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571.
572.
聚磷菌厌氧时吸收乙酸和丙酸的代谢模型 总被引:2,自引:0,他引:2
水体中存在过多的磷是造成水体富营养化的重要原因之一,聚磷菌(polyphosphate accumulating organisms)因为能过量吸收磷而倍受关注。厌氧时,聚磷菌能大量吸收污水中的挥发性脂肪酸,经过一系列的生化反应,为好氧吸磷做准备。经过总结在厌氧条件下,聚磷菌Accumulibacter吸收乙酸和丙酸代谢转化的化学计量方程,并对模型中系数、还原力的产生、糖原降解途径以及厌氧条件下最终产物PHA的组成进行了讨论,得出挥发酸是通过主动运输进入细胞,且糖原经过ED途径提供还原力,多聚磷酸盐水解提供ATP和释放磷酸盐于体外,最终产生PHA的假设过程。但是,经过众多模型试验,一些假设仍没有得到最后的结论,所以应该进一步用富集程度较高的污泥进行精确研究。本文最终希望利用聚磷菌的代谢模型在工程运用中发挥最大效用。 相似文献
573.
随着我院招生人数的逐年增多,以及学生学习压力和就业难度的增大等,我院的平安文明校园建设工程迎来了新的挑战.本文从队伍建设、机制建立、科学预案、科技保障、安全教育及心理健康教育六个方面提出了平安校园建设的对策,并提出了从校风建设、课堂教学、思想政治教育、学生团体组织、硬件建设、活动开展等方面加强文明校园建设的设想. 相似文献
574.
This paper examines the impact of the clean development mechanism (CDM) on China??s progress in building a resource-efficient and environmentally friendly society, referred to as a dual-goal society. It presents China??s CDM activities from the perspective of policy directions, administrative arrangements and capacity building as well as outlines the regional trends and distribution of CDM projects across China??s 30 provinces. Based on regression analysis of 2006?C2009 panel data, the research was able to provide estimates at provincial level of the impacts of CDM activities on China??s CO2 emission intensity, SO2 emission intensity and industrial dust emission intensity. The study concludes that the active CDM projects are mainly located in the less-developed central and west China where they have provided increased opportunities for sustainable development. Furthermore, the successful implementation of CDM projects across the country has significantly decreased the emission intensity of CO2, SO2 and industrial dust, which means that these activities have enhanced China??s ability to build the desired dual-goal society. 相似文献
575.
Guo Dongmei 《中国人口.资源与环境(英文版)》2013,11(4):35-40
Abstract The trade of wastes in the world has been increasing and China has become the largest importer of wastes. This paper examines the import trend of different wastes and finds out that the total import volume to China approved by the Chinese government keeps increasing and the illegal trade can not be banned despite repeated prohibitions; therefore, China is not only “a world factory”, but actually “a global garbage dump”. In order to well understand the implications of wastes import, this paper further analyzes the resource and environmental effects and risks of different wastes imports as well as the strong driving force of wastes imports. Based on these detailed analysis and solid data, policy recommendations are put forward to reduce the demand for raw materials, to further strengthen the inspection of and supervision over the international trade of the wastes that can be used as raw materials by using the life cycle analysis and risk analysis, to improve the environmental standards and strengthen the disposal capacity, to re-export the raw materials produced from the imported wastes, to develop the long-term planning for the import of wastes and to promote international cooperation. 相似文献
576.
In 1999 China adopted the "Conversion of Cropland to Forest and Grassland Program" (CCFGP), a nationwide ecological recovery program, to minimize wide-scale soil erosion and vegetation degradation in China, as well as to improve water budgeting results. In the 10 yr since implementation, the CCFGP has resulted in the recovery and reforestation of >100,000 km of cropland and bare land, though the quantitative effect of this program on catchment water budget is not entirely clear. Therefore, we used the Soil and Water Assessment Tool to evaluate and quantify the effects of the CCFGP on the water budget of the Jinghe River catchment, a tributary of the Yellow River covering the central region of the Loess Plateau. Our results indicated that precipitation had dropped by 12.0% from the 1970s (611.6 mm) to the 2000s (538 mm) and that there was a corresponding 25.2% decrease in humidity index from 0.48 to 0.36. Before the CCFGP's implementation, forest and grassland had been decreasing, while bare land, cropland, and shrub land had been increasing. After the implementation of the CCFGP, the opposite trend was observed. Moreover, streamflow increased by about 15 and 20% for the upstream and middle stream subbasins, respectively, while soil water content also showed an obvious increase. Over the same period, evapotranspiration decreased by 5.2 and 13.5 mm and runoff decreased by 37.5 and 38.6% in the two subbasins. The same trends were obtained in the downstream subbasin, where changes were even greater. As a result of the reduced runoff and evapotranspiration, utilization of water resources was more efficient and ecological environment was improved under the CCFGP policy. Our results indicate the CCFGP resulted in a favorable ecological impact and should therefore be maintained. 相似文献
577.
