排序方式: 共有38条查询结果,搜索用时 123 毫秒
1.
Lara A. Roman Tenley M. Conway Theodore S. Eisenman Andrew K. Koeser Camilo Ordez Barona Dexter H. Locke G. Darrel Jenerette Johan
stberg Jess Vogt 《Ambio》2021,50(3):615
The provision of ecosystem services is a prominent rationale for urban greening, and there is a prevailing mantra that ‘trees are good’. However, understanding how urban trees contribute to sustainability must also consider disservices. In this perspective article, we discuss recent research on ecosystem disservices of urban trees, including infrastructure conflicts, health and safety impacts, aesthetic issues, and environmentally detrimental consequences, as well as management costs related to ecological disturbances and risk management. We also discuss tradeoffs regarding species selection and local conservation concerns, as well as the central role of human perception in the interpretation of ecosystem services and disservices, particularly the uncritical assertion that ‘everybody loves trees’. Urban forestry decision-making that fails to account for disservices can have unintended negative consequences for communities. Further research is needed regarding life cycle assessments, stakeholder decision-making, return-on-investment, and framings of services and disservices in urban forestry. 相似文献
2.
为分析南昌市大气降水离子来源和源区,对南昌市2016年4—9月大气降水样品主要阴阳离子的组成进行了测定分析,并运用PMF(正定矩阵因子分解)模型分析来源和TrajStat软件模拟后向轨迹.结果表明:NH4+和Ca2+是南昌市大气降水中的主要阳离子,加权平均浓度为65.3和23.9 μmol/L,分别占阳离子总量的57%和21%;SO42-和NO3-是主要阴离子,加权平均浓度为60.4和25.3 μmol/L,分别占阴离子总量的56%和23%.c(NH4+)、c(Ca2+)、c(K+)、c(Mg2+)、c(Na+)、c(Cl-)、c(NO3-)之间均存在着较为显著的相关性,说明它们之间可能有相似的来源或形成化合物共同存在.结合PMF模型分析结果表明,Na+、Cl-很明显受到了海盐的影响,也部分受土壤和二次污染影响;K+、Mg2+、Ca2+大部分来自于土壤,海盐、二次污染也贡献了一部分的K+;SO42-、NH4+和NO3-是组成大气二次颗粒物的主要成分,主要由二次污染源贡献;煤燃烧贡献了主要的F-和部分SO42-.后向轨迹模型分析表明,南昌市大气降水主要受局地降雨气团影响,5月、8月、9月受陆源及人为影响较大,海源性离子经过内陆上空时被稀释或沉降,导致6月、7月来自于海洋上空的降雨气团对南昌影响不大.研究显示,SO42-对南昌市大气降水的影响逐渐增大导致降雨类型逐渐由混合型向硫酸型转化,人为影响是造成大气污染的主要原因. 相似文献
3.
A swarm of honeybees provides a striking example of an animal group performing a synchronized departure for a new location;
in this case, thousands of bees taking off at once to fly to a new home. However, the means by which this is achieved remain
unclear. Shortly before takeoff, one hears a crescendo of a high-pitched mechanical signal—worker piping—so we explored the
role of this signal in coordinating a swarm’s mass takeoff. Specifically, we examined whether exclusively nest site scouts
produce the worker piping signal or whether it is produced in a relay or chain reaction fashion. We found no evidence that
bees other than the scouts that have visited the swarm’s chosen nest site produce piping signals. This absence of relay communication
in piping suggests that it is a signal that only primes swarms for takeoff and that the release of takeoff is triggered by
some other signal or cue; perhaps the takeoff of bees on the swarm periphery as they reach flight temperature in response
to piping. 相似文献
4.
Keeping the blood flowing—plasminogen activator genes and feeding behavior in vampire bats 总被引:1,自引:0,他引:1
Tellgren-Roth A Dittmar K Massey SE Kemi C Tellgren-Roth C Savolainen P Lyons LA Liberles DA 《Die Naturwissenschaften》2009,96(1):39-47
The blood feeding vampire bats emerged from New World leaf-nosed bats that fed on fruit and insects. Plasminogen activator,
a serine protease that regulates blood coagulation, is known to be expressed in the saliva of Desmodus rotundus (common vampire bat) and is thought to be a key enzyme for the emergence of blood feeding in vampire bats. To better understand
the evolution of this biological function, we studied the plasminogen activator (PA) genes from all vampire bat species in
light of their feeding transition to bird and subsequently mammalian blood. We include the rare species Diphylla ecaudata and Diaemus youngi, where plasminogen activator had not previously been studied and demonstrate that PA gene duplication observed in Desmodus is not essential to the vampire phenotype, but relates to the emergence of predominant mammalian blood feeding in this species.
