Formation of tidal starting-jet vortices through idealized barotropic inlets with finite length

This paper presents a surface particle image velocimetry study to investigate the dynamics of shallow starting-jet dipoles formed by tidal flow through inlets and their interaction with vorticity formed at the inlet channel lateral boundaries. Vortical structure in the flow field is identified using a local swirl strength criterion evaluated from the two-dimensional flow field. The starting jet dipole vortices and vortices formed as the lateral boundary layers are expelled during flow reversal are characterized by their trajectory, size, and circulation. Using these quantities, a model is developed to predict the size and strength of the expelled lateral boundary layer vortices based on the inlet velocity, channel length, and width of the lateral boundary layer. The expelled boundary layer vortices are found to disrupt the formation of the primary tidal jet dipole through two mechanisms. First, because the boundary layer vortices themselves form a dipole with each half of the starting-jet dipole, the starting-jet vortices are pulled apart and advected away from the inlet mouth early in the tidal cycle, resulting in a reduction in the spin-up time and the amount of vorticity input during starting-jet vortex formation. Second, the advection of each dipole away from the inlet disconnects each starting-jet vortex from the starting jet; hence, the vortices are not fed by fluid in the jet or energized by shear in the jet boundary layers. These influences of the lateral boundary layer on the starting-jet vortices’ formation and propagation are found to be a function of the channel length L, maximum velocity U, and tidal period T, resulting in a predictive value to characterize their trajectory, strength, and evolution.     

围封对内蒙古中东部草原植物群落和土壤线虫群落的影响

2007年8月在中国科学院内蒙古草原生态系统定位研究站的退化样地（对照）、围封5 a样地和围封24 a样地,调查地上部植物群落、土壤性质和地下部土壤线虫群落。结果表明,围封处理能显著提高土壤水分质量分数,土壤深度和围封处理对土壤pH的交互作用显著。随着围封年限的增加,地上植物的多度、生物量和单株生物量都显著增加,而3个样地的多样性和均匀度均为围封24 a样地〉退化样地〉围封5 a年样地;随着围封年限的增加,大针茅（Stipa grandis）、苔草（Carex duriuscula）、羊草（Leymus chinensis）、锦鸡儿（Cleistogenes squarrosa）、双齿葱（Allium bidentatum）的生物量都呈现递增的趋势;围封5 a样地上冰草（Agropyron cristatum）和野韭（Allium ramosum）的生物量最大,围封24 a样地上苔草、羊草、双齿葱的生物量最大。调查样地线虫的密度平均为9.79 g-1（以干土计）,分别隶属于线虫动物门的90个属。植物寄生类线虫和食细菌类线虫分别占到总数的35%和40%,优势类群是丽突属（Acrobeles）和矮化属（Tylenchorhynchus）,二者共占总捕获个体数量的31.4%。围封24 a样地的结构指数显著高于退化样地,其它指标差异不显著。由此可知,围封有助于改善土壤理化性质;从围封角度来看,植物群落比线虫群落的反应明显得多,二者并未出现同步反应。     

不同耕作方式下土壤氮素矿化和硝化特征研究

为探讨长期定位试验田不同耕作方式下土壤氮素矿化和硝化特征,采用室内恒温通气培养法,保持土壤田间持水量在65％条件下,测定不同耕作方式下表层土壤（0～20cm）在不同温度下的NH4^＋和NO3^-含量,并计算氮素矿化量和硝化率。结果表明,随着温度的升高,土壤氮素矿化和硝化作用均增强,几种耕作方式下土壤氮素矿化和硝化作用均表现为35℃〉30℃〉25℃。保护性耕作与水旱轮作和常规平作之间的矿化量存在显著的差异,垄作免耕〉厢作免耕〉水旱轮作〉常规平作。土壤氮素最终硝化率达到了60％～80％,表现为常规平作最高,水旱轮作次之,厢作免耕最低。矿化率与土壤有机质、碱解氮和速效磷对数均成显著正相关,相关系数分别为r^2=0．99,r^2=0．97,r^2=0．96,pH是影响硝化作用的重要因素,硝化率与土壤pH成显著正相关,r^2=0．991。     

基于变异性范围法（RVA）的河流生态流量估算

河流生态系统的生物组成、结构和功能依赖于河流水流的天然动态变化特征,即河流水文情势。变异性范围法（Range of Variability Approach,RAV）被广泛应用于评估河流生态系统是否得到维护。将RVA法的思路扩展到生态流量的计算,提出了一种简便、立足整体河流水文情势的生态流量估算方法。该方法使用均值与RVA阈值差计算了生态流量值,为维持河流健康生态系统提供支持。将该方法应用于南水北调西线一期工程中泥曲河的生态流量估算,得到引水坝址仁达处年可调径流量为6.44亿m3,与其他生态需水估算方法的结论基本一致。另提出了可支配系数反映河流流量可调用状况。南水北调西线一期工程计划从泥曲调水8亿m3·a-1,从RVA法的理念来看,该方案对仁达至朱巴河段的生态系统将构成威胁,需谨慎实施。     

Diurnal vertical migration of Cochlodinium polykrikoides during the red tide in Korean coastal sea waters

The diurnal vertical migration of Cochlodinium polykrikoides (C. polykrikoides), which caused a red tide in the Korean coastal waters of the East Sea/Sea of Japan in September 2003, was examined by determining the time-dependent changes in the density of living cells in relation to the depth of the water column. The ascent of this species into the surface layer (depth of water 2 m) occurred during 1400-1500. The descent started at 1600 and a high distribution rate (86%) at 15-20 m was observed at 0300. During the ascent, the cells were widely distributed at each depth level from 0600 hr and at 0800-1100, the cells were primarily distributed in the middle layer (0-6 m). The concentration of dissolved inorganic nitrogen was generally < or = 2.86 micromol l(-1), but at 1400-1500, the concentration in the surface layer reduced to < or = 0.14 micromol l(-1). Moreover, the concentration gradually increased as the depth increased to > or = 5 m. These results showed that the nutrient-consumption rate associated with the proliferation of C. polykrikoides during a red tide is more influenced by the inorganic-nitrogen resources ratherthan the inorganic-phosphorus compounds.     

