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991.
Rice straw is supposed to be an environment-friendly biomaterial for inhibiting the growth of harmful blooms of the cyanobacterium Microcystis aeruginosa. However, its potential mechanism is not well known. To explore this mechanism, the growth, cell viability (esterase activity, membrane potential, and membrane integrity), photosynthesis, and cell size ofM. aeruginosa were determined using flow cytometry and Phyto-PAM after exposure to rice straw extracts (RSE). The results show that doses from 2.0 to 10.0 g/L of RSE efficiently inhibited the alga for 15 days, while the physiologic and morphologic responses of the cyanobacteria were time-dependent. RSE interfered with the cell membrane potential, cell size, and in vivo chlorophyll-a fluorescence on the first day. After 7 days of exposure, RSE was transported into the cytosol, which disrupted enzyme activity and photosynthesis. The cyanobacteria then started to repair its physiology (enzyme activity, photosynthesis) and remained viable, suggesting that rice straw act as an algistatic agent. 相似文献
992.
World cities and international organizations: Political global-city status of Chinese cities 总被引:3,自引:1,他引:2
In this study, the authors use a political perspective to explore the relative global status of cities in China. Two questions are addressed. Firstly, by using international organizations as the subjects and quantitative analysis of the spatial distribution of their offices, the overall position of Chinese cities in the global distribution of international organizations is estimated. The results show that 22 Chi- nese cities are involved in international political affairs. Beijing, Shanghai and Guangzhou dominate these activities and have high po- litical global-city status. Secondly, through qualitative analysis of Guangzhou City, the authors explore how its status as a center for intemational organizations has been shaped in recent years. The locational decision-making process is analyzed and the factors are demonstrated at both national and city scales. The definition of international organizations as used in this study refers not only to those supranational bodies that have the ability to manage relations across states (such as the European Union), but also those in- ter-governmental organizations (IGOs), international non-governmental organizations (INGOs) and diplomatic representatives and delegations that today also manage and regulate relations between and among states. 相似文献
993.
994.
当气溶胶谱满足Junge分布时,Angstrom指数 (α) 可以准确地描述粒子大小,但真实大气气溶胶很少完全满足这一条件,仅用α判断粒子大小会有较大出入。基于北京、香河、兴隆、太湖4个Aeronet观测站21世纪以来各站历时都超过1年的气溶胶光学厚度资料,获得5511组lnτ与lnλ的二次拟合参数a2,a1,尝试找到一种结合α,a2,a1判断粒子大小的方法。结果表明:当气溶胶为粗粒子时 (Vfine/Vtotal<0.2),α均小于0.75,仅用α就可以较好地判断粒子大小,但当气溶胶以细粒子为主时 (Vfine/Vtotal>0.7),该方法会有较大出入,此时a2,a1可以有效地辅助α判断粒子大小,α>0.75,a2<-0.5或a2<-0.5,a1<-1.0是较好的判据。此外,分析发现国外研究提出的用a2-a1判断粒子大小的方法效果并不理想,尤其在1<a2-a1<2的情况下,粒子的组成有多种可能。 相似文献
995.
996.
This study established wetland microcosms that were either unplanted or planted in monoculture with native mangrove species in Taiwan (Avicennia marina, Rhizophora stylosa, and Lumnitzera racemosa) for the purpose of receiving high-salinity mariculture effluents; additionally, the microcosms operated at different hydraulic retention times (HRTs). Plant growth and the performance of the microcosms with respect to pollutant removal were investigated. The results showed that seedlings of all three mangrove species survived and grew sufficiently well under continuous flooding. The presence of mangroves consistently improved SS, BOD5, and TP removal, particularly under short HRT conditions. The mangrove microcosms removed pollutants from the mariculture effluents with efficiencies of 5.7-27.1% (SS), 4.9-36.3% (BOD5), 18.7-29.9% (TP), 21.2-49.8% (NH4-N), and 5.4-37.7% (NOx-N). A. marina and L. racemosa were more tolerant of continuous flooding than R. stylosa. However, no species displayed consistently superior performance in decreasing all pollutant-related parameters investigated. For all pollutants, microcosms operating at a 2-d HRT exhibited a higher removal efficiency than those operating at a 0.5-d HRT. 相似文献
997.
