改性栗壳吸附重金属离子的动力学及热力学研究

对改性板栗壳吸附Cr(VI)、Cu(II)及Ni(II)3种重金属离子过程的动力学和热力学进行研究。结果表明:改性板栗壳吸附Cr(VI)、Cu(II)和Ni(II)3种混合离子时存在拮抗的竞争关系,竞争吸附顺序为Cu(II)﹤Ni(II)﹤Cr(VI);与单独吸附过程相比,混合吸附平衡时,改性板栗壳对3种离子相应的去除率均有所降低,Cr(VI)去除率比单独吸附时降低20.2%,Cu(II)和Ni(II)分别降低40.7%和35.6%;拟二级动力学方程能很好地描述Cr(VI)、Cu(II)和Ni(II)在改性板栗壳上的单独和混合吸附过程,结果表明此3种重金属离子在改性板栗壳表面以化学吸附为主;热力学研究数据表明:改性板栗壳对Cr(VI)的吸附为吸热反应,对Cu(II)和Ni(II)的吸附为放热反应。     

Numerical study of the effects of Planetary Boundary Layer structure on the pollutant dispersion within built-up areas

The effects of different Planetary Boundary Layer(PBL) structures on pollutant dispersion processes within two idealized street canyon configurations and a realistic urban area were numerically examined by a Computational Fluid Dynamics(CFD) model. The boundary conditions of different PBL structures/conditions were provided by simulations of the Weather Researching and Forecasting model. The simulated results of the idealized 2D and 3D street canyon experiments showed that the increment of PBL instability favored the downward transport of momentum from the upper flow above the roof to the pedestrian level within the street canyon. As a result, the flow and turbulent fields within the street canyon under the more unstable PBL condition are stronger. Therefore, more pollutants within the street canyon would be removed by the stronger advection and turbulent diffusion processes under the unstable PBL condition. On the contrary, more pollutants would be concentrated in the street canyon under the stable PBL condition. In addition, the simulations of the realistic building cluster experiments showed that the density of buildings was a crucial factor determining the dynamic effects of the PBL structure on the flow patterns. The momentum field within a denser building configuration was mostly transported from the upper flow, and was more sensitive to the PBL structures than that of the sparser building configuration. Finally, it was recommended to use the Mellor–Yamada–Nakanishi–Niino(MYNN) PBL scheme, which can explicitly output the needed turbulent variables, to provide the boundary conditions to the CFD simulation.     

Assessing desertification risk using system stability condition analysis

This paper describes a procedure for evaluating the desertification risk in threatened areas. The procedure is based on an eight-equation dynamic model of a generic human–resource system that can be applied to different desertification syndromes. For each application, interest focuses on finding all the possible long-term final states of the system and on defining the conditions that mark out sustainability and long-term desertification by means of unambiguous specific parameter relations. The procedure is applied to three typified cases in Spain: (A) rainfed crops in areas with high soil erosion risk; (B) irrigated intensive agricultural systems; and (C) commercial rangelands. Results show that, in case A, high profit scenarios are responsible for the final extension of desertification but do not determine the specific threshold between sustainability and desertification. They do, however, in cases B and C.     

Nutrient Dynamics in Jiaozhou Bay

Three cruises were carried out in Jiaozhou Bay (JZB) in the neap tide in October 2002 (fall) and in both neap and spring tides in May 2003 (spring) to understand the relative importance of external nutrient inputs versus physical transport and internal biogeochemical processes. Nutrients (, , , , silicic acid, total dissolved nitrogen (TDN) and phosphorus (TDP), dissolved organic nitrogen (DON) and phosphorus (DOP)) were measured. The concentrations of nutrients were higher in the northern part than in the southern part. High concentrations of and DON in JZB demonstrated the anthropogenic input. Ambient nutrient ratios indicated that the potential limiting nutrients for phytoplankton growth were silicon, and then phosphorus. Nutrients showed an obvious tidal effect with low values at flood tide and high values at ebb tide. Nutrient elements were transported into JZB in the north and output in the south (i.e., into the Yellow Sea), which varied with season, tidal cycle and investigation sites. Water exchange between JZB and the Yellow Sea exports , and DON out of JZB, while it inputs , silicic acid and DOP into JZB. Nutrient budgets demonstrate that riverine input and wastewater discharge are major sources of nutrients, while residual flow is of minor importance in JZB ecosystem. JZB is a sink for the nutrient elements we studied except for DON. Stoichiometric calculations demonstrate that JZB is a net autotrophic system.     

Long-term mercury dynamics in UK soils

A model assuming first-order losses by evasion and leaching was used to evaluate Hg dynamics in UK soils since 1850. Temporal deposition patterns of Hg were constructed from literature information. Inverse modelling indicated that 30% of 898 rural sites receive Hg only from the global circulation, while in 51% of cases local deposition exceeds global. Average estimated deposition is 16 μg Hg m⁻² a⁻¹ to rural soils, 19 μg Hg m⁻² a⁻¹ to rural and non-rural soils combined. UK soils currently hold 2490 tonnes of reactive Hg, of which 2140 tonnes are due to anthropogenic deposition, mostly local in origin. Topsoil currently releases 5.1 tonnes of Hg⁰ per annum to the atmosphere, about 50% more than the anthropogenic flux. Sorptive retention of Hg in the lower soil exerts a strong control on surface water Hg concentrations. Following decreases in inputs, soil Hg concentrations are predicted to decline over hundreds of years.     

