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101.
Hyperspectral Characteristics of Canopy Components and Structure for Phenological Assessment of an Invasive Weed 总被引:1,自引:0,他引:1
Ge S Everitt J Carruthers R Gong P Anderson G 《Environmental monitoring and assessment》2006,120(1-3):109-126
Spectral reflectance values of four canopy components (stems, buds, opening flowers, and postflowers of yellow starthistle (Centaurea solstitialis)) were measured to describe their spectral characteristics. We then physically combined these canopy components to simulate the flowering stage indicated by accumulated flower ratios (AFR) 10%, 40%, 70%, and 90%, respectively. Spectral dissimilarity and spectral angles were calculated to quantitatively identify spectral differences among canopy components and characteristic patterns of these flowering stages. This study demonstrated the ability of hyperspectral data to characterize canopy components, and identify different flowering stages. Stems had a typical spectral profile of green vegetation, which produced a spectral dissimilarity with three reproduction organs (buds, opening flowers, and postflowers). Quantitative differences between simulated flower stages depended on spectral regions and phenological stages examined. Using full-range canopy spectra, the initial flowering stage could be separated from the early peak, peak, and late flowering stages by three spectral regions, i.e. the blue absorption (around 480 nm) and red absorption (around 650 nm) regions and NIR plateau from 730 nm to 950 nm. For airborne CASI data, only the red absorption region and NIR plateau could be used to identify the flowering stages in the field. This study also revealed that the peak flowering stage was more easily recognized than any of the other three stages. 相似文献
102.
分析了常州市2017年春节前后各污染物浓度的关联性和差异性。结果表明,除O_3外,春节期间各污染物均值均低于春节前后,春节前后随着污染源的变化,污染物之间的相关性表现出较为明显的差异。SO_2与PM_(2.5)、PM_(10)、CO和NO_2的相关性均较春节前后有显著下降;爆竹集中燃放时间段,CO与综合指数、PM_(2.5)和PM_(10)之间的相关系数0.96;而在烟花爆竹燃放相对较少的初三和初四,该相关系数0.6。工业减产停产和机动车使用减少对空气质量改善有较大贡献,而在不利气象条件下,烟花爆竹可导致空气质量在短时间内恶化。 相似文献
103.
Yang Zhang X.-Y. Wen C.J. Jang 《Atmospheric environment (Oxford, England : 1994)》2010,44(29):3568-3582
The chemistry–aerosol–cloud–radiation–climate feedbacks are simulated using WRF/Chem over the continental U.S. in January and July 2001. Aerosols can reduce incoming solar radiation by up to ?9% in January and ?16% in July and 2-m temperatures by up to 0.16 °C in January and 0.37 °C in July over most of the continental U.S. The NO2 photolysis rates decrease in July by up to ?8% over the central and eastern U.S. where aerosol concentrations are high but increase by up to 7% over the western U.S. in July and up to 13% over the entire domain in January. Planetary boundary layer (PBL) height reduces by up to ?23% in January and ?24% in July. Temperatures and wind speeds in July in big cities such as Atlanta and New York City reduce at/near surface but increase at higher altitudes. The changes in PBL height, temperatures, and wind speed indicate a more stable atmospheric stability of the PBL and further exacerbate air pollution over areas where air pollution is already severe. Aerosols can increase cloud optical depths in big cities in July, and can lead to 500–5000 cm?3 cloud condensation nuclei (CCN) at a supersaturation of 1% over most land areas and 10–500 cm?3 CCN over ocean in both months with higher values over most areas in July than in January, particularly in the eastern U.S. The total column cloud droplet number concentrations are up to 4.9 × 106 cm?2 in January and up to 11.8 × 106 cm?2 in July, with higher values over regions with high CCN concentrations and sufficient cloud coverage. Aerosols can reduce daily precipitation by up to 1.1 mm day?1 in January and 19.4 mm day?1 in July thus the wet removal rates over most of the land areas due to the formation of small CCNs, but they can increase precipitation over regions with the formation of large/giant CCN. These results indicate potential importance of the aerosol feedbacks and an urgent need for their accurate representations in current atmospheric models to reduce uncertainties associated with climate change predictions. 相似文献
104.
105.
106.
