarker compositions of biomass smoke types
is presented here. Defining additional tracers of thermally-altered and directly-emitted natural products in smoke aids the
assessment of the organic matter type and input from biomass combustion to aerosols. The precursor to product approach of
compound characterization by organic geochemistry can be applied successfully to provide tracers for studying the chemistry
and dispersion of ambient aerosols and smoke plumes.
Presented at the 6th FECS Conference on Chemistry and the Environment, Atmospheric Chemistry and Air Pollution, August 26–28,
1998, Copenhagen. 相似文献
403.
混合堆肥过程中挥发性固体含量的层次效应及动态变化 总被引:7,自引:1,他引:6
城市污泥与猪粪混合堆肥表明:升温期和高温期堆体上部有机物降解的差异较大,降温期堆体下部各层有机物降解的差异较大,且堆体内挥发性固体(VS)含量已形成明显的层次效应,腐熟期堆体中部有机物降解的差异较大,堆体内VS含量的层次效应仍很明显;不同堆肥期堆体内VS含量的差异由大到小分别为:降温期≥腐熟期>高温期>升温期,不同部位有机物降解程度由大到小为:上部>中部>下部;VS含量随时间的变化满足一级反应动力学方程,城市污泥和猪粪混合堆肥过程中VS的降解速率约为0.3kg·d-1,VS含量降低了8.2%. 相似文献
404.
商业建筑室内VOCs污染及其控制策略 总被引:3,自引:3,他引:0
分析了商业建筑室内挥发性有机化合物 (VOCs)的来源 ,阐明了防治VOCs的方法并提出了控制VOCs对策。 相似文献
405.
406.
407.
408.
ISAPEC中知识自动获取的设计与实现 总被引:1,自引:0,他引:1
剖析了利用人工神经网络实现大气污染总量控制规划智能决策支持系统(ISAPEC)中知识自动获取的必要性,论述了ISAPEC中知识的自动获取的设计与实现过程,并用一实例进行了验证。结果表明用人工神经网络实现知识的自动获取与知识的人工获取相比既具有更高的时间效率,又能保证更高的质量。 相似文献
409.
冬季降雪过程对城市大气气态汞污染的影响 总被引:3,自引:0,他引:3
2009年降雪和非降雪期间对北京西北城区的气态总汞浓度进行了连续采样,比较了降雪期间、非降雪期间的气态总汞浓度日变化过程;降雪期间气态总汞浓度的降低和恢复过程。结果表明,降雪和非降雪期间大气气态总汞浓度的日均值有显著差异,降雪期间气态总汞的平均浓度为5.64ng·m^-3,非降雪期间的平均浓度为7.43ng·m^-3,前者约为后者的70%。降雪后约7h气态总汞浓度恢复到降雪前水平。研究中分析了气象因素(气压、风速、阵风速度、气温和相对湿度)对于气态总汞浓度的影响,结果表明:降雪期间主要受到风速(r=-0.527)和阵风速度(r=-0.574)的影响;非降雪期间主要受到风速(r=-0.691),阵风速度(r=-0.726)和相对湿度(r=0.692)的影响,并且相对湿度的影响与风速的影响相近。降雪和非降雪期间气态总汞的日变化有所差异:非降雪期间气态总汞浓度在午夜和清晨较高,日变化趋势与相对湿度一致;降雪期间气态总汞的日变化没有明显规律。 相似文献
410.
松花江沉积物汞的新变化:分布、演化与现状及潜在生态风险评估 总被引:2,自引:0,他引:2
分析了第二松花江中下游和松花江干流表层沉积物中总汞的含量水平和分布规律,同期采集了牡丹江、黑龙江沉积物作为对照,并采用地累积指数法以及潜在生态风险指数法,初步评价了松花江沉积物中汞的污染状况和潜在的生态风险.结果表明,松花江10个断面沉积物总汞含量范围0.029~1.317 mg·kg~(-1),均值0.183 mg·kg~(-1).第二松花江3个典型断面沉积物总汞含量均显著高于松花江干流的7个典型断面(P0.05).地累积指数(Igeo)及潜在生态风险指数(Er)表明第二松花江3个典型断面沉积物汞污染程度为偏中度至重度污染,存在高度生态风险;松花江干流7个典型断面为轻度污染,具有较高生态风险.近10年松花江沉积物汞含量变化及空间分布结果显示,现阶段第二松花江沉积物汞含量有所下降,但松花江干流个别江段沉积物汞含量有所上升,应引起重视. 相似文献