深厚覆盖层中弱透水层特性对渗流场的影响

中国西部地区的深厚覆盖层坝基中常存在弱透水层,对坝基渗流场有一定影响。基于非饱和土渗流理论,借助有限元软件Seep/w建立数值模型,得出渗流量和出逸坡降,并结合2个实际工程分析弱透水层深度、厚度、连续性对渗流场的影响。结果表明,采用悬挂式防渗墙或无防渗墙时,深度越小的弱透水层控渗效果越佳;深度越大的弱透水层与防渗墙形成的半封闭式联合防渗体系,越能有效控制渗流量和抑制出逸坡降。渗流量和出逸坡降都随着弱透水层厚度的增大而降低;弱透水层厚度及连续性对采用半封闭式防渗墙控渗时的渗流场影响最大,悬挂式防渗墙次之,全封闭式防渗墙最小。渗流量和出逸坡降随上游、底端开口长度的增加而增大;渗流量随下游开口长度的增加而增大,但出逸坡降随下游开口长度的增加呈先增大后减小的趋势。弱透水层的连续性对渗流场影响较小。采用半封闭式防渗墙时,渗流量和出逸坡降从高到低排序为底端开口、上游开口、下游开口。采用全封闭式防渗墙时,防渗墙承担主要的控渗任务,弱透水层的深度、厚度、连续性对渗流场的影响极小。     

国外大气中消耗臭氧层物质及其替代物的监测概况与启示

大气中消耗臭氧层物质(ODS)及其替代物监测是科学评估履约成效的重要基础。美国等发达国家针对大气中ODS及其替代物开展了长期的网络化监测,中国相关监测起步相对较晚,基础比较薄弱。该文总结了发达国家大气中ODS及其替代物的监测经验,分析了中国的监测现状及存在的问题,提出了中国大气中ODS及其替代物监测的建议:明确监测目标,推进国家大气中ODS及其替代物监测网络建设;加快相关监测设备研发及方法研究进程,形成规范统一的监测技术体系;定期开展监测数据质量评价,加强综合分析利用。通过采取相应措施,逐步形成中国履行保护臭氧层国际环境公约的监测支撑能力。     

城市停车场火灾风险性的评价

城市大型停车场的数量随着经济的发展在迅速增长,这些新建的停车场均向高层和地下空间发展,其投资费用都较大,一旦发生火灾,往往会造成严重的经济损失和人员伤亡事故,国内外停车场发生的一系列火灾事故充分证明了这一点.因此,对停车场进行火灾风险评价具有十分重要的意义.分析了停车场火灾的特点,并从停车场的火灾场景、发生轰燃的烟气条件、释放辐射热的大小、对面汽车被引燃的临界条件等几方面对停车场潜在的火灾风险性进行了探讨.以某地下停车场为例,对其火灾风险性进行了具体评价.     

Trace analysis of airborne toluene diisocyanate as a pentafluorobenzyl derivative by gas chromatography with electron capture detection

Trace analysis of airborne toluene diisocyanate (TDI) vapor was accomplished by measuring the derivative using gas chromatography with electron‐capture detector after collecting gas samples with a microimpinger containing 2 ml toluene, 1 μl pentafluorobenzyl alcohol, and 1 μl triethylamine. The sampling efficiency was determined to be 99.4% for short‐term exposure level of TDI and the 2,4‐ and 2,6‐isomers of TDI were well separated. The derivative was identified to be a new compound with a molecular weight of 570 by mass spectrometry in fast atomic bombardment mode and nuclear magnetic resonance spectrometry. This method is convenient and can be applied in the field where airborne TDI is in vapor form.     

苯和甲醛联合染毒对小鼠脾脏的损伤

为了探讨苯和甲醛联合染毒对小鼠脾脏的损伤以及二者是否具有一定的协同作用,选择BALB/c雄性小鼠30只,随机分为5组,每组6只,设苯组、甲醛组、苯和甲醛联合染毒组及玉米油对照组和空白对照组,对小鼠进行气态甲醛吸入染毒或/和苯玉米油溶液灌胃染毒。染毒结束后对小鼠脾脏进行组织病理学观察,并且测定脾脏的脏器系数以及脾脏组织的活性氧(ROS)和丙二醛(MDA)的含量。结果显示,苯和甲醛联合染毒组小鼠脾脏组织中ROS的含量与空白对照组相比有极显著的上升趋势(P<0.01),脾脏的脏器系数以及脾脏组织中MDA的含量与空白对照组相比有显著性差异(P<0.05)。此外,在脾脏免疫组织形态变化以及脾脏组织中MDA含量这2个生理生化指标上,苯和甲醛联合染毒对小鼠脾脏的损伤具有一定的协同作用。     

