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111.
采用2019年12月天山北部石河子(目标区)和昌吉(对比区)地区的空气质量指数(AQI)资料,对石河子人工改善空气质量的效果进行了分析,提供了基于人工影响天气技术消减AQI的证据.试验为期31 d,其中在13个试验日中进行了飞机作业.采用区域回归方法,建立两地AQI回归方程,计算目标区在未进行人工作业时的AQI期望值,将其与实测值对比,统计分析作业效果.试验期间,目标区与对比区AQI日变化呈高度的相关性,数据样本相关性经t检验满足要求,经F检验可信程度达到99%,显著性非常高.此外,基于两个随机试验验证统计结果的可靠性.结果表明,在石河子开展人工消雾作业期,AQI指数相较于不进行作业时平均减小52,相对减小28.1%.进一步进行90%置信区间估算结果表明,开展作业后目标区AQI平均值减小了23.71,相对减小15.1%.通过两个蒙特卡洛随机试验表明,人工作业对AQI产生的作用超过了试验期间大部分情况下两地AQI自然变化的区别,因此,统计结果有较高的可信度,在样本数足够时,人工作业的作用可以从复杂的自然变化中体现出来.但是,对于单日内的污染过程,其自然变化十分复杂,人工作业的作用难以进行定量化计算. 相似文献
112.
温度及氨氮负荷对曝气生物滤池硝化作用的影响 总被引:10,自引:0,他引:10
采用火山岩为载体填料的曝气生物滤池(BAF)进行实验室小试,研究供氧受限条件下,BAF的硝化反硝化运行特性及温度(10℃~30℃)和氨氮负荷变化(0.069~1.32kg/(m3·d))时对硝化作用的影响。当氨氮负荷为1.10kg/(m3·d),供氧受限时,温度从20℃升高到30℃,反应器的硝化效率仅增加10%左右,表明BAF中硝化作用主要受溶质的传递、扩散速率控制而不是受与温度有关的动力学参数控制;然而,相同负荷下,当温度控制在15℃时,硝化效率明显降低,说明20℃是一临界点。此外,20℃时随氨氮负荷的增加(从0.825kg/(m3·d)提升到1.32kg/(m3·d)),氨氮去除率略有下降,但在第3个取样口处却发现有亚硝酸盐氮累积现象,这是因为在供氧受限时,随负荷的增加,溶解氧相对短缺发生了部分硝化作用。 相似文献
113.
Brett G. Dickson Christine M. Albano Ranjan Anantharaman Paul Beier Joe Fargione Tabitha A. Graves Miranda E. Gray Kimberly R. Hall Josh J. Lawler Paul B. Leonard Caitlin E. Littlefield Meredith L. McClure John Novembre Carrie A. Schloss Nathan H. Schumaker Viral B. Shah David M. Theobald 《Conservation biology》2019,33(2):239-249
Conservation practitioners have long recognized ecological connectivity as a global priority for preserving biodiversity and ecosystem function. In the early years of conservation science, ecologists extended principles of island biogeography to assess connectivity based on source patch proximity and other metrics derived from binary maps of habitat. From 2006 to 2008, the late Brad McRae introduced circuit theory as an alternative approach to model gene flow and the dispersal or movement routes of organisms. He posited concepts and metrics from electrical circuit theory as a robust way to quantify movement across multiple possible paths in a landscape, not just a single least-cost path or corridor. Circuit theory offers many theoretical, conceptual, and practical linkages to conservation science. We reviewed 459 recent studies citing circuit theory or the open-source software Circuitscape. We focused on applications of circuit theory to the science and practice of connectivity conservation, including topics in landscape and population genetics, movement and dispersal paths of organisms, anthropogenic barriers to connectivity, fire behavior, water flow, and ecosystem services. Circuit theory is likely to have an effect on conservation science and practitioners through improved insights into landscape dynamics, animal movement, and habitat-use studies and through the development of new software tools for data analysis and visualization. The influence of circuit theory on conservation comes from the theoretical basis and elegance of the approach and the powerful collaborations and active user community that have emerged. Circuit theory provides a springboard for ecological understanding and will remain an important conservation tool for researchers and practitioners around the globe. 相似文献
114.
