Development of Layered Sediment Structure and its Effects on Pore Water Transport and Hyporheic Exchange

Hyporheic exchange is known to provide an important control on nutrient and contaminant fluxes across the stream-subsurface interface. Similar processes also mediate interfacial transport in other permeable sediments. Recent research has focused on understanding the mechanics of these exchange processes and improving estimation of exchange rates in natural systems. While the structure of sediment beds obviously influences pore water flow rates and patterns, little is known about the interplay of typical sedimentary structures, hyporheic exchange, and other transport processes in fluvial/alluvial sediments. Here we discuss several processes that contribute to local-scale sediment heterogeneity and present results that illustrate the interaction of overlying flow conditions, the development of sediment structure, pore water transport, and stream-subsurface exchange. Layered structures are shown to develop at several scales within sediment beds. Surface sampling is used to analyze the development of an armor layer in a sand-and-gravel bed, while innovative synchrotron-based X-ray microtomography is used to observe patterns of grain sorting within sand bedforms. We show that layered bed structures involving coarsening of the bed surface increase interfacial solute flux but produce an effective anisotropy that favors horizontal pore water transport while limiting vertical penetration.     

淮河流域旱涝易发区农田的陆气相互作用——CO2通量、能量交换和水汽输送的季节变化特征

利用淮河流域旱涝易发区的安徽省寿县农田下垫面陆气相互作用观测试验资料,重点分析观测期内CO2通量、能量交换和水汽输送的季节变化,并讨论了与此有关的辐射分量通量、下垫面反射率、波恩比、能量闭合守恒、土壤温度和土壤湿度的季节变化.结果表明CO2通量、能量分配受地表农作物长势影响明显,其中,水稻灌浆、成熟期,被稻田吸收的CO2通量最大可超过2 mg·m-2·s-1,潜热通量达到正的极大值.稻田光合作用最旺盛时期吸收的CO2通量和释放的潜热通量均大于小麦田光合作用最旺盛时期的对应量.较大土壤热通量对应于较低的土壤水含量.试验观测期的下垫面平均反射率为0.14.作物生长期,稻田表面潜热是下垫面吸收能量的主要消费者,小麦田表面潜热和感热相当.能量闭合率ε的变化范围为0.4～1.     

Information Network Topologies for Enhanced Local Adaptive Management

We examined the principal effects of different information network topologies for local adaptive management of natural resources. We used computerized agents with adaptive decision algorithms with the following three fundamental constraints: (1) Complete understanding of the processes maintaining the natural resource can never be achieved, (2) agents can only learn by experimentation and information sharing, and (3) memory is limited. The agents were given the task to manage a system that had two states: one that provided high utility returns (desired) and one that provided low returns (undesired). In addition, the threshold between the states was close to the optimal return of the desired state. We found that networks of low to moderate link densities significantly increased the resilience of the utility returns. Networks of high link densities contributed to highly synchronized behavior among the agents, which caused occasional large-scale ecological crises between periods of stable and high utility returns. A constructed network involving a small set of experimenting agents was capable of combining high utility returns with high resilience, conforming to theories underlying the concept of adaptive comanagement. We conclude that (1) the ability to manage for resilience (i.e., to stay clear of the threshold leading to the undesired state as well as the ability to re-enter the desired state following a collapse) resides in the network structure and (2) in a coupled social–ecological system, the systemwide state transition occurs not because the ecological system flips into the undesired state, but because managers lose their capacity to reorganize back to the desired state. An erratum to this article can be found at .     

工业废水中测定六价铬的预处理技术

根据复合絮凝剂与阳离子交换树脂两者在分离与处理技术上所起的不同作用 ,提出了将两法联合用作工业废水中测定Cr6 的预处理技术 ,通过一系列条件试验 ,确定最佳预处理条件。结果表明 ,该法具有去色、去浊率高 ,分离效果佳 ,排除干扰离子能力强 ,分析样品重现性好 ,准确度高 ,操作简便、快捷的优点。     

淮河流域旱涝易发区农田的陆气相互作用——CO_2通量、能量交换和水汽输送的季节变化特征

利用淮河流域旱涝易发区的安徽省寿县农田下垫面陆气相互作用观测试验资料,重点分析观测期内CO2通量、能量交换和水汽输送的季节变化,并讨论了与此有关的辐射分量通量、下垫面反射率、波恩比、能量闭合守恒、土壤温度和土壤湿度的季节变化。结果表明:CO2通量、能量分配受地表农作物长势影响明显,其中,水稻灌浆、成熟期,被稻田吸收的CO2通量最大可超过2 mg.m-2.s-1,潜热通量达到正的极大值。稻田光合作用最旺盛时期吸收的CO2通量和释放的潜热通量均大于小麦田光合作用最旺盛时期的对应量。较大土壤热通量对应于较低的土壤水含量。试验观测期的下垫面平均反射率为0.14。作物生长期,稻田表面潜热是下垫面吸收能量的主要消费者,小麦田表面潜热和感热相当。能量闭合率ε的变化范围为0.4~1。     