最严格水资源管理制度政策效果仿真研究——以江苏为例

为探索中国最严格水资源管理制度实施成效,本研究运用系统动力学方法构建最严格水资源管理制度政策效果仿真模型,以江苏为例,首先从横向比较研究的视角,设置无政策和政策延续两种情景,分析有无政策时用水总量、用水效率和水功能区纳污的管控效果;然后从纵向比较研究的视角,分析政策实施后2013—2030年用水总量、用水效率和水功能区纳污控制效果的演化情况。结果显示：(1)横向对比,相对于无政策情景,政策延续情景下的区域水资源需求总量、万元GDP用水量以及污废水中的COD排放总量均有不同幅度的下降,且降幅逐年扩大,政策成效显著;(2)纵向对比,政策延续情景下,2030年区域水资源需求总量将超过国家最严格水资源管理制度考核要求近20亿m3,2025年万元GDP用水量降幅低于“十四五”节水型社会建设规划目标近2%,2030年污废水中的COD排放总量将比2021年升高近24%,政策管控水平仍需进一步提升。     

地铁站火灾时空气幕防烟的数值模拟与分析

随着国内地铁的迅速发展,地铁火灾的防范及应急处理成为重要的研究课题。笔者根据地铁站建筑结构特点及火灾烟气的扩散规律,首次提出将空气幕用于地铁站楼梯口防烟,以保障火灾时人员的安全疏散。并用CFD方法模拟分析一列地铁列车着火时,防烟空气幕对烟气扩散的控制。结果表明,在楼梯口设置防烟空气幕不仅可以保证人员在6分钟以上的安全疏散时间,而且减少了比传统方式所需的新鲜空气量,有效阻止火灾的进一步扩大和控制烟气扩散。     

Role of microorganisms and macrofauna in benthic phosphorus dynamics in the po river--Adriatic Sea frontal system: An experimental approach

Sediment biotic and abiotic attributes were determined during the PRISMA II oceanographic campaigns in the northern and central Adriatic Sea. The radiotracer orthophosphate 32 P was used under laboratory conditions to analyse the role of micro- and macrofauna in phosphorus dynamics at the water-sediment interface. Effects of infaunal suspensivores on microfungal growth were also investigated. Our findings emphasised: 1) significant differences in sediment 32 P uptake as related to the sampling area, occurrence of the pelagic frontal system, sediment grain size, microbial activity, and anoxia; 2) the crucial role played in 32 P dynamics by different tropho-functional groups r - r i.e ., infaunal filter-feeders and epifaunal detritivore characterising the benthic community of the northern Adriatic basin. The significant changes in ergosterol concentration (adopted as an index of microfungal growth) observed in sediments subjected to infaunal activity, eventually provided a comprehensive insight into macrofauna-microorganism interactions. The potential impact of macrofaunal activity in phosphorus dynamics in the Adriatic benthic system is discussed.     

Technological change and fisheries sustainability: The point of view of Adaptive Dynamics

The analysis of a simple model shows that exploitation of fish stocks can entrain in the long run the substantial decline or even the collapse of the stock, as well as difficulties in stock recovery, loss of fishery resilience, and reduction of the mean fish size. The results are in agreement with numerous observations, even though they are obtained with a simple model in which the harvesting fleet and the fish stock are considered as unstructured predator and prey. The study is carried out for the typical case of fleet dimension not too sensitive to the year-to-year fluctuations of the stock and assuming that the sole cause of evolution is technological innovation. The analysis is performed by means of Adaptive Dynamics, an approach born in theoretical biology which is used here in the context of technological change. Although the results are qualitatively consistent with those obtained long ago through the principles of bioeconomics, it is fair to stress that the underlying assumptions are different. In fact, in the bioeconomic approach fleet technology does not evolve and fishing effort varies to produce economic optimization, while in the Adaptive Dynamics approach technological innovation is the key driver. The paper is purely theoretical and the proposed model can hardly be tuned on any real fishery. No practical guidelines for managers can therefore be drawn, if not the general conclusion that long-term sustainability of exploited fish stocks can only be achieved if strategic parameters influencing technological change are kept under strict control.     

CFD方法对突发性化学事故中危险物质泄漏范围的确定

简要分析了目前国内主要用于预测易燃易爆(有毒)物质发生泄漏事故后浓度扩散范围的计算方法。并介绍了国际上比较成熟的计算流体力学相关软件的数学模型及特点和边界条件的设置。针对液氨发生泄漏后氨气在一定大气环境条件下扩散的过程和特征,建立了相应的数学模型并设置了边界条件,通过数值计算得到氨气在水平方向风速环境下在三维空间内浓度分布规律。通过分析氨气扩散后爆炸浓度下限范围,探讨了如何设置警戒区的方法。最后分析了将计算流体力学方法应用于确定易燃易爆(有毒)物质泄漏后浓度范围的前景与不足。