George R. Robinson Steven N. Handel Victoria R. Schmalhofer 《Environmental management》1992,16(2):265-271
With the advent of modern sanitary landfill closure techniques, the opportunity exists for transforming municipal landfills
into urban woodlands. While costs of fullscale reforestation are generally prohibitive, a modest planting of clusters of trees
and shrubs could initiate or accelerate population expansions and natural plant succession from open field to diverse forest.
However, among woody species that have been screened for use on landfills, these ecological potentials have not yet been investigated.
We examined a 14-yr-old landfill plantation in New Jersey, USA, established to test tolerance of 19 species of trees and shrubs
to landfill environments. We measured survivorship, reproduction, and recruitment within and around the experimental installation.
Half of the original 190 plants were present, although survival and growth rates varied widely among species. An additional
752 trees and shrubs had colonized the plantation and its perimeter, as well as 2955 stems of vines. However, the great majority
(>95%) of woody plants that had colonized were not progeny of the planted cohort, but instead belonged to 18 invading species,
mostly native, bird-dispersed, and associated with intermediate stages of secondary plant succession. Based on this evidence,
we recommend that several ecological criteria be applied to choices of woody species for the restoration of municipal landfills
and similar degraded sites, in order to maximize rapid and economical establishment of diverse, productive woodlands. 相似文献
115.
袁丽云 《中国安全科学学报》1992,(1)
国际放射防护委员会(ICRP)是非官方国际学术权威团体。目前世界各国制订自己的辐射防护标准都参考ICRP的建议。ICRP自1928年组建以来,关于辐射防护标准的总建议发布了四次。即第1、2号出版物(1958年,1959年),第6、9号出版物(1962年,1965年),第26号出版物(1977年),第60号出版物(1990年)。本文概述了ICRP历次制订辐射防护标准的原则和依据。ICRP的辐射防护指导思想变化代表了不同历史时期放射生物学、辐射剂量学及与辐射防护有关的其他学科的国际水平。ICRP研究辐射防护标准的历史经验可供其他行业劳动保护参考。 相似文献
116.
John F. Elder Richard H. Fuller Alexander J. Home 《Journal of the American Water Resources Association》1979,15(6):1608-1617
ABSTRACT: Some physical and chemical characteristics of Lake Perris, a new southern California reservoir, were investigated with regard to their influence on phytoplankton biomass and community structure. The concentration of three major nutrients – nitrogen, phosphorus, and iron – was approximately equivalent to the demand ratio of fresh water plants. Large increases in iron and phosphorus concentrations in late summer due to releases from sediments, however, tended to shift the balance toward a nitrogen-limited situation. Nitrogen limitation favored nitrogen-fixing blue-green algae, and after a decline of competing algae during the summer, the blue-green population bloomed in September. Series of measurements taken over one-day periods during summer stratification showed that some iron, phosphorus, and manganese from the hypolimnion could move upward, corresponding to diel shifts in the thermocline depth. Vertical transport of nutrients could thus occur long before complete lake mixing and could support summer/fall algal blooms. 相似文献
117.
This paper discusses the major developments in regional policy in the Netherlands by relating the policy instruments and locations to stages in the socio‐economic and political development of the Netherlands from 1945 onwards. It concludes that, at present, the spatial dimension of economic policy has lost importance, and the support for peripheral regions is restricted. 相似文献
118.
