Unified methodology for site-characterization and sampling of highway runoff

Hydrology, roadway traffic conditions, and atmospheric deposition are three essential data categories for the planning and implementation of highway-runoff monitoring and characterization programs. Causal variables pertaining to each data category could be site specific but have been shown to correlate with runoff pollutant loads. These data categories were combined to derive statistical relationships for characterization and prioritization of the respective pollutant loads at highway runoff sites. Storm runoff data of total suspended solids (TSS), total dissolved solid (TDS), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and total phosphorus (TP) collected from three highway sites in Charlotte, North Carolina, USA, were used to illustrate the development of site-specific highway-runoff pollutant loading models. This unified methodology provides a basis for initial assessment of the pollutant-constituent loads from highway runoff using hydrologic component variables. Improved reliability is achievable when additional traffic and/or atmospheric component variables are incorporated into the basic hydrologic regression model. In addition, operational guidance is suggested for implementing highway-runoff monitoring programs that are subject to sampling and resources constraints.     

Enhancement of activated sludge performance on ammonium removal by clinoptilolite

This study evaluated the influence of clinoptilolite on the performance of activated sludge system shocked by high concentration of ammonium. The ammonium and chemical oxygen demand (COD) removal from the experimental reactor containing clinoptilolite and from the clinoptilolite-free control reactor was determined. The ammonium and COD removal was approximately 8 and 20% higher in the experimental reactor than in the control reactor, respectively. The removal increased with an increase in clinoptilolite concentration over the tested range up to 50?mg?L^?1. The presence of clinoptilolite resulted in the sludge flocs being more compacted with smoother surfaces and edges. Molecular biological analysis revealed that clinoptilolite increased the DNA diversity, richness, and evenness of sludge microbes. The enhanced-performance activated sludge previously treated with clinoptilolite was less influenced by the shock of ammonium than non-treated sludge in terms of the ammonium and COD removal. These results suggest that clinoptilolite enhanced the performance of activated sludge system in the removal of ammonium and COD. Amendment of activated sludge with natural zeolites may thus improve the efficiency of wastewater treatment.     

风雪共同作用下膜结构雪压分布规律的数值模拟研究

对膜结构在风雪共同作用下的雪压分布规律进行了数值模拟研究。首先采用两相流原理对雪漂运动中的空气相和雪相分别进行了数值建模,然后采用CFD数值模拟技术,研究了在风雪共同作用下双坡型膜结构表面的雪荷载分布规律,分析了双坡型膜结构的重要几何参数变化时,雪漂及屋面雪荷载分布的变化规律,总结了双坡型膜屋面在风雪共同作用下的雪压分布规律。结果表明,屋面倾角和屋面宽度是影响风雪共同作用下膜结构表面雪压分布的重要因素,檐口高度和屋面长度是影响膜结构表面雪压分布的次要因素。本文研究为更安全、经济地进行膜结构的抗风雪设计、施工提供了可靠的科学依据。     

基于健康监测系统的大跨度多荷载悬索桥的疲劳与可靠度评估(英文)

在过去的几十年,世界各地建立了许多大跨度悬索桥。通常这些桥梁需承受多种动力荷载,尤其是一些处于多台风地区的公铁两用桥梁。为了保证这些大跨悬索钢桥在运营期内的安全和正常使用,有必要以一定的时间间隔进行桥梁的疲劳和可靠度评估。有鉴于此,许多大跨悬索桥都安装了健康监测系统,但是如何运用其进行准确的疲劳评估仍然是一个问题。本文通过结合计算机模拟技术和健康监测系统的测量数据,以香港青马大桥为例,分析了在多荷载作用下的大跨度悬索桥的疲劳和可靠度。同时,作为利用结构健康监测技术进行结构健康状态评估的这一重要研究方向的有益实践,该研究发展了一系列方法用于评估桥梁的疲劳,以及通过考虑存在于结构的物理模型和计算机模拟中的不确定性用以评估疲劳的可靠度。     

压力容器的可靠性分析

应用概率断裂力学的观点,讨论了压力容器各有关参数的分布特点及允许的失效概率,分析了材料韧性为两种不同分布时压力容器可靠性计算方法,说明了进行压力容器失效概率分析是全面评价压力容器的方法之一.     

综合产品环境审计工具:生命周期清单分析

生命周期清单分析是 ISO 14000环境管理系列标准内容之一 ,是定量评价产品生命周期全过程 (从原材料采掘到最终处理 )环境负荷的重要工具 ,也是实施产品全过程环境管理的重要审计工具 .系统地论述了生命周期清单分析的实施步骤、方法和相关的概念 .     

潮汐河网水环境随机容量研究

根据潮汐河网水环境模型中水文及水质参数具有明显随机性的特点,本文建立了潮汐河网水环境随机模型,给出了随机参数的分布函数形式。用Monte-Carlo随机抽样法求解水项模型 当只抽一个样本时,随机模型的算法与确定性模型的算法一样。计算结果为水环境容量的分布函数,容量结果与保证率成一一对应关系。最后还对随机参数的分布函数形成进行了敏感性讨论。      

Investigating the Uncertainties in the Simple Mass Balance Equation for Acidity Critical Loads for Terrestrial Ecosystems in the United Kingdom

The Simple Mass Balance (SMB)equation has been developed and used as one ofthe principal methods for calculating criticalloads of acidity for forest ecosystems. Criticalloads have formed the basis for informing policyrelated to the control and abatement of emissionsof acidifying pollutants. The SMB equationrelies on a variety of assumptions and dataderived from a variety of sources. Each of thesecomponent constituents has a potential source oferror depending on the method(s) used for theirderivation and the value(s) assigned. The resultis the possibility of generating a range ofcritical load values for a single ecosystem. This paper summarises the SMB equation, examinesthe uncertainties in deriving input values andreviews other works on the key assumptions.     

Atmospheric deposition and canopy exchange processes in alpine forest ecosystems (northern Italy)

Throughfall and bulk precipitation chemistry were studied for five years (June 1994–May 1999) at two high elevation forest sites (Val Gerola and Val Masino) which were known to differ in terms of tree health, as assessed by live crown condition. The ion concentration of bulk precipitation samples did not differ significantly between sites, except for Mg²⁺, while the throughfall concentrations differed in the measured values of H⁺, N-NO₃⁻, Cl⁻, Na⁺, K⁺, DOC and weak organic acids. The results of the application of the canopy exchange model indicated a higher contribution from the dry deposition of N-NO₃⁻, N-NH₄⁺ and H⁺ at Val Gerola, where the damage symptoms were more evident. In addition, the canopy leaching of Ca²⁺, K⁺ and weak organic acids were 47%, 21% and 27% higher at Val Gerola than at Val Masino. Annual SO₄²⁻ deposition fluxes (21.3 kg ha⁻¹ yr⁻¹ at Val Masino and 23.6 kg ha⁻¹ yr⁻¹ at Val Gerola) were similar to those reported for moderately polluted European and U.S. sites. Annual N loads were 13.6 and 13.1 kg ha⁻¹ yr⁻¹ in the bulk input, and 15.0 and 18.0 kg ha⁻¹ yr⁻¹ in throughfall inputs, at Val Masino and Val Gerola, respectively. The contribution of the organic fraction to the total N atmospheric deposition load is significant, constituting 17% of the bulk flux and 40% of the throughfall flux. Measured nitrogen loads exceed the critical nutrient loads by several kg N ha⁻¹ at both stations. In particular the nitrogen throughfall load at Val Gerola was about 3 times higher than the critical values.