用于气溶胶采样预分离的直流式旋风分离器

频繁的滤材堵塞是大气气溶胶采样器(流量大于500 m3/h)运行中常见的问题,安装预分离器是缓解这一问题的有效途径之一。研究了可用于这种气溶胶取样器预分离的旋风分离器,确定了使用轴流进气直流式的结构。在惯性分离理论的基础上,提出了切割粒径的计算方法。建立了流量为700～800 m3/h的预分离器性能测试装置和方法,并对3个旋风分离器性能进行了测试。实验结果表明:3个旋风分离器的切割粒径在12～14.5μm,与计算较好地符合;性能最佳的旋风分离器的切割粒径为14.5μm,10μm颗粒的透过率为73%,符合技术要求。     

四种典型大气环境下7B50铝合金的腐蚀行为研究

目的 研究湿热海洋、干热沙漠、寒冷乡村、暖温高原四种典型大气环境对7B50铝合金腐蚀行为的影响.方法 采用户外大气自然环境暴露试验,通过宏观腐蚀形貌分析、金相显微形貌分析、腐蚀深度分析和拉伸性能分析,对比研究7B50-T7751和7B50-T77511两种铝合金在不同大气环境中的腐蚀行为和规律.结果 暴露试验周期为3 a时,7B50-T7751铝合金在湿热海洋大气环境中腐蚀严重,局部最大腐蚀深度为166μm,抗拉强度和断后伸长率分别下降了5％和25％;在干热沙漠大气环境下腐蚀较重,局部最大腐蚀深度为44μm;在寒冷乡村、暖温高原大气环境下未见明显腐蚀.7B50-T77511铝合金在四种典型大气环境下均表现出明显腐蚀,局部最大腐蚀深度分别为141、80、42、29μm.结论 两种7B50铝合金在典型大气环境中表现出不同的耐蚀性,在微观上均表现为点蚀和晶间腐蚀的混合腐蚀,具有明显的晶间腐蚀和剥蚀倾向.两种铝合金暴露在相同大气环境中时,7B50-T7751板材耐蚀性较7B50-T77511型材略好.     

Oxidation rate in the preparation of polyferric sulfate coagulant

ＩｎｔｒｏｄｕｃｔｉｏｎＡｐｒｅｐａｒａｔｉｏｎｍｅｔｈｏｄｏｆｐｏｌｙｆｅｒｒｉｃｓｕｌｆａｔｅ (ＰＦＳ)ｃｏａｇｕｌａｎｔｗａｓｒｅｐｏｒｔｅｄｂｙＪａｐａｎｅｓｅｓｃｉｅｎｔｉｓｔｓ(Ｙａｎｇ ,1986)ｉｎｔｈｅｓｅｖｅｎｔｉｅｓ.ＳｉｎｃｅｔｈｅｅｉｇｈｔｉｅｓｔｈｅｐｒｅｐａｒａｔｉｏｎａｎｄａｐｐｌｉｃａｔｉｏｎｏｆＰＦＳｈａｖｅｂｅｅｎｗｉｄｅｌｙｉｎｖｅｓｔｉｇａｔｅｄｉｎＣｈｉｎａｂｅｃａｕｓｅｏｆｉｔｓｈｉｇｈｃｏａｇｕｌａｔｉｏｎｅｆｆｉｃｉｅｎｃｙｉｎｗａｔｅｒｔｒｅａｔｍｅｎ…     

试点碳市场配额有偿分配经验及对全国碳市场的借鉴意义分析

我国7省市碳排放权交易试点经过多年实践,积累了宝贵经验。在配额分配方面,多数试点在免费分配的基础上进行了配额有偿分配的探索,形成了各具特色的有偿分配实践。研究表明,试点碳市场配额有偿分配的经验对全国碳市场配额分配具有重要的参考借鉴意义。建议结合全国碳市场建设和发展实际以及配额分配实施方案的制定,科学合理设计有偿分配相关规则,并建立相应的监管机制。     

典型岩溶槽谷区不同地表覆被土壤中多环芳烃的运移特征和来源解析

为探究岩溶槽谷区土壤中多环芳烃(PAHs)的环境行为,选取典型的竹林地、灌丛地和耕地作为研究对象,运用气相色谱-质谱联用仪定量分析土壤中的PAHs.结果表明,土壤剖面中PAHs污染水平表现为竹林地(204.13 ng·g^-1)>耕地(175.47 ng·g^-1)>灌丛地(106.00 ng·g^-1),土壤质量总体良好.3种土地类型均表现为浅层土壤的PAHs含量显著高于深层土壤(p<0.05),表明岩溶区土壤对防止地下水污染具有重要意义;2~3环PAHs易运移至深层土壤,而4~6环PAHs受TOC含量的影响则主要积聚在浅层土壤,富集能力表现为灌丛地>耕地>竹林地;PAHs运移特征主要受控于有机质的吸附和水的溶解两种机制,PAHs和土壤的理化性质是影响PAHs运移的重要因素.结合同分异构体比值法和主成分分析法的源解析结果,得出研究区土壤中PAHs主要源于当地能源燃烧和交通污染,而大气沉降是重要污染途径.