The effect of local ant species on the dispersal success of a myrmecochorous plant, Helleborus foetidus, was analyzed in two populations of the Iberian Peninsula (Caurel and Cazorla, respectively). The contribution of the various
local ant species to dispersal was very unequal. While 5 and 19 ant taxa visited the plants of Caurel and Cazorla, respectively,
most removal activity (67 and 80%) was performed by two species only (Formica lugubris and Camponotus cruentatus, respectively). Visits by dispersers were also unequally distributed between neighboring plants. While some plants were always
visited during the period of seed release, others were never visited. A regression model indicated that this pattern might
be explained by two plant traits: ants preferred to visit plants that released more seeds and whose elaiosomes were richer
in oleic acid. Although it has long been known that this compound triggers removal by ants, it is the first demonstration
that quantitative variations in elaiosome traits contribute to variation in dispersal success. Finally, other variables being
equal, morphological traits (seed size, elaiosome size, and elaiosome/seed size ratio) did not affect ant behavior. Although
myrmecochory has long been considered a diffuse interaction, our results support the idea that, at local scale, a limited
number of ant species may be decisive to its evolution. 相似文献
119.
Dominic Muenzel Kay Critchell Courtney Cox Stuart J. Campbell Raymond Jakub Iliana Chollett Nils Krueck Daniel Holstein Eric A. Treml Maria Beger 《Conservation biology》2023,37(2):e14008
Larval dispersal is an important component of marine reserve networks. Two conceptually different approaches to incorporate dispersal connectivity into spatial planning of these networks exist, and it is an open question as to when either is most appropriate. Candidate reserve sites can be selected individually based on local properties of connectivity or on a spatial dependency-based approach of selecting clusters of strongly connected habitat patches. The first acts on individual sites, whereas the second acts on linked pairs of sites. We used a combination of larval dispersal simulations representing different seascapes and case studies of biophysical larval dispersal models in the Coral Triangle region and the province of Southeast Sulawesi, Indonesia, to compare the performance of these 2 methods in the spatial planning software Marxan. We explored the reserve design performance implications of different dispersal distances and patterns based on the equilibrium settlement of larvae in protected and unprotected areas. We further assessed different assumptions about metapopulation contributions from unprotected areas, including the case of 100% depletion and more moderate scenarios. The spatial dependency method was suitable when dispersal was limited, a high proportion of the area of interest was substantially degraded, or the target amount of habitat protected was low. Conversely, when subpopulations were well connected, the 100% depletion was relaxed, or more habitat was protected, protecting individual sites with high scores in metrics of connectivity was a better strategy. Spatial dependency methods generally produced more spatially clustered solutions with more benefits inside than outside reserves compared with site-based methods. Therefore, spatial dependency methods potentially provide better results for ecological persistence objectives over enhancing fisheries objectives, and vice versa. Different spatial prioritization methods of using connectivity are appropriate for different contexts, depending on dispersal characteristics, unprotected area contributions, habitat protection targets, and specific management objectives. Comparación entre los métodos de priorización de la conservación espacial con sitio y la conectividad espacial basada en la dependencia 相似文献
120.
Linked river basin and coastal water models were applied to analyse the effects of an optimal nitrogen management scenario
in the Oder/Odra river basin on water quality in the Oder (Szczecin) Lagoon and the Pomeranian Bay (Baltic Sea). This scenario
would reduce nitrogen loads into the coastal waters by about 35%, a level which is similar to the load of the late 1960’s.
During summer the primary production and algae biomass in the Oder estuary is limited by nitrogen, which makes a nitrogen
management reasonable. The comparison of the late 1960’s and the mid 1990’s shows that an optimal nitrogen management has
positive effects on coastal water quality and algae biomass. However, this realistic nitrogen reduction scenario would not
ensure a good coastal water quality according to the European Water Framework Directive. A good water quality in the river
will not be sufficient to ensure a good water quality in the lagoon. Nitrogen load reductions bear the risk of increased potentially
toxic, blue-green algae blooms, especially in the Baltic coastal sea. However, to reach water quality improvements in lagoons
and inner coastal waters, nitrogen cuts are necessary. A mere focus on phosphorus is not sufficient. 相似文献