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331.
Many studies explore the feasibility of co-existence between genetically modified (GM) and conventional (non-GM) crops. An important research topic in these studies is the process of outcrossing, i.e., the process of gene flow via pollen flow from GM to non-GM crops. In this paper, we address a new modelling approach to define the environmentally driven processes of outcrossing for maize from existing empirical datasets. In particular, we use equation discovery methodology that combines background knowledge and empirical data from several studies. We induce models that predict the degree of outcrossing rate between the donor (GM) and the recipient (non-GM) maize field from the distance between the fields and the local wind characteristics (speed, direction and duration). This results in highly accurate models, for which both variables (distance and wind) are essential and of roughly equal importance. 相似文献
332.
针对大气污染问题,2013年国务院颁布了《大气污染防治行动计划》,从更高层次上实施国家及区域层面的大气污染协同治理战略。区域联合防控及协同治理是当前情况下治理好大气污染的必然选择,但是尚未形成完整的体系。收集整理了100篇大气污染协同治理相关政策文件,构建了政策工具量化的二维分析框架,探讨了当前对大气污染协同治理的政策工具使用情况,并针对性地提出了强化命令型政策工具、弥补能力型建设工具、完善奖惩福利机制、完善监督监测预警系统等一系列政策建议。 相似文献
333.
Yueqi Jiang Jia Xing Shuxiao Wang Xing Chang Shuchang Liu Aijun Shi Baoxian Liu Shovan Kumar Sahu 《Frontiers of Environmental Science & Engineering》2021,15(5):88
334.
Fluorescence excitation-emission matrix spectroscopy (EEMs) combined with fluorescence regional integration (FRI) analysis was used to investigate the composition and transformation of humic acid (HA) and fulvic acid (FA) from landfill. The EEMs of HAs at different landfill ages were characterized by two typical fluorescence chromophores with Ex/Em pairs at Ex = 420-470 nm/Em = 490-530 nm and Ex = 345-375 nm/Em = 450-465 nm. EEMs of FA were featured by other two distinctly different fluorophores with Ex/Em pairs at Ex = 315-335 nm/Em = 420-440 nm and Ex = 255-275 nm/Em = 425-455 nm. The results show that HA extracted from the refuse disposed in the year of 1989 was formed by connecting small-condensed aromatic structures with protein-like chains. Compared with HA extracted from the refuse disposed in the year of 1992, HA extracted from the refuse of 1996 had a higher fluorescence intensity and lower r(B,A) (the ratio of the fluorescence intensities of peak B and peak A) value. It contained low molar mass components, low aromatic condensation degree, and more easily oxidized substituents. This indicates that the landfill time strongly affects the EEMs characteristics of HA, and that the humification degree of HA increases with the landfill time. A red shift to a longer wavelength region and an increase of fluorescence intensity were observed when the concentration of HA was increased, suggesting that concentration had a great influence on the fluorescence characteristics of HAs. pH (2-12) also had significant effects on the fluorescence intensity, although it exerted no effect on the peak position of fluorescence of HA and FA. The results of FRI show that increasing concentration lead to more interactions among various structure components and that small molecular weight units tend to aggregate or be masked into more complicated and larger structures. The pH influence on the fluorescence intensity of HA seems mainly through molecular configuration, while the fluorescence intensity change with pH may be due to various substituents of FA. 相似文献
335.
易燃、易爆(有毒)重大危险源(罐区)泄漏物扩散模型及数值模拟 总被引:6,自引:0,他引:6
在研究易燃、易爆、有毒的重大危险源和泄漏物扩散模型的基础上,建立了易燃、易爆、有毒物三维数值模拟程序,得到了复杂地形条件下关键点的有害物浓度历史和有害物的时空分布 相似文献
336.
区域农业生态环境质量综合评价方法与模型研究 总被引:24,自引:0,他引:24
为了客观准确的评价区域农业生态环境质量,引入灰色系统理论中的关联度分析法,提出了区域生态环境质量的多级模糊综合评价——灰色关联优势分析复合模型,并以安徽省芜湖市区域农业生态环境质量的综合评价为例,根据芜湖市区域农业生态环境调查与监测资料,进行了实例研究。结果表明:安徽省芜湖市区域农业生态环境已经受到了明显的污染,并且各区域污染水平具有一定的差异;芜湖市区域农业生态环境质量优劣的关联序依次为:南陵县、芜湖县、繁昌县和城市郊区。 相似文献
337.
基于2015—2020年近地面NO2质量浓度数据和2019年哨兵-5P TROPOMI卫星探测的对流层NO2柱浓度数据,采用相关性分析、趋势分析等方法探究新疆天山北坡经济带6个城市NO2污染的时空分布特征。结果表明:(1)从年均值来看,天山北坡经济带NO2质量浓度总体呈下降趋势,尤其2018—2020年下降明显。其中乌鲁木齐NO2质量浓度值最高、博乐最低。(2)从季度均值和月均值来看,各城市NO2质量浓度季节变化明显,其中夏季最低、冬季最高;月均值呈“中间低、两头高”的变化特征。(3)从日均值来看,各城市NO2质量浓度大多呈现双峰型分布,分别出现在早上10:00和晚上23:00。(4)从空间分布来看,NO2柱浓度高值区多分布在人口密集和工业发达的城市地区,尤其是乌鲁木齐、昌吉、五家渠、石河子污染最为严重。 相似文献
338.
侯天兰 《环境监测管理与技术》2004,16(5):40-41
应用统计分析方法,对湖南省湘潭市2001年城区环境噪声网格布点及其监测结果总体进行了区域环境噪声监测点的最优集合,并通过网格布点法与优化布点法对该市2002年和2003年环境噪声监测结果进行了对比检验,结果表明,两种方法监测的等效声级和标准差平均值均<1dB(A),监测结果之间无显著性差异。 相似文献
339.
The root uptake of lead (Pb) by trees and the transfer of Pb by leaf litter deposition to the forest floor were investigated through a pot experiment with Norway spruce. Natural Pb and radio isotopic lead (210Pb) were determined in needles and twigs and in the pot soil spiked with 210Pb. Calculations of the specific activity in plant material and in the supporting pot soil showed that less than 2% of the Pb content of needles and twigs originates from root uptake and approximately 98% are deposited from the atmosphere. Atmospheric Pb has declined by a factor of 7 from 1980 to 2007 but is still a major pathway of Pb to vegetation and topsoils. The conclusion from the experiment is that the internal circulation of Pb through root uptake, translocation and litterfall, gives an insignificant input of Pb to the forest floor compared to atmospheric deposition. 相似文献
340.
K.G. Andersson T. Mikkelsen P. Astrup S. Thykier-Nielsen L.H. Jacobsen S.C. Hoe S.P. Nielsen 《Journal of environmental radioactivity》2009,100(12):1005-1011
The ARGOS decision support system is currently being extended to enable estimation of the consequences of terror attacks involving chemical, biological, nuclear and radiological substances. This paper presents elements of the framework that will be applied in ARGOS to calculate the dose contributions from contaminants dispersed in the atmosphere after a ‘dirty bomb’ explosion. Conceptual methodologies are presented which describe the various dose components on the basis of knowledge of time-integrated contaminant air concentrations. Also the aerosolisation and atmospheric dispersion in a city of different types of conceivable contaminants from a ‘dirty bomb’ are discussed. 相似文献