金水河流域矿物元素生物地球化学交换模式

通过对金水河流域矿物元素生物地球化学交换模式的研究,得到以下结论：（1）在不同空间位置的矿物元素对河水的水质贡献率不相同。河水成分贡献主要来源于硅酸盐风化,在金水河流域生态系统不同空间位置矿物元素对河水水质贡献率方程为：YRiverwater=0.242＋0.203 XRain＋0172 XLitter＋0.471 XSoilwater（r2=0.55）。（2）固-液相界面（土壤-土壤水溶液）离子交换过程拟合表明：离子交换过程符合二、三次曲线模型。（3）区域内碳酸盐岩含较少的Na＋和K＋,且受酸雨等影响。Na＋在土壤-土壤溶液之间的分配行为可能加重土壤盐碱化的趋势。土壤和枯枝落叶层HCO3-和TDS值均处于稳定的范围内。（4）输入性污染分析表明,流域内土壤基本表现出物理性质改善;但却表现出贫养化和生物地球化学性质恶化的极化趋势。人为活动输入污染物影响显著,在全球变化背景下,酸雨和干旱加剧了水溶液组成的变化。     

Polycyclic aromatic hydrocarbon (PAH) deposition to and exchange at the air-water interface of Luhu, an urban lake in Guangzhou, China

Urban lakes are vulnerable to the accumulation of semivolatile organic compounds, such as PAHs from wet and dry atmospheric deposition. Little was reported on the seasonal patterns of atmospheric deposition of PAHs under Asian monsoon climate. Bulk (dry + wet) particle deposition, air-water diffusion exchange, and vapour wet deposition of PAHs in a small urban lake in Guangzhou were estimated based on a year-round monitoring. The total PAH particle deposition fluxes observed were 0.44-3.46 μg m⁻² day⁻¹. The mean air-water diffusive exchange flux was 20.7 μg m⁻² day⁻¹. The vapour deposition fluxes of PAHs ranged 0.15-8.26 μg m⁻² day⁻¹. Remarkable seasonal variations of particulate PAH deposition, air-water exchange fluxes and vapour wet deposition were influenced by seasonal changes in meteorological parameters. The deposition fluxes were predominantly controlled by the precipitation intensity in wet season whereas by atmospheric concentration in dry season.     

Changing effluent chemistry affect survival,growth and physiological function of <Emphasis Type="Italic">Acacia nilotica</Emphasis> seedlings in northwestern region of India

Recycling and conservation efforts for water are the need of the day because of the lack of new water sources and the ever-increasing demand for drinking water. Seedlings of Acacia nilotica L. were irrigated with: canal water (T₁, control); municipal effluent (T₂); textile effluent (T₃); steel effluent (T₄); textile + municipal effluent in 1:1 ratio (T₅); steel + municipal effluent in 1:2 ratio (T₆); steel + textile in 1:2 ratio (T₈) and steel + municipal + textile in 1:2:2 ratio (T₇) with views to observe effluents effect on the seedlings and its adaptability and to recommend safe disposal of these effluents. Seedlings in T₆, T₇ and T₈ showed 50% lesser height and collar diameter than those in control. Seedlings in T₂ attained greatest height, collar diameter, numbers of branches and produced 140 g dry biomass seedling⁻¹. Highest concentration of manganese (Mn), iron (Fe), copper (Cu) and zinc (Zn) and lowest concentration of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in the seedlings of T₄, T₆, T₇ and T₈ resulted in nutritional imbalance, mineral toxicity and reduction in photosynthetic (Pn) and transpiration (E) rates and caused seedling mortality. Seedlings of T₃ had highest sodium concentration and low concentration of Ca, Mg and micronutrients resulting in nutritional imbalance, augmented chlorosis and reduced gas exchange and biomass by half as compared to control. Increased growth, Pn and E and biomass in seedlings of T₅ over T₃ and survival period in T₆, T₇ and T₈ seedlings suggested a beneficial effect of effluents mixing. Unscientific disposal should be avoided and toxic concentration of metal ions␣may be reduced for long-term application and harmless disposal of effluents in afforestation and urban development.     

上海市入境旅游市场发展潜力与旅游外汇收入的关系研究——基于灰色预测和灰色关联分析法

利用灰色预测法对上海市入境旅游11个国家和地区的赴沪旅游者人数和旅游外汇收入进行了预测,推断出上海市入境旅游市场中不同国家和地区的市场潜力;运用灰色关联分析法,探索不同市场潜力等级的入境旅游国家和地区与上海市旅游外汇收入间的关系.针对亚洲和欧美各国家或地区的实际情况,提出了针对性的对策和建议.     

树脂负载Fe3+/Cu2+多相类芬顿降解染料橙黄

制备了新型多相类Fenton催化剂(Fe3+cu2+)/R(Fe3+和cu2+同时负载于离子交换树脂),以橙黄Ⅳ为研究对象,探讨了初始过氧化氢浓度、橙黄Ⅳ浓度、催化剂量、初始pH值及温度等因素对催化反应速率的影响,并对该催化剂重复使用性能进行测试.研究结果表明,该催化剂(Fe3++Cu2+)/R与Fe3+/R相比表现出更好的催化过氧化氢分解的活性,使橙黄Ⅳ的降解率提高10%;催化过氧化氢氧化橙黄Ⅳ的反应遵循假一级反应动力学,反应活化能为10.71 kJ·mol-1;催化剂表现出良好的重复使用性能,Fe3+和cu2+在树脂表面负载比较牢固,具有较好的稳定性和耐用性.同时,电子顺磁共振(EPR)测试结果表明,cu2+的掺杂能有效地促进OH·的产生;X射线光电子能谱(XPS)测试结果表明,反应过程中存在高价态铁物种.因此,在该体系反应过程中产生的活性物种是OH·和高价态铁同时共存.