水热法制备玉米叶基生物炭对亚甲基蓝的吸附性能研究

以农业废弃物玉米叶和玉米秆为原材料,采用水热法制备生物炭,通过批试验方法考察了接触时间、污染物初始浓度、生物炭投加量、反应体系温度及溶液p H值等因素对2种生物炭吸附亚甲基蓝的影响,并对吸附规律进行了探讨.吸附动力学拟合结果发现,准二级动力学能更好地拟合吸附过程(R~2=0.9986~0.9999);颗粒内扩散方程拟合结果表明,2种生物炭对亚甲基蓝的吸附由液膜扩散和颗粒内扩散2个过程控制.玉米叶基生物炭对亚甲基蓝的吸附可以通过Freundlich方程来进行拟合(R~2=0.9898),说明吸附在生物炭表面是多分子层吸附过程;而玉米杆基生物炭对亚甲基蓝的吸附更符合Langmuir方程(R~2=0.9825),说明吸附在生物炭表面是单分子层吸附过程.与玉米杆基生物炭相比,玉米叶基生物炭具有更好的吸附性能,拟合理论最大吸附量为玉米杆基生物炭的1.25倍.     

大气作用下膨胀土地基的水分迁移与胀缩变形分析

运用土体渗流和蒸发理论,建立了大气-非饱和土相互作用模型;以现场观测的气象数据作为边界条件,进行了地基土中水分迁移的数值模拟,得到了大气作用下地基土体含水量的动态分布规律.计算结果表明,地基土中含水量变化幅度随深度增加而递减,3.5m深度以下土体的体积含水量基本不变,从而确定了南宁地区膨胀土地基的大气影响层深度为3.5...     

锑的表生地球化学行为与环境危害效应

锑(Sb)是一种典型的有毒有害重金属元素。由于自然过程和人为活动的影响,锑及其化合物广泛分布于大气、土壤、水体等表生环境中,锑的环境污染日益严重。Sb不是植物必需元素,但能够被植物体及农作物吸收。Sb对人体和动物体产生慢性毒性及潜在致癌性。本文主要通过分析Sb的主要矿物、锑及其化合物在表生环境中的分布与迁移特性,来阐述人体可能的锑暴露途径及由此产生的环境危害效应。     

澳门特别行政区土壤自然消减能力与污染背景

澳门是我国人口密度最大的城市.选择澳门特别行政区不同功能区绿地土壤为研究对象,首先,通过野外布点采样,调查分析了表层土壤中9种重金属元素(Cr、Ni、Cu、Cd、Pb、Cr、Zn、As、Hg)和16种优先控制多环芳烃(PAHs)的分布特征;其次,利用累积频率分布曲线法估算了土壤重金属和PAHs的土壤污染背景;最后,基于...     

沈阳地区冬季空气颗粒物输送路径及潜在源分析

文章利用2016～2017年冬季沈阳地区气象数据和环境空气污染物浓度数据,综合分析沈阳地区冬季环境空气污染特征,分析颗粒物输送路径以及潜在源区贡献情况.结果表明,沈阳地区冬季污染时段内PM2.5是主要污染物,PM2.5平均浓度达到149μg/m3,最大值达到273 μg/m3.沈阳地区环境空气颗粒物除来源于本地排放外,...     

Kosetice, Czech Republic--ten years of air pollution monitoring and four years of evaluating the origin of persistent organic pollutants

The regional observatory Kosetice is a central European background station. Unique continuous monitoring from 1988 on is held here. POP (persistent organic pollutant) concentration values of air samples from Kosetice taken between 1996 and 2005 were statistically processed. Values of Czech ambient air quality standards were not exceeded. Concentrations of polycyclic aromatic hydrocarbons reached two maxima, in 1996 and 2001-2002. Polychlorinated biphenyls concentrations reached the highest values in 1997 and 1998 and hexachlorocyclohexanes concentrations in 1998. DDTs, hexachlorobenzene and pentachlorobenzene were analysed as well. Long-range transport of pollutants between 2002 and 2005 was evaluated using the Potential Source Contribution Function hybrid receptor model. Indicated potential source areas of PCBs coincide with many well-known urban and industrialised areas, while the indicated potential source areas of HCHs and DDTs coincide with many agricultural and/or forested regions and the potential source areas of HCB comprise all land use types.     

