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排序方式: 共有703条查询结果,搜索用时 15 毫秒
181.
本文报道了一种新的测定铜(Ⅱ)的高选择性和高灵敏度的催化光度分析法.基于在氨水介质中,曙红Y与H_O_2的氧化还原反应受铜(Ⅱ)催化使曙红Y褪色,据此建立的测定铜(Ⅱ)的新方法的检出限为3×10~(-10)g/ml,该法用于人发、指甲样品中铜(Ⅱ)的测定,相对标准偏差为5%~6%,加标回收率为88%~114%. 相似文献
182.
Long- and short-chain AHLs affect AOA and AOB microbial community composition and ammonia oxidation rate in activated sludge 总被引:1,自引:0,他引:1
Jie Gao Yu Duan Ying Liu Xuliang Zhuang Yichen Liu Zhihui Bai Wenlin M Guoqiang Zhuang 《环境科学学报(英文版)》2019,31(4):53-62
Quorum sensing (QS) regulation of the composition of ammonia-oxidising archaea (AOA) and ammonia-oxidising bacteria (AOB) communities and functions in wastewater treatment was investigated. Specifically, we explored the role of N-acyl-l-homoserine lactones (AHLs) in microbial community dynamics in activated sludge. On average, the specific ammonia-oxidising-rate increased from 1.6 to 2.8?mg?NH4+-N/g?MLSS/hr after treatment with long-chain AHLs for 16?days, and the addition of AHLs to sludge resulted in an increased number of AOA/AOB amoA genes. Significant differences were observed in the AOA communities of control and AHL-treated cultures, but not the AOB community. Furthermore, the dominant functional AOA strains of the Crenarchaeota altered their ecological niche in response to AHL addition. These results provide evidence that AHLs play an important role in mediating AOA/AOB microbial community parameters and demonstrate the potential for application of QS to the regulation of nitrogen compound metabolism in wastewater treatment. 相似文献
183.
Jennifer G. Duan Richard H. French Julie Miller 《Journal of the American Water Resources Association》2002,38(1):255-263
ABSTRACT: The growth of aquatic plants in open‐channels has many adverse environmental effects including, but not limited to, impeding the transport of water, hindering navigation, increasing flood elevations, increasing sediment deposition, and degrading water quality. Existing control strategies include physical removal and chemical treatment. Physical removal is only a temporary solution and chemical treatment is unacceptable if the water will be consumed by humans. The hydrodynamic method can wash out the encroached aquatic plants by keeping flow velocity higher than the critical velocity required to bend and rupture (lodge) their stems. This approach is a promising, physically‐based, efficient, economic, and permanent solution for this problem. However, the success of this approach requires the accurate prediction of the critical lodging velocity. This paper presents an analytic study of the lodging velocity for the submerged portion of aquatic plants of narrow leaved emergent stems that are wider at bottom than the top. Based on the principles of engineering materials and the theory of turbulent flow, a semi‐empirical formula is derived for the prediction of the critical lodging velocity. It indicates that the lodging of aquatic plants is controlled not only by flow conditions but also the geometric and mechanical characteristics of the plants. These analytic results provide a satisfactory explanation of the lodging phenomena observed in the field and are verified by the available experimental data. 相似文献
184.
两类混凝剂处理公厕水冲物的初步研究 总被引:1,自引:0,他引:1
本文采用无机凝聚剂、有机絮凝剂和有机-无机混凝剂对公共厕所水冲物进行了固液分离研究.条件实验表明,供试的无机凝聚剂中,铁盐对水冲物的混凝速度最快,絮凝体相对于铝盐紧实,而铝盐的絮凝体大于铁盐;有机絮凝剂对供试水冲物的混凝效果随着PAM分子量的增加,效果增强.从处理后的水质看,铝盐普遍优于铁盐.与无机凝聚剂混合使用,能显著加快铝盐的分离,使处理后的絮凝体沉淀体积变小,湿渣的含水量降低2~3倍.气浮处理后的清液,其各项主要水质指标均达到国家污水综合排放二级标准(GB 8978-1996). 相似文献
185.
DUAN Guang-ming ZHAO Jing-zhu LIU Guo-hu KE Bing XIAO Han WU Gang DENG Hong-bing 《环境科学学报(英文版)》2004,16(2):308-315
This paper assess the eco-environmental benefits that may come from the middle route project of China‘s South-North Water Transfer Scheme(SNWT) with principles and methods of eco-economics and planning reports of SNWT‘s middle route project. Some benefits were calculated in monetary units. To make sure that the results can be comparable with normal monetary indices, concrete assessment objects and the parameters are prudently selected according to the major characteristics of the project and its water import region. Primary assessment revealed that in different project construction stages, the benefit could be more than 13.07 billion RMB Yuan in 2010 and 19.79 billion RMB Yuan in 2030, respectively. The monetary value tends to increase with social-economic development. To realize these potential benefits, however, calls for more endeavors. 相似文献
186.
