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501.
Liang Yuan Yan Yin Hui Xiao Jian Hao Kui Chen Xingna Yu Xiaoling Zhang 《环境科学学报(英文版)》2019,31(9):21-38
In-situ measurements of aerosol optical properties were conducted at Mt. Huang from September 23 to October 28, 2012. Low averages of 82.2, 10.9, and 14.1 Mm~(-1) for scattering coefficient(σ_(sp, neph, 550)), hemispheric backscattering coefficient(σ_(hbsp, neph, 550)), and absorption coefficient(σ_(ap, 550)), respectively, were obtained. Atmospheric aging process resulted in the increase of σap, 550 but the decrease of the single scattering albedo(ω_(550)) at constant aerosol concentration. However, the proportion of non-light-absorbing components(non-BCs) was getting higher during the aging process, resulting in the increase of aerosol diameter, which also contributed to relatively higher σ_(sp, neph, 550) and ω_(550). Diurnal cycles of σ_(sp, neph, 550) and σ_(ap, 550) with high values in the morning and low values in the afternoon were observed closely related to the development of the planetary boundary layer and the mountain-valley breeze. BC mixing state, represented by the volume fraction of externally mixed BC to total BC(r), was retrieved by using the modified Mie model.The results showed r reduced from about 70% to 50% when the externally mixed non-BCs were considered. The periodical change and different diurnal patterns of r were due to the atmospheric aging and different air sources under different synoptic systems. Local biomass burning emissions were also one of the influencing factors on r. Aerosol radiative forcing for different mixing state were evaluated by a "two-layer-single-wavelength" model,showing the cooling effect of aerosols weakened with BC mixing state changing from external to core-shell mixture. 相似文献
502.
Baofa Yin Chen Gu Yi Lu Ibrahim M. Hegab Shengmei Yang Aiqin Wang Wanhong Wei 《Die Naturwissenschaften》2017,104(7-8):64
Prey species show specific adaptations that allow recognition, avoidance, and defense against predators. This study was undertaken to investigate the processing of a chronic, life-threatening stimulus to Norway rats (Rattus norvegicus). One hundred forty-four Norway rats were tested by repeated presentation of cat urine for 1 h at different days in a defensive withdrawal apparatus. Rats exposed to urine for short periods showed significantly larger defensive behavioral and medial hypothalamic c-fos messenger RNA (mRNA) responses than other groups. These defensive responses habituated shortly after the presentation of cat urine. Serum levels of adrenocorticotropic hormone and corticosterone increased significantly when animals were repeatedly exposed to cat urine. However, the hormonal responses took longer to habituate than the behavioral and molecular responses did. We conclude that the behavioral and c-fos mRNA responses are “primed” for habituation to repeated exposures to cat urine, while the hormonal responses show “resistance.” The results support our hypothesis that the strongest anti-predator responses at three levels would occur during short-term exposure to cat urine and that these responses would subsequently disappear on prolonged exposure. This study assists understanding the way in which the different levels of defensive responses are integrated and react during chronic stress. 相似文献
503.
Surface junctions between Bi OBr and BiVO_4 were synthesized. The BiOBr/BiVO_4 with 1 wt.%of Bi OBr exhibited the highest photocatalytic activity in the degradation of Rh B under visible-light irradiation. It was found that the highly efficient adsorption of Rh B molecules via the electrostatic attraction between Br-and cationic \N(Et)_2 group played a key role for the high photocatalytic activities of BiOBr/BiVO_4. This efficient adsorption promoted the N-deethylation of Rh B and thus accelerated the photocatalytic degradation of Rh B.Moreover, the metal-to-metal charge transfer(MMCT) mechanism was proposed, which revealed the concrete path paved with Bi–O–Bi chains for the carrier migration in BiOBr/BiVO_4. The interaction between photoexcited Rh B* and the Bi~(3+) in BiVO_4 provided the driving force for the migration of photo-generated carriers along the Bi–O–Bi chains. This work has not only demonstrated the important role of efficient adsorption in the photocatalytic degradation of organic contaminants, but also developed a facile strategy to improve the efficiency of photocatalysts. 相似文献
504.
Since the launch of its first satellite in 1972, the Landsat program has operated continuously for more than forty years. A large data archive collected by the Landsat program sig-nificantly benefits both the academic community and society. Thermal imagery from Landsat sensors, provided with relatively high spatial resolution, is suitable for monitoring urban thermal environment. Growing use of Landsat data in monitoring urban thermal environment is demonstrated by increasing publications on this subject, especially over the last decade. Urban thermal environment is usually delineated by land surface temperature (LST). However, the quantitative and accurate estimation of LST from Landsat data is still a challenge, especially for urban areas. This paper will discuss the main challenges for urban LST retrieval, including urban surface emissivity, atmospheric correction, radiometric calibration, and validation. In addition, we will discuss general challenges confronting the continuity of quantitative applications of Landsat observations. These challenges arise mainly from the scan line corrector failure of the Landsat 7 ETM + and channel differences among sensors. Based on these investigations, the concerns are to: (1) show general users the limitation and possible uncertainty of the retrieved urban LST from the single thermal channel of Landsat sensors; (2) emphasize efforts which should be done for the quantitative applications of Landsat data; and (3) understand the potential challenges for the continuity of Landsat observation (i.e., thermal infrared) for global change monitoring, while several climate data record programs being in progress. 相似文献
505.