Plasminogen activator has evolved through gene duplication, domain loss, and sequence evolution leading to change in fibrin-specificity
and susceptibility to plasminogen activator inhibitor-1. Before undertaking this study, only the four plasminogen activator
isoforms from Desmodus were known. The evolution of vampire bat plasminogen activators can now be linked phylogenetically to the transition in feeding
behavior among vampire bat species from bird to mammalian blood.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
赵淑珍 《中国特种设备安全》2013,(10):10-11
分析了垃圾发电锅炉入料口的正压释放问题,设计的风幕技术保证了此类循环流化床锅炉的安全运行,风幕技术改造结构设计合理,实用性强,值得在同类行业中推广应用。 相似文献
6.
Ventral polarization vision in tabanids: horseflies and deerflies (Diptera: Tabanidae) are attracted to horizontally polarized light 总被引:1,自引:0,他引:1
Adult tabanid flies (horseflies and deerflies) are terrestrial and lay their eggs onto marsh plants near bodies of fresh water
because the larvae develop in water or mud. To know how tabanids locate their host animals, terrestrial rendezvous sites and
egg-laying places would be very useful for control measures against them, because the hematophagous females are primary/secondary
vectors of some severe animal/human diseases/parasites. Thus, in choice experiments performed in the field we studied the
behavior of tabanids governed by linearly polarized light. We present here evidence for positive polarotaxis, i.e., attraction
to horizontally polarized light stimulating the ventral eye region, in both males and females of 27 tabanid species. The novelty
of our findings is that positive polarotaxis has been described earlier only in connection with the water detection of some
aquatic insects ovipositing directly into water. A further particularity of our discovery is that in the order Diptera and
among blood-sucking insects the studied tabanids are the first known species possessing ventral polarization vision and definite
polarization-sensitive behavior with known functions. The polarotaxis in tabanid flies makes it possible to develop new optically
luring traps being more efficient than the existing ones based on the attraction of tabanids by the intensity and/or color
of reflected light. 相似文献
7.
The release of root exudates (REs) provides an important source of soil organic carbon. This work revealed the molecular composition of REs of different plant species including alfalfa (Medicago sativa L.), bean (Phaseolus vulgaris L.), barley (Hordeum vulgare L.), maize (Zea mays), wheat (Triticum aestivum L.), ryegrass (Lolium perenne L.) and pumpkin (Cucurbita maxima) using electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The combination of positive ion mode (+ESI) and negative ion mode (-ESI) increased the number of the molecules detected by ESI FT-ICR MS, and a total of 8758 molecules were identified across all the samples. In detail, lipids and proteins and unsaturated hydrocarbons were more easily detected in +ESI mode, while aromatic compounds with high O/C were readily ionized in -ESI mode, and only 38% of the total assigned formulas were shared by -ESI and +ESI modes. Multivariate statistical analysis of the formulas indicated that the close related plants species secreted REs with similar molecular components. Moreover, the unsaturation degree and nitrogen content were the two key parameters able to distinguish the similarities and differences of molecular components of REs between plant species. The results provided a feasible analysis method for characterization of the molecular components of REs and for the first time characterized the molecular components of REs of a variety of plant species using ESI FT-ICR MS. 相似文献
8.