Ge Yuan Chen Chengrong Xu Zhihong Eldridge Simon M. Chan Kwong Yin He Yan He Ji-Zheng 《Environmental science and pollution research international》2010,17(3):807-815
Background, aim, and scope
Current Australian legislation permits the beneficial application of grease trap waste (GTW) to agricultural soil, viewing it as a beneficial source of organic matter and soil conditioner containing no/low amounts of metals or pathogenic organisms. However, little is known about the influence of GTW on soil bacterial community. A field experiment was established at Menangle in south western Sydney in Australia to quantitatively assess the impacts of different types (GTW CO and GTW CL) and amounts of GTW application on the soil bacterial community and diversity. Furthermore, a municipal solid waste (MSW) compost was simultaneously examined to compare against the other organic wastes. Knowledge about the shifts in microbial community structure and diversity following the applications of organic wastes could help to evaluate the ecological consequences on the soil and thus to develop sound regulatory guidelines for the beneficial reuse of organic wastes in agricultural lands. 相似文献107.
Atmospheric deposition of phthalate esters in a subtropical city 总被引:1,自引:0,他引:1
Feng Zeng Yujun Lin Kunyan Cui Jiaxin Wen Yongqin Ma Hongli Chen Fang Zhu Zhiling Ma Zunxiang Zeng 《Atmospheric environment (Oxford, England : 1994)》2010,44(6):834-840
In Chinese cities, air pollution has become a serious and aggravating environmental problem undermining the sustainability of urban ecosystems and the quality of urban life. Bulk atmospheric deposition samples were collected two-weekly, from February 2007 to January 2008, at three representative areas, one suburban and two urbanized, in the subtropical city, Guangzhou, China, to assess the deposition fluxes and seasonal variations of phthalate esters (PAEs). Sixteen PAE congeners in bulk deposition samples were measured and the depositional fluxes of ∑16PAEs ranged from 3.41 to 190 μg m?2 day?1, and were highly affected by local anthropogenic activities. The significant relationship between PAEs and particulate depositional fluxes (correlation coefficient R2 = 0.72, P < 0.001) showed PAEs are associated primarily with particles. Temporal flux variations of PAEs were influenced by seasonal changes in meteorological parameters, and the deposition fluxes of PAEs were obviously higher in wet season than in dry season. Diisobutyl phthalate (DiBP), Di-n-butyl phthalate (DnBP), and Di(2-ethylhexyl) phthalate (DEHP) dominated the PAE pattern in bulk depositions, which is consistent with a high consumption of the plasticizer market in China. PAE profiles in bulk deposition showed similarities exhibited in both time and space, and a weak increase of high molecular weight PAE (HMW PAE) contribution in the wet season compared to those in the dry season. Average atmospheric deposition fluxes of PAEs in the present study were significantly higher than those from other studies, reflecting strong anthropogenic inputs as a consequence of rapid industrial and urban development in the region. 相似文献
108.
Kun Wang Maofa Ge Weigang Wang 《Atmospheric environment (Oxford, England : 1994)》2010,44(15):1847-1850
The relative rate method has been used to determine the rate constants for the gas-phase reactions of NO3 radicals with a series of acrylate esters: ethyl acrylate (k1), n-butyl acrylate (k2), methyl methacrylate (k3) and ethyl methacrylate (k4) at 298 ± 1 K and 760 Torr. The obtained rate constants are k1 = (1.8 ± 0.25) × 10?16 cm3 molecule?1 s?1, k2 = (2.1 ± 0.33) × 10?16 cm3 molecule?1 s?1, k3 = (3.6 ± 1.2) × 10?15 cm3 molecule?1 s?1, k4 = (4.9 ± 1.7) × 10?15 cm3 molecule?1 s?1. The experimental rate constants are in good agreement with theoretical rate constants calculated by an algorithm of the correlation between the rate constants and the orbital energies for the reactions of unsaturated VOCs with NO3 radicals. In addition, the atmospheric lifetimes of the compound against NO3 attack are estimated and the results show that NO3 reactions contribute little to the atmospheric losses of acrylate esters except in polluted regions. 相似文献
109.
In view of no generally accepted ecological compensation standards and methods at present,this paper discusses the introduction of the negotiation system to the process of ecological compensation for water source areas.That is,the government in water source areas and the downstream regions of river basins should confirm their respective rights and obligations and then establish their compensation standards through negotiations according to the different purposes of water use.The amount of compensation should be determined in the comprehensive consideration of the quality,quantity and compensation price of water.Through open and fair negotiations,an institutional arrangement will be set up,which can make the water source areas and the downstream regions of river basins fully express their true preferences and their independent choices on the ecological environment. 相似文献
110.