中国主要湖泊营养氮沉降临界负荷的研究 总被引:27,自引:0,他引:27
水体营养氮沉降临界负荷是不致使水体产生富营养化的最高氮沉降量。文中探讨了一种依据湖泊氮质量平衡原理计算营养氮沉降临界负荷的方法。用该方法计算表明 ,我国主要湖泊的营养氮沉降临界负荷比较低 ,大部分小于 1keq· hm- 1 · a- 1 ,部分已为目前的氮沉降量或者两者相当接近 ,意味着只接受氮沉降也能导致这些湖泊产生富营养化。但实际统计结果表明 ,氮沉降在导致受工农业生产和生活影响很大的城市和郊区湖泊的水质富营养化的所有氮污染源中所占比例较低 ,而其它来源的氮输入如河道入湖、工业生活废水和农田径流等才是导致富营养化的最主要因素 ,它们的量已远远超过了这些水体可随最高允许氮负荷。因此 ,对控制这些湖泊的水质富营养化而言 ,控制氮沉降并不是目前最紧迫的任务 ,而其它人为污染源的控制才是最急需的。但氮沉降临界负荷在湖泊富营养化的中长远控制中仍具有十分重要的意义。 相似文献
187.
188.
Changes of Land Use and of Ecosystem Service Values in Sanjiang Plain, Northeast China 总被引:6,自引:0,他引:6
Wang Z Zhang B Zhang S Li X Liu D Song K Li J Li F Duan H 《Environmental monitoring and assessment》2006,112(1-3):69-91
Agricultural activities, especially reclamation, are considered major threats to the wetland ecosystems in Sanjiang Plain,
the largest concentrated area of the freshwater wetlands in China. In the past decades, the area of the cultivated land and
its grain production have been increased at the cost of wetlands shrinkage. The large-scale land reclamation severely affected
the ecosystems in this region. However, such effects at the regional scale are seldom evaluated quantitatively. We used three
datasets of LANDSAT MSS and/or TM imagery to estimate the area changes and the transition of land use types from 1980 to 2000.
We also valued changes in ecosystem services delivered by each land category using value coefficients published by Costanza
et al. [Nature 387, 1997, 253–260]. Sensitivity analysis suggested that these estimates were relatively robust. Finally, the contribution
of various ecosystem functions was ranked to the overall value of the ecosystem services in this study. According to our estimates,
the total annual ecosystem service values in Sanjiang Plain have declined by about 40% between 1980 and 2000 ($156284–182572.18
million in total over 20 years). This substantial decline is largely attributed to the 53.4% loss of wetlands. For individual
ecosystem functions, waste treatment, water supply and disturbance regulation account for more than 60% to the total ecological
values. During those two decades, the contribution of disturbance regulation, cultural and recreation decreased, while the
contribution of water regulation, nutrient cycling, food production, raw materials and climate regulation increased during
the same period. We also put forward a few proposals concerning the future land use policy formulation and sustainable ecosystems.
They are adjusting the ‘food first’ agricultural policy, establishing more nature reserves for wetlands, creating systems
for the rational use of water, harnessing the degraded cultivated land and encouraging eco-tourism. 相似文献
189.
岩体裂隙面的形貌特征直接影响其渗流特性,为了分析二者的相关关系,采用劈裂法制备了单裂隙砂岩试样,进行了裂隙面扫描分析和渗流试验,基于分形维数在定量表达不规则曲线形貌特征方面的优势,提出了考虑裂隙面形貌各向异性特征的分形维数计算方法。研究结果表明:(1)基于矩阵理论的裂隙面综合分形维数,相当于用矩阵网格去覆盖整个裂隙面,可以较好地反映裂隙面的整体形貌特征;(2)裂隙面的形貌特征对其渗流特性影响显著,随着裂隙面综合分形维数逐渐增大,裂隙岩体的渗透系数逐渐减小,而且侧向应力越大,渗透系数的减小趋势越明显;(3)分析建立了裂隙岩样渗透系数kf与裂隙面综合分形维数■的相关关系,验证分析表明,该公式计算得到的裂隙岩样渗透系数与试验结果吻合较好。相关研究成果可为裂隙岩体渗流特性分析提供参考。 相似文献
190.