Li Li Wei Lai Jinguo Pu Hengqin Mo Dongjue Dai Guilin Wu Shihuai Deng 《环境科学学报(英文版)》2018,30(7):281-293
PM_(2.5) aerosol samples were collected over 12 hr and 24 hr intervals in an inland background area, Gongga Mountain National Nature Reserve(hereafter shortened to Gongga), during the summer of 2011. Polar organic tracers, inorganic ions and meteorological data were measured. The purpose of this work was to investigate the variation patterns, formation and sources of the secondary organic aerosol tracers in the studied atmosphere. The average concentrations of isoprene oxidation products, α-pinene oxidation products, β-caryophyllinic acid, sugars, sugar alcohols and anhydrosugars were 88.6 ± 106.1, 3.6 ± 5.7,0.13 ± 0.30, 13.6 ± 13.1, 31.9 ± 31.4 and 14.8 ± 10.7 ng/m3 respectively in all aerosol samples.The aged α-pinene second organic aerosol(SOA) tracers(i.e., 3-hydroxyglutraric acid(3 HGA), 3-hydroxy-2,2-dimethylglutaric acid(HDMGA), 3-acetylpentandioic acid(APDA) and 3-methyl-1,2,3-butanetricarboxylic acid(MBTCA)) correlated significantly with each other in the 24 hr PM2.5 aerosol samples, indicating that OH· is the major factor controlling the formation of these α-pinene SOA tracers. Using the positive matrix factorization(PMF) model and the tracer-based source apportionment method, we calculated that isoprene oxidation products, α-pinene oxidation products, sesquiterpene oxidation products, biomass burning, fungi spores and anthropogenic SOA accounted for 21.9% ± 5.5%, 8.4% ± 2.1%, 3.0% ± 0.7%, 5.2% ± 5.3%, 5.0% ± 6.2% and 31.4% ± 7.8% of organic carbon respectively during the sampling period. 相似文献
9.
Xiaochen Wu Xiaocong Cao Qiao Xing Shanhu Hu Wenshuai Xu Rongfu Xie Aidan Xian Wenjing Xie Zhaohui Yang 《环境科学学报(英文版)》2023,123(1):417-429
Based on one-year observation, the concentration, sources, and potential source areas of volatile organic compounds (VOCs) were comprehensively analyzed to investigate the pollution characteristics of ambient VOCs in Haikou, China. The results showed that the annual average concentration of total VOCs (TVOCs) was 11.4 ppbV, and the composition was dominated by alkanes (8.2 ppbV, 71.4%) and alkenes (1.3 ppbV, 20.5%). The diurnal variation in the concentration of dominant VOC species showed a distinct bimodal distribution with peaks in the morning and evening. The greatest contribution to ozone formation potential (OFP) was made by alkenes (51.6%), followed by alkanes (27.2%). The concentrations of VOCs and nitrogen dioxide (NO2) in spring and summer were low, and it was difficult to generate high ozone (O3) concentrations through photochemical reactions. The significant increase in O3 concentrations in autumn and winter was mainly related to the transmission of pollutants from the northeast. Traffic sources (40.1%), industrial sources (19.4%), combustion sources (18.6%), solvent usage sources (15.5%) and plant sources (6.4%) were identified as major sources of VOCs through the positive matrix factorization (PMF) model. The southeastern coastal areas of China were identified as major potential source areas of VOCs through the potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) models. Overall, the concentration of ambient VOCs in Haikou was strongly influenced by traffic sources and long-distance transport, and the control of VOCs emitted from vehicles should be strengthened to reduce the active species of ambient VOCs in Haikou, thereby reducing the generation of O3. 相似文献
10.
Positive polarotaxis in a mayfly that never leaves the water surface: polarotactic water detection in Palingenia longicauda (Ephemeroptera) 总被引:3,自引:2,他引:1
Tisza mayflies, Palingenia longicauda (Olivier 1791), swarm exclusively over the river Tisza (from which the name of the mayfly was derived). This river is bordered
by a high vertical wall of trees and bushes, which hinder P. longicauda to move away horizontally from the water. During swarming, Tisza mayflies fly immediately above the river in such a way that
their cerci touch the water frequently or sweep its surface. This continuous close connection with water and the vertical
wall of the shore and riparian vegetation result in that Tisza mayflies never leave the water surface; consequently, they
need not search for water. Several Ephemeroptera species move away far from water and return to it guided by the horizontal
polarization of water-reflected light. To reveal whether also P. longicauda is or is not polarotactic, we performed a field experiment during the very short swarming period of Tisza mayflies. We show
here that also P. longicauda has positive polarotaxis, which, however, can be observed only under unnatural conditions, when the animals are displaced
from the water and then released above artificial test surfaces. P. longicauda is the first species in which polarotactic water detection is demonstrated albeit it never leaves the water surface, and
thus, a polarotactic water detection seems unnecessary for it. The polarotactic behaviour of Tisza mayflies explains the earlier
observation that these insects swarm above wet asphalt roads running next to river Tisza. 相似文献