在桂林市2013年机动车保有量数据的基础上,参考清华大学开发的中国多尺度大气污染排放清单模型(MEIC)中的排放因子,估算流动源对大气细颗粒物的贡献。结果表明:桂林市区和桂林3大区域的流动源PM_(2.5)排放量分别为71.96和118.87t;按使用的燃料来分,柴油燃料对桂林市区和桂林3大区域PM_(2.5)贡献率较大,分别为94.07%和90.44%;按机动车类型来分,桂林市区和桂林3大区域的流动源PM_(2.5)主要贡献车型均为重型载货车、大型载客车、中型载货车,3大车型PM_(2.5)贡献率之和均超过80%。 相似文献
506.
507.
Influence of pyrolysis temperature on production and nutrient properties of wastewater sludge biochar 总被引:12,自引:0,他引:12
Mustafa K. Hossain Vladimir Strezov K. Yin Chan Artur Ziolkowski Peter F. Nelson 《Journal of environmental management》2011
The important challenge for effective management of wastewater sludge materials in an environmentally and economically acceptable way can be addressed through pyrolytic conversion of the sludge to biochar and agricultural applications of the biochar. The aim of this work is to investigate the influence of pyrolysis temperature on production of wastewater sludge biochar and evaluate the properties required for agronomic applications. Wastewater sludge collected from an urban wastewater treatment plant was pyrolysed in a laboratory scale reactor. It was found that by increasing the pyrolysis temperature (over the range from 300 °C to 700 °C) the yield of biochar decreased. Biochar produced at low temperature was acidic whereas at high temperature it was alkaline in nature. The concentration of nitrogen was found to decrease while micronutrients increased with increasing temperature. Concentrations of trace metals present in wastewater sludge varied with temperature and were found to primarily enriched in the biochar. 相似文献
508.
509.
基于协调度与熵权法的绩效评价新方法 总被引:2,自引:0,他引:2
自人们意识到绩效评价的重要性以来,越来越多的研究集中于绩效评价的方法。以往的绩效评价侧重用数字表象进行评价,而忽略了政府、企业系统及其与社会经济发展之间的特性。基于此,根据既有的信息熵理论研究成果,提出了协调度与熵权法复合评价模型,并运用该模型对2009年度河北省区域创新绩效进行了实证分析,既科学、全面地衡量绩效情况,又便于政府、企业及其与社会经济发展之间的系统分析,是一种绩效评价方法的创新,具有一定的普适性和通用性。 相似文献
510.
Assessment of bioaccessibility and exposure risk of arsenic and lead in urban soils of Guangzhou City,China 总被引:5,自引:0,他引:5
Ying Lu Wei Yin Longbin Huang Ganlin Zhang Yuguo Zhao 《Environmental geochemistry and health》2011,33(2):93-102
Soil ingestion is an important human exposure pathway of heavy metals in urban environments with heavy metal contaminated
soils. This study aims to assess potential health risks of heavy metals in soils sampled from an urban environment where high
frequency of human exposure may be present. A bioaccessibility test is used, which is an in vitro gastrointestinal (IVG) test
of soluble metals under simulated physiological conditions of the human digestion system. Soil samples for assessing the oral
bioaccessibility of arsenic (As) and lead (Pb) were collected from a diverse range of different land uses, including urban
parks, roadsides, industrial sites and residential areas in Guangzhou City, China. The soil samples contained a wide range
of total As (10.2 to 61.0 mg kg−1) and Pb (38.4 to 348 mg kg−1) concentrations. The bioaccessibility of As and Pb in the soil samples were 11.3 and 39.1% in the stomach phase, and 1.9
and 6.9% in the intestinal phase, respectively. The As and Pb bioaccessibility in the small intestinal phase was significantly
lower than those in the gastric phase. Arsenic bioaccessibility was closely influenced by soil pH and organic matter content
(r
2 = 0.451, p < 0.01) in the stomach phase, and by organic matter, silt and total As contents (r
2 = 0.604, p < 0.001) in the intestinal phase. The general risk of As and Pb intake for children from incidental ingestion of soils is
low, compared to their maximum doses, without causing negative human health effects. The exposure risk of Pb in the soils
ranked in the order of: industrial area/urban parks > residential area/road side. Although the risk of heavy metal exposure
from direct ingestion of urban soils is relatively low, the risk of inhalation of fine soil particulates in the air remains
to be evaluated. 相似文献