Degradation of carbon tetrachloride (CT) by microscale zero-valent iron (ZVI) was investigated in batch systems with or without organic ligands (ethylenediaminetetraacetic acid (EDTA), citric acid, tartaric acid, malic acid and oxalic acid) at pHs from 3.5 to 7.5. The results demonstrated that at 25°C, the dechlorination of CT by microscale ZVI is slow in the absence of organic ligands, with a pseudo-first-order rate constant of 0.0217 h(-1) at pH 3.5 and being further dropped to 0.0052 h(-1) at pH 7.5. However, addition of organic ligands significantly enhanced the rates and the extents of CT removal, as indicated by the rate constant increases of 39, 31, 32, 28 and 18 times in the presence of EDTA, citric acid, tartaric acid, malic acid and oxalic acid, respectively, at pH 3.5 and 25°C. The effect of EDTA was most significant; the dechlorination of CT at an initial concentration of 20 mg l(-1) increased from 16.3% (no ligands) to 89.1% (with EDTA) at the end of 8h reaction. The enhanced CT degradation in the presence of organic ligands was primarily attributed to the elimination of a surface passivation layer of Fe(III) (hydr)oxides on the microscale ZVI through chelating of organic ligands with Fe(III), which maintained the exposure of active sites on ZVI surface to CT. 相似文献
578.
Numerical simulation for impacts of hydrodynamic conditions on algae growth in Chongqing Section of Jialing River, China 总被引:6,自引:0,他引:6
Hydrodynamic conditions are important factors for planktonic algae growth, through introducing two parameters which express the optimal velocity and the velocity range for planktonic algae growth, a new velocity factor was put forward for the formula of growth rate. Therefore, the two-dimensional unsteady ecological dynamic model for algae growth was established to analyze the effects of hydrodynamic conditions on algae growth in Chongqing Reach of Jialing River in China. The temporal and spatial distribution of Chlorophyll-a (Chl-a) concentration was simulated numerically for various water levels, under climate conditions in period of high frequency for algae blooms of Three Gorges Reservoir and nutrition status at present in the research reach. The corresponding locations and areas of likely algae blooms were analyzed and forecasted. The results showed that about 0.04 m s−1 was the optimal velocity for algae growth, and the occurrence of algae blooms in large scale is almost impossible because of relatively high water flow velocity for Jialing River. 相似文献
579.
Deming Dong Zhiyong Guo Xiuyi Hua Ying Lan Jinting Zhou Xiaoou Ding Qianqian Qiao 《Environmental Chemistry Letters》2011,9(3):361-367
The sorption by solid materials is one of the most important processes that affect the fate of hydrophobic organic pollutants
in aquatic systems. Current studies focus on the sorption of hydrophobic pollutants by single natural solid material, whereas
few studies compared the sorption behaviors of different solids. Furthermore, natural aquatic environment is a complex system
where hydrophobic pollutants coexist with many other pollutants, but only limited studies reported the effects of coexisting
components on the sorption. Here we studied the sorption of dichlorodiphenyltrichloroethanes (DDTs) by three common solids
in natural water, i.e., biofilms, suspended particles and sediments. The effects of typical coexisting heavy metals on the
sorption were also examined. The results show that the sorption is described by a dual-mode sorption model. Compared with
sediments, more DDTs were sorbed by biofilms and suspended particles. Coexisting Pb, Cd and Cu increased the sorption of DDTs
on sediments while decreasing the sorption on biofilms slightly, with little effect on the sorption on suspended particles.
The different sorption behaviors of the solids were mainly determined by the composition of the solids: more organics were
observed in biofilms and suspended particles. 相似文献
580.