998.
Shiliang Su Dan Li Xiang Yu Zhonghao Zhang Qi Zhang Rui Xiao Junjun Zhi Jiaping Wu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(6):737-746
Given the important role of land ecosystem in social-economic progress at regional, national, and international scale and
concurrent degradation of land ecosystems under rapid urbanization, a systematic diagnosis of land ecological security (eco-security)
for sustainable development is needed. A catastrophe model for land ecological security assessment was developed in order
to overcome the disadvantages in subjectivity and complexity of the currently used assessment methods. The catastrophe assessment
index system was divided into hierarchical sub-systems under the pressure-state-response framework. The catastrophe model
integrated multiple assessment indices of land eco-security according to the inherent contradictions and relative importance
of indices without calculating weights. Specifically, membership degree of higher level index was calculated based on the
membership degrees of lower level indices that were subjective to suitable model, such as cusp, fold, swallowtail and butterfly
model. This model was applied to evaluate the state of land eco-security in Shanghai. Mann–Kendall’s test was utilized to
characterize its temporal trend between 1999 and 2008. Significant downward trend was identified for land eco-security, in
terms of pressure sub-index, state sub-index, response sub-index and synthetic index. All these implied that land ecosystem
conditions were not optimistic for Shanghai and such situation should draw the attention of policy makers. The calculation
procedure presented in this paper does not require a high level of technical expertise to determine the membership degree,
making it simple and operational. Being applicable to similar land ecosystems, the catastrophe model is thus believed to provide
an alternative approach to land eco-security assessment. 相似文献
999.
Nutrient sources and composition of recent algal blooms and eutrophication in the northern Jiulong River, Southeast China 总被引:6,自引:0,他引:6
The natural process of eutrophication is accelerated by human activities worldwide that interrupt nutrient biogeochemical cycles. Three algal bloom events have been monitored in the northern tributary of the Jiulong River since 2009. The inflection points in a robust locally-weighted regression analysis (LOESS) of the relationship between TN and TP concentrations in the river water, and a TN:TP comparison with nutrient source loadings, suggested that both external loading and internal nutrient cycling contributed to these algal blooms. Nutrient release from the sediments may have played an important role in regulating the nutrients in the overlying water column. In particular, excessive nutrient inputs from various sources and ubiquitous river damming caused further accumulation of the nutrient loading. In-situ autochthonous primary production was enhanced in this relatively stable "river" to "lake" water body. Thus, attention must be paid to the effects of river damming and the consequent internal nutrient release. 相似文献
1000.
The origin of spongy texture in minerals of mantle xenoliths from the Western Qinling, central China 总被引:1,自引:0,他引:1
Ben-Xun Su Hong-Fu Zhang Patrick Asamoah Sakyi Yue-Heng Yang Ji-Feng Ying Yan-Jie Tang Ke-Zhang Qin Yan Xiao Xin-Miao Zhao Qian Mao Yu-Guang Ma 《Contributions to Mineralogy and Petrology》2011,161(3):465-482
Spongy textures are observed in mantle peridotite xenoliths hosted in Cenozoic kamafugites from the Western Qinling, central China. These textures are mainly developed in clinopyroxenes and spinels, and occur as spongy rims consisting of low-Na clinopyroxene, ilmenite, and bubbles, enclosing nonspongy cores. The ilmenites and bubbles exhibit shapes and sizes that vary with the width of the spongy rims. The spongy-textured minerals preserve primary shapes and well-defined grain boundaries and do not show apparent interaction with contact minerals or observed melts except the subsequent melts forming melt pockets. The xenocrysts display reactive zoning textures with host magmas rather than spongy textures. Compositionally, the spongy rims are enriched in Ca, Ti, and most trace elements, have high Cr#, and are depleted in Na, Al, Fe, AlVI, and AlIV/AlVI compared with the cores. These observations suggest that melts/host magmas did not play any significant role in the formation of the spongy textures. We therefore propose that spongy-textured clinopyroxenes and spinels in Western Qinling peridotite xenoliths developed from a decompression-induced partial melting event prior to formation of melt pockets and xenolith entrainment in host magmas. 相似文献