吸力式桶形基础多桶组合结构承载力特性研究

海洋采油平台结构中一般采用多桶组合基础型式,然而迄今对多桶组合结构尚缺乏理论分析和实验研究。本文针对我国第一座吸力式桶形基础采油平台CB20B,基于单桶基础在复合加载模式下的承载力特性,建立了双桶、四桶组合基础的三维有限元数值计算模型,探讨了对称多桶基础结构与单桶基础结构的承载力特性之间的相互关系,阐述了不同桶间距的多桶组合结构地基破坏机制,为工程设计提供参考依据。     

基坑开挖对临近地基极限承载的影响性状数值分析

采用弹塑性有限元分析方法,分析了悬臂式排桩支护的基坑开挖对邻近地基条形基础下极限承载力的影响性状。主要考虑了在基坑开挖深度、荷载与基坑的距离、荷载宽度、支护刚度等因素的影响下地基极限承载力的减损性状。研究表明,基坑开挖深度H较浅时,对地基极限承载力P_u的影响较小,P_u随H的增大略有降低,随着开挖深度的增加,H对P_u值的影响显著增大,且P_u值显著降低;当L/H≤2时,荷载与基坑的距离L对地基极限承载力P_u的影响很大,地基极限承载力P_u随L的减小而显著减小,当L/H>3时,L的影响逐渐减小,且P_u逐渐趋近于无基坑开挖时的值;P_u随地基荷载作用宽度B的增大而呈线性增大;支护桩的位移越小,P_u值越接近无基坑开挖时的地基极限承载力。     

Critical environmental indicators: performance indices and assessment models for sustainable rural development planning

Sustainable development planning must be based on environmental and biophysical baseline indices that effectively define comparative development potential and environmental constraints. As such, indices must define the comparative advantage of the natural resource base and measure the fundamental capacity to sustain production rates of natural resource goods and services used to create societal well being. Complex biophysical and socioeconomic characteristics affect the identification and selection of sustainable development strategies. When derived from effective baseline indicators, indices may be used to define the spatial and temporal distribution of economically viable production opportunities and may be expressed in derived indices that realistically describe basic production opportunities and guide the selection of feasible, long-term development strategies. Specifically, representative indices are critical in the identification of development goals and realistic objectives and can be used to evaluate, select and implement sustainable development strategies and plans. It is stressed that the relevancy and effectiveness of public policies depend on the identification of representative evaluation models and baseline indices to define development strategies that are both environmentally sustainable and economically viable. In this context, the role of baseline indicators that define natural resource production capacities is discussed. This includes potential resource uses, derived benefits and their economic and environmental impacts. Key thematic indicators are suggested that may be especially useful in identifying development alternatives and impacts. This suggested that clearly defined environmental pollution limits or impact standards be used to define public risk tolerance limits and carrying capacity constraints. It is argued that these measures may be more effective in directing policy choices than economic valuation of non market goods and services that represent environmental externalities associated with resource exploitation options and economic development strategies. To this end, examples of thematic indicators and derived indices are introduced that may prove effective in resource assessment, economic evaluation and strategic development planning.     

The influence of potential reproductive rate and variation in mate quality on male and female choosiness in the sand goby, Pomatoschistus minutus

Recent models of choosiness in mate choice have identified two particularly important factors: the potential reproductive rate (PRR) of the choosing sex relative to that of the chosen sex, and the variation in quality of potential mates. This experimental study tested how these factors affected choosiness in male and female sand gobies, Pomatoschistus minutus. We manipulated relative PRR by means of water temperature, and mate quality by means of body length. The choosing male or female was offered a choice between two mates with either a small or a large difference in body length representing a small or a large variation in mate quality. Choosiness was measured as (1) preference for the larger mate, and (2) as whether or not spawning occurred with the smaller mate, while the larger mate was visible but screened off. We found that females preferred large males, and that their level of choosiness was affected by variation in male quality, but not by their own relative PRR. Males, on the other hand, seemed unselective in all treatments and were in general more likely than females to spawn with their provided partner. This suggests that in the sand goby, variation in male mate quality has a greater influence than relative PRR on facultative changes in female choosiness. However, a general difference in PRR between males and females may be one important factor explaining the observed sex difference in choosiness. Received: 17 April 2000 / Revised: 24 June 2000 / Accepted: 17 July 2000