Water use efficiency of a mixed cropping system of corn with grasses

A new cropping system of corn mixed with grasses was tried to make full and efficient use of water and to ease environmental problems such as soil erosion by water and wind in grain and forage feed production practices. Field experiments were conducted to investigate the water use efficiency under this mixture cropping system. Six treatments with two replicates were arranged as: bare field, corn only, rye only, alfalfa only, rye–corn mixture and alfalfa–corn mixture. Lysimeters were used to measure different components of water consumption in the crop fields for water use efficiency estimation. From the yields and water consumption of crops under different treatments, combined water use efficiency of corn and grasses were estimated. The results showed that WUEs in the mixed cropping fields of corn–grasses were much higher than those in the fields where only corn or grass were grown. Averaged WUE was 3.71 kg/m³ from the corn and rye mixture fields, 30% higher than that from the plots where only corn or rye were grown. Averaged WUE was 4.55 kg/m³ from the alfalfa and corn mixture fields, 60% higher than that from the fields where only corn or alfalfa were grown. Under the same conditions of irrigation, yields from the rye and corn mixture plots increased by 33%, as compared with those from fields where only corn or rye were grown. The yields from alfalfa and corn mixture fields were 61% higher than those from fields where only corn or alfalfa were grown. The experimental results also indicated that corn and alfalfa mixture cropping is better than a corn–rye mixture system.     

Effects of La3+, Ce3+ on nitrogen removal in sequencing batch reactor

Batch experiments were conducted to study the short-term biological effects of rare earth ions (La³⁺, Ce³⁺) and their mixture on the nitrogen removal in a sequencing batch reactor (SBR). The data showed that higher NH₄ ⁺-N removal rate, total inorganic nitrogen removal efficiency, and denitrification efficiency were achieved at lower concentrations of rare earth elements (REEs) (<1 mg/L). In the first hour of the aeration stage of SBR, the presence of REEs increased the total inorganic nitrogen removal efficiency and NH₄ ⁺-N removal efficiency by 15.7% and 10%–15%, respectively. When the concentrations of REEs were higher than 1 mg/L, the total inorganic nitrogen removal efficiency decreased, and nitrate was found to accumulate in the effluent. When the concentrations of REEs was up to 50.0 mg/L, the total inorganic nitrogen removal efficiency was less than 30% of the control efficiency with a high level of nitrate. Lower concentrations of REEs were found to accelerate the nitrogen conversion and removal in SBR.     

湿法脱硫系统设计无旁路相关问题的探讨

介绍国内电厂首次投运的无旁路脱硫系统,其具有无GGH、引风机和增压风机合并、"烟塔合一"的特点。通过与其他脱硫系统的比较,讨论了无旁路脱硫系统吸收塔、烟道、公用系统以及除尘器的设计和选型特点,总结了其易出现的问题及运行中的控制方法。根据调试经验,给出了无脱硫旁路系统的运行步序原则。     

西安市灰霾天气时间和区域分布特征及影响因素

依据1961—2005年共45年,西安、户县、长安、蓝田、临潼、高陵和周至7个气象台站灰霾观测资料,分析了灰霾天气时间和区域分布特征,并根据1996—2005年近10年西安逐月平均灰霾日数与近10年逐月主要气象要素相关性分析,得出:西安市20世纪70年代是灰霾日出现的高峰时期,并呈逐年减少趋势,灰霾发生的中心区域也在向郊区东南部转移;从影响灰霾天气形成的气象条件来看,气温越低,降水量和风速越小,日照越少,气压越高,越有利于灰霾天气的形成。     

An assessment of China-Japan-Korea Free Trade Agreement’s economic and environmental impacts on China

Recently, China, Japan, and the Republic of Korea (Korea) are conducting a government-commissioned feasibility study on the Free Trade Agreement among the three countries (CJKFTA) to form a regional free trade zone in East Asia. Considering that freer trade can cause unexpected impact on domestic environment, there is a need to evaluate the environmental impact of such a trade policy. This move should be made to help negotiators understand and pay more attention to environmental issues during CJKFTA negotiations, and to help lobby with the government to carry out appropriate policy instruments for adaptation or mitigation. Following the Chain Reaction Assessment Method that integrates and links the elements of trade, production, and environment, the present research aims to quantitatively assess CJKFTA’s possible impact on China’s environment. This is done by estimating the variations of China’s major conventional pollutants and greenhouse gases (GHGs) emission in two policy scenarios to represent CJKFTA’s scale and composition effects on China’s environment. Estimating the variations is based on a static Computable General Equilibrium model, working with Global Trade Analysis Project (GTAP) 7 database and China’s energy-environment statistics. Based on these assessments, CJKFTA is predicted to lead to notable environmental impact, including increased emissions of agricultural total nitrogen, agricultural total phosphorus, chemical oxygen demand, and GHGs. On the other hand, decreased emissions of industrial SO₂ and dust are also expected to happen. Suitable policies need to be made to combat negative effects and amplify positive ones, while aiming at a more sustainable regional freer trade system.